What to do with all these batteries? old laptops

The user name is clever.

Get a hobby charger* and check their capacity with a charge/discharge cycle. I've checked hundreds of salvaged 18650s, some are 600mAh, some are 2400mAh, personally I keep anything over 1800mAh and send the rest for recycling.

*and some magnets to stick onto the terminals and grip with croc clips

internal resistance?

10fenny said:

internal resistance?

Click to expand...

Whenever electrons flow through something it causes resistance. The inside of a battery is no exception. Some materials have more resistance than others. Basically, how many electrons actually pass through matter without colliding into atoms, I believe.