Hector Martin

Directly charging over-discharged li-ion cells with my bench supply. Definitely nothing unsafe going on here.

I directly charged a Ryobi 18V pack (it's just 5 18650s in series) with a lead-acid-battery charger the other day

just needed a few seconds to get the pack voltage up above like 6V or so, at which point the charger accepts it again

Yeah. 3.7V tablet battery, bypassed protection, couple mins at 100mA brought it from 1.8V to 2.7V and now it's happily charging.

I *think* 1.8V is still above the "it's gonna go boom if charged" range, but... we'll see.

2.5V is the lowest I'll let one go. Beyond that it hits the bin.

It varies by manufacturer, but the numbers I read are in the 1.5V to 1V range. Though of course you have to slow charge up to ~2.5V.

Eh, that's cutting it extremely close. I've had my share of old batteries turn into blimps in front of me, it's quite nerve-wracking. X3