2007 Jeep Cherokee Smoking Alternator & Bad Battery

So my sister’s 2007 Jeep Cherokee Laredo died, seems all the lights went haywire, it started to smell like something burning so she turned it off. I took a look at it, seems the battery went bad with a bad cell (sucker was pretty darn hot). I replaced it to find the negative battery cable sparked like crazy when I connected it and the alternator was smoking. I disconnected the battery. Looked to be some smoke damage on the alternator and the B+ post cover had completely melted. The cable harness & fusible link was fine although the wire sleeve was melted in places. I have replaced the alternator.

2 questions, could the battery failing cause the alternator to go; or could it be something else like the starter? Apparently the last few weeks the car was starting weirdly and driving odd until it warmed up.

Where can I get a insulating cap for my Jeep Cherokee? I tried the dealer and they wanted to sell me a whole new engine harness.

While not a common occurrence, a bad battery can definitely damage an alternator.

One way occurs during the natural charge/discharge cycles of a battery as debris slowly falls off the plates to the space at the bottom. It’s called sulfation.

As that material builds up in the bottom, it can eventually reaches the plates - causing a short circuit between two cells. Alternators don’t like it when that happens, as resistance drops considerably, current goes up, and the subsequent heat damages the alternator.

Thanks, that is along the lines of what I was thinking (I have a limited background dealing with EE). I just wanted to be sure it wasn’t something else.

Not all cars have insulating caps for batteries, a coat of vasoline will stop them from corroding.

oldtme 11, well it had it to start with. also my concern is having it uncovered could lead to a potential short since it’s positively charged (B+ terminal)?

When a battery loses a cell, it quickly drops to 10 volts…The alternator tries to charge it back to 13.5 volts but it can’t, it overloads, gets hot and can destroys itself. There is a protective circuit to prevent this but it does not always work…This assumes you did not reverse the polarity when you installed the new battery…Remove the alternator and have it tested off the car…

I’ve had good luck pulling terminal covers like that at junkyards, especially the you-pull-it-yourself yards. Typically, they just slip off with a little effort.