LSD=good. Now what about LOD?

[Nubo]

Rechargeable batteries have 3 Achille's heels. Seems like we've got 2 of them beat now. Overcharge protection solved by smart chargers. Self-discharge practically solved by new LSD chemistries....

That leaves over-discharge as the one weakness that can turn a cost/energy effective rechargeable cell into a very expensive dud.

While most folks here are well educated on the care and feeding of rechargables, the average consumer will be greatly turned off when their expensive rechargeable batteries barely hold a charge after a few cycles. And, even for those in the know, this aspect limits device usefulness. For example, what if I fall asleep with my LED lantern on? Or, wouldn't you like to put rechargeables in that child's toy? But you know they will run that robot/car/etc right down to a dead cell(s).

Not too many devices are "smart" enough to turn themselves off when voltage gets to the danger level for rechargeable cells. Meaining, for example, going below 1.0 or .9 volts on a NiMH cell, etc... So... what are the prospects for adding that intelligence to the cells themselves?

 

[Fallingwater]

Protection circuitry is common on many kinds of LiIon cells, most notably 18650, RCR123 and 14500.

 

[Nubo]

Protection circuitry is common on many kinds of LiIon cells, most notably 18650, RCR123 and 14500.

I now these have protection against over-current, but I am talking about shutting down a cell before it gets too fully drained. I didn't think that was built-in, but maybe I am wrong? I don't have experience with those cells. Most consumers don't use LiIon rechargables directly, but in devices which tend to be designed around the battery and smart enough to turn themselves off at the proper time. I am thinking more of NiMH. But also for LiIon individual cells -- if those are intended to become popular, I think the over-discharge issue would be even more important for those, if used in simpler (not "smart") devices such as flashlights, toys, etc..

editing OP for clarity....

 

[Fallingwater]

I now these have protection against over-current, but I am talking about shutting down a cell before it gets too fully drained. I didn't think that was built-in, but maybe I am wrong?

Actually, all protected cells are protected against overdischarge. Many of them, not all, are also protected against overcurrent/short circuit.

I am thinking more of NiMH

IIRC, NiMH don't suffer much from overdischarge. It's still better to not run them down to 0 volts, but even if you do negative consequences are unlikely.

But also for LiIon individual cells -- if those are intended to become popular, I think the over-discharge issue would be even more important for those, if used in simpler (not "smart") devices such as flashlights, toys, etc..

Which is why protected cells are available

 

[SilverFox]

Hello Nubo,

I believe that falls into a circuitry issue, and is not necessarily a battery issue.

The people who design the circuits in toys and other applications should design them to be NiMh friendly. They could incorporate a switch that allows an alkaline cell to be run down to 0 volts, or to limit the discharge to 0.9 volts for NiMh cells.

An example of this is the newer GPS units. Mine has 3 settings, Alkaline, Li-Ion, and NiMh.

Tom