My original 2005 battery went tits up a couple months ago. I picked up a sears diehard platinum group 65 battery. The battery is larger and the battery posts are on the front of the battery instead of the rear like the stock one. Because of this I had to extend the main battery cables. I saw a couple of threads where people had asked about where the battery cables went and how to replace them etc. The positive battery cable goes to the starter and the negative battery cable goes to the engine block close to the starter. The rest is pretty self-explanatory it's just sort of a rats nest to undo.



Unplug everything you can from the harness so you have some wiggle room, then cut off the convoluted tubing, take off brackets, clips etc.


You should end up with this hot mess.


I used stinger 0g power wire and kicker battery terminals (which are awesome!)


Finished product. She fired right up. Separating the wire bundle is the only tedious and somewhat difficult job. You should be able to get the gist of it but let me know if you need any help!

I am currently trying to replace the battery cables on my 2006 4runner and started looking At it and saw it going into the wiring harness and didn't know if I could separate them from the harness and didn't want to get too deep in the project and not be able to get to work. Looks like that's exactly what you did so I was just wondering what year yours was and if I could pull something like this off. Thanks and hope to hear from someone soon.

Great post by the way and hope I can do exactly this

I'm pretty sure on the V8 model one of the factory wires goes somewhere under the block, making it very hard to perform this. But man I'd love to upgrade my charging system

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Yup. It goes to the starter. Which is inconveniently located under the intake plenum. What in the actual f%$k, Toyota?

I thought the same thing when I first got my '03 V8, now at 216k miles.
The starter has a very low failure rate being on top of the block, since it is protected from all the road grime and crap if it was on the bottom.

@michaelreed
My original 2005 battery went tits up a couple months ago. I picked up a sears diehard platinum group 65 battery. The battery is larger and the battery posts are on the front of the battery instead of the rear like the stock one. Because of this I had to extend the main battery cables. I saw a couple of threads where people had asked about where the battery cables went and how to replace them etc. The positive battery cable goes to the starter and the negative battery cable goes to the engine block close to the starter. The rest is pretty self-explanatory it's just sort of a rats nest to undo...


Couldn't you have just turned the battery around for the post to be at the rear? I know that would flip flop the neg and pos terminals but would be at the rear, I mean is there really a "front" and rear since a battery could be rotated in any direction.

I recently did a similar project but I opted to go the crimp route and made my own cables... I cleaned up ALL the factory connections, improved the grounds (it measured 0.75 ohms before and 0.02 after), and used the popular very heavy duty mil-spec battery terminal posts which are great for multiple solid connections.

All end connections are water tight with adhesive lined shrink and hydraulic crimped to achieve a solid cold weld.

That said, I didn't increase the gauge or length of the cables. The factory positive is a bit short, and I think there are some voltage drop improvements to be had, so that is a revision/project for another time.

I didn't see this comment until now...

Im actually really particular about this... IMO the OP did it the right way for the battery that was purchased.

If he rotated the battery 180 degrees the positive post would be close to the chassis side of the engine bay, and in the event of a side impact collision, has a much greater chance of a direct short which can cause an engine fire...

The factory setup is actually the most optimal from a safety standpoint... I dont want to criticize the OP, but he/she should have went out of their way to find the correct group size (24F) with the terminal orientation for that reason alone (front impact).

I tried to do the same when I did my dual battery setup... I made sure the positive terminal was towards in the inside of the engine bay to help prevent a short in the event of a side impact...

Here is a shot of the 2nd battery installed on the passenger side of the 4Runner.

is the main power wire going to starter or alternator? reason i ask is when i did the big 3, i thought that the main lead goes to the alternator and not the starter.

I had this issue in my 03, the battery I got would only work with the terminals to the front. When you flipped it, the terminals were backwards, and the wire terminals would not reach whatsoever. It really was more trouble than it was worth so I got a different battery

FYI for anyone that cares, the Group 24F battery is the exact battery that is used in my 1965 Mustangs and 1967 Econoline. Somewhere in the dimly lit places of my mind, I remember the "F" in the 24F was for Ford because the terminals were reversed. I have been buying these batteries for 40 years!

There are two positive cables and one does run to the starter. However with the Big 3 upgrade you're supposed to go from the Alt to the Positive because that's where you're getting your charging from. That said, this guy didn't do a big 3 upgrade, he just straight upgraded and redid the whole system.

I see I see. Still with l that work he did, I would still do a big 3 since everything is out the way and he has the cables and terminals for it.

Very informative thread going on. So we know the their are 2 main positive, and 2 main negative wires.

Positive 1 - From alternator to battery
Positive 2 - From starter to battery

Negative 1 - From frame to battery (the short one just to the right of the battery)
Negative 2 - ???

Where does Negative 2 lead too?

Negatives go to frame/fender and to engine block. When I did my big 3 upgrade I just ran the engine block negative to the bolt holding the alternator.