Battery Relocation Tech

NickMaul

NickMaul

Well-Known Member
Joined
Jul 4, 2009
Location
Norfolk, VA
Electrical gurus step on in.

I am relocating my battery to the back of my Cherokee XJ. I know how to properly size the cables running from the front to the back. What sort of ground and power distribution system do I need to have so I don’t impact the current system negatively?

I’ll probably throw in a kill switch on the ground in the path from the front to the back for safety and security purposes as well.

TIA :D


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Shorter wires are better. Bigger wires are better. Uncorroded wires with clean connections are best. Do whatever you can to achieve those 3 points and you will have no issues. Maybe I missed it in another thread, but why are you relocating it?
 
On my Toyota I used a blue sea shut off switch as a distribution block where the battery used to be. I ran a single 0 gauge wire to the battery in the rear and ground the battery where is is.
 
Nick my ground is about a foot long. Straight off the batter to the unibody. Attached with a self tap screw. Works perfect until it gets rusty.....
 
jeepinmatt said:
Shorter wires are better. Bigger wires are better. Uncorroded wires with clean connections are best. Do whatever you can to achieve those 3 points and you will have no issues. Maybe I missed it in another thread, but why are you relocating it?
Click to expand...

I am narrowing the front clip on my XJ and cutting the fenders away so the original battery location is gone.

I was unsure where the ground off of the battery should be located. In the back of the Jeep right off of the batter or run a ground back to as close as where the old ground was. Sounds like I’ll ground it somewhere in the back away from exposure to the elements.


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There are two schools of thought on how to do this safely.

The first is to run a single power cable from front to back, and protect either just the battery end or (ideally) both ends with a high amp fuse or circuit breaker.

The second is to run two power cables from front to back; one for the alternator and electrical loads (protected by a fuse or breaker, etc), and the other cable from a trunk mounted starter solenoid to the starter. The starter cable then becomes a "powered only when starting" cable, so the only unprotected area of that cable is the short run between the battery and the starter solenoid. The nice part about that is being able to use a fuse/breaker for the electrical loads, without having to size it for intermittent starting loads as well. The downside is that you have to buy two cable lengths, and buy a standalone starter solenoid that's decent quality (always spend the extra money).

There are other methods as well, but they're just variations on those methods, like adding extra relays to disconnect power to certain things for rollover safety, but those are mostly related to racecars and things that are rule-specific to adding an external kill switch. Shutting everything off when running is very, very different than preventing something from starting.

Any way you slice it, you need to protect the power cable between the battery and the engine bay, at the battery end. If you want to add a disconnect switch, use a circuit breaker that has a combined switch/breaker function.

i have to be careful here; "kill switch" and "disconnect switch" are very different things. One implies that everything can be shut off while running, and one implies that the battery can be disconnected from the electrical system. A kill switch can be used as a disconnect, but needs extra functions to actually kill everything while the engine is running. You're not disconnecting one cable and shutting the entire vehicle down when running, basically. Because alternator.

Anyway, just doing a simple battery relocation is pretty straightforward.
 
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Is there a cage in the vehicle? I'm a fan of welding a 3/8 bolt to a cage floorplate as a grounding lug to connect the battery to.
 
grapehead said:
Is there a cage in the vehicle? I'm a fan of welding a 3/8 bolt to a cage floorplate as a grounding lug to connect the battery to.
Click to expand...

Not yet. But there is a decent amount of unibody plating in the works where I can probably weld on a bolt.


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I just moved mine to the back. I used a disconnect as a junction block under the hood. I'm pretty happy with how it turned out. I bought my battery cable from airgas and had them cremp the connectors on.
This is the disconnect that I used. It's probably overkill but winch is connected to it as well.
https://www.amazon.com/Blue-Sea-Systems-Battery-Switch/dp/B00445KFZ2/ref=sr_1_6?crid=2HMSBN6DP4MQ9&dchild=1&keywords=marine+disconnect+switch&qid=1582821738&sprefix=marine+disco,aps,169&sr=8-6

I welded a 3/8" bolt to the rear pass side coilover tower for my ground. The engine, body, and winch are all grounded to the frame in the front of the vehicle.
 
@Fabrik8

I agree with you and will add a 3rd method (which is what I do):

1 wire from positive terminal to kill switch/isolator to starter and fuseblock
1 wire from positive terminal to charge stud of alternator.
1 wire from negative battery terminal to ground

If you turn the kill switch off, the whole vehicle electrical system is off except 1 wire, the one that goes to the alternator. You can use a dual circuit isolator to kill that one too (that's what I did on my buggy).

I'm using the same isolator switch as @1stgenxxx, except I bought the dual circuit model off of the same link. The back looks like that:

61VjAYrs61L._AC_SX425_.jpg


I'm not concerned by long runs of wire if they are properly sized and protected. IMO putting the kill switch wherever you can access it in case of fuck up will be a better solution than something close to the battery but that's not easily reachable when you're strapped in and your vehicle is tumbling down an obstacle.
 
Bebop said:
@Fabrik8

I agree with you and will add a 3rd method (which is what I do):

1 wire from positive terminal to kill switch/isolator to starter and fuseblock
1 wire from positive terminal to charge stud of alternator.
1 wire from negative battery terminal to ground

If you turn the kill switch off, the whole vehicle electrical system is off except 1 wire, the one that goes to the alternator. You can use a dual circuit isolator to kill that one too (that's what I did on my buggy).

I'm using the same isolator switch as @1stgenxxx, except I bought the dual circuit model off of the same link. The back looks like that:

61VjAYrs61L._AC_SX425_.jpg


I'm not concerned by long runs of wire if they are properly sized and protected. IMO putting the kill switch wherever you can access it in case of fuck up will be a better solution than something close to the battery but that's not easily reachable when you're strapped in and your vehicle is tumbling down an obstacle.
Click to expand...

That's a variation of first method I posted, with two wires instead of just one wire. You have to make sure to use an alternator with internal load dump protection if you switch the alternator wire, as you're disconnecting all alternator load when you flip the switch. Many have that, but make sure it does before you use that method or you'll kill the alternator in short order.

Blue Sea does make switches with an alternator field disconnect to prevent the load dump condition, but that would depend on the type of alternator you're using (you would need to have an alternator with a field wire, etc).
 
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I will correct my original terminology. I am definitely only interested in a battery disconnect switch.


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Put that junk in the trunk, get longer power and ground cables and interrupt the main power cable with the kill switch. I am redoing mine right now.
49597313368_bb49e1fc85_b.jpg
 
pitbullcruiser said:
Put that junk in the trunk, get longer power and ground cables and interrupt the main power cable with the kill switch. I am redoing mine right now.
49597313368_bb49e1fc85_b.jpg
Click to expand...

And protect the power cables at the battery end. Unless you're in the market for a new, un-burned vehicle if you get body damage.
 
Fabrik8 said:
No, with a fuse or circuit breaker.
Click to expand...
Nothing like a dead short 8 feet from the battery turning into a 2ga. glow worm! It'll cook til the battery dead shorts or the wire falls into. Why, during a crash involving a pin in ems will absolutely destroy anything in the path to getting cables cut.
 
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