So, still waiting on 1 thumbs up before I start the big repairs on my Jag, looking for little things I can do in the meantime with stuff I have laying around....

So, I have a great battery, a Group 65 (XS Power D6500) I want to get in the jag to replace the wet cell garbage that's in there. Only 1 problem: The posts on my XS have the terminals on the wrong end of the battery for this car and the POS wire has 0 slack I can steal! So, I see I have few options:

Spend the big coin on the correct fit battery OR mod the POS power wire to get me some extra length and flip my XS battery posts to the front of the car/lengthen factory wires.

So, I have a few questions:

More involved method- The + to starter... Whats under the starter boot? This 1 wire is where I need the extra slack. Are these wires connected to the starter somehow or can I just pull the boot back and drop a new 0 gauge cable and ring terminal to it? The other ring term pos wire has slack, so I can route that NP (I think)

Less involved- Sniping the factory terminals off, adding a 8? gauge AGL 250/300AMP fuse at the end to allow me to add wire on the other end. How do Jags take to a fuse-able link in the main starter run? Bad idea?

Have about 6ft of OFC 0 gauge wire laying around, so I plan to add/replace: The main Battery ground, a full run from Alt post to battery, whatever is needed above, and the engine to chassis ground, which I need to locate...

 

You want to follow the wire back to the starter as the factory wiring runs from the battery to the starter and then over to the alternator. So, replace the wire between the battery and start and call it good.

As for splicing the wire, that is not a good idea with wires that carry large currents. The splices tend to cause large voltage drops.

 

The X-type (like a lot of modern cars is fitted with a smart charging system.
This means that the battery will discharge to the starter motor which draw a heavy current, as you'd expect. Under normal driving conditions the alternator produces plenty of output to run the various systems on the car, including providing spark and of course charges the battery. However under heavy load such as higher than normal the control unit for charging reverses and the battery is then drawn upon for extra current for the engine.
The cables between, battery, starter and alternator are quite carefully designed with certain levels of resistance etc built in.... I'm not saying don't go ahead with your cable mod, but do take all this into consideration.