How to Check AA/AAA Alkaline Battery Using a Voltmeter




Introduction: How to Check AA/AAA Alkaline Battery Using a Voltmeter

We all run into a situation when batteries in our remotes, toys, keyboards/mice run out. If we don't know how to check a battery we might throw out a perfectly fine battery (especially when we have a pile of them somewhere in the drawer).  

This electronics tip has to deal with checking common alkaline AA/AAA batteries or AA/AAA rechargeable batteries for proper voltage with a voltmeter.

Disclaimer : some people might say that a battery should always be tested under load but I have found that in most common household applications this is insignificant and will not change the results of the testing too much. 

Things that you will need :
+ Voltmeter
+ Alkaline battery

Basic facts : 
The proper voltage for AA/AAA alkaline battery is 1.5V
The proper voltage for AA/AAA NiCd/NiMh rechargeable battery is 1.25 Volts

To test the battery, turn on your voltmeter, put the voltmeter on DCV and make sure that it is far above the battery voltage, on most voltmeters there is a setting "20" in the DCV area, so switch your voltmeter to that setting. 

With the battery in front of you, put the red probe to battery's nipple (+) and the black probe to the battery's flat side (-). Notice the voltage reading on the voltmeter.

If the reading is more than 1.3V for alkaline battery (not rechargeable battery) then the battery still has some juice left in it, don't throw it away. Otherwise, properly discard of the battery.

Tip : do not use old and new batteries in the same device at the same time. Try to use batteries that have same amount of energy stored in them. 

Another tip: I sort my batteries according to Voltages, 1.35+ Good, 1.2V-1.3V Ok (but almost out), 1V-1.2V Discard.

I will attach some pictures of measurements in action. 

Instructions on how to use a multimeter are out of scope of this Instructable, you can find some information here:

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31 Discussions

I'd like to offer a few corrections, additions, and pointers.

Testing a battery with a multimeter will only tell you what the voltage of an UNLOADED cell is. In other words... you could have two batteries that read with an identical reading of voltage... but when you connect them to a load... let's say a motor... one will spin niely and the other will fail... run slow or stall.

Why? Because the CAPACITY of the failed battery has diminished. Let's take the example of a AA battery... if it has a 2000mAh capacity, that means that it can support a load of 2000 mA for 1 hour... or 1000 mA for 2 hours. This means that if you were running a toy that drew about 200 mA... it would run for 2000mAh/200mA or 10 hours.

So how do you check the battery? Under a load. Let's use the example above... we don't want to draw 2000mA on the battery... that's a huge load all at once. But instead... let's draw 1/10 of it's capacity... 200mA. We can take the voltage 1.5 volts / 0.2 amps (200mA = 0.2A) and get 7.5 ohms. So if we find an 8 ohm resistor and put it across the battery... it should still be close to 1.5v... but if it drops way down... to less than a volt for example... then it is likely discharged or going bad.

Another issue with the 1.5 volt battery... a NON-RECHARGABLE battery is rated for 1.5v fully charged. but... a NiCad battery is rated for 1.2V FULLY CHARGED. And I believe a lipo is like 1.25V if memory serves me.

I actually use this fact in my projects... an Atmel runs 3.0v to 5.5v...

4 AA batteries.... at 1.5v = 6.0v which would be high for my 5v Atmel processor...
4 AA batteries.... at 1.2V = 4.8v which is just fine.

I hope that helps.

10 replies

The article was pretty clear that this was for testing an alkaline AA or AAA. Also, the test is for determining whether the cell was depleted or not, not whether it had malfunctioned. If the cell tests fresh under no load, but drops below 1.2 v under load, you are either overloading the battery, or the battery is defective (or both)

I know this comment is 6 months old, but I am going to reply any way in case someone reads this later.

As askjerry indicated, testing a battery (of any chemistry) unloaded is pretty much a useless endeavor. The ONLY way to test a battery is to estimate the current draw scenario, and 200mA is a good base case scenario, and test it with an equivalent load. When you test a battery unloaded you can get nearly the full "new" voltage on a battery with very little capacity left. Just use a 1/2 watt (or greater) resistor as a load and you can get a true estimate of whether the battery is good or bad.

Hi, is the resistance going to make any difference during the test? For example I have couple 50 ohms laying around, which should draw a much less current, will it show different result from 8 ohms?

My multimeter has a simple bat test mode. For 1.5v it measures the voltage under a 100mA load.

To the point...Does testing the battery under load really matter? No, not for most electronic devices. It might matter a little bit if it runs a motor, or perhaps a flashlight. Still, we are talking about deciding whether to dispose of an inexpensive battery or to replace it with a new one. I see no need to overthink this and go searching for load resistors. If in doubt-throw it out!

Awesome - I want a multimeter that applies a load during testing! What kind do you have and do you remember where you found it? I ask people at hardware and electronic stores if testers or meters that apply load during testing exist, and they don't even understand the concept, let alone know if and where those might be in the world.

And when I search online, I must not know what search terms to use, because I've found nothing.


"If in doubt-throw it out!" UNLESS you're one of those weirdos like me who is concerned about things like not being wasteful, not polluting, caring for the environment, caring about other people and stuff like that.

Odd... my link for the Ohms Law chart didn't work... I'll try again...'s_Law_Pie_chart.svg

It will show a slower decay time for a good cell... but a crappy cell would still drop rather quickly. For example.. presume a 2000mAh battery... let's say a NiCad at 1.2 volts... let's look at the current differences for 8 ohms vs. 50 ohms at that voltage. OHMS LAW CHART

I (current) =  E (voltage) / R (resistance)

1.2v / 8 ohms =  0.150 A (150 mA)
12v / 50 ohms = 0.024 A (  24 mA)

So for a 2000mAh battery...
...the 8 ohm should run up to 13 hours.   (2000 / 150)
...the 50 ohm should run up to 83 hours. (2000 / 24)

So if it drops to near zero in a relatively short time... then it's bad.

Jerry, You are so right about a load test. If you take your car to a mechanic and have the battery tested he always brings out his battery testing gear that test the battery under a load. That 12 volt battery has to turn over your engine and recharge by alternator for the next start. If it fails the test you are not going to be a happy camper come morning!

"If the reading is more than 1.3V for alkaline battery (not rechargeable battery) then the battery still has some juice left in it, don't throw it away. Otherwise, properly discard of the battery."

Would you please prove this statement? I am currently writing a report inspired by this.

Thank you

Do batteries in a remote (say four batteries), discharge unevenly, and if so why? for example the device could stop working because one battery has drained much quicker than the other batteries so we should only be swapping out the one battery, not all four.

Hi Jerry & msurguy - thanks for the tips!

Do you happen to know
if there are any resistance/resistors inside the ol' Radio Shack battery
testers (mine is pictured here w/"Radio Shack" label, but nowadays new
ones may have"Enercel" label on it)? If so, how much resistance?
I'm wondering if these Radio
Shack battery testers put any load on the battery when testing.

I keep trying to Finalize this Reply, but nothing happens when I hit
the "Reply" button, so THIS Reply effort will now be withOUT the
attached picture I mentioned above. If this goes through, I'll try a follow-up WITH the picture again.

Radio Shack battery checker tester.jpg
4 replies

Thank you for your reply. The question remains, though. How can I test the available 'power' for the batteries if the higher voltage read batteries won't light a flashlight while the lower voltage ones will?

Your edit went through... sometimes the page gets goofy... dunno why.

I'm sure they had some resistance in the tester, not sure how much. Likely it would have been at least a 1/4 watt or possibly 1/2 watt resistor... 100 ohms would be my wild guess. I'm thinking that since the tester does NOT have a battery in it, then you should be able to put an ohm meter across the leads and read the resistance directly. Yes, there will be a bit added from the resistance of the meter... like 20K or so... but you should see the main load...

now if the unit DOES have a battery... don't use an ohm meter as the voltage may damage it. But I really think it's just a meter and a load resistor... so you should be able to determine the resitance-ish.

Ah yes/duh - I do know barely enough about electricity that I should've thought to put multimeter to battery checker terminals and measure resistance. SO....

AA/AAA terminals read 10 (not 100) Ω (ohms).
9V terminals read 0.86KΩ

Now, here's where my savvy stops. Would 10Ω and 0.86KΩ be enough of a load for measuring 1.5V and 9V, respectively?

Thanks, Ted

Well, let's do a little dare I say it... MATH.

Current = Voltage / Resistance

1.5 volts / 10 ohms = 0.15 amps, or 150mA.

9.0 volts / 860 ohms = 0.0104 or 10.4mA.

I kind of expected the 150mA... but 10mA on the 9v is surprising... I would have thought it too would pull about the same... 150 mA. That would play out like...

9.0 volts / .150A (150mA) = 60 ohms

Are you sure that wasn't an 86 ohm resistance?

That would be...

9.0 volts / 86 ohms = 105 mA

Eh... I don't design voltage testers... what do I know?

I'm trying to be environmentally conscious, but I'm baffled. I have a whole slew of AA batteries. I want to test them with my multimeter. Two batteries test at 1.403 volts, but won't light my flashlight. Two other batteries test at 1.373 and they light the flashlight! They are all the same brand with the same style contacts. (I also tried taking one of the good batteries out and replacing it with one of the 'bad' (1.403v) ones and it still wouldn't light. If I can't rely on the result of the multimeter test, I can only test batteries using a flashlight, and frankly that would be a lot more time consuming. What is going on?

1 reply

Well it depends upon how much power does the cell have, in your case you have mention that low voltage batteries lit the flashlight while higher one didnt . It is clearly visible that higher voltage battery dosent have enough power(or current in this case to run the flashlight). Power is product of voltage and current.

Hope this helps