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Unread 03-13-2014, 03:21 AM   #1
Method916
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Jeep backup battery idea.

I currently carry a small battery jump starter device with a built in light and useless air compressor. I want to eliminate this extra piece of gear and relocate just the battery aspect of it to under the hood.

All I desire is the ability to jump start the jeep when if I kill my battery due to forgetful moments such as leaving an inverter or radio on too long. (I've done this a couple times.) The small jump starter gadget has luckily saved the day each time so far, but its getting old and is a pain to keep recharging.

Inside the jump starter is just a small motorcycle like battery. So my thought is to find the best bang for the buck battery that is small enough to mount directly below my main battery. I have seen and read about how to handle the wiring.

I am wondering if anyone else has added a second battery purely as a jump starting backup rather than to power devices. In otherwords I'll still use my main battery for everything, 99.9% of the time.

If so, in your search of batteries, what did you find to be cheapest bang for your buck (motorcycle/lawn mower ... )? Hoping to be no larger than 1/2 the size of the main battery.

And where might you have mounted the smaller battery?

I've just got the good ol' little 4 banger. I'm wanting to stay smaller for weight and space issues.

Thoughts?

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Unread 03-13-2014, 04:32 AM   #2
superj
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lots of people just add a second full size battery. they make battery trays that allow this
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Unread 03-13-2014, 05:33 AM   #3
1320yj
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With a couple of pieces of scrap angle iron and my mig welder I extended my existing battery box and installed a smaller battery in front of the stock one. I made a simple bracket out of scrap to relocate the fuse box. I couldnt see paying big bucks for a fancy battery tray.The aux. battery is from a Honda but it cranks the Jeep with no problem.

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Unread 03-13-2014, 08:35 AM   #4
Louie4
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You need to read the JeepHammer bible.

http://www.jeepforum.com/forum/f8/du...lding-1231432/
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Unread 03-13-2014, 12:11 PM   #5
Method916
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Quote:
Originally Posted by superj View Post
lots of people just add a second full size battery. they make battery trays that allow this
Thanks, I have read a bunch of threads on this. I'm specifically wondering about folks who have ran smaller motorcycle size batteries though. All info is helpful but I and considering weight and size.

I'm an avid backpacker... and I treat my 4 banger like its a backpacker too. 10 pounds is 10 pounds. Thats what I aim to do. Yes; I understand this may seem silly to some but its my approach towards best mpg and getting over steep hills.
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Unread 03-13-2014, 12:17 PM   #6
Method916
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Quote:
Originally Posted by 1320yj View Post
With a couple of pieces of scrap angle iron and my mig welder I extended my existing battery box and installed a smaller battery in front of the stock one. I made a simple bracket out of scrap to relocate the fuse box. I couldnt see paying big bucks for a fancy battery tray.The aux. battery is from a Honda but it cranks the Jeep with no problem.

Thanks for the photo and ideas. That woud likely cover my space issue but I'm just not sold on needing two large batteries. I'm thinking to both save on weight and cost of my backup battery.

Off hand hand does anyone knoe the cranking amps recommended for the 2.5L?
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Unread 03-13-2014, 12:23 PM   #7
Method916
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Quote:
Originally Posted by Louie4 View Post
You need to read the JeepHammer bible.

http://www.jeepforum.com/forum/f8/du...lding-1231432/
Ah, I did need to read it, and I do need to read it some more. The diagrams on there are much more simple than other wiring diagrams I had come across.

Thanks.
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Unread 03-13-2014, 12:27 PM   #8
Louie4
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Quote:
Originally Posted by Method916 View Post
Ah, I did need to read it, and I do need to read it some more. The diagrams on there are much more simple than other wiring diagrams I had come across.

Thanks.
No problem. Here is some more good JeepHammer info on wiring in general. Very detailed and interesting.

http://www.jeepforum.com/forum/f8/ba...arted-1340134/
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Unread 03-13-2014, 01:07 PM   #9
XJ93
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500 CCA is what I find in our system at work, the problem you would have with that jump pack battery is recharging it. Are you going to remember to recharge it every so often or will you one day need to jump it and think "Crud I forgot to recharge that..."? A second battery is a much better option and can be wired right in, with a disconnect, that will allow your alternator to charge both but to keep one isolated for starting only. I understand you are trying to save weight, but that 30# difference is really worth it and in the long run a better alternative to being stranded with a dead battery and one so weak you can't even crank the engine.
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Unread 03-13-2014, 01:20 PM   #10
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Quote:
Originally Posted by 1320yj View Post
With a couple of pieces of scrap angle iron and my mig welder I extended my existing battery box and installed a smaller battery in front of the stock one. I made a simple bracket out of scrap to relocate the fuse box. I couldnt see paying big bucks for a fancy battery tray.The aux. battery is from a Honda but it cranks the Jeep with no problem.

Are your batteries the same Amperage? or on an isolation system? Otherwise they will charge at different rates and you'll end up killing one or the other...
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Unread 03-13-2014, 01:39 PM   #11
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First hooking both battery's up at same time is a waste if u drain one they both drain. First you need a battery selector switch. Which decides which battery is pushing power. Some i these do get crazy so you can charge both or jut one another(aux relay interchange) but I would just go with the normal 3 way switch. It is proven and all military vehicles that run a lot of extra goodies use this method. So if you main goes out your Aux switch is thrown to start your engine and recharge your main battery. There has to be a link out there to how to wire. I will go hunt one down. And the aux batter should be a car battery. Some times picking up a use one of this application will work.
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Unread 03-13-2014, 01:48 PM   #12
hardluk
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I've heard of something you can wire inline to your battery so if you leave your lights on or something of the like it will kill the circuit with enough juice for a start. I've also seen guys on the forum wire in a buzzer that will go off if stuff is on. If your worried about weight these would be better options unless you just want another battery.
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Unread 03-13-2014, 01:49 PM   #13
crouse11c
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I found so many links on it just google the wiring set up. EHOW goes over it nicely(if lost mobile homes and boats come stock with this and you may be able to find a cheap used battery switch there.) But for using a motorcycle battery it can work and some have more than enough power but they cost more than a car battery. My Harley battery cost 238 in hawaii so that would prob be 180-190 and it has the CCA to start almost anything. But remember there is a reason they are smaller. They may provide the power but they will drain faster and not last as long.
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Unread 03-13-2014, 01:55 PM   #14
1320yj
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Quote:
Originally Posted by 1320yj View Post
With a couple of pieces of scrap angle iron and my mig welder I extended my existing battery box and installed a smaller battery in front of the stock one. I made a simple bracket out of scrap to relocate the fuse box. I couldnt see paying big bucks for a fancy battery tray.The aux. battery is from a Honda but it cranks the Jeep with no problem.

Actually the way I have it wired up now I have one battery I use as a start battery and the other is wired to my winch.But if need be I can swap the positive cables around and use the winch battery to start the Jeep.
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Unread 03-13-2014, 08:47 PM   #15
plym49
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My suggestion is to flip things around.

Use your main battery for all normal vehicle operation.

When parked with the motor off and your accessories on, flip a transfer switch to run things off the smaller motorcycle battery underneath.

To recharge, use the same transfer switch to connect the two in parallel.

This way you always have your large, main battery to dependably start your engine.
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