Testing dead car batteries.

[earthman]

Alternator testing - this has to be one of the best videos like this I have seen.
Useful, concise, in depth video made by a professional that knows what he is talking about and how to convey it.

I'm glad he mentioned ecu controlled ones, I fitted a volt meter to the dash of a new to me car once, got into a panic when it read 12v whilst driving along at 70. Lol

 

[Matrixx]

A simple rule is if it is out of warranty and failing , just replace it.

To clean a batterys plates it seems you neeed to "gass" the battery, i.e. over charge for a period , not recomended unless you know what your doing.

 

[Robotstar5]

......My digital tester was £25 on eBay, I'm slowly replacing the duff batteries on my vehicles by buying batteries off of Facebook, I bought a Yuasa battery that has a 94% capacity of it's original stated capacity for £20 last Saturday, new price was about £85.

I bet they love it when you turn up with your tester and declare their "mint condition" battery duff

 

[Wendelspanswick]

I bet they love it when you turn up with your tester and declare their "mint condition" battery duff

I do message them first to try and find out how old the battery is and if they mind me testing it first.
I've messaged 7 people and bought 3 decent batteries, the other 4 either never replied or the battery sounded dubious so I declined.
The most I've paid was £25 for a commercial 850 CCA battery with 88% capacity for the John Deere tractor, book price was about £140.
Most sellers seem to be people who've had to scrap their vehicle and they've whipped the battery out before the scrappies turned up to uplift the car.