Beginner Friendly Lithium Battery Capacity Test Method 

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I've been using the same tester for months in my review videos and it works great. You can also power it via 5v usb instead of needing to plug it into the wall. Good for testing outdoors.

low voltage limit - each double click adds 10 value per click, Thanks for this video, I would never have figured this machine out with the Chinese English directions. This video was soooo helpful!!

Will, you can do 20 amps at over 13 volts with this tester if you make some changes in the setup alarm screen called > 185 W. After you have noted what the TEMP reading is on your data screen while drawing 184 watts for a few minutes with a 12v, LiFePO4, drop in battery, (my unit reads 70 Celsius in my house), you can set the tester in a cooler full of frozen water bottles, or do what I do and set it on the face of a portable desktop fan, or any other trick that cools the heatsink better. You should see the TEMP go down a lot. Now you can increase the > 185 W threshold to 260 W. While you are cooling the heatsink more efficiently with whatever technique you decide to use, you can ramp up the amps until the TEMP gets back to where it was when you started. I can now do a 20 amp draw on a 100 AH battery for a true .2C rate test, as long as I set the tester on the face of the portable desk fan. The TEMP stays below 70 Celsius. You can't set the threshold very much higher without the extra cooling or you will burn up the MOFET under the fan and heatsink assembly. I tried it so others wouldn't have to ( that's me saving face, LOL) Hope this is useful to someone.

Will, from everything you've said about Battle Born that's where I was headed for 2 of them. But you are giving me the confidence to build my own battery bank & save Serious Money instead!!! THANK'S Will.. TAKE CARE..

Great review ! But, the "low voltage protection" does not disconect the load. It only use a buzzer to warn you. So if you are not here you can kill your single cell without BMS

2:55 Wow, you really do try hard for us! Thank you

You can modify the heatsinked version for nearly 300w. Good to combine with a LVD in certain test cases. Did a video on this a month or so ago. Good stuff :)

I love your videos and I have watched this one several times. I would love to see another dedicated video to finding out a battery’s capacity. I’m still left with a bunch of questions, like…… Do you charge the battery to a certain voltage? What voltage do you then stop at? If I have a 3.7 volt battery, what do I charge it with? What voltage do I charge it to? If I have a 12 volt battery, what do I charge it to? Is there a universal charger? I would just love to see a super in-depth video crossing all battery voltages, charge voltages, discharge voltages, chargers, and examples. Thanks a lot!

I'm a little late to the game, but I bought one of these and really like it. It's super-easy to test with.

I have the same load tester and, like you, I had a preconceived notion that it would be cheap and inaccurate. Imagine my surprise when I compared the voltage and current values the load tester reported with readings from my high dollar Fluke multimeter. Less than 1% difference! Be careful to always turn both the course and fine current adjust knobs fully CCW before connecting a battery source. Should you forget it will cost you about $5 to replace the mosfet. Thanks for the great video.

Hey Will I just want to thank you for all your videos. Because of your videos I’ve learned much about solar abs actually put together my own 12v 2580kwh system. This video actually taught me to check the capacity of my batteries (running as we speak lol) but yeah thanks again

I bet your workshop stays warm. Good video.

I switch from agm to lithium in my rv. I bought eco worthy for a super low price. The first thing I did was charge 100 percent the hooked up this tester. Each of my batteries (4 total) is rated at 150ah all 4 tested from 151ah to 159ah.... I love this tester.. no more guessing

First I really enjoy your videos and the amount of research you carry out before posting. When I first ran across this device I was ready to buy and held off only because many have posted the "unit fried" or it didn't work out of the box. It would be great if details on why they fail and how to fix them that is if the failure is something simple. I am a middle of the road hobbyist but don't have the tools to replace those tiny SMD components.

Gi’day Will, always a pleasure watching ya mate, luv from downunder…✌️

I just wanted to let you know that I purchased one of these capacity testers like I said I would and I have a total of 3 lithium iron phosphate batteries that I wanted to get tested. On the third one the load tester popped and sparked and the big main mosfet in the middle failed!! I'm glad that I ordered this from Amazon and I have started a return!!

I got one of these last week in the mail. Its pretty cool. have used it to check the life of some of my old portable phone charger banks. tonight I will use it to check the capacity on my new LG Chem li-ion 120AH modules. It would take to long and get way to hot with a regular RC charger. the cooler does a good job. I also will put a small heat sink on the back for heavier loads.

Probably said by others but the power lost in the leads is not included in power measured. I.e. the capacity measured would be somewhat lower than actual. A "four lead" unit compensates for this as the extra leads measure the battery voltage at the cell and the power consumed then includes the lead losses. Great work Will! you are awesome :-) .

One word of advice, those fan testers are known to fail at some point in time and they fail in a dead short. Always add a fuse between the battery and the tester.

I picked up one of those little heat sink/fan combo testers the other day, hooked it up this morning to a 4-cell 280Ah LiFePo4 pack. Sucker works great! Ten hours in and it's not even halfway through the expected capacity.

Thanks for the video Will. I needed a way to test my battery packs for my ebike's.

Good basic testing info, thanks. One comment: At 0:58 when you characterize 116 Ah as a "ripoff" for grade B cells, I think that's a bit harsh. That's 96.7% of rated capacity; for grade B cells, at that price point, is quite reasonable in my opinion.

Could you test Edison Nickel iron battery, love your tests and videos.

yes there are lots of shady crooked dealers on... it seems like most of them have shop and then along... thank you very much this is a very good tutorial.....

Good video, of course! One question to anyone. Is the low voltage setting on this device an actual disconnect or just a warning alarm? Just to be clear does the low voltage setting on this capacity tester turn automatically turn it off when the low voltage is reached on the battery or does it just produce a warning alarm?

Thanks Will but you didn't cover the Test result part. How do you know your capacity? Is it just a readout on the display? And how does the low voltage cutoff factor in to the calculations? Since you are only testing its capacity to a certain low voltage level, how do you determine entire capacity if you ran it down even further?

I got this Tester for the last year or so and do all my Amp tests on this unit when I do 18650 Lithium packs up to 200Amp

Is there anyway to do rapid testing to estimate overall battery capacity? Maybe through the use if variables like internal resistance and such?

On the topic of capacity testing....have you retested any of your cells after some cycles or time? See if the 10yrs/1000s of cycles life are true. Would be interesting to see after cycles and after "floating" for weeks or months.

Why not just power your inverter through an inline DC Power meter? The power meter logs Amp-hours, power, voltage, current, peak current, min voltage and more, and only costs €10 on eBay from China and will withstand 100 Amps. The procedure would be to just start up your inverter and power your usual loads (computer, lights, whatever), and read off the Ah value from the meter when depleted. Advantage is that the energy isn't wasted as heat, it's used to run useful appliances that you'd have run anyway. And the max discharge rate is way higher than the 300W of this load tester so it would finish faster. If you're going to look it up on eBay, it's the one with the blue case and the two-line dot matrix display. The title of the cheapest one is "LCD Digital Battery Analyze Monitor Watt Meter DC Ammeter RC Power Amp 60V/100A"

This is awesome, exactly what i needed. Last Time i used my fishing trolling Motor. Had to write down every hour the A to get like 90% what a Pain....

These do NOT turn off the load properly. As soon as the load turns off from low voltage, the voltage goes back up and it draws more current until it drops again.

Will thank you for all the time you've put into these videos and sharing your knowledge. Many have no idea the time and energy it takes just to publish these. Something I'm always curious about is sort of a lessons learned video, we all know what happens when we short these bad boys...lots of sparks and honestly on the higher capacity cells possibly lethal. I'll never forget trying to do my dad a solid back in the early 80's when I attempted to install his new car battery in his 77' Chevy Nova. I learned that when you leave the large plastic insulator block that came on the bottom of auto batteries in that day to insulate from poor storage (i.e. concrete floors); that if, you leave said block on the battery and install said battery and slam shut the hood it is very possible (100% chance in my case) that the hood of the car will short circuit the battery. My dad was none too pleased to see two large silver dollar sized holes in his hood :) Do you have a video of lessons learned? If not is it something you would consider making? Thank you again!

It would also double as a handy tent heater for my next inland bike tour.

Hello from Brazil; I like your project to test the cells. You are cutte guy.

Where does the 185 watt number come from? You tested all 3 of these at 185w, why that number?

Great tutorial! To speed up the test, can I use 2 of these in parallel?

Dude your reviews are so professional! I’m trying to build a bms for Nissan Leaf modules…I have wired them to 15.8 volts so I can use them for car audio amplifiers…any thoughts? These are extremely powerful batteries and I bought a bunch of them

Well said Will. Nice video !

I bought this capacity tester to test a cheap "135AH" LIFEPO4 battery off ebay Australia, it came back as 70AH LOL.. I returned it, but the seller has since sold hundreds to unsuspecting people & they are even leaving positive feedback.. I also used it to test a "90AH" AGM I bought off ebay a couple of months back, it tested at 15AH!!!! Also returned.. Definetley worth the investment! I have since found a decent "100AH" LIFEPO4 from LanPlus Australia, it tested at 98AH. Happy enough with that.

Update please, links don’t work to AliExpress

okay I got two of those fan battery capacity testers please have a video on how to use the particular ports and how to test the gt4000s

I would love to see a more detailed video about the C-Rating. I'm still confused about that. I see 20-C (on the battery), and a 1, 2, 0.1, 0.2, and so on in your on-screen postings and i'm confused. and, how would i use the c-rating when testing or comparing battery / system setup and what-not's. thanks.

Love your videos! I noticed that the voltage at the battery with NO LOAD verses voltage at the battery WITH LOAD (.2C) are substantially different. Which voltage measurement should determine the top (3.65v) and bottom (2.6v) voltages?

So I don't know exactly why; but I just tried to set up the capacity tester for a test and was starting to increase the watt knob up to around 100 W when suddenly the unit started to fizzle and pop and suddenly burst into flames. Scared the heck out of me and also could have burned my house down. Just an FYI on safety of the unit. Luckily the test was only starting when the fault occurred while dialing the watts.

Question: Will, on your videos when you test battery capacity, you're looking at a computer monitor. What are you using; I like the graph and I'd rather order that. Thanks!

i have made a "simple" setup for testing a battery not loosing all the energy to heat. ( battery1 to test (with bms) --> energy meter --> inverter to AC --> battery2 charger --> battery2 (with bms) ) battery2 is much bigger than battery1 and practically empty ;)

according to the amazon listing the reason for turning down the load settings to 0 before connecting the battery is because you can burn out the load transistor and resistors. can you use a anti spark xt90 connector is it a matter of the inrush that destroys the unit?

If you want to test higher c ratings couldn't you just connect 2 in parallel?

Because of not null internal resistance of the battery you need to test it at the same current every time. Test results made at different currents incomparable. In the datasheets of the good brands batteries usually exists chart with usable capacity vs discharge current.

Another great video. A little off topic...but close... how do you increase voltage into the thousands? And test it? I’m thinking portable electric fencing (got chickens?) as a diy project.

If you want faster testing can you just run two of these at the same time? I don't see an obvious reason why not, but curious if there's anything I'm missing.

Cool video as usual! If all goes well this year I plan to upgrade from my 12v AGM system to a Lifepo4 either 24 or 48v one, hopefully over 300ah total. Found a deal on used PV panels. The question is, do I need to check just to voltage to make sure they are working or the Amps as well? In either case would I also need to test them on a Sunny day or would part sun work?

Will it sounds like a good camping heater? Maybe convinced The dealer to throw in a carbon box it can stay in

I got that exact one, I could not disagree. A very important tool. I likely will be forced to build a 48V battery for my 10kw solar panels. Batteries are impossible to get here in the Philippines. Cells are had to get and iffy at best in quality.

Will, very time I have a question about batteries all I have to do is look on RU-vid and there you are with the answer !!! Thanks William Orange county, ca.

Thank you for the video so far Will, I learned a lot from you. Can you review the DL24 version? It looks like DL24 is an upgraded version of what you reviewed in this video.

Question! can I safely hookup this monitor to a 36v/55Ah lithium battery? Question no. 2~ can I plug it into a 120v outlet?

Single cell with BMS capacity test. Could you just connect all (4) leads to the positive terminal? Theoretically it should give the same results for each connection. What do you think?

Great video, going to buy one of these myself. Could you please tell me what the "two wires connected to an xt 60" are and where I can buy them

Will, how Would you recommend I do a full capacity test on a used battery that I'm considering purchasing? I can't Arrange a 6 hour test, What I don't wanna get ripped off on a large lithium battery purchase... Help!

Thank you, your video helped me Will

I thought you could run lithium batteries down? I thought that is why they are so expensive? What can you run them safely down to then? Cheers for Video BTW 👍👍

Can you put two load testers in parallel to speed up discharge?

Did you test the USB input? Especially USB-C is a nice feature if it works good I think.

MY QR code says my cells are from 2021. I just bought them new. Is that a Problem?

Take the positive voltage on the buzzer, thru a 1K resistor to a 2N2222 to a relay that will disconnect the load. Solved.

I bought a 300Watt B&K Precision DC Electronic Load tester that was a demo unit. Saved a lot of money by buying a demo unit, but even as a demo unit these units are many, many times more expensive and really do no make since to own for DIY. Buy a $100 lead acid float battery and a $1000 DC load, or buy a $1000 LI battery and a couple $26 DC Loads. Oh...the choices in life.

Very good information Thanks

Who do you buy from at aliexpress? I had 2 orders with different sellers; and nether delivered.

Well I bought one of those load testers was messed up saying voltage of battery increased as I added amps lol , saying it was at 18.5 volts while at 180

I just picked up one of these capacity testers off eBay and I can't get it to work. I think I got wrapped off. The knobs will never make the amperage or voltage move. I can't figure it out. Any ideas?

U are the King 🙏

What? No more heat gun?

Ordered one immediately when I saw this. It is going as I am having a beer out. Hope it cuts off at 2.6v

Thanks for sharing this info on such a neat device. Can you test super capacitors to see if the Farad value claims match what is sold? I am interested in buying these 16.2 Volt 83.3 Farad super capacitors sold on ebay and Amazon. Are they really what they are.

can you get away with not having to turn down the load knobs before each test by using an anti spark xt90 connector? the anti spark xt90 connectors are used to pre charge the capacitors in devices and they do it by having a resistor that is connected inline to the load thereby you dont get the big jolt of power that can damage connectors and sometimes even blow reverse polarity protection diodes (that is a flaw in the cheap battery spot welder where the inrush current can blow the diodes in the trigger section).

Hi Will Thanks for all that you do. Great help I have 4- 12V 200Ah batteries. I am having trouble with the batteries shutting down. Is there a way to load test the batteries to fine the bad battery . A multi meter reads 27.9v on all 4

Great vid professor will 😁😎❤

Ordered one not long after this video posted Wish I could say how it worked but I still haven’t even gotten it lol And my dumb azz is considering a 48 cell 200ah battery order lol. I’ll have it by Christmas I’m sure

Great video very interesting Thank you

HI, Thanks for the video. I have no clue on how to use this tool... what settings do i need to use in order to test a 36V 12.8Ah battery? Thanks a lot!

Thank You for the informative vids. Can anyone recommend a programmable/adjustable low voltage disconnect for a 20-30vdc system?

Thanks! What is OCPD? Did you add a fuse between the tester and battery or do you mean the battery has it?

With thin leads I guess the voltage readout is some 0.5V lower at 20 Amps. Does the test unit have some I*R cable voltage drop compensation or maybe separate test leads? At high current you may disconnect to early if you do not compensate for the cable voltage drop.

Hi, Will. Do you know a lithium battery charger where we can specify the maximum charge voltage. I've been trying to find one that let's me charge for example to 4.0V instead of 4.2V. I've the Opus charger and Skyrc Imax B6, but the minimum voltage the skyrc let's me use is only 4.14V. Thanks and congrats for this great channel.

I’m stumped! Need advice. I bought 2 PowerUrUs 12V 200amphr batteries for my Class A diesel pusher. I’ve got a magnum charger/inverter. I set it CUSTOM w 14.4v Absorb, 13.5 Float, 14.4 Equalize (per BattleBorn/Magnum setup video). It bulk charges at ~133 amps, then absorbs around 60amps, then floats at 0amps. PowerUrUs app is quite worthless. Ran capacity test with this tester. Zeroed it, set it at 150W, ~13amps and the test on both batteries was only ~21 amphrs, not 200+ when the BMS shut the test down. Test only took ~2hrs, not 15 hrs. App says low voltage protection, PowerUrUs charger applied. All lights are green and no amps being added when the battery is fully discharged. It’s 61 degrees outside.

The device you are using in this video comes with a USB port and the USB cable with positive and negative internals on one end, and USB on the other. Can this be used instead of using the positive and negative terminals on the device?

I see you use your computer now to do your battery capacity tests. Do you have any links to the software and hardware you use? Thanks!

Thx. Great tut.

Wish I could find an actual manual for this thing. I cant get the usb-c input to do anything.

Does this work for lithium ion?

What is the cheapest tester for checking the capacity of my 15 year old 36v Lithium Cycle battery?

I would also like to see how Iron Edison (Nickel Iron) battery's compare to the Lithium batteries.

If you use this on a newly charged LGM Sealed Lead Acid, and don't set a minimum test voltage, did you just destroy the battery when you get back? I mean isn't it bad to run that into the lowest voltage (like 0)?

You the MAN

So what is the difference between the 150W and 180W versions? The 150W version would take longer to discharge the battery?

I been playing with mine. I thought it did shut down when the voltage got below the setpoint but maybe I was distracted by the beeping. The voltage levels are really hard to adjust. They go full scale in one direction 300V or zero and they won't reverse direction. This may go back.

What if the LifePo4 battery has a BMS with Bluetooth? Would the BMS Bluetooth reading be accurate enough if you hooked the battery to a load in order to find out the Ah's of the battery?