# [SOLVED] adjustable dc step up



## lalo 123 (Sep 12, 2012)

hello, i am trying go get three pins 2 positive and the center negative, i am trying to power a printer in a car, i was wondering if i could use 2 adjustable power step ups like this one 

1pcs LM2577 DC DC Adjustable Step Up Power Converter Module | eBay

the voltage i need is 16v and 32v while sharing the negative terminal they are no greater then 1 amp


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

Why go through all the headaches when you just pick up an inverter and run the terminals through your fuse box. 


Amazon.com: Cobra CPI1000 1000W 12V DC to 120V AC Power Inverter with USB Port: Car Electronics


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

unnecessary battery drainage, and heat


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

doesn't seem logical to me to go from 12v dc to 120 ac then back to 16 & 32 dc


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

Out of curiosity; Have you taken apart the printer and are using just the inside carcass to run connections from the printer's pcb to the car battery ?


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

No I haven't, the 3 pins plug in directly in the printer, there is a power inverter seperate from the printer


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> No I haven't, the 3 pins plug in directly in the printer, there is a power inverter separate from the printer




The reason I asked is because a vehicles alternator is not a consistent flow, the alternator switches on/off to charge the battery. A typical alternator gives out 14.2 to 14.5v D/C at 80 amps. The power supply has to be regulated for your idea to work, you will have to calculate the amount of current that will run through your printer by using ohms law or risk serious damage to your wiring harness and the vehicles on board computer. 



:danger: Do not run your connections without them being fused or anywhere near an air bag system or power train modules you risk serious personal injury if the air bag accidentally deploys.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

I was unaware that there is such high risks involved, but what if I run the power directly from the battery with. 2amp fuse, surely there should be no problem because u are able to jump another vehicle direcly from the battery, and of course put a switch on it to power it off when the car is off, and doesn't the link that I posted insure a constant flow? I contacted one of the sellers and explaind what I needed it for and they told me it would work. I am not going by what they said, afterall they are doing it for the business


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> I was unaware that there is such high risks involved, but what if I run the power directly from the battery with. 2amp fuse, surely there should be no problem because u are able to jump another vehicle directly from the battery, and of course put a switch on it to power it off when the car is off, and doesn't the link that I posted insure a constant flow? I contacted one of the sellers and explained what I needed it for and they told me it would work. I am not going by what they said, after all they are doing it for the business






You could run it directly from the battery as long as its fused there shouldn't be a problem. You need to be aware of a couple of things though: 1) A vehicles wiring is all done in parallel _not_ in series. In parallel circuits the voltage remains the same but _current_ increases. In series circuits the current remains the same but the _voltage_ increases. 2) You will need the vehicles wiring schematic to avoid burning out the vehicles computer drivers. 3) There may be additional components such as relays, current limiters, heat sinks, fans to dissipate heat to be added to the project before final connections are made. 

If you could post the make, model, year, engine displacement of your car and picture of the printer you want to install, we could come up with a schematic you could work with along with some crafty ideas on how to make this work.


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## gcavan (Aug 13, 2009)

*Re: adjustable dc step up*

@ Octane: I am wondering why what lalo is considering different from installing any other 12volt accessory in an automobile. You suggest using a DC - AC inverter which would, in fact also need to be hard wired into the system. How is installing a purpose-built DC - DC converter any different? Yes there are fusing and wiring capacities to consider, but that is a consideration with any addition to the automobiles original equipment.


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

@gcavan


From my understanding Lalo's requirements are 16 and 32v to get the system up and running. These are 2 distinct voltages that a vehicle power management system does not produce, but can be artificially augmented by means of a voltage multiplexer. The problem with doing it that way is that it has to be hard wired and other factors need to be considered. 

Installing a printer in a vehicle has already been done by using an inverter that has a steady A/C sine wave output by just wiring it to the car's battery. It has to be separate because a printer's power consumption ranges from 300 Watts for laser printer and 150 Watts for an inkjet. The power consumption is enormous and by doing it the way Lalo wants will require modifying the vehicles charging system.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

Hello, sorry for the late response, the vehicle is a 2000 chevy express, and I'm pretty sure the printer is a psc 1310, I will double check when I get time. You said that cars are wired in parallel, so wouldn't wiring the printer directly off the battery be parallel with everything else? And I also ordered one dc step up just to see how it works, and to see if the output voltage would stay the same while the input changes.


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> Hello, sorry for the late response, the vehicle is a 2000 chevy express, and I'm pretty sure the printer is a psc 1310, I will double check when I get time. You said that cars are wired in parallel, so wouldn't wiring the printer directly off the battery be parallel with everything else? And I also ordered one dc step up just to see how it works, and to see if the output voltage would stay the same while the input changes.




Yes it would be. But as I mentioned in my previous post, printers require allot of wattage. Thats why printers that are installed in cars are run only when engine is running. Printing directly off the battery with ignition off will kill the battery in 2 minutes of printing time.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

I do plan on only using it when the engine is running, I also have a 12 volt battery I have from a belkin back up internet battery, I'm not sure how many amps it is and the printer only says it uses 600ma on one and 1000ma on the other, I'm not sure on which ones though


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

The battery I am talking about is 12v and 7.2Ah that is 86 watts, would that be efficent enough, the only issue is how will I charge it?


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> I do plan on only using it when the engine is running, I also have a 12 volt battery I have from a belkin back up internet battery, I'm not sure how many amps it is and the printer only says it uses 600ma on one and 1000ma on the other, I'm not sure on which ones though


The specs you mention are on the power bar_ not_ the printer's power consumption. This is what the 1310's power specs are and i've circled what you need to look for.


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> The battery I am talking about is 12v and 7.2Ah that is 86 watts, would that be efficent enough, the only issue is how will I charge it?



86 Watts is barely making the power requirement, and I doubt its reserve capacity will be sustainable for any extended use. It will need to be constantly charged for the demand. To charge it You will need a battery charger.


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## Basementgeek (Feb 7, 2005)

*Re: adjustable dc step up*

If I remember correctly if you are wanting to step up 10 V to 120 V, that is an increase of 10. The watts required will be increased by 10 also.

I would use a commercial available inverter. I am pretty sure most of the bigger ones have a low voltage shut off. i.e. won't drain the car battery down to keep it from starting.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

My ultimate goal is to step up 12 volt dc to 16 and 32 volts dc, I could convert 12v dc to 120v ac then back to the 1f and 32 that I need but that seems unneccessary and expensive, and also excessive power drainage and heat.
Octaneman, come to think of it the maximium watt usage would be when making a copy of a colored photo, I'm not saying I won't be scanning but I will be mostly printing, the lights on the scanning tray are where most the power is being consumed, correct me if I'm wrong.


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> My ultimate goal is to step up 12 volt dc to 16 and 32 volts dc, I could convert 12v dc to 120v ac then back to the 1f and 32 that I need but that seems unneccessary and expensive, and also excessive power drainage and heat.
> Octaneman, come to think of it the maximium watt usage would be when making a copy of a colored photo, I'm not saying I won't be scanning but I will be mostly printing, the lights on the scanning tray are where most the power is being consumed, correct me if I'm wrong.




True. The scanner CFL will draw allot more power than when you are only doing ordinary printing tasks. But when you are working in the field you would want that extra power reserve to handle those rush jobs at any given moment. 


What I have a hard time understanding is why you need the voltages instead of just using an inverter. The DC converter card's output voltages are done manually not automatically on the fly. If you look carefully on the card the output voltage is adjusted through a trim pot by using a small flat head screwdriver in conjunction with using a DMM to find the correct voltage setting. It won't give you the 16v one second and then automatically switch to 32v the next. The card is not designed as a multiplexer with multiple outputs, its only a single output with one voltage setting.


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## Basementgeek (Feb 7, 2005)

*Re: adjustable dc step up*

Good luck on your quest, but I feel you are trying to invent a better mouse trap. A 
12VDC to 120AC is the only way to go.

What are you going to do about your printer with all the road shock it is going to get riding around? Remove the print cartridges ? I would or you could have a really dirty copies.

BG


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

I think there might be a misunderstanding, I plan on buying two of those and have one give me 16v and the other give me the 32v. There are 3 pins for powering the printer the 16v negative and 32v, as a last resort I would buy the inverter but I would like to avoid it if possible.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

Basementgeek, aren't the printer cartriges on the side when not in use? I don't plan on using it while driving, and if they were to get messy doesn't the. Printer clean it before each printing?


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## Basementgeek (Feb 7, 2005)

*Re: adjustable dc step up*

Some printers may be different. I don't know. 

I just think you are you are possibly throwing money away buy something with no guarantee that it will work or trash the printer.

My 400Watt 120AC are under $50.00, plus it has low voltage cut off, a "fault light" , two 120 outlets and one USB port. Since I never used it more 100-150watts I put a cigarette lighter plug on it.

Heat and draw most likely depend on the load you put on it.

Again, good luck.

BG


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> I think there might be a misunderstanding, I plan on buying two of those and have one give me 16v and the other give me the 32v. There are 3 pins for powering the printer the 16v negative and 32v, as a last resort I would buy the inverter but I would like to avoid it if possible.


The printer's power supply gives out the voltages because the inverter is built into it; Unless its burned out and you cant find a replacement. The way I see it is you want to hardwire the cards to the printer's motherboard using your vehicles fuse box as a power supply to power it up.


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## gcavan (Aug 13, 2009)

*Re: adjustable dc step up*



> The printer's power supply gives out the voltages because the inverter is built into it; Unless its burned out and you cant find a replacement. The way I see it is you want to hardwire the cards to the printer's motherboard using your vehicles fuse box as a power supply to power it up.


Not even close. Many HP deskjets use a wall wart power pack which supplies +16 and +32 volts DC. OP simply wants to use the existing power cable after replacing the wall wart with a pair of DC to DC converters. I see no issue with that. Only problem I can foresee is whether the chosen converters can supply stable power at load.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

@ last!! Someone that understands exactly what I am saying
Octaneman, was it better hearing it from gcavan, I know I am not very good at exxplaining things, and isn't my car battery at least 700 amps? In which case the 80 max amps is nothing for the car battery


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

Gcavan that is my main concern right now, I posted earlier that I purchased one of those step ups mainly out of curousity to see if the voltage output will stay the same while changing the input, could any of u guys say what will happen because the suspense is killing me!


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> @ last!! Someone that understands exactly what I am saying
> Octaneman, was it better hearing it from gcavan, I know I am not very good at exxplaining things, and isn't my car battery at least 700 amps? In which case the 80 max amps is nothing for the car battery




Ok, I get the picture. There's 1 critical issue that you should be aware when it comes to wall wart connectors. 

There's no standards for these type of connectors. They run different voltages through the same connector either AC or DC. You don't know what voltage your printer will take in first, you could easily run the wrong voltage through it and burn the printer.


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## Done_Fishin (Oct 10, 2006)

*Re: adjustable dc step up*

What is the spec for the input voltage ?? Most dc-dc converters tell you how they handle for fluctuating input voltage and your car battery should not fluctuate more than about 2 volts 

what I am concerned about is teh 80 amps you mention .. maybe I missed something earlier in the thread bt I personally wouldn't draw 80 amps through a cars wiring .. it would need direct wiring to the battery via a fuse !

also I seem to remember that car batteries are rated at ampere hours (AH) and the one that I have on the floor in front of me is 55 AH .. where did you find the 700 amps ?? Perhaps you are confusing power rating with amps?

I also have to admit that when I first saw your thread and project, at first glance the modules looked like what you are looking for, but what load can they handle ?? Do they need heatsinks and external bypass transistors to handle the printer load ??


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## Done_Fishin (Oct 10, 2006)

*Re: adjustable dc step up*

My apologies .. a lot has been added to this thread since I first saw it and I have just looked back and found some of the info that was missing 



> Description:
> 
> 1.Wide Input voltage: 3V-30V
> 2.Output Voltage: 4-35V (Adjustable)
> ...


*1.Wide Input voltage: 3V-30V*

the car battery voltage should vary no more than about 2 Volts (minimum 12Volts and max 14.2 volts when fully charged or charging). The circuit should be able to handle that variation without problems (12.Voltage regulation: ± 0.5%)

*2.Output Voltage: 4-35V (Adjustable)*

covers your 2 basic voltages 


*3.Output current: rated current 3A MAX ( Heat-sink Needed)
4.If you need its output power greater than 15W, please add with heat-sink*

you WILL need to add heatsinks
I saw that you showed the specs for the power consumption as 16V @0.625A & 32V @ 0.94A.

Whilst the 16volt circuit might be loaded only with 10Watts ( 16*0.625=10) a heatsink IMHO would be recommended. 

The 32Volt Circuit will be drawing nearly 1A in current so we are talking more than 30 watts, definitely requires a heatsink according to the specs.

*5.Conversion efficiency: Up to 92% (output voltage higher, the higher the efficiency)*

Now lets consider the input current .. in order to boost 12 volts to 16Volts we have a factor of 1.25 so the current being drawn at the 12 volt supply will be a minimum of 1.25 * output current assuming no losses and 100% efficiency, which it is NOT!

Remember that Power In should equal Power Out! So Voltage times Current at the input should be equal to Voltage times Current at the output plus an amount for losses in the conversion.

0.625 * 1.25 = ~700 mA 

efficiency at best will be 92% so the 700 will need to multiplied by 1.1 

0.625 * 1.25 * 1.1 = 860mA 

This of course s the best case scenario, we don't actually know how much current the circuit will require unless we measure it with full load connected. 

Likewise the 32 volt circuit will be drawing (according to the specifications) 0.94 A 

12 Volts to 32 Volts is a factor of ~ 2.666 so if the current being drawn at the output is 1amp then the current at the input will be 2.666 times higher assuming 100% efficiency. Since again the efficiency is at best 0.92 an extra loading of approx 1.1 is necessary for the best case scenario 

0.94 * 2.666 * 1.1 = 2.76 Amps 

you would need to protect your circuits with one or more fuses that would cover the above current consumption




*A word about Fuses and current in dc-dc converters *

when a dc-dc converter starts to work it draws a very high initial current for a very brief period of time. This startup current can be several times higher than the actual current required for the load. If you use a standard type fuse (Fast Blow) you may well find that the fuse will blow immediately unless you use one that is rated for 3A or more which will give you no protection in the event that your circuit starts to take higher than usual current. 
Another point about fuses is that they tend to blow at about 1.5 times their rated value ie a 1A fuse will not blow immediately when 1A passes through it If the current flowing through the fuse slowly increases towards 2A the at some point it will blow when the current reaches around 1.5A yet again not immediately. Fuses blow because the wire inside reaches melting point and when the current through the fuse changes slowly the temperature changes slowly too! If the current changes extremely quickly then there is every chance that the resulting sudden change in temperature will make the fuse blow immediately (as per surge current at start up) . 

to overcome these problems do not use Fast Blow fuses but Slow Blow types.

Slow blow fuses are fuses that are doped in some way to delay blowing in the event of sudden surges. Other than that the fuses react in very similar manner, the current passing through them heats up the wire inside, which will melt when the temperature reaches a critical level (melting point of the wire).

A Fast blow fuse can normally be recognised by the letter "F" in front of the fuse rating ie "F1A" or just the rated value "1A"

A slow Blow fuse can normally be recognised by the letter "T" in front of the fuse rating ie "T1A" 

The letters F & T are as far as I know abbreviations from the German, Flinke & trage

Words by letter q - German dictionary - Lingi.com


> quick reacting fuse .....	flinke Schmelzsicherung


Words by letter s - German dictionary - Lingi.com


> slow blowing fuse	....... träge Schmelzsicherung



*
I have just noted that the specs are not for your printer but something else that was introduced as a guide .. you will need to check and calculate according to your printers specs *


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*



octaneman said:


> Ok, I get the picture. There's 1 critical issue that you should be aware when it comes to wall wart connectors.
> 
> There's no standards for these type of connectors. They run different voltages through the same connector either AC or DC. You don't know what voltage your printer will take in first, you could easily run the wrong voltage through it and burn the printer.


what do you mean by connectors? the DC-DC step up?


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*



Done_Fishin said:


> What is the spec for the input voltage ?? Most dc-dc converters tell you how they handle for fluctuating input voltage and your car battery should not fluctuate more than about 2 volts
> 
> what I am concerned about is teh 80 amps you mention .. maybe I missed something earlier in the thread bt I personally wouldn't draw 80 amps through a cars wiring .. it would need direct wiring to the battery via a fuse !
> 
> ...


i took a look at the battery and it was over 800ca thats 800 cranking amps. i also did order heatsinks and thermal paste because the amps on the specs of the step up are borderline, and direct connection is what i wanted to do initially with a a fuse and power switch
:stop: question for everyone: would it be difficult to wire the printer directly and have it turn on when the ignition turns on? i have never done anything like that so i wouldn't know.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*



Done_Fishin said:


> *A word about Fuses and current in dc-dc converters *
> 
> when a dc-dc converter starts to work it draws a very high initial current for a very brief period of time. This startup current can be several times higher than the actual current required for the load. If you use a standard type fuse (Fast Blow) you may well find that the fuse will blow immediately unless you use one that is rated for 3A or more which will give you no protection in the event that your circuit starts to take higher than usual current.
> Another point about fuses is that they tend to blow at about 1.5 times their rated value ie a 1A fuse will not blow immediately when 1A passes through it If the current flowing through the fuse slowly increases towards 2A the at some point it will blow when the current reaches around 1.5A yet again not immediately. Fuses blow because the wire inside reaches melting point and when the current through the fuse changes slowly the temperature changes slowly too! If the current changes extremely quickly then there is every chance that the resulting sudden change in temperature will make the fuse blow immediately (as per surge current at start up) .
> ...


thanks for that input, it would have drove me crazy if i ran into that problem, now for extra protection it wouldn't hurt to put a fast blow fuse after both step ups correct?


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## gcavan (Aug 13, 2009)

*Re: adjustable dc step up*



> would it be difficult to wire the printer directly and have it turn on when the ignition turns on?


Take power for your circuit through the vehicle's fuse panel. Look for the Accessory (Acc) terminal. The vehicle does not actually need to be running but the key has to be in the On or Acc position. This will allow you to turn off power to the printer by turning off the key.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*


```
http://www.manualowl.com/am/Chevrolet/2000-Express%20Van/Manual/324?page=315
```
 i don't see an accessory terminal on the diagram, and would it be ok to pull all those amps through the accessory terminal? if that is a problem what about putting a relay on the accessory terminal you are talking about?


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## Done_Fishin (Oct 10, 2006)

*Re: adjustable dc step up*



lalo 123 said:


> thanks for that input, it would have drove me crazy if i ran into that problem, now for extra protection it wouldn't hurt to put a fast blow fuse after both step ups correct?



it wouldn't hurt at all, although the output is current limited electronically to 3A so should a fault arise a fuse will help to limit (but not avoid) damage to your printer circuitry


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> question for everyone: would it be difficult to wire the printer directly and have it turn on when the ignition turns on? i have never done anything like that so i wouldn't know.







No It wouldn't be difficult at all. You would wire the printer the same way as installing a radar detector, the principal is the same. 


First, you would need to put your power connections in part of the fuse box where there's 2 amps running through it. The radio would be the prime choice location because you do not want the printer to drain battery power when ignition is off. 

To make your power connections get yourself an add-a-circuit connector. ( see pic) There are 2 type of connectors so make sure you get one for the right size fuses your vehicle. Insert the connector the to the 2 amp fuse slot in your fuse box and then just crimp the wire lead to the power side.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*



octaneman said:


> No It wouldn't be difficult at all. You would wire the printer the same way as installing a radar detector, the principal is the same.
> 
> 
> First, you would need to put your power connections in part of the fuse box where there's 2 amps running through it. The radio would be the prime choice location because you do not want the printer to drain battery power when ignition is off.
> ...


Ok, so now that I know how to wire it, would it be safe for the car? You were saying that that much power is dangerous to just wire into the car, or is a fusebox taken directly from the battery?


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

By putting the add-a-circuit connector yes its safe. You are taking power from the fuse box so if anyhing happens the fuse blows first. If you were going to wire it directly from the battery without inverter or circuit protection then you're risking overloading the harness.



Question; 


Does your truck have the small fuses or big ones ?


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

ok, now everything is coming together, i took a quick look at the manual that i posted earlier, and there are 2 radio fuses 1 is RADIO-1 Radio (Ign, Accy), Upfitter Provision Relay and the other is RADIO-B Radio (Battery), Power Antenna, which one would be the appropriate one to use? and for the fuse size, i roughly calculated that it would use 3.4 amps so should i put a 5 amp fuse or 4 amp? the output listed on the transformer says 32v 940ma and 16v 625ma


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

You will use Radio-B. You will insert the fuse into the add-a-circuit connector thats already in the box for that socket. Why ? Because the fuse amperage is tailored to that circuit. Fuses are rated by their color code, on blade type fuses they can range from 1A to 40A.

Black = 1A
Grey = 2A
Purple = 3A
Pink = 4A
Light Brown = 5A
Dark Brown = 7.5A
Red = 10A
Blue = 15A
Yellow = 20A
White = 25A
Green = 30A
Blue/Green = 35A
Orange = 40A


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

Great news!! the dc step up finally came in and when i tested it the output voltage stays the same regardless of the input! i regret not ordering 2 of them but i did place the order and i also ordered a heatsink, the heatsinks for the dc step up are made to place the whole entire board on it, but wouldnt it be better to place the heatsink directly on the LM2577 chip?


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## Done_Fishin (Oct 10, 2006)

*Re: adjustable dc step up*










The IC is plastic so very poor thermal conductivity to the heatsink

the rear of the board has that mesh of through-plated holes ans solder which hs better thermal conductivity AND direct contact through to the IC heatsink so far better thermal contact. use thermal paste to reduce thermal resistance between heatsink & pcb.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

Yes, I did notice that, and I will be using thermal paste, but I was wondering if I could desolder the chip from the mesh and bend the chip 180 degrees and apply a heatsink directly, is there any other components on that board that need a heatsink?


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## Done_Fishin (Oct 10, 2006)

*Re: adjustable dc step up*

possibilities are that you will damage the chip trying to remove it .. and then with the weight of the heatsink you would need to stabilise it .. there will be vibration that will make it "wobble" and not just from outside sources .. also the current flowing it, which after time will cause fractures on the legs or the plastic .. I assume these people know what they are doing and the heatsink method will be the safest for the circuit and the components


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

Ok, you do have a point, but the dots on the botton of the chip are mostly hollow so I will just try to force some thermal paste in the holes to prevent air pockets


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

hello again i recived the second dc step up today and i got the wiring ready and i am getting 16v across both negative terminals ( they are subtracting each other 16v and 32v) i was afraid of this before, so i am thinking a simple diode will solve this issue


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## Done_Fishin (Oct 10, 2006)

*Re: adjustable dc step up*

I take it that you have placed a common ground point and are measuring from there ?? you should get a 16 volt difference between the rails and a common reference point 

tie the two inputs together in parallel

tie the negative outputs together 

keep the remaining two positive outputs separate 

you should be able to create your +16Volt & +32Volt outputs from your boards


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

ok so ive gotten everything i need and i wired it all up using the battery i was talking about, the battery is a 12 volt 28 watt, the problem is the battery hasn't been charged in over a year! the battery is capable of turning the printer on but thats about it, so i was thinking if i can get a charger to charge that battery from the car battery, that way i can wire it up so the battery is only going to be charged while the engine is running and when it is off it will be using the 28 watt battery to keep it on standby so there will be no need for the printer to boot up every time the car is turned on, and i also wont have to wait for it to boot up before i can use it.
thanks again


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## Done_Fishin (Oct 10, 2006)

*Re: adjustable dc step up*

to charge the battery you will need a charger capable of giving 13.8V ~ 14.2V (max!!) to the battery being charged

you will need to block any possibility of feeding the 12Volts from the 28 watt battery to the other!

you may need another circuit to increase the 12Volt car battery output to a voltage capable of fully charging the 28watt battery, otherwise the 28watt battery will never charge to more than the car battery voltage less the losses of any circuit placed between the two batteries.

final note .. if the28 watt battery hasn't been used i a year it may well be ready for a trip to the recycling station .. they build up oxidation on the internal connections when unused for a period of time rendering them useless for anything but very light work 

to check the internal resistance, with the battery fully charged, place a 60watt car bulb acroos the battery terminals, whilst measuring the voltage across the battery terminals, note how much voltage is lost when the bulb lights up. If the Battery is good the Voltage drop will be less than 0.5V and the internal resistance will be equivalent to or less than 0.1Ω (V = 0.5, I = 5A, .. R=V/I) 

as you might be able to understand, as the internal resistances increases the voltage loss increases. If you have an internal resistance of 1Ω and draw 5amps from the battery then your output voltage will drop by 5 Volts


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

I was thinking about a charger that has an input of 12 volts to charge the battery but couldn't find anything online, and I also plan on wiring both batteries with diodes, and as for testing the battery, I will try to do that tomorrow, I am thinking that the battery is still good because I use it all the time for testing electronics for the past 4 months or so and it hasn't died on me yet


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> I was thinking about a charger that has an input of 12 volts to charge the battery but couldn't find anything online, and I also plan on wiring both batteries with diodes, and as for testing the battery, I will try to do that tomorrow, I am thinking that the battery is still good because I use it all the time for testing electronics for the past 4 months or so and it hasn't died on me yet




You cannot use diodes to seperate the batteries the current draw is too high from the starter when you crank the engine. To isolate the batteries will require the use of a battery switch and a distribution bus. The distribution bus will convert the large battery wires to smaller ones for your printer. The switch will seperate both battery banks but use the same alternator to charge them. To determine the proper size switch, the rule of thumb is 1amp/cubic inch engine displacement = crank rating. Consult the manufacturer for the specs on the amperage draw for the starter.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

Im not sure if i am understanding you correctly, you are saying to have the alternator charge the small printer battery directly? and as far as the amp draw from the starter, i was going to wire the "charger" for the small battery from the fuse box location we were talking about earlier so it would only turn on after the engine has started, please correct me if i am misunderstood


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

I thought you were going to use your main vehicle's battery with the add-a-circuit connector to power up your printer. I'm a little confused when you mention on post #51 that you are going to use a 12V 28 amp battery. Chevrolet express uses allot more than just 28 amps. Are you using 1 or 2 power sources ?


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

yes i would like to use 2 power sources, the 12 volt 28 watt to keep the printer on and running, and also print a couple pages without having to turn on the vehicle, one reason for this is that every time the printer is powered it prints a test page, i tried to resolve the test page issue by following the instructions but it resets after it sits around with no power for about 10 minutes. and i would like to have the car battery charge the 12volt 28 watt battery when the engine is running, but i am unable to find a charger that does this, do you have any suggestions for a charger? correction it is a 12 volt 28 watt battery


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

ok so scratch everything about the 28 watt battery, i just got a new battery after replacing the old one in my chevy express, the battery is fine, its just that after leaving the door open for about 20 minutes it no longer starts the engine. it powered up the printer with no problem even before i charged it, the old battery is fairly new just out of replacement warranty (no more then 5 years old). so now i want to be able to charge the old battery with the new one only when the engine starts


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

So its a dual battery setup right ? Do you want to use the batteries independant from one another ? ( 1 for the engine 1 for the printer) or having an external charger for the printer battery only?


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

yes, i will upload some pics in a couple minutes


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

the voltage after about a minute removed from the charger was about 12.5 when the printer is powered off after about 30 minutes of it being on and scanning and printing about 10 pages it goes back to about 12.45, (if i have correctly attached the photos you can see that the standby voltage is 12.35)
View attachment Attachments_2013128.zip


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

Can't open the zip file for some reason. Can you please re-load them one at a time ?


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

sorry about that i kept on getting an error message. What about a battery isolator? like this one

```
http://www.ebay.com/itm/Delcotron-Battery-Isolator-Installation-Kit-Delcotron-Battery-Isolator-Install-/280967536729?pt=LH_DefaultDomain_0&hash=item416af86059
```


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

I see the installation kit with what appears to be a circuit breaker but not the actual isolator. The isolator is a box that should have 4 terminals with a minimum of 80-90 amp tolerance to connect both batteries. 


Should look something like in the pic.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

I realied that a couple minutes after I posted but wasn't sure, I will look online to see what I can find when I get a chance


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

I forgot to mention this in my previous post. Before you decide to purchase one, its very important find out the output specs of your alternator. Depending on what your engine displacement is, your alternator could put out as high as 120 amps. So make sure you get the right one for your truck.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

thanks for the warning, i found one on ebay and i searched up the alternator size on my van and the number 124 amps keeps popping up, the isolator i found is 160 amps, is it fine to go over?

```
http://www.ebay.com/itm/Multi-Battery-Isolator-Sure-Power-Model-16023-160-amps-/190792012909?pt=Motors_Car_Truck_Parts_Accessories&hash=item2c6c17146d&vxp=mtr
```
also while looking for this i found 2 different things that looked familiar to me
















the second one is mounted on my boat and the first one is a switch that is also in the back of my boat with other emergency parts, i know the one that is mounted on my boat is to turn on the battery for just the engine or just the lights/ stereo or both, but does this mean that i have an isolator in my boat? or is the switch all it has? i have never taken a good look back there to notice an isolator but it is a possibility, by the way i do have 2 batteries in my boat just to clarify


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

160 amps is plenty to handle the load. The lower picture is the isolator switch which is what you need to run both batteries on your truck. One battery will be for your start/ignition the other for your printer. Some isolator switches go with charge relays to manage the system that connect to the switch, once its turned on the alternator can charge both batteries at the same time.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

So I would need to get more then just the isolator? I want to have the engine battery alwars on just like it is now, the only thimg I would want to turn off is the printer battery but only some times, so couldn't I use the first picture, which is basically just a switch right?


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

You could use just the switch it wont be a problem, the ACR (automatic charge relay) is just another method of doing the exact same thing. The difference is the ACR is automatic switching while the isolator switch is manual.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

im a little confused now, i thought that the isolator separated both batteries while sharing the alternators charger power. if i am correct then what does the acr do? are you saying that this is another solution to an isolator or the switch? i wanted the switch just as a master kill switch to the printer for when i am not using it and dont want it on standby


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

What the acr does it senses the voltage across the batteries. When the alternator is charging the relay closes, that allows the alternator to charge both batteries. When the alternator _*is not charging*_ the relay opens, disconnects the 2 batteries from each other *isolating * them.


When the acr and switch are connected together with the 2 batteries, the switching is done automatically with minimum power loss. The traditional method was connecting the 2 batteries with the type of isolator on post #63. These type of isolators got hot and was wasting too much energy. The most common method today to connect 2 batteries together is with an acr. RV's , Tractor trailers, etc... have the same system intalled in them because of different loads needed.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

ahh i get what you are saying, you are talking about a completely different method, i had a feeling there had to be a much smaller way to do this then the isolator, but couldnt find anything, so i found 2 acr's and i am leaning towards the first link because of the higher amperage rating and slightly cheaper, the second one is a marine acr which seems unnecessary and the amperage is borderline, please let me know your opinion

```
http://www.ebay.com/itm/XSCORPION-RL200-200-AMP-BATTERY-ISOLATOR-OR-RELAY-/150625709754?pt=LH_DefaultDomain_0&hash=item2311fdeeba&vxp=mtr
```


```
http://www.ebay.com/itm/BEP-Marine-Voltage-Sensitive-Relay-Dual-Battery-Charging-fully-Automatic-/130840714386?pt=Motors_Car_Truck_Parts_Accessories&hash=item1e76b6dc92&vxp=mtr
```
edit: i found one even cheaper with a higher surge amperage 

```
http://www.ebay.com/itm/SOLENOID-RELAY-MARINE-BATTERY-ISOLATION-SWITCH-12V-300-AMP-/130815145770?hash=item1e7530b72a
```


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

I'm leaning toward the XScorpion solenoid, I like the discharge prevention feature on the primary. 


The car-go solenoid IMHO is a little excessive even though it has a higher amp tolerance. You really don't need that much unless you're running a generator. 


The BEP relay I'm a skeptical about it. I feel that there is something missing.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

i liked that one also for other reasons, now before i go purchasing this i will only need wire and wire connectors in addition to this, correct? and of course fuses


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> i liked that one also for other reasons, now before i go purchasing this i will only need wire and wire connectors in addition to this, correct? and of course fuses



Yes. Don't forget to get the on/off switch to toggle the solenoid. For added piece of mind its best to contact the supplier and get info on what gage wire you will need to connect it. 

For the on/off switch use your alternator's amp rating to get it all into spec. IE; 12v 120 amp switch. The switch you can purchase at any auto parts or electronics shop. Do not use any random switch OK ? Once everything is connected the printer should fire up nicely.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

you just brought something to my attention, doesn't the solenoid charge the main battery or just the spare battery on its own, meaning i can switch the solenoid off when i don't want to charge the second battery?
as for the actual switch i will look up the rating on the spare switch that i have posted in post #66, that will do just fine if it is the right rating which it should be, correct?


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> you just brought something to my attention, doesn't the solenoid charge the main battery or just the spare battery on its own, meaning i can switch the solenoid off when i don't want to charge the second battery?
> as for the actual switch i will look up the rating on the spare switch that i have posted in post #66, that will do just fine if it is the right rating which it should be, correct?


Yup, the solenoid will charge both batteries together or individually. The switch on post #66 is perfect for the job, it will allow you to have full control to switch from one battery to another or connect both at the same time.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

one more thing, where should the battery be placed :facepalm: i was thinking of putting it inside the airtight box i am going to build to put the printer in, but i am afraid of hydrogen buildup, but i dont know how much hydrogen can build up from a battery, also the fear of it exploding, i will look under the hood to see if there is room to mount it in there but i doubt it, i thought about behind the driver or passenger seat but i feel like that is to close to the driver, and also in the back but i would need to protect the battery from getting hit with tools and heavy objects, there is a thick metal wall separating the front of the vehicle from the back but it does have air-holes if it matters (the printer is going to be placed between the 2 seats)


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

How about using a 12v motorcycle battery ? The dimensions are allot smaller and you could squeeze it underneath or between the seats.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

The printer is going between the seats and there is room for the battery to fit next to it, but I don't want hydrogen build up in the box I will construct, but if you are saying it is ok to put it under the seat then it should be fine behind the seat, correct?


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

As long as there is adequate air circulation with no metallic objects lying around that would make contact to body ground that would short out the battery terminals then it should be OK. There is hydrogen leakage but very minimal when the battery is in its normal state. I'm not saying that its 100% safe because there is leakage coming out from the battery vents whether we like it or not, but the only time it becomes very noticeable is when the battery begins to boil from being overcharged. The sulfuric acid fumes and hydrogen will circumvent the cabin making it a risky environment. The best way to keep the cabin ventilated is to leave your window open 1/16 th of an inch in winter and wide open in the summer with a no smoking sign in the cabin.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

The hydrogen comes from the water in the battery being separated, correct? Meaning that the volume of hydrogen is very low because the water level in the batteries barely moves in a couple years of time if any, and the volume inside the car is much higher, so placing it behind the seat or in the back shouldn't be a problem, right? and smoking is not an issue. And is the solenoid that I am getting capable of charging 2 batteries with different cca?


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



> The hydrogen comes from the water in the battery being separated, correct?



No, The hydrogen comes from the chemical reaction from the sulfuric acid and the lead plates. Sulfuric acid is very corrosive it will burn holes in cloth and if it gets in your eyes it can blind you. If sulfuric acid gets on your skin flush it right away with water for at least 5 min. 




> the volume of hydrogen is very low because the water level in the batteries barely moves in a couple years of time if any, and the volume inside the car is much higher, so placing it behind the seat or in the back shouldn't be a problem, right?


I can't tell you how much hydrogen will be produced from the battery at any given time, it all depends on what state the battery is in. For example ; In a brand new battery adding the sulfuric acid to a dry cell will give off hydrogen instantly. A battery being overcharged will give off fumes because its trying to re-constitute the lead plates to their original status. Placing the battery behind the seat is OK as long as there is air circulating to dissipate the fumes so it shouldn't be a problem. 



> smoking is not an issue


:danger: Smoking is a big issue. *Never* smoke near a battery or be near an ignition source when you are working on one. The gasses produced are explosive so don't take any chances. 




> is the solenoid that I am getting capable of charging 2 batteries with different cca?


Yes, the solenoid is designed to separate the batteries, it doesn't matter how many cca's each one has.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

So before I go putting the large battery in the car I can use the small 28 watt battery, right? Just to see if it will hold long enough because it is a sealed lead acid battery (no hydrogen), when I said smoking isn't an issue I ment that there won't ever be anyone smoking in or even near the car


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> So before I go putting the large battery in the car I can use the small 28 watt battery, right? Just to see if it will hold long enough because it is a sealed lead acid battery (no hydrogen),


Yup.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

i received the isolator today, i found out how it works, basically it is a coil with a rod in the center, and when the coil is energized (from the ignition) it pushes the rod forward activating a switch. this raises the question to me on how it will prevent overcharging the smaller battery. when the switch in the isolator is activated the primary battery and the secondary battery are wired together in parallel, isnt it dangerous to have 2 different sized batteries (although 12 volts) wired in parallel?


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*

No, 12 volts will remain 12 volts when batteries are wired in parallel only the current running through both batteries will be higher. When the alternator is charging both batteries, it will charge them at the same output voltage the alternator puts out. It is the _current_ going to the starter during initial engine start up will be higher. The _current_ coming out of the alternator once the starter disengages will be constant to charge both batteries. 

Note: Keep in mind in parallel a weak battery will drain the stronger one when they are connected to a load. It wont affect the voltage going through the load because it is the same 12 volts, but the run time of the battery (ampere hour) will be longer when batteries are at their best condition.


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## lalo 123 (Sep 12, 2012)

*Re: adjustable dc step up*

i know the voltage will be the same, im concerned about the larger battery overcharging the smaller one while the isolator is connecting the two batteries together when they are being charged, to rephrase what i was saying, imagine connecting both batteries alone in parallel, this would be a bad thing, correct? but if they are connected in parallel while a charger is attached this would be fine?


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## octaneman (May 13, 2009)

*Re: adjustable dc step up*



lalo 123 said:


> imagine connecting both batteries alone in parallel, this would be a bad thing, correct? but if they are connected in parallel while a charger is attached this would be fine?



No it wouldn't be a bad thing. Batteries being connected in parallel is done all the time even without an isolator. The difference is when one battery is weaker than the other the weaker battery will drain the stronger one even with ignition off. The isolator prevents that from happening.

What is a bad thing is when you have batteries on a charger even when its set at trickle charge over several hours, the batteries will boil becoming overcharged and the life expectancy of the battery is greatly reduced. 

If you turn off the charger while batteries are still connected to the charger, the charger will become a load draining both batteries until they both die.


----------

