How to capacity test NiMH Rechargeable AA batteries

[@Svafard]

Super useful for someone who uses a lot of rechargeable batteries but has no idea what those V and A mean, and especially how to use a multimeter. Thanks to you I figured out the culprits in my battery collection.

[@racketrick]

Boy, do I need a very basic intro to batteries video lecture/tutorial !!! I learned a little when studying the different 18v NiCd batts for my old Bosch cordless hand tools; but I need somebody to speak to me like I don't know nuthin'!

[@spagooter9]

Listen. I just found an unopened 8-pack of white Eneloops that are 15 years old and decided to see if they would still be any good. Mind you, this is the first time I've used rechargeable AA batteries since I started using them for my VR controllers. I knew nothing about NiMH batteries other than 1.2V runs fine on most devices requiring 1.5V alkalines. Anyway, I went down a deep rabbit hole until I found this video while trying to figure out how to check the battery capacity. The words multi-meter and capacity tester have never even crossed my mind until today. But you explained everything so well and at such a perfect tone and pace that it made me just want to keep learning despite this being completely out of my skill set. I probably won't get these testing devices, and instead just charge up the 15 year old batteries and hope for the best. But now thanks to you, if someone ever mentioned "multimeter" or "capacity tester" I can finally say "Oh yeah I know what that is. 😎"

[@ConeJellos]

What in the absolute fuck did I just read?

[@stevec9669]

I didn't know you can directly measure their amps like that and not ruin anything. Very handy and quick method. Thanks much.

[@summetj]

It only works because the total amp output of a AA battery is less than the 10 amps the meter can handle for a brief amount of time. You are essentially measuring the current powering a dead short. (In the multimeter, so you certainly wouldn't want to do it with a larger battery.)

[@Herbridge]

Having been looking for this for years...Thank you Jay

[@PaulSmithUSA]

Great video, I finally found out how to use my multimeter correctly and was able to test my rechargeable batteries and throw the ones away that didn't work. Many Thanks

[@OXP-r4k]

were you able to test the mWh using multimeter?

[@HamidKarzai]

@@OXP-r4k i dont think its possible to test the capacity with a multimeter, at least not in a way that isn't very inconvenient. maybe you could hook the battery up to something with a known fixed power draw like a LED light then you could measure how long it takes to discharge (perhaps using the time-lapse functionality found on most cameras). you could then multiply the time the light was kept on by the power draw of the light to get the capacity. or you could not bother with such hassle and buy a capacity tester like the one in the video

[@Horvath_Attila_1126]

Exactly the information I looked for! 🙏🙇 I bought rechargeable batteries in 2012 and they started draining super fast now in 2024, like in a few weeks while the recharge pod said they are fully charged in like 20 minutes. The worst rechargeable battery resulted 0.015 in 10A⎓ 😅, but it is still able to run my analog-clock like two weeks before it stops. The one with 2.810 in 10A⎓ is still able to run my work PC wireless mouse for a month. I tested it! It gave up on the 41st day. So it's still usable, I just have keep in mind to recharge monthly. 🤷👍 PS. Rechargeable batteries are awesome! The mines are AA, Uniross, Ni-MH, 2100mAh lasted more than a decade with good care. Putting them in refrigerator in not used, charged them before fully drained). I hope the new ones (as I reach the need of buying more) last just as long! 🙏 Thanks again for the precious knowledge and the very well made visual demonstration! ⭐

[@summetj]

10 years is a good run.

[@rondarider4382]

This is money tips! Good tips on using multimeter to evaluate the good and bad battery and segregate it for difference purposes👍👍👍

[@rhm504]

Yes! This is EXACTLY the explanation/test I was looking for. Thank you for the post. Well done video.

[@jimhoward1655]

Fantastic! I was about to order a fancy charger tester but thanks to you i can save my money! I have a working charger and lots of multimeters and woth the knowledge you've shared i can weed out the weak cells. Thank You 😊

[@lagosite]

What a great tip! Been looking for a testike this for a while as I have a pile of rechargeables that I couldn't tell for sure we're good or bad. Thanks!

[@F16_viper_pilot]

Your video helped me reclaim a seriously messed up NiMh battery that would not hold a charge after sitting in storage for about three years. It would hold about 7 milliamperes then the PowerEx MH-C9000 charger would refuse to charge it, giving a status of “HIGH”. I would try to discharge it, and it would quickly discharge, but an attempt to charge would result in the same issue of minimal charge. I tried both the cycle option and analyze option of the charger, but they refused to cycle properly due to the “HIGH” condition during charge. I tried various charge/discharge current combinations (both high and low), but nothing worked. For the heck of it, I decided to try to short the battery through my multimeter current setting. I saw about 2 amps for about a second or so before the measurement would quickly decrease. Surprisingly, when I went to charge the battery, I got about 40 milliamperes of charge before it would refuse to charge further. I shorted the battery once again through the meter, and saw about 3 amps flow with a longer duration. I then started the charging process again and the battery charged properly. In fact, it charged about 500 milliamperes past its rating, which worried me as to whether it is damaged since the other batteries of the same make are about half an amp under the rating. I’m currently running it though cycles to ensure it will work properly before putting it back into service. Your video inspired me to try shorting it through the meter as a means to shock the battery, and I’m hoping it turns out to be a possible method for dealing with troublesome batteries that refuse to respond to other methods.

[@summetj]

Smart chargers will sometimes refuse to charge a battery if the voltage is too high or too low. A "dumb" power supply can be used to "top up" a low battery until it holds enough charge for a smart charger to accept it. In your case, with the cell voltage being too high, I would expect that there is something chemically "wrong" with the cell, and would not expect it to provide full capacity even if you are able to "kick start" it. It sounds like by drawing a short high current pulse of power out of the cell you lowered the voltage enough for the smart charger to start to deal with it. However, I would suspect that cell will never be "as good as new".

[@F16_viper_pilot]

@@summetj Yeah, the victory was short lived. It was acting erratically during charging and discharging, giving inconsistent capacity levels during charges and discharges. It also was sensitive to current levels during the charging, not accepting the full amount then suddenly accepting it. It went back to its previous behavior of not accepting more than a few milliamperes then registering “HIGH” again on the charger. I finally measured the internal resistance at somewhere between 380 and 450 milliohms. Looks like this battery is not salvageable. I don’t think this battery set ever got used, simply charged and stored. That seems to be one potential downfall with these rechargeable cells is that they don’t like being ignored for long periods.

[@goxy287]

Didn't know about the 10amp trick, very useful.

[@duncanlemay7446]

Great video on the subject! This was super helpful to me since I am using rechargeable batteries with wireless microphones and trying to figure out when to replace them. Thanks!

[@johnviera3884]

awesome video those Panasonic Eneloops are indestructible

[@summetj]

I've been pleased with them.

[@fattoamanowoodwork3638]

Really great informative video. Didn't have a clue before. Thank you good man.

[@E85_STI]

I have a fluke 77 but it won’t read the mah with the method you tried but I just need to see what these double As are reading and they are new at 1.5v I’m wanting to use an AA to D adapter so I can easily use that as a D size battery for a fan but I don’t want the mah to be too high and mess the fan up as that happened one time and I had to replace the fan.

[@jonwzee]

Great video! I just wish you gave some review/info on the OPUS internal amperage "quick test" mode. I don't have an amp measuring multimeter, so I'm hoping the OPUS quick test is a good measure of how well a battery can provide power to small motors.

[@bikhard1078]

I have a question when you checked the AA battery the voltage should be around 1.2 volts and then you checked the amps which some were around 7 -9 amps. Does this apply to AAA batteries @ 1.2 volts and 7-9 amps is good ? And 9 volt batteries what voltage and amp is acceptable?

[@summetj]

Any NiMH cell will be around 1.2 volts fully charged. For AAA batteries, I would expect less current production. {CAUTION: Don't try it with C or D cells, as they may make enough current to blow the fuse on your multimeter, as all of that amperage is going through the multimeter.}

[@larsbecker2003]

I bought new aa nimh batterys, tested them and the multimeter says 1.3V and 3.5 A but when i put them in a charger they get really hot and the charger too. Could it be that they are fully charged? I dont want to overcharge them. The Batterys are 1.2 NiMh AA rechargeable Batterys and i try to charge them with a 1.2V 200mA 1x4 charger.

[@Zuzoz]

Just 2 questions about the amp fuse rating of the multimeter: - If it's rated 10 amp, why is it bad to short the batteries (producing 7-8 amps) through the fuse for not a very short but longer time? I mean it's lower than what the fuse can handle, so why would it hurt the fuse? - If a meter has a 20 amp fuse, would it be much safer to do the amp test or just a bit?

[@summetj]

In this case I am thinking about the safety of shorting the battery, not the fuse. Shorting the battery means that you will draw as much current as the batteries' internal resistance will allow, and this high current draw will heat up the battery quickly. When doing it for just a second, the thermal mass of the battery will prevent this heat from getting too high but if you keep it up for longer you may have chemical changes in the battery that are bad for it due to excessive heat. (Potentially up to a runaway thermal event, although that's more likely in lithium batteries than NiMH. I certainly don't recommend doing this with a lithium battery as they have a much lower internal resistance and can produce a lot higher amp output.)

[@glleon80517]

Rather than a dead short, I recommend that a series resistor in between the battery and the meter to create a voltage drop and save the fuse. I use a cheap 200 ohm linear potentiometer which can be adjusted so a fresh battery with good voltage can draw about 500 ma. A bad battery will not draw even that with the pot turned to minimum (zero amps) as you showed. A double A 1.3 volt rechargeable battery should be good for about 1,300 maH. Not sure but a dead short even for a second could be hard on the battery even for a NMiH. Good video!

[@summetj]

Agreed that would be safer, but for AA's I omit it just for the speed.

[@macboat1]

I have an Opus BT-C3400 charger, similar to the one you're using. It too can charge at four batteries at 1000 mA. Why did you choose 500 when you could use 1000? I'm assuming it is bad for the batteries to charge that quickly, is that correct?

[@summetj]

Yes, I would not recommend charging faster than the "1C" rate unless you are in a hurry. 1A probably would be fine for a NIMH AA cell, but no harm in using the default 500mA level.

[@ChibiKeruchan]

this video are so useful since I am planning on buying several battery powered LED bulb that turn off and on with motion and light sensors. Do you have a version for lithium capacity test?

[@summetj]

Output current capability is not a great analog for LiIon battery capacity (even weak cells can put out a lot of current). Most 18650 cells will easily put out 10 amps and blow the fuse in your multimeter if you tried this. About the only way to reliably tell the capacity of LiIon batteries is to use a charge/discharge tester like I show in the end of this video or this video: kzbin.info/www/bejne/p3uVeoerd9F1m5o

[@vnitmechite2003]

Hi there...nice video I have two questions: 1. Can I use combination of 1800 mAh and 2400 mAh rechargable battaries in my apple magic mouse. Both are 1.2v. does mAh rating will create any issue in d mouse ?? 2. My other AA rechargable battaries are showing amperes in the range of 200-300 mAh when checked in multimeter ( these are actually supposed to supply atleast 1800 mAh). Are these batteries dead ?

[@summetj]

You can mix batteries with different capacities as long as they are both NiMH cell chemistry. However you will only get as much power as the weakest cell. You cannot measure true capacity with the multimeter technique but if they are not pushing at least a full amp and they are double a cells it is likely they are weak.

[@R3cce]

Is it safe to short nimh batteries (the amp test you have done)? I mean, can the batteries explode or something

[@summetj]

The bigger worry is that you will blow the fuse in your multimeter. Mine has a 10 amp fuse, so I can do this with double A's and triple A's but probably wouldn't want to do it with a d cell. Shorting the battery for half a second won't raise its internal temperature enough to be a fire risk.

[@R3cce]

@@summetj Thanks for answering. My multimeter can actually do 20 amps but it has no fuse. It says “20A max unfused”

[@summetj]

@@R3cce It's probably safe to use it to test AA batteries in this way (mine has a 10 amp fuse and has never blown it). But you wouldn't want scale up to larger batteries, because as soon as a battery is able to deliver more than 19 amps it may at some point cause something inside the multimeter to "act" like a fuse, and since you can't just replace the "fuse" it would basically ruin your multimeter.

[@R3cce]

@@summetj I have an interesting case here. 2 of my nimh batteries show zero volts on my multimeter. I charged them all the way and they still show zero volts (even after fully charged). I am not sure if i should dispose of them or is there a way to “jumpstart” them to show voltage. They are a few years old and i left them unused for a long time. It is really strange because i got 4 in a pack a long time ago (2x 2000 mah and 2x 2450 mah). Both the 2450 mah ones has the above issue. The 2000 mah ones still work great.

[@summetj]

@@R3cce If they do not have any voltage after charging, it is time to dispose of them at a household hazardous waste site.

[@Magolote]

Thank you brother! So, a AA battery is fine on a 7 Amps reading; what about a AAA battery?

[@summetj]

I'd expect a good AAA battery to provide at least 3 amps to a short.

[@flashcraft]

Thanks for the video. I haven't tested for amperage before. I just check for output voltage with a battery tester or multi-meter.

[@summetj]

That works fine for alkaline or lead acid cells or the voltage is directly correlated to the charge level, but within NIMH cells they can maintain a high voltage even with low capacity.

[@miksterr]

Question- what about either larger capacity cells and also packs- say 4x AA for hobby use? How can capacity be checked?

[@summetj]

I wouldn't do C or D cells this way, as they can produce enough amps to burn out your multi-meter fuse. Theoretically a pack of 4 AA's IN SERIES could be tested in the same way, as the amps would be the same, but the voltages would be higher (but most multi-meters can go up to hundreds of volts). However, if you tested a set of series cells and found it had a low amp draw, you would then have to test each individual cell to see which one or ones caused the problems. [Assuming you didn't want to throw out good cells along with bad cells...]

[@KellyBrainard]

What would your minimum amperage rating be to keep a battery? Seems like over 6 is pretty good, under one not much use. Would you keep ones between 1 to 3 amps for remotes etc.?

[@KellyBrainard]

Also, thanks so much for this video! I sure seems like at this point there should be an easier way to test these suckers!

[@summetj]

I guess *perhaps* for a remote a 1-2 amp AA might work, but in my experience anything under 4-5 is mostly shot.

[@allanpennington]

@@summetj Mine at 1.2 V 2300mAh AA energisers. Amp reading of the best is 2.01 and the worst are between 0.06 and 0.25. Does that relate to the mAh rating? So would the one measuring 2.01 still be useful?

[@summetj]

@@allanpennington This is measuring the instantaneous power the cell can provide, not the overall energy capacity of the cell (amps, not amp hours). So it is only loosely related to the 2300 mAh rating of the cell. New cells can typically do 5-7 amps even if they are only rated at 2.3 amp hours (2300 mAh) for a brief period of time. The 2 Amp cell may still be usable for some applications, but it is certainly not as good as a new cell. (the 0.06 and 0.25 are probably completely useless).

[@allanpennington]

@@summetj Brilliant thank, they are NiMh cells, I suppose there’s no way of charging/discharging that will bring them back to life? Is there rechargeable Li AA batteries? Would my AA charger work with these? I have a car charger which has an intelligent restoration cycle and I think I can dial down the voltage and it has several modes for different battery types. Wonder if that’s worth a try unless there’s no hope for a an old well used NiMh battery

[@GANHEDDO]

Great video, thanks a lot. Now I understand why my Eneloops Pro don't last too long even though there is enough voltage presence. Question: can we use the multimeter test with Alkaline batteries? Thanks again and thanks for sharing :)

[@summetj]

@@GANHEDDO yes, you can for small ones like AA. The voltage level on alkaline gives you a good idea of the remaining capacity so it's not necessary to test how much current they can put out.

[@GANHEDDO]

@@summetj Ok thanks! Last question, would I hurt my AA alkaline batteries if I use a multimeter and your proposed test to check how much current they put out?

[@summetj]

@@GANHEDDO As long as you only short them for less than a second they will be fine, but doing a voltage reading is sufficient for alkaline chemistry batteries as the voltage level is very correlated to the capacity remaining.

[@fpvkabo]

when it discharges, what voltage is the stop voltage to use to make sure we match up to assuming it IS going to give u rated mah?

[@summetj]

This test is really only useful for charged batteries. If the battery is already discharged, I wouldn't expect it to be able to provide many amps.

[@fpvkabo]

@@summetj when u are discharging a fully charged battery, what voltage is the stop voltage to use to make sure we match up to assuming it IS going to give u rated mah? For example on a aaa batt discharge it to 1.1v? I would imagine diff cutoff values for aa, c, or d batts and whether nimh, loin, alkaline etc. I have a 180watt discharger that I can plug any (fully charged battery of course) battery into, set cutoff voltage (CC constant curr), hit the start button and in the end I get a report of mah used.

[@summetj]

@@fpvkabo 1.0 volts per cell is the value typically used for all NiMH batteries (A,AA,C,D or other size) as the chemistry dictates the voltages curves, not the physical size.

[@6StringPassion.]

I have a 6-cell NiMh pack (7.2v). What amperage should I be looking for to determine if the pack is still viable? Thanks!

[@summetj]

I would not short the pack through a multimeter, as depending on the cell size it might be able to drive more current than your multimeters fuse can withstand. (Unless it is a pack of AA batteries?) If the batteries are all in series then it would be around the same amperage as a single AA, only the voltage would be higher.

[@6StringPassion.]

@@summetj The pack has 6 AA in series, 1.2v each for a total of 7.2v output. So, in series, I believe the current should remain the same for the pack as for a single cell. Only the voltage would increase. That being the case, would it be safe to test with a multimeter? Thanks again.

[@summetj]

@@6StringPassion. Yes, as long as your multimeter fuse is 10A (or more).

[@robl1967]

Could you do that first test with 18650 batteries?

[@summetj]

@@robl1967 No, they produce too many Amps, and would blow the multimeter fuse

[@robl1967]

@ thank you for the quick reply almost learnt the hard way just now 😅

[@pn670]

I have a device that is powered by 3 AA batteries. I'm using 3 eneloop batteries with panesonic basic charger and that needs battery in pair to recharge them. So my problem is how can I charge 3 batteries using this charger?

[@summetj]

The only way is to swap batteries in and out while charging, and it is very difficult to balance the charge that way. I recommend that you buy a charger that charges each battery individually

[@jpperry2117]

When checking with multimeter, what amperage is good for a AAA battery? Is it the same as AA?

[@summetj]

I have seen AAA in NIMH batteries give 5 to 6 amps when good.

[@AutoXMac]

@@summetj What is a "bad" amp reading on a aaa NIMH battery, i.e., when should you recycle the aaa battery?

[@summetj]

@@AutoXMac that depends on your application if you're using it in something that only requires a trickle of electricity like a remote control you can probably keep using them down to half an amp. Generally I would say anything under one or two amps is probably not going to hold much of a charge.

[@AutoXMac]

@@summetj What is a "bad" amp reading for a NIMH AA battery, i.e., when should you recycle the AA battery?

[@summetj]

@@AutoXMac Again, depends upon your intended use. I generally side-eye a AA cell that can't deliver at least 4-5 instantaneous amps, but for some low current applications (TV remotes, for example) a "less than new" NIMH battery can still be useful.

[@pattyrekow1078]

Do you know what nimh 2/3AA 650mAh 1.2v batteries run?

[@summetj]

Sorry no.

[@itoldutruth669]

I did not understand amps/capacity test. Let's say I have1.2 volt Ni MH Duracell battery , it is 1000 mah. So what is supposed to be its reading on voltmeter ? 1 amp as it is 1000 mah or what ?

[@summetj]

It is more a test of internal resistance than a capacity test. If the battery can not provide instantaneous amps it has too much internal resistance and is bad.

[@itoldutruth669]

I charged and checked with a voltmeter 1.2 volt 1000 mah AAA Ni Mh battery and it came with 1.38 volt, ~ 1.70 mah.

[@Anthony_The_Chicken_Licker]

Did you try refreshing the battery

[@summetj]

I did not try to refresh the batteries that delivered less than 1A. I tried for a few of the 2-3amp batteries, but they did not get better after a few cycles.

[@_c_y_p_3]

Thanks for explaining, I been thinking about getting a bat tester for ages then I just realized I have a multimeter which might have even been in the same drawer some time over the years……. 🤔 💡

[@treyb9952]

Absolutely great video! And great explanation!! Extremely helpful! Definitely help me!! Thank-you! Have you test which AA rechargeable batteries test best for being under load such as the brand? I know the batteries made in Japan are supposed to be far superior to the ones made in china!

[@summetj]

I have not tested different brands head to head, but the eneloop ones I have seem to be doing well.

[@treyb9952]

Ohh wow! Thanks for such a quick reply. Thank-you very much for that information! Eneloops seem like the way to go.

[@mikeharrington5593]

Very useful.

[@Jozef_Drab]

When I set multimeter to A+COM (limit 10A) and switch to A it shows only 0.000. What is wrong?

[@summetj]

@@Jozef_Drab It will show zero amps until you pass current through it by touching the battery. Also you need to make sure the test probes are in the amp and common setting. And finally if your fuse is blown it may never pass current to detect any amps.

[@Jozef_Drab]

@@summetj I opened the multimeter and the 10A fuse is blown, I have to buy it tomorrow, thanks ;).

[@summetj]

@@Jozef_Drab so shorting a AA nimh battery should only produce 6 to 8 amps max which is not enough to blow a 10A fuse, but if you try this technique on a D-cell or a lithium ion battery it could potentially blow your fuse.

[@Jozef_Drab]

@@summetj Thanks again, your video helped me a lot. I tested all of my older bateries, 30% gone ;).

[@TheGoodContent37]

What happens to the batteries if you do this for too long?

[@summetj]

@@TheGoodContent37 They overheat, which isn't good for them, so only do it long enough to get a reading.

[@TheGoodContent37]

@@summetj Thank you very much! 🙏

[@motto666]

Eneloop AA capacity is 2000 mah, why the meter shows 7 amp?

[@summetj]

This test measures instantaneous power (amps) not total energy capacity (mAh). If a nimh AA battery can push 7 amps, it probably has a good amount of it's original capacity, so this is a quick and dirty way to test the cells without doing a full charge/discharge test.

[@motto666]

@@summetj I see, thanks.

[@TurboEncabulat0r]

Thank you, sir.

[@HDXFH]

If ya hold down quick test on those chargers you will get the ESR reading

[@scottwho6271]

Why didn't you use the charger to check the internal resistance.

[@summetj]

Mostly an oversight, as I started off demoing the multi-meter, although I've found that the amps they provide under load generally gives you a good idea of their IR if your charge/discharger doesn't have an IR checker built in.

[@reveme]

I hoped there was a method to do a capacity test without a capacity tester :) But it's fair enough. Just a warning: the instant current test is actually a short circuit. NEVER short circuit a battery. maybe a NiMh battery is not dangerous, but a LiIon would explode with that test... and maybe you can melt your multimeter with that battery :)

[@summetj]

The fuse in your multimeter would blow to protect the battery and meter, but yes, this method is not for any battery that can deliver more than the fuse rating of your meter.

[@vhfgamer]

"Any one that flashes a red light or won't charge, you can just dispose of those." Negative. These smart chargers people have today are overly sensitive to the condition of the cell, and will absolutely give false positives. If you have a cell that won't charge, try bridging it with another good charged cell. Sometimes that will put a little energy back into the cell, and let the smart charger charge it normally. Sometimes you may have to charge and discharge it a few times to wake it up. If that doesn't work, try using a dumb charger. They don't care about the condition of the cell for the most part, they just dump power in there until it reaches the Negative Delta V of the cell. No fancy brains involved. If that STILL doesn't work... then maybe consider chucking the cell.

[@mati211p]

High internal resistance can be used in solar light till they didn't fail completely

[@summetj]

Yes, that is true, they work OK for low discharge situations (but they typically have low capacity as well....)

[@rajd7614]

Excellent technical info . How-ever the " Opus BT-C3100 V2.2 4Slots LCD Display Smart Intelligent Universal Battery (Plug: US Plug) " Costs $112.89+ taxes in canada. for $ 1 battery to be tested no point in spending $ 120 on asset to be used intermittently

[@summetj]

That is why I showed the multimeter procedure first. I also make use of the opus for a lot of lithium ion battery testing so it makes sense for me.

[@wcndave]

A BC700 charger also has the same exact features. (and is about $30) BTW: the reason it showed different amps in there, was, I believe, because it uses about half the discharge rate as charge rate. The default is 200mA charging and 100mA discharge. How do you know it was good/safe to bump this up to 500?

[@summetj]

@@wcndave these AA batteries are rated at about 2,000 milliamp hours, so I figured a charge or discharge rate of 1/4 C would be fine. For AAA batteries I might use the default rates.

[@wcndave]

@@summetj Thanks. I read a lot of places that said 200/100 max charge/discharge rates. However I now checked more after your video, and I also see a lot suggesting 1A fast, 0.5A slow. Nice video, thanks.

[@j7ndominica051]

Surprising how a camera draws so much power. I found none of my old cells worked in a camera when I needed to take a picture. Do not short a 9V battery. It contains an intentionally thinned fusible metal strip that requires the battery brutally cut open to repair. They want us to throw out batteries in great condition (powerful enough to burn the fuse). The Opus charger is good. But with more than 2 cells at 200mA the fan comes on.

[@fildowns]

Imagine not only owning a multimeter but also using rechargeable batteries for over 25 years and not knowing this! Who could be that dumb? 🤦‍♂Doh! 😂

[@danialtun5431]

Like this test is dangerous no load test 1.2v can test 4.2v 9v like this test problem meter very hot

[@summetj]

Yes, it works for AA batteries because they can't generate enough Amps to blow your meter's fuse, but shouldn't be used for larger batteries. (And should be done quickly.)

[@HDXFH]

Those chargers are grouse