Testing batteries with a plain old multimeter (and a resistor)

[@TheCooperman666]

How much resistance is needed to test 12v car/truck batteries

[@8bitsinthebasement]

I've been asked this question quite a few times since I posted this battery test video and to be honest I thought that the method shown here was really not up to scratch for battery testing in a car or truck. But I found this all about it the resistance is provided not by a resistor but by running the engine. Let me know how it works out for you and thanks for watching ;) www.jdpower.com/cars/shopping-guides/how-to-test-a-car-battery-with-a-multimeter

[@TheCooperman666]

@@8bitsinthebasement Running the engine is not quite the same as the alternator will start charging the battery. A battery starting at lets say 12.5v will jump up to 13-14v's if the alternator is working, this I how I do fast and dirty test to see if alternators are working/charging. I do vehicle dismantling for parts/scrap so most of the time the vehicle will not turn over and so a test of the battery outside the vehicle after its been charged up is very useful. I will try out a 50 ohm big ceramic resistor and see how it works out.

[@CamelCasee]

Battery tester with a cold cranking amps test, a lightbulb will probably give a quick and dirty go/no go test however.

[@anurasenarathna1703]

A useful simple technique. Most of the low cost battery testers from On-line vendors are just voltage testers without no load. Thank you very much.

[@8bitsinthebasement]

You're welcome and thanks for the comment ;)

[@Perplexer1]

These proper and correct videos are very rare it seems. Most of them just tell you to measure the voltage with no load or if they do mention a resistor, they don't show how to use it (in series or parallel).

[@8bitsinthebasement]

When I went looking for how to it took me a long time to find any reliable information on testing batteries, so once I found out how I made this video. I hope that it helped you out

[@websurfer1585]

This explains a lot, I've been baffled by how many 'good' batteries don actually work.

[@nonshatter7]

I enjoy videos like this with good clear explanations.

[@8bitsinthebasement]

Thanks very much ;)

[@mtibbens82]

Why does the 100 ohm resistor work with 1.5 to 9V batteries, but not with a 3V? ..and 4.7K seems like quite a jump? Great video, though! Alot of people leave out the necessary load.

[@8bitsinthebasement]

That's a really good question, actually for each and every battery (depending on voltage and internal resistance) you should use a different value of resistor and if you search the net you will find examples stating 100 ohm for 1.5V, 360 ohm for 9V and various other values for different battery types. In this video I wanted to show a quick and easy way to see if a battery was good without the need to have a bunch of different resistors on hand. The 100 ohm is perfect for 1.5V AA batteries while at the same time being good enough for testing the others. When it comes to small button cells like the CR2032 a 100 ohm resistor will work but it will start discharging the battery during the test. This is the reason a 4.7 kohm resistor is used instead (higher value resistor = less current draw). This discharge happens because button cells have quite a low capacity of +/- 260 mAh, while the others are in the 1600 mAh plus range (the larger load has nothing to do with the fact that the CR2032 is rated 3V). So, the load is more or less chosen to stress the battery enough to show if it can give a high enough voltage reading on the multimeter while striking the balance of not draining it (too much) at the same time. At least that's my understanding of it. Thanks for watching Mark, I hope this answers your question.

[@promechanics2395]

Same question came in my mind but i have seen that you have already answered it .great

[@sageRJRJ]

@@8bitsinthebasementwill the 100 ohm resistor really discharge a coin cell enough for it to matter though? Since it’s only like 2 seconds.

[@andynonimuss6298]

4.7K ohm resistor for CMOS battery... got it! As low as 2.8 under load it's still good. Awesome, thanks!

[@8bitsinthebasement]

That's it! at 2.8V it's still good but it won't have a huge amount of life left in it. Thanks for watching :)

[@pattygonzales9605]

Thank you so very much for learning and posting this video with a resistor. I learned it from you today. ❤❤❤

[@8bitsinthebasement]

@@pattygonzales9605 you're very welcome, I'm glad that it was useful for you.

[@guesswhomartin9249]

Good video.. so how would I know what size resistor to use depending on the size battery ? I deal with 3v batties of many sizes, and 12v batteries both 4ah and 7ah.

[@dignitas1980]

Did u find out what size resistor you have to use? I`m looking for a resistor to match the 18650 batteries, the one used in Bosch/Makita screwdriver with 3.5 V.

[@stevetrubilla755]

This is a very good video. I have leaned somethings from it. Thank you for taking the time to do this.

[@stevennahulak6696]

Thanks. Last question. If I use a 10 Ohm resistor instead, wouldn't I be stressing the batteries even more. Using only a 100 Ohm resistor is ONLY stressing the battery by 15 milliamps whereas a 10 Ohm resistor would be stressing the battery by 150 milliamps. Wouldn't that is better? Stressing an "AA" or "AAA" battery to 15 milliamps would be acceptable but checking a "D" cell battery that is used in a flashlight would require more amperage to light and stressing the "D" cell battery with the lower Ohm would be better? What your opinion on this. Thanks

[@8bitsinthebasement]

You could but I'd suggest that you stick to a 100 Ohm for testing. The reason I used a 4.7K Ohm for the Cell batteries is because the 100 Ohm can actually start draining the cell type batteries during the test. I'd imagine that a 10 Ohm resistor could start draining triple, double A and D cells in the same way. Which would in effect defeat the purpose of testing the batteries in the first place.

[@ptreth]

A 10-ohm resistor connected to a 1.5-volt source will dissipate nearly a quarter watt. Make sure your resistor is rated for that power. In fact, use a half watt resistor. A lower wattage package might get a bit hot. P = E^2 / R.

[@stevennahulak6696]

Good explanation. Does it matter what the wattage of the 100 Ohm resistor is? Can you use a 25W 100 Ohms resistor or even a 1/4W 100 Ohms resistor? Thanks

[@8bitsinthebasement]

Hi Steven, I used 1/4 watt resistors. You could use 25W 100 Ohm ones they should work fine too. Thanks for taking the time to watch and comment ;)

[@pTrailers-yt3sw]

Hi good day. Can you use 1W 100 ohm resistor to test 1.5V batteries?

[@8bitsinthebasement]

@@pTrailers-yt3sw Just saw your comment, yes you can use a 1W 100 ohm resistor to test 1.5V batteries

[@IliyaOsnovikov]

Very good and useful video. However that 100 Ohm resistor value might not be optimal for all sizes of batteries. The old BT-168 battery tester (with analog indicator) allegedly has 4 Ohm and 215 Ohm resistors for 1.5 V and 9 V batteries accordingly. And it takes up to 375 mA of current from it's 1.5 V input to move meter's niddle all the way up. The BT-168 PRO unit that I've recently bought does not have any real load for the batteries built in. It takes just about 7 mA from battery terminals and that makes it much less accurate. My guess is that could be related to the measuring range from 1.2 to 4.8 V. One size load resistor might not be optimal for all batteries. I am planning to modify that tester and put there a few load resistors with some small maintained position switches. Let's discuss what resistor values might be good for all types of round batteries including 18650 Li-ion.

[@why_do_you_want_to_know]

Load resistors won't work as circuit has boost to drive digital display

[@dp2418]

Excellenty video. I'm wondering what size resistor I would need to test 3.6v, 1200mah, 1/2 aa lithium (alarm batteries). About half of these prove low/weak for alarm PIR use at purchase. The power draw of the alarm is 12 mA. Thank you!

[@ps7539]

I got the same batteries and I bought a 300ohm resistor. Without it, used batteries show 3.6v (full). With it, they show under 3.1v. Alarm starts complaining around that voltage it seems. However, still don't know if 300ohm is the correct/ideal resistor for these batteries. Can anyone help?

[@newkeepon]

@@ps7539 I'd use a load that the battery would typically see and test with that resistance.

[@deniscainero481]

Excellent video. Very helpful. Thank you

[@8bitsinthebasement]

My pleasure Denis. I'm glad that you found it helpful and thank you for watching and for your kind comment.

[@dude...are-you-sure]

So there isnt a mode on the meter that you can set the dial to, to get a relavent reading to know if the battery is good. A resistor rig must be made to do this....?

[@8bitsinthebasement]

No, some meters have a setting that will check a battery properly. The thing is that there are a bunch of cheap meters available that work great for testing voltages etc. but don't have a way of properly testing batteries (I've got 3 of them).

[@jaredvw]

I've never understood why the reading changes when you put the resistor across the leads with the alligator clips like that. You would think that the current would take the path of least resistance and just go through the multimeter leads and skip the resistor, thus giving you the same reading on the multimeter for the volts. However, it clearly does not and does go through the path with the resistor. What am I overlooking? Sorry if this is a dumb question!

[@8bitsinthebasement]

I don't think that it's a dumb question at all, in fact it's one I asked myself more than once when I started fooling around with electronics myself. I suppose that the easiest way of looking at it is that by putting a passive component into the circuit like that, you're changing the circuit's properties. The current takes the path of least resistance, but the entire path has had it's resistance increased by the simple fact that a resistor has been placed somewhere along it. A simple analogy might be; If a drop of red dye is put in a bucket of clear water all the water in the bucket will turn red no matter where on the surface of the water the drop falls. I don't know if this really answers your question but it's the best I can do ;) Thanks for watching Jared VW

[@ptreth]

When it is used as a voltmeter, the multimeter's input has a very high resistance. The current flows almost entirely through the resistor. When tested, current also flows through the battery itself. The battery has an internal resistance, which forms a voltage divider with the external load resistor. The higher the internal resistance (i.e., the more worn out the battery), the less current will flow, and the lower the voltage reading will be across the external resistor.

[@why_do_you_want_to_know]

Multimeter internal resistance is much, much greater than load resistor's. Manufacturers do this so meter can read voltages accurately.

[@SoMoMule]

Exactly right. If you study electronics you learn how having resistance in series or parallel changes the total load. The input impedance of a meter is so high that it doesn't have much effect (if any) on the total circuit. 99.9% of the current is thru the resistor.

[@amishpatel80]

I was wondering on why the 100 resistor for a 1.5v AA battery. Wouldn't that put a load of 15ma? That is tiny as most AA have a capacity of 2000mah. Also this is only for a couple of seconds. So even a button cell with 30mah could be put under load for 2 hours straight with a 100 ohm resistor. How would a 2 second test drain the button cell? I'm a noob, but what am I missing?

[@rty1955]

What you are missing is NOT the capacity of a battery (mah) but you are measuring the voltage of a battery. Think of it this way a battery will put out, lets say 1.5v for a period of mA for 1 hour, if the battery at any point in time is less than 1.5v the battery is at end of life, because as the delivered current gets low the voltage will drop. Another way to think of this is a bucket of water (battery) has a small tube (resistor) on it, the water will flow out of this tube and hit a target so many inches away ans will remain that way until the bucket runs low on water, then the stream of water will not be as powerful and turn to a trickle instead of a stream. So what you are measuring is the battery hitting a target (voltage) consistently. A 1.5v battery should be at that rated voltage until the current (volume of stored energy) has gone down, this reducing the voltage. The measurement of a battery miat be done inder a small known load. A large load might drain the battery too fast. Just drain it a little... Hope that helps

[@stevec9669]

Why the 100 Ohm resister can't be used to test the button cell battery, 3v which is between 1.5v and 9v?

[@8bitsinthebasement]

Hi Steve, sorry for not answering sooner, I'm going to paste the answer to your question as I've already been asked it... For each and every battery (depending on voltage and internal resistance) you should use a different value of resistor and if you search the net you will find examples stating 100 ohm for 1.5V, 360 ohm for 9V and various other values for different battery types. In this video I wanted to show a quick and easy way to see if a battery was good without the need to have a bunch of different resistors on hand. The 100 ohm is perfect for 1.5V AA batteries while at the same time being good enough for testing the others. When it comes to small button cells like the CR2032 a 100 ohm resistor will work but it will start discharging the battery during the test. This is the reason a 4.7 kohm resistor is used instead (higher value resistor = less current draw). This discharge happens because button cells have quite a low capacity of +/- 260 mAh, while the others are in the 1600 mAh plus range (the larger load has nothing to do with the fact that the CR2032 is rated 3V). So, the load is more or less chosen to stress the battery enough to show if it can give a high enough voltage reading on the multimeter while striking the balance of not draining it (too much) at the same time. Hope this answers your question you. Thanks for watching ;)

[@stevec9669]

@@8bitsinthebasement Thank you very much for the in-depth and clear explanation. I understand the selection now. Enjoyed and learned from your videos.

[@thomasharlos6872]

Thank you. I did not know I needed a resistor to properly check my batteries. Wasted all those years and maybe batteries, doing it wrong !

[@8bitsinthebasement]

Happy it helped you out, thanks for the comment Thomas ;)

[@आनंदतुळपुळे]

I learned a lot by this video. Thank you.

[@8bitsinthebasement]

I'm really glad that it was useful to you. Thanks for the comment.

[@m.m.95.2]

Hi 8bitsinthebasement , what kind of resistor should i use for a LR626H button cell battery (1,5 V, 20mah) ?

[@8bitsinthebasement]

Hi M. M., you could use a 4.7K ohm or try a 10K ohm resistor to test. That should let you know if the battery still has charge or not. Thanks for watching :)

[@m.m.95.2]

@@8bitsinthebasement Thank you

[@CyberhugTechnologies]

Thanks for bringing this up, it is usually overseen - Happy new year!

[@8bitsinthebasement]

It's a simple thing but not everyone is aware of this. I remember testing a box of used batteries a few years ago and finding that all of them were OK. I found out about this method when none of the tested "good" batteries managed to power things. Thanks for watching and a very happy new year to you too.

[@CyberhugTechnologies]

@@8bitsinthebasement Exactly, it is essential and again thumbs up! i admit i have forgotten many many times to do it properly :-)

[@koningklootzak7788]

How do you test a flashlight battery to see if it's high drain or low drain?

[@grambam]

Great informative and right to the point thanks so much!

[@8bitsinthebasement]

Glad it was helpful!

[@marijandesin8226]

What load should I use to test 9.6V 2000mAh RC car battery please?

[@8bitsinthebasement]

If I were testing such a battery I would most likely use a 100 Ohm load like I used in the video you could go lower if you wanted to. But, I imagine the batterys you want to test are recharagable, if this is the case then you would be better off using the "internal resistance" test method (you can find loads of videos about how to do this on youtube) it tests how well a rechargable battery can hold a charge as opposed to how much charge is left in a disposable battery. Hope this answers your question. Thanks for watching Marijan.

[@marijandesin8226]

@@8bitsinthebasement Amazing! Thank you. I'll look it up.

[@williamdavis4542]

I had a Radio Shack tester that had a low-medium-high load switch. Eventually I noticed the switch was having no effect. I don't know how I could have done that. I never hooked it up to any serious voltage. Since then, I have wished for the knowledge for how to create a load circuit. Now I know. Thanks!

[@8bitsinthebasement]

Glad I could be of service ;)

[@motto666]

I see other videos which they test the batteries with 10A on multimeter, no need a resistor. Isn't it better, more convenient?

[@8bitsinthebasement]

@@motto666 if your multimeter has built in resistance then yeah it's much more convenient, the problem is that the cheaper meters don't have this option.

[@motto666]

@@8bitsinthebasement I see. So 100 ohm resistor, how many watts? Is 1/4 w ok for 1.2v to 9v batteries?

[@8bitsinthebasement]

@motto666 1/4 watt is exactly what I used in the video

[@__-hh3gt]

Hello, thank you very much for the info. How much the resistor to use for inspection lithium ion 3.7 battery 18650 ? Thanks. Greetings from Saudi Arabia.

[@ChibiKeruchan]

what resistor do you suggest for testing 18650 batteries?

[@riprob93]

Wonderful video!! Thanks so much!!👍👍

[@8bitsinthebasement]

Thanks for visiting

[@psysoul]

Great! Thanks for sharing the good way to measure!

[@8bitsinthebasement]

You're more than welcome my friend ;)

[@FAIL-ps2vr]

for double A batteries, 100♎ 5W resistor is sufficient?

[@8bitsinthebasement]

The resistors I use in the video are 1\4 watt, 5 watt resistors will work fine. Thanks for watching ;)

[@FAIL-ps2vr]

thanks for the reply and clarification sir! appreciate it much!

[@glytch5]

I am having an issue with 9v batteries that seem good but won't completely run a circuit. Using a 100 ohm resistor with a voltage of around 7.9 the 9v batteries won't run my tool... what is a dead range for a 9v?

[@8bitsinthebasement]

7.9v is very low for a 9v battery. Normaly on a good 9v you would see a reading of 8.8 at the very lowest. Of course, it also depends what the battery is being used for, a battery can read low and work well enough in a remote control for example where as the same battery won't work at all in the likes of a torch. Hope this helps. Thanks for watching

[@glytch5]

@@8bitsinthebasement so 7.9 under load is "dead" for high drain circuits?

[@8bitsinthebasement]

@@glytch5 Hi, I may have answered too quickly and not very well explained what I ment. Normaly a 9v battery that was just on the verge of being spent would give a voltage of 8.8v or a little less when tested under load. A battery reading like this might work for a while longer in a low drain device but would need replacing. In your case a reading of 7.9v under load would indicate a well spent or dead battery.

[@glytch5]

@@8bitsinthebasement gotcha. Alright! I am testing a ton... what is interesting is this znter 9.4 lithium battery... stays at 9.4 volts under load due to circuitry... and rechargeable. Thanks for the video!

[@jactac879]

Great video but I'm still confused. There is so much conflicting advice on the net regarding resistors and battery testing ! I have two multi testers that both have on board battery testing function, one checks 1.5v batteries at 30ohms, the other tester does it at 100ohms, so which one is putting more load on the battery, and which would be more accurate ? I've read lots on info on the net where some advice recommends testing 1.5v AA batteries at around 30ohms and other advice recommends around 100ohms ? My understanding is that the lower the ohms of the resistor puts less drain on the battery because the lower ohms cause less current flow which then reduces the amount of voltage being taken from the battery that is being tested, is this correct or is it the other way around ?

[@8bitsinthebasement]

The best you can hope to get on testing batteries like this is a ball park on how good the battery is. The main thing is to get a reading while the battery is under load. Actually the lower OHM rated resistors put a greater drain on the battery. You can think of it like this; in a tightly packed concert hall it is very hard to cross the room because you have to make your way accross pushing between lots of people (high resistance). You could cross the same room in no time at all if there were few or no people in the hall (low resistance). Keeping this in mind you can easily imagine how a battery drains more quickly with a lower value resistor. That's why I used a 4.7K resistor to test the button cell. Hope this helps in your quest to better test batteries. Thanks for watching ;)

[@jactac879]

@@8bitsinthebasement , Thanks for replying and explaining. I'm actually in a bit of a debate with an electrician at work about how the resistor works. In your analogy I guess the concert room hall would be the 1.5v battery, but you say you could cross that room easier if the room was almost empty (low resistance), so Im guessing you mean that higher the resistance rating does NOT actually mean more resistance, it equates to easier flow ? So can I use the analogy that my electrician colleague at work is using. So let's say we have two 1.5v batteries, which we'll say for this project are two garden taps, which are then connected to 2 different sized hose pipes, 80mm diameter (80ohms resistor) and a 100mm diameter(100ohms resistor) we turn on both taps (1.5v batteries) and because of the smaller 80mm diameter pipe (80ohms resistor) there will be less water flow (current) going through the 80mm pipe than the 100mm pipe , if both were pushing water (current) through them at the same time. Hope your still awake at this point LOL. So if the water flow (current) is reduced going through the smaller diameter pipe (the 80ohms resistor), then there will be less drain from the tap (1.5v battery) , therefore the tap (battery) connected to the 80mm pipe (80ohms resistor) will hold more volts ? OR. Are you saying the battery (our tap) has to work harder to push the current (water flow) through the smaller 80ohms resistor (80mm pipe) even though the rating figure of the lower resistor tends to imply that it has less resistance ? I think this might be where confusion might be when looking at resistor ratings ?

[@jactac879]

@@8bitsinthebasement , So a 4.7k resistor is bigger than say a 100ohms resistor, which means less resistance as it lets through more current which equates to less drain on the battery ?

[@8bitsinthebasement]

Hi jactac, in my concert hall analogy the concert hall is the resistor. The higher the value of the resistor the more people are in the hall. You crossing the hall are the current from the battery. The less people present in the hall (the smaller the resistance) the faster you can get from one side to the other (the more quickly the battery drains). The more people that are present in the hall the more slowly you can make your way from one side to the other (less drain on the battery). So, higher resistance = lower drain and vice versa. If you want to use the water pipe analogy, imagine a huge barrel of water with a pipe at the bottom to let the water out. The barrel of water is the battery and the water it's charge. The pipe is the resistor. You gave the example above of an 80ohm resistor being a 80mm pipe and a 100ohm resistor being a 100mm pipe. I think that this is the crux of the misunderstanding. In fact the greater the value of the resistor the smaller the diameter of the pipe. So the 80ohm resistor would be the 100mm pipe and the 100ohm resistor the 80mm pipe. With no resistance a battery will drain quickly With high resistance it will drain slowly Also, the higher the resistance the more the voltage from a battery is reduced (that's why resistors are used when powering LEDs and why this battery test is effective) Hope this helps Now I got to go sleep ;)

[@8bitsinthebasement]

The 4.7Kohm has more resistance than the 100ohm resistor, 47 times more in fact. This means that the 4.7Kohm will let a lot less current through than the 100ohm would which means that the 4.7Kohm will drain the battery less.

[@utubeape]

This is just what I needed, I want to dismantle broken 18v tool batteries and add new cells but need to find out which batteries to keep - I havent bought a multi meter yet, there is a bewildering choice. Do you know if any multi meters have it built in so that I don't need to build the little resistor cable that you made, or just switching to the Ohm stting will do the same thing?

[@8bitsinthebasement]

Glad I could help

[@9675gappa]

Great video. Can you tell me what size resistor you would use to test LS14500 Saft "AA" (2.6 Ah) & LSH20 Saft "D" batteries (13 Ah)? Both are 3.6 volt

[@8bitsinthebasement]

Hi, sorry for taking so long to get back to you. I don't know anything about the batterys you want to test. I did however have a look for you and found the following site that recomends using a 200 OHM resistor to test LS14500 Saft batteries www.shearwater.com/announcements/performing-saft-batteries/ I hope that this is some use to you.

[@mattg2106]

you can use an online calculator. You need to know what the ah/mah rating of the battery is and you should aim to test no more than 1/10th of this. You can then plug this mah value and the volts into ohm's law and find the appropriate ohm battery. The reason 100 ohm is used for AA and similar batteries is that they can deliver a pretty high amperage safely. button cells deliver much lower power (20-100mah typically), so you need a higher resister (and 4.7k ohm seems to be used in a lot of videos!) to ensure you don't damage the button cell by drawing to great a current. All mistakes in the explanation are mine :-) suggest you use proper calculators before doing anything daft!

[@benhaze1010]

@@mattg2106 Great approach. Now you are pointing us toward the right mindset if wanting to test other batteries.

[@kashyap1991]

what if it’s a rechargeable battery does the voltage changes when the battery charge is low or charge is high

[@8bitsinthebasement]

Yes it does, but the true test of a rechargeable battery is how long it can hold it's charge for. As a rechargeable gets older it needs to be recharged more and more frequently. Thanks for watching

[@keepitshortnsweet]

@@8bitsinthebasement Do you have a video tutorial for testing rechargeable LiPo batteries?

[@agittrain]

this is very informative for a total electronic newb - question - where can I pick up one of those 100 ohm resistors with the clips? I am in the US.

[@8bitsinthebasement]

Hi agittrain, thanks for watching and your kind comment. I bought my clips and resistors from Ebay and assembled them myself. I can't say that I've ever seen them sold pre-made. But it makes for good soldering practice making them yourself and it's cheaper than a battery tester (if you have a multimeter of course).

[@SteveSmith-kf9on]

Good vid mate, many thanks 👍

[@8bitsinthebasement]

Glad you enjoyed it

[@Buck2901]

WoW! Super good information. Thanks for posting this test video.

[@8bitsinthebasement]

Glad it was helpful!

[@hphp7587]

i would like to test 3.7v liion / lipo batteries for battery backup time. Could i just hook up a 100ohm resistor and test the voltage dropping over say 3 minutes on a known good battery and use that data to compare other batteries? also how much watts should the resistor be?

[@zonykel]

What resistor would you use for a hybrid battery module from a Prius? The modules are 7.2V and have a nominal capacity of 6,500 mAh.

[@rty1955]

Simple, do the math..... Suppose you want to drain 20ma from the battery, you would two resistors 1 for current limiting the other for a load assume each resistor will drop 3.6v each (1/2 of 7.6v) the resistors will have a current flow of 20ma (.02) Ohms law will dictate that each resistor should be 180ohms. Since each resistor is consuming 3.6v @ 20ma the wattage (again using ohms law) would be .07 Watts. Now 20ma is tiny compared to the battery capacity so you should size your resistors to draw much more current to get an accurate voltage level of the battery. Try a a value of 1/100 of the rated value. And leave it on for an hour, then do the math amd see if the actual capacity of the battery is correct. UPS systems do this all the time to give you an idea of how long the UPS will last, unser the current power draw. If the time is too low, you will get a warning light to change the batteries. For example if a battery is rated for 1000mAh this is full load. Meaning the battery will deliver the same voltage @ 1000mAh (1 amp) for an hour. If you place a resistor that will draw 100mAh, the battery should last 10 hours (100 x10) you can easily calculate the expected capacity of a battery

[@fabriziodalembert5916]

Would you suggest a "rule of the thumb" to pick the most appropriate resistance for testing any household battery? Is it related to the mAh value?

[@8bitsinthebasement]

a 100 ohm resistor seems to work well for most anything. The choice of resistor is related to the mAh value the rule is the lower the mAh value of the battery the higher the value of the resistor used. Hope this helps.

[@acs8-bitzone651]

Very good technique. I have been taking the shortcut approach too often lately. I'm going to make up the little loads now!

[@8bitsinthebasement]

I'm happy you found it useful.

[@marcialperal7155]

Thanks for the informative video. Did you use 100 ohm 1W?

[@8bitsinthebasement]

I used 1/4 watt resistors because that's what I had on hand. You can use 1 watt if that's what you've got. I'm glad you found it useful ;)

[@Progressive.G]

Brilliant video mate 👍

[@mug2y]

Cheer fella, good instructional video 👍

[@8bitsinthebasement]

Delighted you found it useful ;)

[@Deee-yz9rj]

Thanks, where can I get a resistor?

[@8bitsinthebasement]

You should be able to pick up a resistor in most any electronics shop or a quick search on ebay will find some.

[@Gigantortacoma4x4]

Well tell us where we’re supposed to get that wire resister at to perform this test.

[@8bitsinthebasement]

Hey, you can get these 100 ohm 1/4 watt resistors in any electronics shop or ebay, thanks for watching.

[@brain2g]

Great video. So I have readily available 1&2 k resistors would this be suitable for testing AA,AAA,cr123's and 2032's ?

[@8bitsinthebasement]

You could go ahead and try them. Although the 1K resistance is a little high for the AA and AAA batteries you should still get some indication weather the batteries are good or bad. Putting two 2K resistors in series will give you a 4K resistor which is fairly close to the 4.7K you need for the 2032s. So you could use what you have on hand. In any case they will let you know of a batteries health better than if you don't use a resistor at all. Thanks for watching Brian.

[@jackMcRyder]

@@8bitsinthebasement any idea about the CR123 ? It’s a 3v but probably strong mAh.. I’m thinking it could go with the 100Ohm again.

[@davidanderson4091]

How about testing Lithium AA 1.5v - still use a 100 Ω resistor?

[@8bitsinthebasement]

Sorry for the delayed response David. The problem when testing lithium batteries is that they are designed to give maximum voltage until they are spent, this means that even if a 1.5V lithium had very little power left in it it would test as good using this resistor method. To be honest I know very little about lithium (single use) and lithium-ion (rechargeable) batteries but from what I've read about them (your question sparked my curiosity) it is difficult to gauge just how much charge they have left using any method, it seams that a common way to get an idea of remaining charge is to place them in a device such as a camera or GPS which is capable of showing the battery power remaining. It's not much of an answer, I know. I'm sorry that I can't be of any more help than that.

[@davidanderson4091]

​@@8bitsinthebasement Thanks for getting back to me. I own a small camera shop, and one of the difficulties I face is that when customers bring me an AA powered camera with lithiums installed that won't power on, there is no immediate test to determine if its flat batteries or a dead camera other than breaking out a fresh lot of batteries. If "voltage under load" is the deal here, then I might do a little experimenting. I have a 200 Ω rheostat in my worship, so could try placing a brand new AA lithium under load and adjust the rheostat to see how much load is required to get a significant drop off in voltage. I could then compare that with some known flat AA lithium batteries that won't power a digital camera. From there it should be simple enough to find an approximate point where the resistance will supply the necessary load test. I'm picking it will be quite low, therefore high current so I²R applies - the resistor might need to be a couple of watts rating.

[@stefanssonman]

@@davidanderson4091 I don't know this for sure personally but according to bloggers this battery tester is a very good reliable tester for household and button batteries... But expensive as hell... But as you run a business that relies on an accurate reply to customers it may be well worth it... ZTS Multi-Battery Tester (MBT-1), on Amazon it is 183$ Canadian. I did a web search and ebay has them for a bit less and I did see a online store in New York that was selling for 67$ US but they never answered my email question regarding shipping to Canada. Hope this helps.

[@johnnyflanker6553]

Good day ! My question is very similar to Mark’s …..what criteria did you use to determine the resistor value for testing ? By the way great demonstration !!

[@8bitsinthebasement]

To be honest, there is a formula to determine the resistor values to be used dependeant on the battery to be tested's make up but I know little about it. I simply did a little research on the web a couple of years ago and combined the information from a number of sites to cobble together the method (including the resistor values) I've shown here. I'm happy you liked it and thanks for taking the time to comment.

[@benhaze1010]

@@sarsaparillasunset3873 You mean while pushing on a button to create a load? I doubt par\tic loads are enough to test batteries. Also not sure it is the best way to test 2 batteries in parallel.

[@Etcher]

I was given an old 486 motherboard a while back with a 20 year old lithium 2032 battery. Now I know why I was seeing 3v on that battery!

[@8bitsinthebasement]

Glad I could help you solve that mystery.

[@miguelbarrero5572]

Which resistor should I use to test 1.2v NIMH batteries, is a 100 ohm good ??.

[@jamescordon8133]

I'm reading the comments looking for the same information?

[@stevec9669]

Can I use this resistor method to test a lead-acid car battery? Using a 100 ohm or 3K ohm resistor? Thanks.

[@8bitsinthebasement]

Honestly, I'd stick to using this method only for batterys you would find around the house. Car batteries are much more powerful than batteries that power household objects and so would need larger loads that could cope with stronger currents. You could try if you really wanted to but I'm not sure how accurate the results would be.

[@stevec9669]

@@8bitsinthebasement Thank you for the info.

[@nigeldenning5810]

May I ask you to confirm the resistor sizes, please? It makes no sense to me that the bigger batteries need a 100 ohm resistor to test them, but the little button battery needs a 4,800 ohm resistor! I'd expect it to be less. Can you explain, please?

[@8bitsinthebasement]

I confirm that the values are correct. It is weird that the smaller the battery the higher the load and I wondered about that myself at first but let me paste in part of a response I made to the same question a year or two ago to try to explain the reasoning. "for each and every battery (depending on voltage and internal resistance) you should use a different value of resistor and if you search the net you will find examples stating 100 ohm for 1.5V, 360 ohm for 9V and various other values for different battery types. In this video I wanted to show a quick and easy way to see if a battery was good without the need to have a bunch of different resistors on hand. The 100 ohm is perfect for 1.5V AA batteries while at the same time being good enough for testing the others. When it comes to small button cells like the CR2032 a 100 ohm resistor will work but it will start discharging the battery during the test. This is the reason a 4.7 kohm resistor is used instead (higher value resistor = less current draw). This discharge happens because button cells have quite a low capacity of +/- 260 mAh, while the others are in the 1600 mAh plus range (the larger load has nothing to do with the fact that the CR2032 is rated 3V). So, the load is more or less chosen to stress the battery enough to show if it can give a high enough voltage reading on the multimeter while striking the balance of not draining it (too much) at the same time. At least that's my understanding of it." I hope this answers your question Nigel. Sorry for the late reply and thanks for watching.

[@nigeldenning5810]

@@8bitsinthebasement Ah, that makes sense. Thanks

[@brightonmusic]

What Ohms resistor to test a 12v car battery?

[@berwynsasek9046]

What load do you use for CR123A battery for testing?

[@P_Lou]

What a freaking video I stumbled upon. This video combined with this picker upper I just smoked I feel like I can’t be stopped. WOOOOW.😢 Thank You. It’s like you just helped be solve The God Theory, now I’m in my way to solve the world and fix EVERYTHING in my To Do List Rolodex. #UDaRealMVP

[@8bitsinthebasement]

Excellent, happy to help. Who'd have thunk that the key to fixing everything was wrapped up in testing batteries? Take care of yourself and thanks for the comment ;)

[@xenarthranex]

Is a 5k Ohm resistor close enough for a CR2032?

[@8bitsinthebasement]

I'd say give it a shot, it should give you a good indication of weather the batteries good or not.

[@shahidzaman4955]

Sir I have 18650 batteries.when I checked it's voltage then it showed 3.7 voltage ( good condition) but when I put them in my powerbank then it's back up was very weak almost 10 minutes for 5 18650 cells is the cells amps zeo? Regards

[@8bitsinthebasement]

I have very little experience with Li-ion rechargeable batteries like the 18650. I believe that the best way to test them is using the internal resistence method (you can find plenty of videos on this on youtube). I'm sorry that I can't be of more help to you than that.

[@shahidzaman4955]

@@8bitsinthebasement thanks for your help Regards

[@dicekoh1498]

I have to subscribe and like this video it was very informative ❤❤❤❤❤

[@8bitsinthebasement]

Thank you so much, I'm really happy that it was of use to you ;)

[@bradspitts3077]

Does this same test work for rechargeable AA batteries like lithium-ion 18650 batteries?

[@8bitsinthebasement]

You could use this test for rechargeable AA batteries if you wanted to. 18650 batteries however I don't know a lot about apart from the fact that they are larger than AA batteries and give a voltage of 3.6/3.7 volts when fully charged. I believe that testing on this type of battery is more accurate if you use the internal resistance method. Thanks for watching Brad.

[@pTrailers-yt3sw]

Hi good day. Can you use 1W 100 ohm resistor to test 1.5V batteries?

[@8bitsinthebasement]

You can, I used 1/4W resistors so 1W should work just fine. Thanks for watching ;)

[@236vic]

Hi so how do you work out what type of resistor size to use ?

[@8bitsinthebasement]

To be honest, when using this method I would use whatever resistor I have lying around (usually around 100 ohm), it's not all that scientific I'll admit but testing this way is useful to gauge if a battery has power left in it or not. But please keep in mind that it's not a good method to test rechargeable batteries at all. Checking those involves testing how long they can hold a charge more so than the charge that they have. Thanks for watching.

[@szar2257]

hello on equick question ,this small cirquit with battery and resistors considered to be in series on paraller?

[@8bitsinthebasement]

Hi, if I understand your question correctly the answer is neither. To have batteries in a serial or parallel configuration you would need to have two or more batteries connected. Negative to positive poles if in series and positive to positive and negative to negative poles in a parallel configuration. In this test I am simply joining the positive to negative of one battery through a resistor and measuring the voltage. I hope this answers your question.

[@szar2257]

@@8bitsinthebasement thank you

[@tertia0011]

@@szar2257 Battery and resistor connected as in the demonstration is a series circuit - a single resistor connected in series with the DC battery.

[@sky16678]

This video is awesome not just because of the correct information but because of the elaborate explanations and replies, so much time u took for all of it, thank you for being kind to everyone.❤ Also does this method apply to rechargeable batteries? I mean if we fully charge them and do this load test, will the results be interpreted the same way as non rechargeable batteries?

[@8bitsinthebasement]

Thanks for your great comment ;) This method is not great for testing rechargeable batteries as they can charge fully and retain their charge even at end of life (so they would show up good with a resistor test such as this one). The problem is that an old rechargeable battery doesn't hold its charge for very long under use... so, it might test as good but provide power for just a few minutes before needing to be charged again. Hope this answers your question

[@sky16678]

@@8bitsinthebasement okie so basically rechargeable batteries would show reduced usage time and that will be the sign that need to be rested in peace✌️. Thank you again .

[@Chuckolicious]

I used a 25 watt, 3 ohm resistor to test D batteries, seemed like the selection of choice amongst the various sources I found.

[@8bitsinthebasement]

Thanks for that Chase's Things. I made this video to show how to quickly test batteries around the house. In a perfect world each battery to be tested would have it's own exact value of resistor, so I suppose that it makes sense that a 3 ohm resistor is used on a D cell, the battery would have a much higher mAh rating.

[@paulbecker1843]

Can you use a 4.7 ohm resistor to test button batteries, or does the resistor need to be a 4.7k ohm resistor?

[@8bitsinthebasement]

Hi Paul, No, a 4.7 ohm resistor won't really do much good for you in this type of test. You want to have a lot more resistance to simulate a load on the battery. A 4.7K ohm resistor gives 1000 times the resistance of a 4.7 ohm (so, 1000 times the load that a 4.7ohm would give). Hope this helps.

[@paulbecker1843]

@@8bitsinthebasement Aprreciate you taking the time to reply.

[@bradysolaem2467]

What about car batterys how many ohm?

[@reifenabhobeler4331]

Thanks for the video and the simple solution for using a DMM for battery testing :) What I miss is which current are used if using the resistors

[@8bitsinthebasement]

Sorry, it's been 5 months since you left a comment and only now I'm answering you. The resistors I used in the video are 1/4 watt. Thanks for watching

[@jonathanmason2569]

100 ohm resistor. How many watts?

[@8bitsinthebasement]

I had 1/4 watt on hand so that's what I was using

[@englishrupe01]

Great info.....many thanks!

[@8bitsinthebasement]

Glad it was helpful!

[@bradysolaem2467]

Excellent love it testing car batteries w load them so i knew there had to be a way for these

[@oscarlofgren8592]

Thank you! This is just the information I've been looking for as I'm about to order some resistors for battery testing :) Could you recommend what Watt-rating is appropriate for the resistors in this case? Cheers

[@8bitsinthebasement]

Hi Oscar, I bought a large selection of through hole resistors a couple of years ago. They are all rated 1/4 Watt. I use these for many of my electronics projects and it was these same 1/4 watt resistors I used to test the batteries. Glad the video was helpful to you. Take care ;)

[@cuanhogan4330]

@@sarsaparillasunset3873 The TV remote does not put the battery under sufficient load

[@IrishFuryan]

How do I determine what ohm resistor to use testing an 18650, 3.7 nominal cell, lithium ion.

[@8bitsinthebasement]

Sorry for the delayed reply. This way of testing is great for alkaline batteries but not so much for recharagable batteries like the 18650. A much better method for testing lithium ion cells is to use the "internal resistance" test method. Internal resistance will let you know if the cell can hold it's charge once it's been fully powered up and by extention if the recharagable battery is still any good or not.

[@djnixmixMTL]

Finally someone that confirmed what I suspected 🤭

[@8bitsinthebasement]

Happy to be of service ;)

[@DetroitBecomesBuddha]

For a 18650, how many ohm resistor should we use?

[@8bitsinthebasement]

You could use a 100 ohm to test it but really as it's a 18650 rechargable battery the thing to test is not how much charge it has left but how long it can keep it's charge (how long it can function between charges). This is tested using the internal resistance method of testing. Hope this helps. Thanks for watching.

[@DetroitBecomesBuddha]

@@8bitsinthebasement thanks. I will do as you say.

[@Nordraw]

Why can’t they make a tester with a resister built in?

[@8bitsinthebasement]

They do, well most of them do anyway. I made this video to show how to test a battery if you only had a multimeter at home. Thanks for watching ;)

[@jdt6450]

1/5 watt 100ohm?? Or?

[@8bitsinthebasement]

I used 1/4 watt.

[@30mAkills]

Battery measurement - Unity UT151A multimeter : 12 V = Built-in load resistance: 240 ohms 9 V = Built-in load resistance: 1.8 K 1.5 V = Built-in load resistance: 30 ohms

[@davidfalconer8913]

A ( very simple ) way to test 1v2 to 3v7 tube cells is to take a 4 Volt Tungsten lamp from an old Christmas tree light string and add two test leads .... compare the bulb's brightness with a new or fully charged cell ( tried - n - tested ) DAVE™🛑

[@sanjogkumarbarik7460]

nice video ... clear explane...

[@8bitsinthebasement]

Glad you liked it

[@jungleb]

Thank you legend!

[@8bitsinthebasement]

Happy it helped you out :)

[@chifonlesley3011]

wow thats great thanks very much sir

[@8bitsinthebasement]

Thank you very much.

[@sightseer1000]

I always thought, under load, meant testing the battery while is on operation. I learned something today Thanks

[@rhm504]

Nice video.

[@8bitsinthebasement]

Many many thanks

[@lara1731altaweel]

does anyone know the scientific reasoning on why it gives such a low voltage when connected to a load?

[@Sulfen]

Because the batteries are very low but when you test them without a load it can output the same amount of voltage as a brand new battery most of the time. When you put a load on it the battery shows its true weakness. Sort of how you can roll a car downhill and it seems light but when you try to push it uphill (under load) it suddenly shows its true weight.

[@danielcapitao240]

very good information Thank you

[@8bitsinthebasement]

You're welcome ;)

[@carlsimmons3347]

Thanks

[@8bitsinthebasement]

Welcome

[@MadScientist1001]

what about rechargeable batteries

[@bradysolaem2467]

Dont have load tester at home just in the shop

[@shadowpapito]

THX

[@8bitsinthebasement]

You're very welcome ;)

[@miijjk]

But I'm getting a 1.68

[@DIYHouseGenius]

enjoyed but to test laptop batteries appreciate

[@8bitsinthebasement]

Sorry for taking so long to reply to you. A laptop battery is rechargeable and requires an internal resistance test. This testing method requires a data sheet for the battery you want to test and some math after taking readings. There are plenty of documents describing this test method on the web. I may make a video on it some day, but I'm making no promises ;)

[@lesstime1678]

were is the old multimeter?A old meter is a meter W/needle ,,,,,,,,,(ANOLOG) meter not a digital meter assho888888888888888888,like the ones i have ,,,meters w/tubes from 1950 ,,,that is a old meter assho***********..........not a digital meter ,,,,,,,please d:ont call that a old meterplease

[@8bitsinthebasement]

Should work just the same with an old analogue meter. You know that digital multi meters came out in 1977, making the tech 46 years old right? Now I see your point, but I fail to see how the title of the video makes me an asshole but whatever.

[@lorenzodeimoz6028]

The idea is to teach how to use the Voltimeter

[@8bitsinthebasement]

No not really, I made this video to show that in a lot of cases a resistor needs to be added to a voltimeter to give an accurate reading when testing batteries, that's all. When first I got a multimeter I used it to test a bunch of batteries I had in a drawer and most all of them tested fine (I had looked online to see how to test them and the method I found used no resistor at all). When I used my "good" batteries I found that they were empty, so in trying to find out where I went wrong I learned that a battery must be under load when being tested. That is all that the video is showing. Thanks for taking the time to leave a comment it's much appreciated ;)

[@koningklootzak7788]

How do you test to see if a flashlight battery is high or low drain?