How to Check AA/AAA Alkaline Battery Using a Voltmeter

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


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38 Discussions

0
Reluctant Poster
Reluctant Poster

7 months ago

Today I had a major name-brand digital thermostat fail, driving my house temperature to 80° before the failure was caught, wasting a lot of expensive energy as well. The thermostat is battery powered, and when checking the two AA’s it uses, the voltage on each was 1.32 and 1.33V, respectively. in some cases, that voltage may be usable, but in this application it was insufficient to power the relay that shuts off the furnace. Just be very careful of your particular application.

0
bdannh1
bdannh1

Question 1 year ago on Introduction

The other day i needed to check the voltage in a couple of AA batteries. I plugged the cables into my analog multimeter and touched the leads to the ends of the batteries and measured the voltage. When i finished i was putting everything back in the box and noticed i had forgotten to put the batteries in the multimeter but it still worked. Doesn't the meter need batteries to check voltage?

0
philnjune67
philnjune67

Answer 7 months ago

Analog meters use power from the battery being tested to swing the needle. Digital testers require an internal battery to work

0
moosetooth
moosetooth

Answer 8 months ago

I believe the battery in a multi meter are necessary for ohm function. It sends a small current through the circuit to measure resistance. Also necessary for continuity checks.

0
RourkeM
RourkeM

Question 8 months ago on Introduction

"Tip : do not use old and new batt..." I hear that tip all the time, but have never once seen an explanation accompany it. I think it is an oft repeated, unsubstantiated tidbit that is as helpful as the tip, wait 30 minutes after eating before swimming. I've had to use old and new on countless occasions and regularly eat a whole turkey before during and after my swim and have yet to see any detrimental effects if you can overlook an abundance of glow in the dark turkey farts.

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0
am27wYOC79l7uDMd
am27wYOC79l7uDMd

Answer 7 months ago

If old and new batteries are similar voltage it’s no big deal. If old has 1/2 capacity of new they’ll simply equalize and you’ll lose some capacity from the new battery. Again no big deal. It’s only $.

1
DavidP236
DavidP236

4 years ago

With the multimeter in the photo you can test unloaded and loaded. The battery test (loaded) position is at the upper right on the dial in the 1:00 position. Set to this, put the red lead in the middle hole and the black in the bottom. You should read 4.0 mA (milliamp) for a AA or AAA battery.

0
mlah
mlah

Reply 10 months ago

To those who stumble upon this, this is why you need to test the battery under load. The voltage of an unloaded battery will not change significantly as it dies. A fresh battery and a dead one will both show similar voltages unloaded.

0
johnlax27
johnlax27

Reply 4 years ago

I think he is talking about testing for voltage while the battery is under load. You're talking about amperage--two different things.

1
askjerry
askjerry

7 years ago on Introduction

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.
Jerry

0
SteveR46
SteveR46

Reply 4 years ago on Introduction

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)

0
XgudwilX
XgudwilX

Reply 2 years ago

thank you. common sense.

1
MichaelW328
MichaelW328

Reply 4 years ago

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.

0
iptest0125
iptest0125

Reply 4 years ago on Introduction

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?

0
SteveR46
SteveR46

Reply 4 years ago on Introduction

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!

0
ted939
ted939

Reply 3 years ago

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.

Thanks!

0
ted939
ted939

Reply 3 years ago

"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.

0
askjerry
askjerry

Reply 4 years ago on Introduction

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

https://upload.wikimedia.org/wikipedia/commons/7/78/Ohm's_Law_Pie_chart.svg

0
askjerry
askjerry

Reply 4 years ago on Introduction

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.

0
barry.wind.3
barry.wind.3

Reply 5 years ago on Introduction

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!