Camry starting issue

I am trying to diag my parent's Camry.

A few months ago it wouldn't start. I jumped it and cleaned off the massive amounts of acid and corrosion on the terminals. It was fine until last week, it was driven to the store and parked in the lot for 40-50 minutes and then wouldn't start. Jumped it again and it was fine.

My dad had the battery tested and it was fine. Cleaned the terminals and put a new positive terminal on and it was fine until Sunday when it wouldn't start.

I tried charging the battery and it won't even crank, just a click. The terminals have acid and corrosion on them again after only a week. I measured the battery voltage while attempting to crank it and it dropped from 12.8 to 11.5-8 or so. The positive terminal also starts smoking while trying to crank it.

Starter tested good and the relay looks fine. Any ideas? Should I just go ahead and replace the battery?

Sounds like the battery cable is probably toast. They will corrode under the insulation at the terminals. Sometimes you can cut the cable back to good wire and replace the terminals. It depends on how much slack you have.

Not much slack, I'll probably have to replace the whole thing.

Any idea why it corroded so much? Or is it just a compounding problem that started out with a little corrosion and that causes it to corrode faster?

I guess I forgot some important info.

99 Camry, 5SFE 4 cylinder.

Usually the corroded section will cause a current drain all on it's own. Throw a little acid and moisture on it and presto, galvanic and/or crevice corrosion. I used to run into this problem a lot when my golf cart was still electric. That's part of the reason I converted it to gas.

If they have a radar detector or gps, tell them to turn them off when the car is parked. That constant small load seems to compound the problem. Particularly when the car is parked for a few days.

I owned a '98 Camry with the 5SFE and when I saw this thread the first thing I thought of was the awful corrosion I would get on the battery terminals. Looks like you've covered that, so the cables are a very likely candidate (as others have mentioned).

I had similar start/no start symptoms on my '94 Chevy K1500 and new cables solved the issue. In that application one cable ran near a heat source, and so it was common for them to go bad...

I'll have to check the cables tomorrow, the corrosion was pretty bad and I wouldn't be surprised if it went up under the insulation.

They don't have any devices plugged in ever. They put maybe 5k miles on it in a year, all around town.

Nippondenso starter, with the big square solenoid housing? You may need about $5 worth of contacts replaced inside the solenoid.

I tested the starter at Advance Auto Zone, it was fine. No square solenoid housing.

My in-law's Camry has the same stinking corrosion problem. I bought a little spray can of "red colored battery terminal corrosion prevention stuff" from the parts store and it seemed to help keep the growth to a minimum.

Good times.

Check your ground connaection. It sounds like high resistance through the ground.

cables and also dont forget about the brushes in the starter.

It's fixed. When my dad replaced the positive terminal he didn't tighten down the nut enough so there was a small gap between the contacts. I cranked it down to compress it together and it started right up.