Testing Batteries with Multimeter

[Kayak]

I would like to check some of the batteries in my drawer for their condition.

1. How much of a voltage drop is allowable for a battery to be considered "still good," for example I note that slightly used AA's are down to about 1.4 volts?

1. Is their a percentage drop that could apply to all batteries - say

10% or so - or are there different threshholds for AA's, C's, and D's?

Many thanks in advance.

Dwight

[Joseph Meehan]

That depends on the type of battery, and to some extent the tester. Some would be gone by 1.4V and others fully charged are ready to go at 1.3V

I suggest you use a set until they no longer function as you would like and then test them. Try testing some when they are about half way there to see if you can measure any meaningful difference.

Usually the best test is testing them under load. Not convenient, but it is generally better.

[TURTLE]

This is Turtle.

I got on a kick one time of checking the battery voltage when the low battery lite come on to my volt and amp meters. When ever the low battery lite came on. i would take them out and put fresh ones in there and check the voltage. Everytime on 1.5 volt type batterys they would read 1.45 volts to 1.49 volts but this would very because of time in between time lite came on and when you checked them. I have seen this. everytime you see less than

1.5 volts out of a 1.5 volt battery. It does not work well at all in my meters.

Auto car batterys are the same. If you see less than 12 volts out if a auto battery / unconnected from car and has sit with no use for 5 minutes. It is bad. You can take a car battery and draw it down to nothing with your head lites on over nite and the next morning disconnect the battery from the auto and let it sit for 30 minutes with no use and you will see 12.0 to 12.6 volts if it is good. If it killed it or hurt it, you will see less than 12 volts, even when it is not able to do anything. Just getting carried away again.

TURTLE

[George E. Cawthon]

Sure you can. But whether they will operate an appliance depends on the appliance. I've been checking rechargeable and other batteries for years. And no you don't need to worry about voltage drop under load if you are using relatively low draw appliances such as radios.

In general, fresh, fully charge batteries run upto 1.6 volts per cell. That is a 1.5 v battery (which is a cell) should read about 1.56 to 1.59v when new. At 1.35 volts those batteries won't run my Walkman. Flashlights are different, but the light will be pretty weak at 1.35 volts also. I replaced an old 9v battery in a smoke alarm that read 6.8 volts and was still working, but I think that is pretty unusual as the current draw is minuscule.

For your purposes, you don't need to worry about current draw and voltage drop under load. If the battery reads 1.45 or above at rest, chances are that it will work fine for a while. If it reads 1.35 or below, it's dead or will be shortly; between 1.35 and 1.45, it's weak but may operate some appliances.