Great question. Also, you didn't tell them you think it is the megafuse did you? It is a sad reality that this day in age the following happens: Customer tells mechanic they think the problem is A. Problem is actually B, but B is far less costly to repair than A, so they actually repair B, but tell customer problem was indeed A, charging customer more since they already would have believed A was the problem. I have seen this happen, there have been lots of investigative reporting uncovering this kidna thing. Not trying to be negative, but just a reminder to not offer what you think a problem is unless you are absolutely sure it is the actual problem.

 

I unscrewed neg on main batt., then positive, took off frame holding batt. Wrapped neg in sock so it wouldn't contact anything. Took out straw thing (Gas discharge tube?) from side of batt. Replaced main with new one. Connect pos, connect neg, connect tube, install frame. Try to close trunk, nothing happens. check doors, everything's dead. Open door w/mech key, nothing inside works.

No sparks, no electrical explosions (I have seen those, almost killed by one once), no noises, just dead elec. Never told the mechanic anything but dead elec sys.

Mechanic report says "terminals incorrectly attached" which is impossible as the neg cable isn't long enough to reach if you actually try to install the wrong way. They said they tightened the terminals and reset the BMS.

Looked at the batt and it seemed to be the ORIGINAL BATTERY FOR THE CAR, which was over 10 years old, it had the number 10 14 on the terminal. Both batteries tested full charge with the multimeter.

All the problems I was having with the car stalling, dash gauge panel not turning on, not starting are gone now. It even sounds different (in a good way) starting.

 

Again post what the numbers are? What did the battery read after sitting all night?
My 2014 XJR OEM battery lasted 10.5 years so yes it could be an original battery which means change it out NOW!

If the car was repaired (I think it is but it's not real clear?). I think we have to believe what your mechanic said? How could he have fixed otherwise?
Have you asked him what he meant? Maybe it was not swapped cables that was wrong but something else? Loose connections could have been the problem as he posted.

Don't understand resetting the BMS as that's done when a new battery is installed. Did you install a new battery?
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I forgot, but the charge on both measured full, it was 12.5v(?) The number I was advised at the time to base readings off of. I put the new battery in before taking it in.

 

Generally 12.6 VDC is the minimum we like to see after the car has sat all night. But that should be good enough.
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