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Old 11-08-2015, 05:22 AM
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Single battery JK - how many amps "always hot" is ok?

I have two devices that are on and always pulling 2 amps each (connected to a Painless Fuse block). I have a 2015 Rubicon and (stock) single battery and was wondering if I should be worried/concerned about battery life.

Is this an ok setup as is? What is the safe total max amperage for something which is always on?

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Old 11-08-2015, 02:22 PM   #2
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Not OK. That's going to draw you down pretty fast.

What's pulling that much juice?

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Old 11-08-2015, 02:47 PM
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Not OK. That's going to draw you down pretty fast.

What's pulling that much juice?
One is my Engel fridge, the other is a micro-computer (I'm a programmer and want to geek out). Though the fridge won't be always on - I want to be prepared for times when it is. The micro computer I would like to always be on.

So this means I should be looking at a dual battery setup then? I'm leaning towards putting the battery in the trunk rather than do the Genesis/National Luna dual battery setups - I may do something like this:

Portable duel battery

Thanks again Sparky!
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Old 11-09-2015, 08:32 AM   #4
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Dual battery might be the way to go. If it's in the rear the box is a good idea to contain it. Cabling from the front needs to be heavy duty. Look at welding cables, they are very flexible. It will need isolation, look at RV setups. Primary battery for the vehicle, secondary for powering the added accessories.
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Old 11-09-2015, 09:16 AM   #5
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The battery will have a couple of ratings that you can look up. There's CCA (cold cranking amps) which is the max that you can get when you hit the key, and then theres Amp-Hours, which is the one you want here.

If you have a 70 amp-hour battery (for example) in theory it should be able to supply 70 amps for 1 hour, 35 amps for 2 hours 1 amp for 70 hours etc.

It's important to remember that this number is only applicable to a brand new, fully charged, room temp battery. Also, every bit of juice that you suck out of it will detract from the amount of CCA that you have left over when you hit the starter.

4 amps seems like a lot to pull on one car battery. I would guess that for most single battery setups, 12-16 hours would be about all you could get out of it while still having enough juice to crank the starter and if you do it regularly, you are going to be killing the battery life.
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Old 11-09-2015, 10:38 PM
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Thanks everyone - great info.

As far as batteries - do I need to get one that is the same capacity (or even type and brand) as the one that is currently in my Jeep? Any recommendations on specific batteries would be great.

On the article I linked to above, he uses a Sure Power battery isolator - I've looked at a few others (by Blue Sea Systems,NOCO, etc) and was wondering if anyone has a recommendation there as well.
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Old 11-09-2015, 10:47 PM   #7
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Maybe a marine battery would be something to look at. Running a battery almost dead and then recharging it is hard on regular batteries. Eventually, they get a layer of electro-crud (hydrogen sulfide I think?) in the bottom that will build up and short the battery out, effectively killing it. Marine deep cycle batteries (the kind used to power trolling motors) fight this simply by having a taller case which allows more open space below the plates so that they last longer.

Maybe somebody else will be able to give you more detailed advice.
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Old 11-10-2015, 08:16 AM   #8
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^ Agree, use a deep cycle for the accessory battery. They are designed for long slow draw as opposed to the surge available from a starting battery.

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