Are over-discharged lithium cells safe?

Go on then, hook up a LiPo to the mains....

Brandon, I see the "cut off point" for these cells is 2.5 volts which is a lot lower than where my Opus stops discharging. That might account for a difference in capacity. Thanks for link to data sheet.

The main thing I've seen happen when left under-discharged for too long is the cell puffing up. While clearing a drawer, I found an old spare Fujifilm camera Lithium Ion battery which I no longer have the camera. It was puffed up and showed a zero volt reading on the meter. Similarly, I took out an old Nokia 6300 phone, which the back cover had popped off. Turned out its battery had puffed up also and gives a zero volt reading. What I suspect is both had self discharged over the years untouched in the drawer. At least they didn't leak like several old Ni-MH batteries I came across.

Seán Byrne

Thanks for useful comments Brandon. Interesting.

Clive, I love you, man. Sound included, never had a problem with it. Two things I'd like to mention is that while getting rid of the dreaded black surface was a big step, glare still raises its ugly head here and there. Another - not relevant to this video, but still - please use the scope more often, even just to demonstrate how the circuit works. (no, I'm not their sales rep :)

great video Clive

Stuart Goggin

I'd usually consider even 2800mah to be within spec for a "3000mah" cell. LG seems to claim a flat 3000mah though - when charged following their voltage /current and cutoff values, listed in the spec sheet here: <a href="https://cdn.shopify.com/s/files/1/0674/3651/files/lg-hg2-spec-sheet.pdf?18079372476502823776" rel="nofollow noopener" target="_blank">https://cdn.shopify.com/s/files/1/0674/3651/files/lg-hg2-spec-sheet.pdf?18079372476502823776</a>

Now I want Clive to hook up a lithium cell to -12V...

Btw, I see Clive is still alive so the Stilton episode seems to have caused no harm!

Very informative as always. A good "learn". It's amazing how people just rabbit off what they've heard and take it as conventional wisdom. I like it when Clive strips away the "crowd wisdom". On a related topic I have a Q which has been puzzling me. Any light cast would be welcome .... I am rebuilding a 20 volt Dewalt tool battery and have some top notch LG 3 Ah high drain capable cells for the job. I thought I would check the capacity of these new cells, as one does, in my Opus BT-C 3100. Did a few charge/discharge cycles to settle the cell in. I got a capacity of approx. 2850 mA. Opus stopped charge at 4.24 V and stopped discharge at about 3.3 V. Is there a recognized "full" and "empty" point from which cell capacity is measured in the industry? Maybe my Opus is a little conservative at the "empty" point. Thoughts?

Thanks Clive, this is great information. I've always been curious about the real risk.

Over discharging is not good long term in my experience. But mostly harmless and better than throwing away a cell. Overcharging is sure fireworks.

Tilman Baumann

Beaut! Thanks for finding and linking to the Nature article and adding your interpretation and extrapolations in your distinctive style. Twas something that had been mildly puzzling me for yonks. Much to digest in the article. Once again the world becomes slightly more fathomable.

L. Brait

What do you use to hold your camera above the desk?

David Glover-Aoki

I've recovered LiPo batteries before, its always a bit nerve racking, but i've never had a problem.

Greg