over-discharge 1x AA (NiMH)

[Jarl]

I'm just wondering, is it possible to over discharge a single AA battery? I'm looking to get some voltage curves for a project, but on the higher discharge rates i'm a bit worried about how the battery will hold up if I leave it on for too long (i.e, discharging at 1.5 amps, and for whatever reason I disconnect it after 3 hours rather than 2 or so). I'll just be running it through a resistor, so as the voltage drops, so will the current, but for the current draw to be zero, the voltage also needs to be worryingly low (far worse than 0.9V which is the "norm"). Will this damage the batteries?

 

[Mr Happy]

I believe it will not cause much harm to discharge a single NiMH cell down to zero volts for a short time, but do not leave it like that as it will suffer degradation if stored in that condition. If you don't do it too often, and if you charge it up again soon after the discharge you should be OK.

 

[Kremer]

Years ago I built a discharger out of stuff in my parts bin. It holds 4x AA/AAA in parallel and runs them through a couple parallel diodes (for current handling) and a 1 Ohm power resistor then through a rigged up ammeter scavenged from a tape deck.

I load it up with the cells of choice and when the meter is down (couple hours to overnight) I take them out and they are right at .62V. I don't know if it's suggested practice anymore to run cells down this much, but I use it sparingly.

EDIT: The discharge cycle of my C808M only seems to take cells down to 1.10 -1.15 or so.

~Dougk