Charging small electrical devices

[Rocinante]

Apologies if this shouldn't sit here, but I thought some of the battery experts on here might advise.

I've got a pair of bluetooth earphones. Very cheap from Amazon, but they do the job. I've had them maybe a year and so and still doing well, but I was wondering the best way to charge them, after reading on here the discussions on charging the cars. I've no idea what batteries are in them, (the description says "The latest polymer battery provides more than 8 hours of continuous play.")

Maybe 20 years of more ago, I remember the advice on charging batteries (for phones and the like), was to fully empty them and then fully charge them. Maybe I'm misremembering or given bad advice at the time. The current advice with the cars seem to be 20 to 80%.

At the minute I usually wait till they tell me "low battery", or even till they shut themselves off, and then charge them to full.
Any thoughts ?

 

[5teep]

Fully emptying a battery applied ONLY to Nickel Cadmium batteries because they had a charge state memory issue and needed to be 'reset' every so often.

No other battery has this problem despite a million internet 'experts' telling you they do. NiMH, Lead Acid, Lithium batteries all work best when discharged partially but not all the way.

So you're doing ok with your earpieces, use them down as far as you like but not empty and recharge, or use them a little bit and top them up, makes very little difference to lifespan.

 

[Hairyfool]

Lithium based batteries can have catastrophic failure (lots of smoke) if abused and the most obvious example would be if they were directly attached to an inappropriate supply. Therefore they tend to have Battery Management Systems between the terminals and the battery itself, these protect the battery from such abuse including overcharging, over discharging etc. If the battery "shuts itself off" it is almost certainly this that has disconnected the battery not that it is actually flat

Lead Acid batteries will suffer permanent reduction in capacity if fully discharged, unless marked up as "deep discharge" they should only be taken down to 50% charge at worst. Therefore a 100Ah battery is effectively 50Ah, the equivalent Lithium is 68Ah.

LiFePO4 (EV) batteries should only be rapid charged up to 80% then the charge current reduced or they overheat, again the BMS should take care of it. As they get further towards 100% then the energy used tends to increase for each percentage point so for energy efficiency some argue that fully charging them is wasteful unless there is a need for maximum range. They should be safe down to 10% but consider the 20% to 10% section the "find a charger" emergency reserve, i.e. there if really needed but don't.