battery tester -dry cells

I suggest that you not worry so much about the load and just let the circuit measure the open circuit voltage. Any time I take alkaline cells out of service I find the voltage is 1.2 or lower. A fresh cell is always higher than 1.4 volts. My mouse eats a pair of AAAs in a month or so and the terminal voltage is about 0.9 open circuit.

What the load test tells you is the internal resistance of a cell. That can rise as the cell nears the end of life, but is just duplicate info to the open circuit voltage. The internal resistance can tell you something about rechargable cells however. They will have a very different open circuit voltage being a bit above 1.2 for a fresh NiCad. I think their open circuit voltage is fairly constant until nearly depleted, but more importantly the internal resistance will rise as they get worn and won't hold as much charge.

Err...Alkaline cells nominally read 1.65 brand new to as bad as 1.55V "fresh" but sitting around for a while. The Radio Shack tester 22-090 uses 1mA load for 1.5V button cells and

And it is rather useful to test under load; a weak battery may initially indicate near full voltage, but will show a sagging reading as the meter is left connected to it (2-15 seconds). Note a no-load test will not show a weak battery.

On Wed, 04 Jun 2014 13:55:27 -0600, Lew Hartswick wrote as underneath :

These type testers are so cheap (even cheaper from China!) its not really worth messing around with... I dont use for more than a second if testing on button cells! The load resistor is the same for all ~1.5v types, higher for PP3. eBay item number:

Thanks. That is what I was looking for. somewhere around 30 and 10 ohms. ...lew...

Copied from their website:

Battery Tester (220-0090) Specifications Faxback Doc. #

Current Drain During Test for each type of battery is as follows:

Battery Size Current