sealed (air tight) rechargable battery technology

I'm really surprised they lasted that long. ...though low temperature doesn't tend to ruin L-A batteries (unless they freeze). They *couldn't* have had much capacity at those temperatures (-40C, or worse?)

No, it was rather embarrasing when I found this out. I had to snake out of a design probem by telling field-service to replace the batteries every one to three years insted of eight (which would have meant that they never would have been replaced). "Come on! The damned bateries are worth $15!" :-(

How about captuing the energy from the people shivering? ;-)

So says Network Solutions, anyway. ;-)

Dunno, even cell phone LiIons are having "expoding in flames" problems.

I think I agree, but the temperature issue is interesting.

In article , Ian Stirling wrote: [... batteries in nasty environment ...]

The Lithiums I was looking at didn't like the cold and yes were very costly.

I could also never get it on paper that they had solved the "exploding in flames" problem on the higher power ones. I could for the smaller ones though.

In the end SLAs just looked like the right one to pick.

In article , keith wrote: [... SLA in tough environment lasting a year ...]

The most common failure was due to the plates being mechanically weak. In some versions of the battery, the plates are held in place only by the lead joint that also serves to hook the cells together. In the better ones, the plastic case has a tight fit on the plates holding them firmly in place.

We developed a simple test. You hold the battery in your hand and shake it. If the insides rattle, the battery is no good for the purpose.

It seems that, there are two factories in China that make all the SLAs in the world regardless of the makers labels. One factory makes good ones, the other makes bad ones. The various labels contract with which ever offers the lower price. The result is that the exact same part number from a given maker can suddenly be a totally different battery inside. A competing brand could then suddenly be the former version.

At low temperatures, a 3AH SLA can still make a few hundred mA when charged. When they run they tend to warm up a bit. At cold temperatures, the batteries can't ever be fully discharged for fear of raising the freeze point too high. As a battery discharges, the electrolyte becomes more like just water. The gelling agent, I believe, makes the ice crystals tend to be small and isolated but does not prevent the eventual freeze up.

I've had to face the same embarrasement. The numbers in my case are $6 and $150.

When you are just about to freeze to death, you stop shivering, so we had to reject that idea.

AIUI, only charging at very low temps is a problem.

As long as you don't screw up on the charge control, or overheat them by packing too densely, or not taking care of temperature and charging, or discharging, they are fine.

Still good, in many cases. Annoyingly heavy in many others though.

I had no control over the temperature of the environment. I could control the charging but I did have to charge them in any temperature.

Yes they ended up being most of the weight of the product. That was considered OK. If they had more energy per unit volume, it would be better. Zinc-air would be a lot better from that point of view but they can't be sealed in use.

IIRC, it is only in very low temps, -20C? A small heater is an obvious solution. However, if SLA works.

In theory they can, but then you need a source of oxygen, which gets messy, and is almost certainly not worth it.

Ah yes, your comment about the Peltier under the armpit. ;-)

In article , Ian Stirling wrote: [....]

One of the other engineers suggested a SNAP unit. This met all the requirements but there were some minor problems with the regulations so I went with SLA.

...

It is bad to charge a lithium-ion or lithium-polymer battery below zero degrees C. The graphite can't absorb the ions and you start plating out lithium metal. More details on this are at