'shoebooty', if you're designing a battery tester, see itsme000's reply above.
If you need to know this because you're designing an electronically controlled discharger with an end point, that's fine.
On the other hand, if you're just aiming to discharge batteries through a resistor from a starting charge rate, until they're empty, be aware that completely flattening any rechargeable battery is likely to do it irreparable harm. You must set a voltage cut-off point below which you never take it.
Last edited by Alan T; Jul 22, 2009 at 4:45 AM.