OK, so I have a remote control that likes to have a good 3.0V worth from two AAA batteries, else the signal isn't bright enough to switch the gadget it's pointed at.
I hate alkalines (should be ~1.55V open circuit). I have had too many leak in remote controls before to even contemplate ever using those filthy things, I'd only use them if I know I will use them up fairly quickly and chuck. Given they can last a while in a remote control and I have had them leak even before they stop working, it's why I always use NiMH in them. I have had hundreds of NiMH over 20 years, and I can recall only ever two having leaked, and that wasn't dribbly sticky stuff, it was just a bit of dry powder (not sure what that was exactly?).
The remote's ok with NiMH when fully charged (~1.40V open circuit ) but just a little use and once it drops to ~1.33V the remote gets unhappy.
It's not an uncommon thing in many circuits, where 1.5V batteries are 'recommended' and NiMH aren't, for this exact reason.
So I was just looking up getting some non-rechargeable lithium batteries, which are built with better non-leak construction and have a very long storage life. I've not really examined the chemistry before but did hesitate to wonder how lithium, with its 3V electropotential, works in a 1.5V cell. Well, a cathode of iron disulphide seems to fix that, which produces a combined open cell voltage of ~1.74V. This drops rapidly under load, so works very well in high current 1.5V applications especially as the construction is a spiral-wrapped type giving a very large surface area for the chemistry to do its stuff.
Well, that's just all background info. The thing I was wondering here is [as always!!!!] how best to use it despite the manufacturer's instructions. It's what we do here, isn't it!?
So these things are not to be recharged. Yeah, sure!... All chemistry is reversible, but the question is whether these batteries can be reversed safely and if so how many times and under what circumstances.
First off, I would be dead certain that recharging these with low or high State-of-charge would be bad. If the construction is not meant for reformation of the ionic species then the electrodes will regrow in very peculiar ways and become damaged easily. So, first off, I guess the SOC strategy would be to ensure a 40%-60% operating range.
Secondly, they are high surface area devices which would mean they will draw a big current as the input voltage exceeds the cell voltage. So this would have to be a current-controlled recharge strategy rather than a voltage controlled one, else the heat build up will be dramatic and very quick! Also, I suspect that hot-spots would form rapidly where the electrodes regain mass at different points. I would hope/suspect, then, that short pulses would encourage reformation of the electrodes whilst the in-circuit internal resistance could help load the cell during switch-off periods so that the electrodes grow uniformly.
So I figure I might have a go at recharging these suckers once they are at no less than 40% SOC back up to 60% with a pulsed-cycle current-limited scheme. I was figuring y'all might have something to say about this, and if my understanding of attempting to recharge this cell-type is 'not even wrong', or worth a go!?
I suppose, thereagain, I should concern myself about the possibility of a recharged lithium battery going up in a puff of flames, though. It's what they are famed for!!