Test 18650 cell capacity at different rates: what's the optimum rate of discharge?

Today I'll be testing the LG 3350mAh 18650 cells at different rates: 200mA, 300mA, 500mA, 700mA, and 1A. I want to find out which rate is the most accurate, yields the best result, and at the same time takes the least amount of time. Warning: this contains graphic material. Tread with caution.

[@Alex-us2vw]

Discharging slow or fast is not anything like driving a car fast or slow. It all depends on the battery, some are meant for high (fast) power draw, others are more suited to slower usage. But all will provide a 1 amp draw no problem, testing 18650 at 0.2amp or even 0.5amps is kinda crazy, that’s for testing much smaller li-ion batteries like 14500 or even AA/AAA NI-MH cells.

[@Alex-us2vw]

With driving a car fast or slow it’s the air resistance at high speeds that begin to affect efficiency significantly beyond 60MPH. There is no air resistance pushing back in an electrical circuit or in the battery

[@vuaeco]

@@Alex-us2vw Hi Alex, how about you and I compete in a 100 meter distance to see who spends the least energy. I'll walk real slow and you will sprint with all your might. Let's see who's gonna spend the least amount of energy to get to the 100 meters. :D The point of this is you will get there probably 10 minutes before me. Is that the 10 minutes you gain for free? I don't think so. You will have to pay for it by spending a lot more energy than me.

[@Alex-us2vw]

vuaeco that’s not how electricity works though

[@vuaeco]

@@Alex-us2vw When you discharge faster, you can complete it in less time. Are you saying the time you gain is free? You are breaking all kinds of rules in nature.

[@Alex-us2vw]

vuaeco what? Of course when you discharge at a higher rate a battery will empty faster. You were talking about discharging slowly being more efficient though, which is not how it works with electricity then giving examples which have nothing to do with electricity. They physics is very simple (Joules = watts x time) there is no efficiency gained by using less watts it’s just will take more time vs a higher draw. So discharging at 1 amp in a few hours or 0.2 amp over a day will yield the same value on a capacity tester

[@dillonmccormick2511]

Nice scene with the dead rat and maggots. Exactly what I was looking for in a 18650 capacity testing video.

[@gerardjachymiak5822]

where at what time

[@nfreddyyy]

Quality maggots for quality video

[@nfreddyyy]

@@gerardjachymiak5822 1:57

[@thethinker6257]

Right. I was like...WTH?

[@LukasKraehling]

OMG That was legit the best laugh I got in a while xD

[@mahdixn]

the issue with that test is that you are testing different cells, even if you discharge the at the same rate, you'll get different results. You need to take the same battery and test it with different discharge rates, sure it's going to take longer but it makes more sense.

[@MrMaxeemum]

You should have discharged them all at the same rate in the same unit and in the same slot for a base result then repeated at different rates and produced the results in a percentage of the original base result. Your theory of discharging faster giving less capacity should be true as a higher discharge rate will produce more heat / wasted energy.

[@felonebike9859]

Dude great video! Why can't other people make it so simple? Now I have to check your other videos out!

[@jasonbrown467]

i appreciate the video, had you considered redoing it so that all batteries get shuffled through the different discharge rates? i would like the know if your lowest capacity battery maintains the lowest rating through all the tests, or if there is something else going on.

[@ZafarU512]

It's all about cell internal resistance. Means, that cell gives you more discharge time who having more internal resistance. Sometimes people get confused when they noticed that same capacity holder sells gives different discharge time. You should check internal resistance of those cells. For example you have two 2000 MAh cells. On same load . One cell discharged in 10 minutes and other cell discharged 1 hour , it means that faster discharging cell has less internal resistance , and other cell has high internal resistance . Thank you.

[@FM-fn7eo]

i have LiitoKala Lii-500 when is better to measuring internal resistance ,when is full charged or when is discharged ? it is very different value like 10-90

[@princewillwp]

Is 2011mAh a cell good enough for a battery pack for my bike?

[@MrMAMAO2011]

Dear sir , I need an help to how to test 18650 cell from old laptops batterys using litokalla . I use normally NORTEST with 700 mha charge current. Because I want to garantee the discharge rate is good .

[@2061526]

how to test 18650 battery total capacity without lowering the cut off voltage too much?

[@robertmotion]

Great video. Question - can you recommend a lithium battery C-rate tester to purchase. I build ebike batteries and need a solid c-rate tester. thanks. /Bklyn👑

[@thonatim5321]

In order to have accurate data, you will need to test all 5 batteries in all discharge conditions. Then you can compare each battery to each other based on the same discharge rate. Only then can you determine what discharge rate provides the highest capacity. You are assuming each battery has the exact same capacity but you are only guessing. Peukert is your friend.

[@Chaosfury50]

Every battery has an internal resistance which could even vary depending on how much charge it has and thus the slowest one could have been discharging at a resistance just high enough to see those results

[@thecelldoctor8890]

Different cells are built for different tasks. The best way to choose the current for discharging is by reading the datasheet to understand what is the rated discharge rate. We are doing a giveaway for 4 megacell chargers for testing cells in case you want to do more automated testing for multiple cycling etc

[@rb-ex]

your intuition and experience is generally correct that bigger loads reduce capacity. this is because more heat is usually generated by higher loads. the trouble with this test is that due to equipment limitations the discharge loads are too small to generate the kind of heat you get from real loads, and in the range of testing, you are probably in the flattish part of a convex temperature curve. (by 'convex' i mean it increases at an increasing rate). with temperature rising very slowly from 200-800mAH, total thermal energy released (measured in an energy unit like calories) was largely a function of the time the cell spent in discharge rather than the discharge rate, so you saw increased capacity up to 800mAH because you had big reductions in time spent in discharge and only small increases in temperature. then you had a little drop in capacity at 1000mAH because the temperature curve is moving into a steeper slope here, enough for energy released as heat to overcome the shorter discharge time. if you tested the cells at increasingly higher discharge rates above 1000mAH, e.g, 2A, 4A, 6A, 8A, 10A, you would get into steeper portions of the temperature curve, and i predict you would find the trend you expected. but in the low range your equipment can test you're seeing this unexpected effect due to convexity of the temperature curve.

[@ErusNotitia]

I used to drive for a living, and my understanding is that gas mileage is determined more by revolutions per minute (rpm’s) than by speed. There are sweet spots at different gears, that if one drives at those rpm’s in those gears, they will burn less fuel, also a sharp increase in acceleration, especially on an incline, will burn a lot of fuel. So, an increase in speed doesn’t necessarily burn more fuel.

[@freedomunrestricted]

You would have to test the same cell multiple times at each discharge rate to get a more accurate average. Testing the same cell twice at the same discharge rate will give slightly different results. Comparing one cell discharged at 200mAh to one discharged at 1000mAh isn't a very reliable test.

[@keokio7]

what you could've done is retest again, take the 200ma discharge rate battery and change it to fastest 1amp and see if you get more capacity. Same with 1amp discharge rate battery and discharge it at 200ma and see if capacity is lower. Would tell you if its the battery or discharge rate that is affecting your capacity

[@bobsoft]

I have the same OPUS charger and so far it has been discharging the Samsung ICR18650-22E cells at the same rate (500ma).

[@standeyoe7468]

is there any way to mix laptop batteries and power tool batteries in the same pack considering the different discharge rate ? thanks for the great videos .

[@pgpilot3884]

You can mix them without any problem when used for low drain applications, for example in a power wall. You can find tons of info on secondlifestorage.com

[@marbesky]

Also if you put 1 cell on the 1st slot on the left it will charge with 2 amps

[@timmccall8318]

I have tested 1 of the Onn 3350 mah 20650's and 2 from a 6700 mah power bank. From the single cell pb in 4 -1 amp discharge tests were: 3440,3403,3414& 3458 From the 2 cell bank: 3369&3500

[@Ziplock9000]

After capacity testing, do you charge back up to nominal voltage for storage?

[@E-BikingAdventures]

It's recomended 3.80v but I prefer 3.70v

[@roncooke2188]

Did have a good sleep?

[@marbesky]

I opened this charger today and I noticed when charging 4 cells at 1 amp the cells,springs and motherboard inside gets very hot and that fan is pretty much useless in cooling the whole unit so I mounted a bigger fan right underneath in the middle of unit extracting air thru the cells on the top and makes a big difference

[@demolitionwilliams7419]

Same

[@AlexAlex-ch7ff]

How big is the fan u have mounted/model...?

[@marbesky]

@@AlexAlex-ch7ff 5cm fan

[@hycarl.1623]

Very educational

[@ciprianbeniuga5042]

Hi . If these is high rate cells is normal , they perform as same like a laptop battery in this range off discharge rate BUT they start shining in performance when you put them in 8-10 discharge load . Well opus can’t do that .

[@gustavinus]

During the 15 hours of slow draining you also had more passive loss of energy. Like when you leave a cell unplugged and it slowly loses charge.

[@user-ug9nn]

li-ion is not like Lead Acid Battery... it has almost same capacity for discharge rates until 1C, (in your test discharge rates are under 0.5C)

[@nathank5140]

Variation between cells. Heat from surrounding cells affecting local temperate of cells.

[@mastersaha]

The less capacity trend may be due to power losses which occur wrt time

[@DBLDREW]

Should of tested the SAME cell once at 1A and then again at 500ma etc that way you are seeing the difference just in the testing. Unfortunately because of variation in the cells this test is useless.

[@Xandercage312]

why showing decomposing bodies???

[@ianikize]

Hello, I remember seeing a video of someone testing an electric car in eco and turbo modes, and at the time in turbo mode, it made more miles than eco mode, I thought it was strange, but now when watching the video maybe it makes sense, we are not seeing why, maybe it has to do with temperatures, or how the battery releases the energy.

[@vuaeco]

There might be some truth to it. Li ion batteries have an optimum temperature where they operate at. But my test with these batteries, they are all tested at the same temperature at the same time. If there's any change in performance, all 5 cells should all change, not just one.

[@pooorman-diy1104]

Please repeat the test using only one battery ... not 5 battery at the same time ..

[@donovanho1965]

Does the charger work with Ni-mh?

[@motohead077]

Yes, I have it. Works for Ni-CD also. For Li-Ion the cut off V is 2.8 to 4.2. Wouldn't have got this if I knew that since testing capacity will be kinda useless, since almost every battery is rated at a 2.5V cut off & some are 2.0V. Some are 3V.. If you open it up, there is a switch on the motherboard to goto 4.35V.

[@brizee993]

Try swapping the cells around and repeat the same test. Be interesting to see if some of what you saw was individual battery capacity variations

[@arifahammed6702]

Expecting all cell to have identical capacity is a wrong idea. You should have tried different current on same cell to see if there is any difference.

[@stooory]

Maybe the cells have a sweet discharge current, where they are more efficient. Much like the gas engine rpm if you drive the car at low or high rpm the engine becomes less efficient.

[@vuaeco]

That might be true in this test! :D. The sweet spot is at 700mA. Either too much or too little is not good.

[@diydan6045]

I'm having the same issue. I tested cells at 1a then tested again at 500ma and got half the capacity. After having capacity issues during discharge. Very frustrating when I'm trying to match the capacity in each pack.

[@motohead077]

Have this charger too. Use it mostly for Ni-MH & I think the charger gives very inaccurate readings. I know it does for impedance. Same thing happened to me & for Ni-MH there should be a noticeable difference between 200 & 700mA discharge rate.

[@solomonamsalu8280]

try it with more current. 1A is so easy for li ion batteries. so it doesn't matter if you try it with 1A, 0.5A, 0.3A or 0.2A. they will all be equally effective.

[@starwoods2007]

Many batteries have a standard discharge capacity. the place where we can learn this is to look at the datasheet of that battery. standard discharge current according to the discharge test is to do. Usually 420 mA is specified as standard. So the correct discharge current is 400-500 mA range.

[@E-BikingAdventures]

It's not true that if you drive faster, you get less milage/fuel efficiency. Cars are moe efficient closer to 70 miles per hour.

[@cgreene3745]

Hi, I'd like to have seen you baseline the testers first before testing the batteries. As you mentioned the batteries won't be identicle, and the testers won't be either, and similarly each slot will have it's slight variance. You are right about the lower discharge rates should show higher capacity, but as you didn't baseline your test, the results are suspect. The battery in slot 1 you discharged at 200mA may well be the worst battery you have, so had you used the 700mA discharge rate, it could well have read even LESS but who knows....

[@adelasa689]

My friend... the reason is heat.... batteries dont like cold temperature.... you load them more.... more current is more heat so the cell works best

[@Thomas-op8of]

Hello guys, Anyone can explain why is this test called NOR? Is there a logic behind like NOR gate or?

[@jamescoghlan2097]

Normal

[@MAD20248]

i believe the temperature affected your test. everything in life is a function of temperature. higher discharge rate means higher temperature,means more losses. these batteries have an internal resistance and this resistance changes with temperature.

[@dennise4163]

I just bought one of these chargers and it seems to reach the cut off voltage prematurely. Every battery I have tested is 75 to 84% of the manufacturer rated capacity. I don't know if it's the batteries, the chargers program or both. Lets say one battery is being tested at one amp and another of the same model battery is tested at 200milliamps. The higher load causes the battery to drop in voltage to the chargers cutoff point(2.8volts I think) while the smaller load doesn't bring the battery to the chargers cutoff point as soon. When the higher load battery slot stops discharging the voltage bounces back to 3.6volts(as an example) while the 200ma discharge battery bounces back to only 3.3volts after cutoff. It would be nice if the charger's cutoff point could be modified(secret menu anyone?).

[@dennise4163]

I also forgot to mention I live in the USA and the OPUS BT-C3100 I am using has a European plug. Is the discharge routine dependent on 50 cycle AC current?

[@vuaeco]

When you discharge at 1A, it's a whole world of difference when you discharge at 0.2A. Discharging at a higher rate makes it less efficient hence you get lower capacity. You can complete it faster but the gain in shorter time has to be paid back by lower capacity. It is more accurate to discharge at a slower rate. It's just simple physics. Read my pinned comments above with Alex1911

[@LeeFall]

The voltage cut off for this charger is 2.8 volts but cut off for most 18650 is 2.5 so you lose a bit there.

[@vuaeco]

2.5V discharge is way too much and it will damage the battery. There's a reason why the charger only discharges the battery down to 2.8 and not 2.5

[@toveryonder1115]

All battery manufacturers discharge to 2.5v and charge to 4.2v.= rated capacity

[@motohead077]

Yes, was gonna say that. I just got this charger and didn't know that. Is that's standard for most chargers? Seems kinda useless for testing capacity since almost all 18650 batteries are rated at 2.5V cut off & some are 2.0V. Also, some charge to 4.35V (at least the 16650s do).

[@motohead077]

@@toveryonder1115 Not all. Some are more or less, but never heard of 2.8V cut off.. Maybe this charger is so inaccurate they set it at 2.8V to make sure that it will never go below 2.5V.

[@E-BikingAdventures]

Fusing over those small differences is not going to tell you much especially since you didn't test them all at the same rate to begin with to find out how they compare. I don't think you will see much difference until you start testing at differences above 1 amp.

[@aNDy-qh1em]

IMHO, first, each cell still has its own internal resistance characteristics, even those look the same brand new. Secondly, opus is not professional piece of equipment for trustworthy results. Third, but not least you use 2 pieces of equipment and you charge 1 cell by means of first one and 4 cells with the help of the other. To get comrarable results better to use one piece of equipment testing cells one by one.

[@alexs3523]

I myself like slow discharge,slow charge, But temperature plays a major difference other than discharge rates (in my own testing)

[@alexs3523]

Try a test in a cool room vs a warmer room with the same batteries.

[@motohead077]

Or put in garage in winter, if it gets into 30s or into fridge.

[@drivespl]

And record them at their finished voltage at the 3 hour through the 15 hour finishes. The heat generated by the cells moves up the line as they shut down. Cooling stabilizes and a self regen stabilization occurs in the chemistry bringing the cell back away from its lowest point with a large gap between each cut off time for discharging. Too bad you couldn't give the slowest discharge a headstart so they would all finish at the same time. Still heat buildup would affect cells before starting if side by side. Testing was great though. I appreciate your time and willingness to share your data. Thanks

[@taunteratwill1787]

So this 'test' tells you NOTHING! At best it shows that ALL batteries are slightly different and react with charging and discharging slightly different. Should have tested the internal resistance before doing any 'testing'. :-))

[@MrProooosit]

With Opus you will not get full capacity of the cells becouse it only discharge down to 3,21v i use volt meter on every battery directly after discharge with my opus and all cell was 3.21v i think buy alot of opus i buy one but now i use Liitokala Lii 500 it discharge down to 2,81v and now i see more real capacity but some battery cells are specified down to 2.5v but have not found any charger that can discharge down to 2.5v but i like Liitokala Lii 500 it´s good enough for me and it don´t have a fan that can fail.

[@vuaeco]

That's true the the Opus only discharged down to something like 3.0V and not 2.8V. But I think that's good for the battery because these batteries do not like to be discharged down to zero. You only do that a couple of times and the battery will be dead. Just ad a couple hundred mAh to the total and that should do it. It's much better than draining down the battery all the way to zero.

[@MrProooosit]

@@vuaeco yes that´s true, but you will see less capacity and use less capacity but the batterys will live longer time.

[@alcusminix5527]

Your original thinking should prove to be correct with more testing. I have done similar tests and agree that the results you just got are not likely to be trusted.Test one cell only, in one bay only and repeat at various rates to remove most discrepancies. Higher discharge rate should ultimately result in lower mah results but keep in mind that cells tend to work better once they get to optimal temperature. For instance, many racers will charge and discharge a cell a number of times at a high discharge rate to warm the cell before racing to get slightly better performance from it. Maybe you could heat all cells to 30'C before testing.I have a fairly powerful charger so I always test my 18650 cells at 1C using regenerative discharge. This way it takes pretty much the same time for cells of any capacity that I am testing.PS - Mostly I am working with power tool cells that are rated at discharge rates higher than 1C. I always check the specs first. I never exceed maximum specified discharge rate.PPS - Been following your channel for a while now. Love the work you do and happy to be of assistance. Hope this helps!

[@vuaeco]

Thanks Alcus. You're right. These cells have an optimum temperature where they would give the best performance. But the thing is, all of them are tested at the same time at the same temperature. So if there's a change in performance, it would affect all of them, not just one.

[@alcusminix5527]

Hi Vuaeco. You have the same room temperature but not necessarily the same cell temperature. Let me try to be clearer. The cell tested at low discharge rate is likely still at room temperature and therefore maybe not delivering as many mah as it might. The cell discharging at the highest rate may be warming up to close to its optimum temperature and delivering those extra mah. You are also using different bays. There is no guarantee that the cut off voltages, top and bottom, actual discharge rate, etc are identical from one bay to another.

[@scratchercatcher6760]

you should do the same test but with the same battery as they all slightly different even they new. take just 1 battery and discharge it , you will see no difference. Don't mix up electric with petrol. Bad example. It is the same like compare cheese and carrot :)

[@nfreddyyy]

Pigs can fly and pigs can also become flies 😂

[@markkennard69]

Throw her into the lake. If she floats then she is a witch. ( python )

[@jancaydegalvez6457]

Internal resistance is the solutions

[@daeyvidd]

MaGoTs

[@derricklewis8720]

your theory on fuel to elaborate on it, maybe the 500-700 discharge rate is like the perfect speed just like 56mph gives most miles per gallon

[@milvolts1]

Try same test by removing nickle strips. Resistance could be a factor. Lito kala chargers shows resistance.

[@vuaeco]

The resistance should be negligible because it is welded to the terminal. It becomes one with the terminal. There might be some resistance if the strip is connected to the terminal at some length.

[@JoseLopez-th1es]

I think those chargers are not reliable because they are the cheap kind

[@jamescoghlan2097]

I dream of your accent.

[@vuaeco]

You mean it gives you a nightmare?

[@prawny12009]

Why does your accent in English sound American South? Ye haw cowboy