Very interesting Alan, thanks for that reply,

Reversing a cell is definately not desirable. When discussing this topic the distinction needs to be made between single cells and batteries, batteries of course being groups of cells in series and/or parallel.

If you take a single cell and discharge it by putting some sort of load across it there is no way to reverse it. However if you have a number of cells being used in a device (as is usually the case) and you attempt to fully discharge them there is a real risk of reversal as you have pointed out.

I was certainly giving bad advice by suggesting that you run the rechargables completely flat inside a device. I fully discharge my cells (on the rare occasion that I've needed to) by using a load on the individual cells. That method is a fair bit of mucking for the average user so I quickly tried to think of an easier alternative while I was writing the post above. You are quite correct that in this case it would be advisable to stay above a volt or so.

You may be interested to know that single Lithium Polymer cells are approximately 3.7V when fully charged and can be seriously damaged if they are discharged below about 3V!! Electric powered model aircraft which run on Lipos often have devices in them which disconnect the pack from the motor when the voltage reaches a certain level eg. 9V if you are using a pack of 3cells in series.

Rob.