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: http://www.ladyada.net/learn/multimeter/

I'd like to offer a few corrections, additions, and pointers. <br> <br>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. <br> <br>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. <br> <br>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. <br> <br>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. <br> <br>I actually use this fact in my projects... an Atmel runs 3.0v to 5.5v... <br> <br>4 AA batteries.... at 1.5v = 6.0v which would be high for my 5v Atmel processor... <br>4 AA batteries.... at 1.2V = 4.8v which is just fine. <br> <br>I hope that helps. <br>Jerry
<p>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) </p>
<p>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?</p>
<p>My multimeter has a simple bat test mode. For 1.5v it measures the voltage under a 100mA load. </p><p>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!</p>
Odd... my link for the Ohms Law chart didn't work... I'll try again...<br><br>https://upload.wikimedia.org/wikipedia/commons/7/78/Ohm'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<br> <br> I (current) =&nbsp; E (voltage) / R (resistance)<br> <br> 1.2v / 8 ohms =&nbsp; 0.150 A (150 mA)<br> 12v / 50 ohms = 0.024 A (&nbsp; 24 mA)<br> <br> So for a 2000mAh battery...<br> ...the 8 ohm should run up to 13 hours.&nbsp;&nbsp; (2000 / 150)<br> ...the 50 ohm should run up to 83 hours. (2000 / 24)<br> <br> So if it drops to near zero in a relatively short time... then it's bad.
<p>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!</p>
<p>you are testing the battery without a load and the test results will be incorrect, you should put a 5 or 10 ohms load resister in parallel with he test leads. </p>
<p>This is exactly what I wanted to know. Thanks a lot!</p>
Thanks. You verified what I tried yesterday. I even have the same multimeter!
<p>It would be nice if some of you Tech guys would simplified this, for some of us who use regular every day Wallmart or other cheap batteries,</p><p>example</p><p>New 9V 9 V Dead 9V --------what?</p><p>AAA</p><p>AA</p>
<p>Quite easy, and the instructions of @askjerry helps alot as well</p>
I general use my tongue to test the batteries, <br>It tastes sore when it has some power. <br> <br>Am i rit?, dose it works? <br>
1.2 volt and below is NOT a dead battery! In fact there is something like 25% of potential energy still sitting in there! <br>It's just a battery in need of a new project. <br>Might I suggest starting with a http://www.instructables.com/id/Make-a-Joule-Thief/ ? <br> <br> <br>True, anything below around 0.9V is deader than a door nail, but even then, you can get a surprising amount of work out of a cell. Probably a couple hours of light out of red led's.
Lol, that's very cool use of zombie batteries =) Thanks for attaching a link of a Joule Thief, I was wondering what those things were. <br> <br>I'm sure there are lots of uses of at-the-grave's-door batteries but In most household cases the battery that's below 1.2V wouldn't be of much use, for example toys or even IR remotes don't like low voltages... <br> <br>Thanks for your input Ironsmiter!
Sorry, didn't mean to be rude. It was unnecessary, apologize ;)
Apology accepted =)

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