Why does storing Li-ion batteries at 100% charge damage them?

[XTAR]

When storing the 18650, 21700 Li-ion batteries of your dive lights for a long time, it's better to partly charge them to around 3.6V or round 40-60% charge. This avoids full charging because high voltage makes the batteries more chemically active, leading to damaging reactions.

When a Li-ion battery gets fully charged, the voltage is at its maximum, which means a high amount of lithium ions have moved to the negative electrode. Over time, this high energy state can cause unwanted chemical reactions, leading to the degradation of the battery materials. It will reduce its capacity and lifespan.

Lower voltage, cooler temperatures help prevent battery wear. So for long-term storage, keep the batteries at a partial charge to reduce damage.

 

[Pearlman]

Uh oh … too late.. it's been many years for my batteries now!

 

[astr0b0y]

The dendrites will get you in the end!

 

[Russjstewart]

Thank you

 

[GF99/99]

So for long-term storage, keep the batteries at a partial charge to reduce damage.

Also for long-term storage remove them (where possible) from the device and store them properly. Yes lithium batteries thou very rare can still leak and yes they will ruin your $1,000 shearwater computer. And throwing loose batteries in a big box for storage where all the terminals are touching each other is not a good idea either. Same goes for keeping them in that hot AZ sun baked garage.

 

[Badger7]

Its always been the same advice for lithium ion batteries, whether we're talking power tools, R/C, e-bike, or otherwise. Storing them at partial charge will prolong their life, throughput, and give you more charge/discharge cycles. When stored full charged, as they self-discharge over time chemical reactions occur inside the cell which reduces their total output over time. When stored fully discharged, individual cells can react in manner that they refuse to take a charge at all, or leak, after an extended time. That's typically what you're seeing when you pop an older Milwaukee or Dewalt pack on the charger and it just flashes at you and refuses to start charging. Given one option or the other, you're much better off storing them fully charged than fully discharged. Ideally, you're running your flashlight lithium batteries down to about 50% and you just leave it there and charge them the night before your next dive. I don't, I'll forget, so I just charge up my cells the morning after a dive when I'm packing my now-dry gear back up for the next trip.

 

[Eric802]

My wife was wondering why I had my dive lights running in the kitchen sink when she got home yesterday. Had to tell her about this thread. Ran all my 18650's down to 3.5-3.6v.

Had to change the subject quickly when it went from "What's up with this?" to "Wait, why do you have so many flashlights?"