Did not read every past post but can relate that the graphic indicating battery locations is for 166 and is not correct for 164.

the 164 auxiliary battery is just next to the main battery under the passenger seat. If you’re replacing the main, it’s a good time to replace the aux

ease of changing a positive cable is determined by ease of finding both ends … obviously.

If by browned out you mean the insulation around the cable looks burnt then measure the resistance in that cable and compare to specifications.

Yes, that is what I see. The red cable is browned and the area on the old battery near that cable is melted a bit.

Well, ultimately, what counts is the resistance in that cable. So find either end and measure it according to specifications, which I don’t know what are.

Why was your GL parked in the first place?

Thanks for the response, Max.

• Have not checked the resistance yet, but see the images below. Cable is browned and the top of the old battery is somewhat melted.
• GL was parked because the turbo went bad and I was shopping around for someone to replace it (shops), but they all wanted upwards of $5K to do it. Finally a buddy and I replaced the turbo with a new one, all gaskets and seals, and now we are here with electrical issues. Car won't turn over. Lots of voltage codes and the computers are not talking to each other. (See this post)
  
  

I saw something similar on my boat battery last year. The positive cable was loose, so it looked like it was arcing from the cable end to the battery and melted the battery around the positive post. The cable itself was fine, the arcing creates localized heat that damaged the insulation a little. But the metal conductors inside were fine. I had to replace the battery of course, but the terminal on the cable was still ok so I was able to tighten it onto the new battery post. I don't know what exactly is going on with your cable and battery, but maybe there was some arcing going on from the positive cable to the post? Also, from the look of the melted part of the battery, was the positive cable coming in at the wrong angle and the insulation pressed against the battery? Ideally the cable should be routed so that it doesn't touch the plastic part of the battery.