Hi guys.

I had a battery issue a few weeks ago, car wouldn't start so jumped it. After jumping I was driving and the the nav, interior, exterior, and dash lights flashed. Nav restarted, traction and abs (I think, I don't fully remember) lights turned on for a second, and the revs dropped. Car drove for a few additional minutes but then just totally shut off while driving and I had to jump it again. I thought it was battery related.
I replaced the battery (optima yellowtop). Today the same thing happened again, car died so I jumped it. Very odd due to the brand new battery. Then the same Rev issue happened again. I stopped driving and had to jump to get it back on. The entire car electronics don't respond at all when the car was off. I couldn't get into the trunk, no lights worked, no dash when pressing ignition. But as soon as I even connect my jump pack to the terminals, without starting the car even, everything is back and car starts up without any problems.

I've been looking this up, but wanted to get your opinion. Main things I've been seeing is terminal connection. I've tried yanking on my terminals and they're on tight. Doesn't move at all. I've also sanded both the clamp and the terminal. Battery grease as well to prevent any corrosion.

Other than that, could it be the main relay? I'm happy to replace it and see if it resolves it.

Alternator was replaced when I did my water pump and belt around 40k miles ago at my 100k service.

Anyone else have a guess?

2012 TL, fwd, 140k miles.

Thank you!
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It sounds like you have a loose connection somewhere, it could be from the battery to the starter/fusebox, or it could be the negative cable. You'll have to follow both sides of the wires and check them.

The alternator could be on it's way out; it should be always putting out 14V+ to charge the battery when the car is on. You should have the alternator tested; it could be also causing damage to the battery if a diode is bad.

 

Thanks! I'll take another look at the leads. I checked the negative already since it was right next to be battery and it looked good, no rust or loose connections.

 

Welp this was easier than I thought.

Traced the neg end to the frame - tight as can be. No rust, no corrosion.
Traced the pos end, nothing wrong either.

Turns out: i was tightening the wrong nut on the positive end. There are two nuts on my bolt on the positive side of my battery terminal. I thought it was tight, but it kept on getting loose.

I looked at the terminal and there were two nuts - I was tightening the outer nut against the inner one. While the inner one was the one that is supposed to be tight so it actually clamps down on the battery post.

Stupid mistake! Could not see the inner bolt due to the plastic cover. Took the cover off to make sure there was no broken wires/corrosion on the terminal and found the issue right away!