Using power tool batteries to jump start cars

[Bogie]

I've seen Real Geniuses put a drywall or deck screw between the battery post and the terminal.
 
Lots of folks here in the 'hood unclamp their batteries to keep their cars from betting stolen/repoed.
 
Do Not Be That Genius, kthnx?
 
If you need to shim it, take a piece of beer can, fold it in half, and put the shiny sides out. They'll help, a little, but you really need to just have tight lead-to-lead contact.
 
And enough amps available on the battery. They don't rate 'em "cold cranking amps" for nothing.
 
If  you have a serious science project going on, we can spray the battery post/terminal with something, or you can just pour some coca-cola on it.
 
Or just have the parts monkey check it at the parts store, and it will either pass, will croak soon, or fail outright. If you have had problems (croak soon), put a new battery in.
 
DO NOT BUY A VOLKSWAGEN. Some of the (^%(*&^ things require a complete reflash to work properly.
 
Or Audi. Or anything german that hates you. Including H&K...
 
Don't buy a Neverstart battery from Wally World - a lot of them get "activated" in China. And go in a container. And on a boat. For how long? I like parts store batteries (but Autozones seem to test bad more often), but Menards and Home Despot are cheap. Don't buy Wally World, but I think I said not to buy Wally World already, because you shouldn't buy Wally World...

[Boomhauer]

I’ve had brand new Deka batteries *expletive deleted*it the bed. I’m not convinced anyone makes a quality battery anymore and I just buy cheap and replace when they die.

[zahc]

Ryobi sells a jump starter that runs off their batteries. The other brands probably do too.

https://a.co/d/eCYyup3

[griz]

I've got a battery question and figured I would post it here rather than start a new thread.  My car built up a lot of corrosion around the positive post.  Only the positive one.  Since that battery was dying (the reason I had some jump start experience) I figured it was related to that.  The new battery works great, but is again building up powdery, light blue corrosion on the bottom of the positive post.  Why, and why just the positive post?

[Bogie]

The plastic case only seals so well. When the battery gets hot, or is developing heat while charging, acid/vapor can come out of any opening. It may be a few ten thousandths of an inch, but it is an opening. That's what makes  your science project. It'll also eat some terminals. Coca cola will mitigate it somewhat, or you can spend money on something called terminal cleaner.

[K Frame]

I’ve had brand new Deka batteries *expletive deleted*it the bed. I’m not convinced anyone makes a quality battery anymore and I just buy cheap and replace when they die.

A 20% failure rate is the cost of doing business and the break even point for profit vs. sunk R&D/manufacturing cost.

[Bogie]

Compare warranties, and get what is easiest to warranty for the longest period.
 
I am close to a China Fright, so most of my hand-held power tools are the Bauer level.

[dogmush]

I've got a battery question and figured I would post it here rather than start a new thread.  My car built up a lot of corrosion around the positive post.  Only the positive one.  Since that battery was dying (the reason I had some jump start experience) I figured it was related to that.  The new battery works great, but is again building up powdery, light blue corrosion on the bottom of the positive post.  Why, and why just the positive post?

Bogie is correct on the cause.

Get you a can of this: https://a.co/d/3pN6ezY take off the cables, and clean the terminals and cables really well with a wire brush.  When all the corrosion is gone, hook them back up and give them a solid coat of the terminal protector.   It'll seal them up and almost completely mitigate your corrosion issues.

[Boomhauer]

I've got a battery question and figured I would post it here rather than start a new thread.  My car built up a lot of corrosion around the positive post.  Only the positive one.  Since that battery was dying (the reason I had some jump start experience) I figured it was related to that.  The new battery works great, but is again building up powdery, light blue corrosion on the bottom of the positive post.  Why, and why just the positive post?

Bogies answer, and very hot/humid environments seem to make these issues happen more

[230RN]

No.  That's not how it works.

OK.

I guess I'm misunderstanding the issue.

[griz]

Thanks guys, I didn't know there was a way to semi-seal them. 

[Bogie]

The battery is actually venting battery acid/vapor out of what you see is the base of the terminal. Which isn't actually the base.
 
If you think that the parts store is charging too much for your batteries, and you have a few hand tools...
 
https://youtu.be/kNGg0P7B5fI?si=szkVVmS7EyDuJr0R
 

[Boomhauer]

OK.

I guess I'm misunderstanding the issue.

You are partially correct. The car’s ECMs and sensors do need sufficient battery power to manage the engine and control the starting circuit.

But the starter still has a large gauge cable going to it to power the starter motor itself

[dogmush]

The key with the ECM et. al. Is that the starter is by orders of magnitude more current hungry AND the solenoid to feed it requires more voltage to close than the ECM to power up.

So there is no situation where the battery has enough power to start the car, but not enough to power the ECM and you just need a little boost to bring the computers up.  If the main bat is too low to power the ECM, you will need to boost it enough for that AND the starter, and if you can run the starter, you will bydefault have enough power to fire the ECM.

Unless the ECM power failure is due to a fuse, circuit breaker, or wiring fault between it and the battery,  in which case boosting the battery STILL wont help.

[Bogie]

You either get clicky clicky or whomba whoba screw you...