How I test lithium cell and power bank capacity.
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- เผยแพร่เมื่อ 31 ธ.ค. 2018
- A common question I get asked is how I test the capacity of lithium cells and power banks. It's pretty straightforward due to the incredible charging efficiency of lithium cells.
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The complexity of this video exemplifies the reason we should be measuring cell capacity in watt hours.
nah mAh
Bit much for batteries watt hours 😂😂😂ffs unless ya made a big pack and running something that lasts days then yeh but single cell pointless stay with mAh or Ah
For non techy, non electrical people like me, who just enjoy Big Clive's soothing voice, watt hours would be good ESPECIALLY since that's what electric car batteries are measured in. I don't really know the difference between a watt and an amp, I definitely don't know how to convert between the two. As electric cars become more popular and people get used to car battery capacities, charging rates, cost of electricity per kWh etc.... you get my point.
@@themonkeydrunken Typo. The rule of thump is actually: Watts = Amps * Volts. Amps = Watts / Volts. ( P = U * I).
And it's probably a good idea to always include some kind of disclaimer about AC, where VA is not the same as W because it's complicated by capacitance/impedance/etc unlike DC.
@@AsphaltAntelope FFS bro ya best for get it if ya think like that .......start small then go big or ya got a death wish .......the size of the packs or cells in EVs eg there's like over 5000 18650s in there ....but all it does is make the number smaller for dumb people 😂😂😂 cus of lack of brain cells 😂😂😂😂 and there's no difference between watt and amps .......... amps and volts is energy applied to the circuit...... the watt is a measure of used or wasted energy ....if ya wanna go basic lol
It's nice seeing videos like this that respond to the "internet experts" who claim things, but have no practical experience of what they're talking about... :)
I test them by putting them in the microwave. The ones with the largest explosions and most poisonous gas are the ones with the highest capacity. The extra high quality ones have fumes that make me cry blood.
if it ain't gonna kill you it ain't worth doing - that's my rule for life
I once used a saline solution to test one. It was taken as a salt and battery, and I faced a few charges. 😂
@@gordslaterYa gotta use a FULL WAVE BRIDGE RECTIFIER! 😅
The Ruideng UM34 USB tester is very accurate but it has a few quirks you need to be aware of. It is definitely a good idea to turn the display off (or very dim) because it eats a lot of power and if testing at higher than 5V, the internal voltage regulator in the tester gets very hot. Another problem is that the lowest measurable voltage is just 3.94V, because below that the unit turns off. The capacity recording threshold mentioned by Clive has bugs too and can produce wrong capacity readings. There are a full reviews of the UM34 and the UNI-T tester on my channel if you want more details.
The reason why you always measure less capacity (mAh) going out of a USB power bank than in is partly due to the losses in the step-up converter as Clive mentioned but mostly because of maths. For example, a Li cell producing 1A for 1hour at (average) 3.6V has a capacity of 1000mAh and delivered an energy of 1A*3.6V*1h = 3.6Wh. These 3.6Wh get converted to the same energy on the USB side but 3.6Wh on 5V means the current is only 0.72A for 1h (ignoring losses in the converter). So the capacity measured on the USB side is only 720mAh and in reality, even less if the conversion losses are factored in.
I thought it was 3.64v before they cut out but it MIGHT just be because the ones we have had made with/by R&D are slightly tighter tolerance/rated components not just a cheap mass production run type 20-40% rated component used.
thats a very interesting review, bit over my head but very interesting but one thing I don't get is why this device measures an input voltage up to 24v, isn't USB 5v
@@amigaman9433 5V is the default but even back in 2012, devices could negotiate a higher voltage and current if both the device (e.g. phone) and the charger / power bank agreed with each other. Voltages were initially 5V, 12V and 20V and USB2.0 added 9V. There are also different currents that are negotiated and the way how these negotiation protocols work and have evolved over the years is quite complicated. The UM34 by the way recognises some of the older protocols and lists them on the screen if it detects that they are being used. It doesn't understand the more modern ones but that is no problem as it will always show whatever voltage and current has been agreed even if it doesn't understand the used protocol.
Well the low voltage doesn't really matter because you'll be using this thing for USB anyways. If you want to measure non-USB things you'd get a professional power logger.
Thanks for such an educational video. Links to the products you recommend would be very useful and could make you a bit of money too!
Happy New Year to Big Clive and the rest of the gang!
Thanks for this, Clive. Having RTFMed the instructions with the UNI-T UT658, I got sucked into measuring the charge delivered by a powerbank. However, your video made me realise that the powerbank's boost converter will draw some of the cell's stored charge to boost the voltage to 5V so, inevitably, it delivers less charge to the load.
As you point out, the only fair test of a cell's capacity is to measure the charge that a charger delivers to it through a powerbank's dropper-type charging circuit. I think you later discovered that even the upmarket Duracell PB2 powerbank doesn't have a buck converter that would draw less charge from the charger than it delivers to the cell.
Clive, in the DIY Powerwall/second life hobby world, we use the Opus BT3100 to test capacities discharging at 1 amp. This helps to standardize results. It tests 4 at once and does the charging, discharge measurement and recharge and then we just write the mAh value on the cell. Can speed things up a lot by pre- and post-charging with a rack of TP4056s or other chargers. With 10 Opuses we can test around 200 cells per day. Those that get hot during 1A charge are rejected as well as those that get excessively hot during discharge. (A good cell should never get hot during a 1A charge, but is ok to get a little warm on discharge).
Then let stand for a week or two and measure voltage again - any that have self-discharged less than about 4.10V should also be rejected and go for recycling.
Using this method I have over 1000 good cells after testing over 3000 cells and always looking for more to do!
I have noticed a pleasing quirk in human nature that makes us harvest lights, solar panels and power storage devices. Is your power wall vented to outside in case of any incidents?
this is pretty much the way I check my salvaged Li cells, charge to 4.2 discharge to 3.0 then charge to 4.2 that will give me a ballpark figure of the mAh, leave for 2-3 weeks any that are 4.0v or lower are discarded (sold on ebay)
it helps to have the datasheet as most power tool battery packs contain low mAh but high discharge generally 20A or higher where as most laptop packs are high mAh low discharge.
I've been using my old SkyRC iMAX B6AC V2 but at 1 cell at a time I'm tempted to splurge on the SkyRc MC3000... might need to get a Patreon account tho lol
@@bigclivedotcom Powerwall still under construction but I will use it for an ebike with a trailer for extra range, so won't be used indoors except for power outages. Have had no incidents since working with cells over the last 2 years - except for cuts and bruises while spudging laptop packs!
It takes a lot of time to evaluate each cell and enter into a database for tracking histories, and for sizing allocation to make equally-sized cellpacks.
Yes, safety is an important consideration - if and when I do make a permanent powerwall then it would be surrounded by paving slabs or live outside. Not practical at the moment in a 3rd floor flat.
I made four 120W portable solar panels using 6 A3 sheets of foamboard that weigh just over 1kg each and all fit in a backpack so I can ride hundreds of miles for free.
First I made a 2kWh 14S16P ebike battery 18 months ago and that works really well. I'm still in the process of building a 7kWh battery out of the remaining 800 cells to go in a trailer.
Now I make a portable solar tracker using 3D printed worm drives, steppers, arduino and a gps module and that's taking my time right now. The gps module allows me to calculate the elevation and azimuth of the sun anywhere in the world and I'm hoping to be able to mount the 480W of panels on it and all for a really minimal cost.
@@amigaman9433 Get an Opus or 2 or 3... follow HBPowerwall, jehugarcia, Average Joe, DIY Tech & Repairs, Vortecks, Andy Kirby - and you'll also learn a lot from them.
(This is my list of movers and shakers in the 18650 world)
@@ahaveland Have you made an Instructable about those 120W solar panels? I'd like to see whether I could make one myself... Although I can't quite see how 6 sheets of A3 foamboard fit into a backpack... :-/
Good job Clive. Keep up the good work. Love your channel dude!
Thanks Big Clive. I love your reviews and Happy New Year to you!
Hi Clive
Every time i watch one of your videos I learn something , and i realy enjoy that. Don't know a lot about electronics ,but always try to find out what or why something failed
Happy New Year Clive! Please have a safe, enjoyable & extremely prosperous 2019!
Wow clive an upload at gone 4AM? I am not going to complain one bit about this as this has made me smile thanks clive.
G'Day B'Clive 👍
Great to see you back in the new year!
Interesting video Clive. Thanks for answering questions I never knew I wanted the answer to but am glad I now know.
Happy new year.
Great timing! I just got a Ruidang USB volt-amp meter this last weekend! Happy New Year, Clive! : )
Hi Bigclivedotcom big fan of your videos whenever I come back from work I always put one of your videos on and it's fun to watch you take something apart and find out what's inside and you do a great job of explaining everything, I think a good video for you in the future would be taking apart a laptop's battery and explaining how you could repurpose the cells and explaining how the charge controller works
You have quite a few tools that are more convenient than the sort in my engineering group. I would be in heaven seeing your workshop up close.
Thanks for the informative video! ended up getting myself a Uni-T meter after this to test various batteries around the house now
You are so good Clive. Love the soothing Scot accent.
This was going to be my question for the next Q&A session. Thank you!
Hi Clive
On your New Year's Eve live stream you mentioned you old dentist. David is actually my oldest friend from school days. We used to play in bands together, him on lead guitar and me on organ.
We used to make fuzz boxes and wah-wah pedals , sound activated light boxes and all sorts of gadgetry.
Excellent video, thanks. I bought 3 on eBay along with 3, five volt, 6 watt solar panels. I am a big fan of 18650 lithium cells. Salvaged from discarded power banks. Always on search for disposable vape devices.
When at all possible I generally try to gain access to the bare cell(s) in the power bank and cycle them 3-5 times on a reasonable quality hoppy charger that has been calibrated against my HP 6.5 digit bench meter. I would say your method is far easier for most people and you can test the entire power bank with the limits it has been factory programmed with.
Happy new year, Clive! A couple of comments- first you touch on failure modes, and how energy density is a root cause more than particular chemistry. One additional factor that I've heard that's relevant is potential for "thermal runaway"- how in some specific conditions, past a threshold the cells enter a self-sustaining reaction where their temperature increases dramatically. Some chemistries are very prone to this, while others are not at all, with only vague connection to energy density & cost, much more a function of when they were developed. Is this true?
Also, for your testing "rig," in addition to the instruments and the pie tin, have you considered a dedicated smoke detector? They've become very small and cheap. I'd be so happy to see you include a smoke detector, especially in your overnight testing setup.
Love the videos; thanks for taking time out to keep us entertained & educated!
You're right about the blue power bank. I have the exact same one (sold under the Vivitar brand), two no-name 18650s wired parallel. Ridiculously SLOW charge. It does, however, work quite well.
Thanks Clive nicely explained, was your new year resolution less leds as I only saw two, yes two. Happy New year mate.
Happy New Year, Clive, lovely video as always.
I'd like to embellish your statement @13:30, that you wouldn't get 3Ah out of the power bank containing a 3Ah lipo cell because of the step-up conversion losses. It's not because of the conversion losses as much as it is the voltage difference. With an ideal lossless conversion you'd pull, say, average 3.7V * 3Ah = 11.1Wh from the cell and put that same energy out at 5.0V, meaning 2.22Ah @ 5V.
michaelditto , this is exactly why he always measures lower capacity than stated .. he measures mAh @ 5v then compares it to the stated capacity @3.7v and always concludes that the actual capacity is less than stated .. he tends to forget the voltage difference.
That's why the unit Ah is crap.
theR6969 if you advertise a power bank as having a certain Ah rating, I think it’s fair for the consumer to expect to be able to pull that many Ah from the device. Stating an internal current value the user of the device will never see is misleading. I do understand the manufacturers probably buy the cells by Ah and simply re-state that number in their marketing, but is that the right thing to do?
I agree with you that it is not right. However, it is common practice, making it difficult for a single manufacturer to do it right, as they would have a lower Ah rating than the competitor.
It would be much better to specify the number of Wh.
Whether you use Ah or Wh (both have different advantages and disadvantages, neither tells you everything) for a capacity rating to be valid, the load resistance and end point voltage, or the load current and end point voltage, or the load power and end point voltage also need to be stated.
In reality, use the figures as a rough guide. As the capacity will fall over time/usage anyway.
I don’t see any drive for manufacturers/suppliers/shops to change, as (1) the fakes are skewing the market on eBay and other similar web sites and (2) to the ordinary user with little or no knowledge of electronics/electricity, the capacity whether stated in Ah or Wh is just a number where bigger is better and nothing more...
Great video clive
Another great video. After I saw you using the mini Uni-T clamp meter I had to get one. Now I want the Uni-T usb tester. *waits patiently for the Duracell bank to be taken to bits.
There are many better UPM's available than that.
I've reviewed several of them on my channel.
Always good to see video's about power banks :) I would like to know how well the TP Link Ally ones stand up as they claim high capacity.
Nice roundup on Lipo batteries
Thanks for sharing👍😀
(not a lipo)
Lithium-polimer/ion - slightly different electrolyte chemistries alloy doping and nominal voltages but the same pixies drive them. The value is it's the same principles that can be applied to any battery to measure it's capacity, even if not rechargeable.
For the 18650 (and similar) cells, I like the BT-C3100 NiCd/NiMH/Li charger/discharger. For the wired cells, I use a dummy 18650 cell with solder tabs to connect the cell under test to the BT-C3100. The charge and discharge currents are settable and the unit can be set to the repeated charge/discharge mode - excellent for getting a new cell to its maximum capacity.
Seeing the fireworks - and the Fire Department's question about live ammo - from Rick's Disney car fire, I'm glad I opted for older technology (lead-acid AGM batteries) for my small solar system. The 82AH (8 hour) or 90AH (20 hour)12HX330FR batteries are very capable, being rated to deliver 586 amps for 2 minutes and 3700 amps short circuit current, but the voltage tolerances aren't nearly so stringent as the lithium cells. If the charge voltage gets a little above the float voltage of 13.65, it's not a problem as DataSafe recommends occasional charging to 14.4 volts in what would be an equalization cycle for a flooded battery - but only 4 or 5 times a year. For a 6 battery, 540AH battery bank in the basement, I'd much rather have the larger AGM batteries.
Great video Mr Clive Sir... cheers.. Happy New year's to you and yours
Happy New Year, Clive. 🍺😀
Looking forward to you testing the Duracell power bank. I recently got the 10 amp one and am wondering how close to its stated capacity it will achieve.
6:20 ooowyhea, can’t wait to see that opened up
I’m pretty sure the anker power banks also have switching dc-dc converters for charging ... at 12W in from 5v ... no way they can stay luke warm over the entire charge cycle
Have you done comparisons between the mAh/Wh going into and coming out of power bank? Like measure while charging and then use a load with similar current and measure while discharging. I would be interested to know the ball park "roundtrip" efficiency of a power bank (maybe comparing the resistive and switching ones or name brand vs. chinese).
Holy cow I think this was the longest: "I run em flat and charge em up again" I have ever heard.
But verry intresting and entertaining nontheless keep it up.
Yeah, but it's the way you run 'em flat and charge 'em up again...
I've got videos on the whole charging/discharing cycle for all available outputs for the powerbanks I test :)
And then run em flat again, because you also want to know the difference between how much goes in and how much comes out ;)
@@thany3
In my case... 8 inches goes in and 4 inches comes out ‼️😂😂
The devil is in the details.
if that's all you got out of that video than it went over your head.
We've been working with a company called R&D and they've done great in providing us a range of these ammeters with tight specs (we've created 4types with them atm & have a couple of false load devices in the pipeline atm) there is great monitoring software with them aswell😉
Thank you for making this video!
You sir are a national treasure 🙏
I'm very curious about the clock you made and had shown for testing.
RuiDeng make very good digital power supply and USB tester. I have the blue one with OLED and it has a low power draw which I like. For propper testing I use my Agilent power analyzer
Clive, ever since I started watching you you've been testing cells. So how many do you think that you have tested? It's got to be hundreds by now.
And on a related note, if I have something (say a touch) that I wanted to run off a USB supply rather than batteries, what would be the best way to do it?
Happy new year...
I have a cheap USB power bank (soshine E4S) that I got from ebay that has spring loaded contacts for easy replacement of 18650 cells and can measure capacity. For measuring power banks I use a device similar to what you have here, but I measure both a charge and a discharge cycle and take the geometric mean of the capacities to compensate for loses in the charging/discharging circuit.
Good stuff! Does the ambient temperature make a difference to capacity of lithium cells during charging and discharging? Electric cars charge slower and have less capacity at low temperature (30°C is optimal), and alkaline delivers most capacity at 20°C during discharging...
Happy new year, Clive! I assume either this video was recorded earlier or you have remarkable powers of recovery...
I actually moderate the amount I drink carefully when I visit those particular friends.
How for you account for the losses from the power bank circuitry heating early on that you mentioned?
Now a days respectable battery makers list the power in Watthour instead of mAh .. it gives more accurate indication of how much power the battery can store .. every time you test a battery capacity you state that it took "x" mAh which is less than the capacity listed .. yet you seem to forget that you're measuring the mAh @ 5V .. while the rated battery capacity is listed @3.7V .. that's how you always end up with lower mAh "nominal" capacity while the true Wh measured capacity is actually higher. example: that Duracell power pack, it listed the capacity of 6.7 Ah @ 3.7v .. your test measured 5.4 @5v .. but 6.7x3.7= 24.79 Wh, while 5.4x5= 27 Wh. which makes sense .. it's the battery capacity + all the losses in the circuits .. thus their listing if capacity as 6.7ah is true.
theR6969 - there are also disadvantages with the Wh unit... Wh is less useful if you want to use a cell or battery to directly supply a load that requires a constant voltage and you want to know how long such a load will run for.
If the Duracell power bank has a switching charger then what you said is true, but most power banks use linear charging ICs. With linear charger IC's the mAh rating is correct regardless of the charge voltage since the current is the same throughout the circuit - it acts as a resistor.
Mark 1024MAK ,I understand .. my point was referring to Clive always coming up with less capacity than listed .. he's always measuring input capacity @5v while batteries stated capacity is always at the battery's nominal voltage.
Skruffles , no matter what type of circuits are used .. there's always losses and efficiency. my point is, he's expressing capacity the wrong way .. capacity in mAh changes with voltage.
@theR6969 but the battery banks are rated at 5 V, so their Ah rating should match when measuring at 5 V...
Great video - but you didn't show any of your test loads. I have a resistive one and also the electronic one, with the heatsink with the tiny fan on it, and I get different results with each. mAh doesn't take voltage into account so I always convert to Watt-hours.
Clive, do you have any recomnedations for good, high capacity, but not ridiculously expensive, 18650 cells? I have a set of 4 in an external battery pouch which came with some bike lights, but the capacity if terrible and the lights just chew through the pack in less than an hour, even on the lower settings. Cheers
Can you link to the one you're using? (The yellow one) I'm definitely interested in doing some tests myself.
Interesting video :) If you want to know a little more on the RD UM24 (green) and UM34 (yellow) UPM's, I've got videos on both on my channel (or if you don't remember how to work the menu ;))
Although I differ in opinion from you on getting a capacity-measurement : I'll discharge a powerbank at a certain current and monitor that along the way. I'll do this for every charging mode the powerbank supports.
Clive, easiest way to check charged/discharged capacity of 18650 or similar cells is just to use dedicated charger like LiitoKala Lii500 or cheap IMAX B6 for almost all kinds of chemistry.
I use this technique to test cells sealed inside equipment.
@bigclivedotcom would you be interested in reviewing a niche battery technology, LIPO? I'm a radio control model car enthusiast and would love to see your opinion of this batterys' performance on your test.
For testing normal li-ion cells analysing chargers are better, for example opus 3000 or liitokala li-500. They are quite accurate in measuring capacity, and can measure capacity when charging and when discharging. For switch mode power banks I think it's better to measure not Ah, but Wh, as Ah is voltage dependent. You put in 1A for one hour at 5V, you get 5Wh in charging circuit. Almost the same ammount of energy is then put in battery but with lower voltage/higher current, but total power put inside the cell will be around the same amount (with some loses in charger, around 5-10% is a safe bet for losses). If there is no Wh written on power bank, you can calculate this by multiplying Ah by 3,7V
You are an early bird again.
An interesting vlog, but would you like to tell us more about the yellow (Rudaing??) controller?
you have a link for the little yellow tester?
I have a Imax b6 charger. They are on Ebay for like 20 bucks. They have all the connectors and can charge/discharge most any type of battery. I have used it a few times and works pretty good.
Can you recommend an AA battery analyser? Project Farm did a great video to test the actual capacity of a few brands. He used a Powerex device but it's quite expensive at about £60.
I always test the cells on their own whenever possible, and measure the capacity from fully charged to flat (using one of those imax chargers/dischargers)
That neat little 3W aluminium flashlight adapter can be got from Amazon or eBay quite cheaply. ETA: Also that USB Tester Power Meter - mine is a UM34C USB tester costing £26.99 from Innovateking-EU, but can cost a lot more so it pays to shop around.
Bonne video 👍 bonjour de la France 🇫🇷
Another thing though, I watched some of your earlier videos and you were using one of those little load testers with winding resistors you can get off eBay for like 1USD -- As opposed to a light.
Did something happen to that device or is the light just more convenient?
The light is a good indicator of when the bank has cut off.
Clive, please can you tell me what an acceptable quiescent current is for those circuit boards are?
Some draw as little as 10uA in standby, but others draw a surprising amount of current.
Are those modules the U24 or the U34 Bluetooth????
Still got a question for 18650. Personally when i test mines, i drop them to 3.6v and stop at 4.2v or vice-versa. Are there some official standard for initial and ending voltages?
I once got a no-name power bank has 2 18650 cells in series and they boosted the voltage when charge, step down the voltage for the output, they have 2x3Ah cells in it and the board design looks quite nice with a big inductor, wondered why did they do that? Is it possible because of stepping down the voltage when output is more efficient than boost it up like regular power bank do?
It should provide more current with better efficiency for the output at least, it's easier to PWM the voltage down at high current rather than boost up the voltage of several amps.
Thanks for sharing. Im interested in testing my NiMh AA cells and see what capacity they have and when I should dispose of them.
Depending on how many you use on a regular basis it could be worth getting one of those analysing type charger deals. The charger I have for NiMH AA/AAA and 18650 lithium ion cells has options to charge, discharge, run cycle tests, etc (I think technically C cells and 26650 fit too but never used them in it so far)
My criteria for discarding NiMH batteries are roughly as follows: I'll put them through a charge, discharge, charge
I note down the initial internal resistance (IR), discharge capacity, IR after its final charge. And then also check their voltage a day later (and if really paranoid maybe run another discharge test on them then. For ideal usage I write the measured discharge capacities on them too, this way regardless of age/cycle count you can easily put together a set with similar capacity for things that need more than one battery.
But basically I have observed two reasons so far for occasionally discarding some: high IR even after putting them through a cycle (making them useless for high drain purposes) or somehow they seem to have a slight internal short and lose voltage/capacity really quickly over time. NiMH batteries do seem to be pretty robust though many Eneloops that have gone through more cycles than I can count are still going strong. I have occasionally discharged them to the point they'd show up as reading 0V on the charger and they recovered from that with a useful capacity remaining (this happens with long standby times on things I forgot in drawers). Very rarely there's also a few that have such a high IR/can't retain any capacity that they'll shoot up towards 1.45-1.50V right after putting them on the charger and are nowhere near their rated capacity.
I have however pretty much transitioned to low self discharge only in the pile of NiMH batteries that still see active use, the little bit of extra capacity you get in "high capacity" non-LSD cells is pretty much wasted if they sit around for longer than a week or so after charging. Easier to have batteries that don't need to be charged before every single time you plan to use say that flash module for your camera or whatever (and your spare batteries in the bag will be charged too!).
As for what charger to get? I quite like my SkyRC MC3000 (expensive but worth it for the convenience) however for many use cases it is hard to justify buying one of those especially when you're only going to be testing NiMH batteries. For NiMH the Maha Powerex MH-C9000 has traditionally been highly recommended but that's also not cheap and based on a quick glance on my usual go to site for batteries and chargers this situation hasn't chaged the last few years www.nkon.nl with availability.
For not so regular usage I would suggest to just charge them as you normally do and test IR yourself: if I remember things right this is pretty easy to measure with two multimeters, some resistors to simulate two different loads and measuring both current and battery voltage with both loads. Then do some math and you should have your answer, you could probably even make do with one multimeter and assume the resistance of your load is constant and derive currents from the voltage and resistance if its needed for the math (last time I did this was too many years ago, fancy chargers and other dedicated tools capable of doing this for me have made me lazy).
U Oude Hampsink The simplest solution is to buy one of the many NiMH chargers currently on the market that not only measure the total mA-hr input to the cell but also include a built-in charge cycling capability that will first charge the cell to 100%, then discharge it at a programmed rate, then will recharge to 100% and will then display the final capacity of your battery. When charging most NiMH batteries I find you will get the best results if you select a 1/4 to 1/2C charge rate (that is, 1/4 to 1/2 of the battery’s stated capacity) - with 1000mA as my highest suggested charge current for AA cells - as then good batteries will charge within 3-5 hours and will charge to an even capacity without excessive heating. At higher charge rates the capacities even within otherwise matched sets will tend to vary significantly, but at 1/2C, or less, they pretty well charge evenly. I use several PowerEx MH-C9000 chargers, purchased from Amazon, for my NiMH battery charging needs as they can not only charge the batteries at a programmed rate but can also be setup to cycle test and then recharge the batteries automatically. The only downside is that these are not “set and forget” type dumb chargers, so you have to input your program settings for each cell you wish to charge each time you insert a cell, but fortunately it only takes a matter of seconds to do so once you learn how to use the charger (though if all you want to do is charge you could just accept the default charge program if lazy) - but this model is fairly easy to program compared to some others as it does not nest button functions the way some models do when they try to make a button do multiple functions depending upon press duration, this charger has the necessary compliment of four buttons to make things straightforward with only one function per button). I typically keep around 50-60 AA and AAA NiMH cells charged at all times for emergencies.
the green one has bluetooth so you can log the info on a computer or smartphone, i use this to monitor pulling Li out of sleep mode (over drained)
Is the true or closest measure of a LiPo cell during charge from minimum voltage, discharge at a constant rate to minimum voltage, or both?
I have a "smart" charger (an icharger 208B) where I can set the charge current, and has a function where I discharge at a constant current, and it counts the Ahr during either one.
For a LiPo cell (3.7v @ 2000 mAh) I usually set the charge current at about 400 mA and when I use the discharge function, the discharge current at 500 mA. I use the measured capacity from the discharge as the available capacity of the cell. Should I use the charge capacity instead? or will either one work?
Recommendations/opinions?
If you want to know how much power you can pull from the cell (arguably the more practical number), use discharge capacity.
I charge my lipos at 1C.
In the case if Li-ion and Li-Po cells specifically, the power you will get out is greater than 99% of what you will put in with proper charging, so it makes little difference. If you use a linear charging circuit (which is most common for these powerbanks) then the easiest way to determine the mA-hr rating is to fully deplete the battery to cutoff voltage then charge it using a USB power monitor that records accumulated mA-hr and figure that mA-hr rating at about 3.6-3.7V if you want to calculate W-hr. When discharging these power banks where there exists a 5V boost switching supply circuit you do not get an accurate recording of battery capacity because the boost circuit will have only 85-90% efficiency plus you need to account for the added mA-hr drawn from the battery to boost that 2.8-4.2V battery voltage up to the 5VDC (about 1.4x average multiplier) that is being output, so a lot more math is involved if you want to estimate actual battery capacity from the discharged power, hence measuring charge mA-hr is a much more straightforward alternative provided a linear charge circuit is being used by the device - if you encounter the rare powerbank that uses a buck switching regulator for charging then you are back to estimating battery capacity as you must then, again, account for the difference in voltage between input and output (5V to 2.8-4.2V) and the efficiency of the buck regulator, but most powerbanks use a linear charging regulator circuit for simplicity which make measuring charged capacity easiest. On the other hand, if you are measuring bare batteries (no intermediate circuitry other than charge protection) then for Li-ion you can simply measure charge or discharge power since they should differ by less than 1%, though with most other battery chemistries you would ordinarily want to measure discharge capacity to get true useful capacity.
I acquired a lot of knowledge from this Vlog. I was wondering if they would be changing the meter from USB A to USB C or would an adapter be sufficient ?? Have you looked into the Handwarmer +power banks???
It has extra connectors for micro USB and USB-C on some models. I took one of the hand warmer packs apart in another video.
Clive, how do check the capacity of Non re-chargeable batteries i.e. Zinc, alkaline etc. Have you ever checked the capacity of Lidl’s Areocell batteries?
The RUIDENG UM34 Voltmeter Ammeter displays & records mAh and mWh’s.
I have a crude AA test setup that gives a useful indication of all AA style cells. It's a modified clock.
Thanks for this useful informative video Clive, much appreciated here... 👍🏻 😉 🐍
Just like to say your channel has been my best discovery of 2018. Long may you buy cheap trashy electronics and test them
Question! If a power bank has a 10,000mah with a 2.1amp port and a 1amp port, if I use the 2.1amp will it just be faster or will the battery be using double the power compared to 1amp.
The 2A and 1A ports are usually in parallel with the difference being the way the data pins are used to signal the current availability. It's to make some phones charge properly. Sometimes the total current available is still just 1A.
could you use a constant load device to measure the capacity of a battery?
Lithium is actually pretty safe, and an essential food supplement. It's Nickel and Cadmium that are a bigger environmental concern.
Just as a heads up I have a battery charger that will test the capacity as well as charge them, it's also not very expensive. You might even find it interesting, it's called MiBoxer C4. Got it on Amazon for less than $30 usd.
The only issue I have with this type of charge testing (And I do it myself) is that the readings are distorted by the efficiency of the 5vUSB to CellVoltage conversion. I believe this method will always measure the capacity with about a 10% over-read. The same stands for the discharge of the cell. They will typically under-read by about 10-15% due to the measuring at 5v as you said around 14:00. I guess these numbers are close enough for general use though.
I built, but never published, a tester based on an Arduino and a couple of constant current drivers that I feel gave better values for capacity. It measured the capacity using time and a fixed current of either 1A, 100mA or 25mA based on voltage triggers. I might drag it out and publish it sometime soon as I've never seen this done anywhere else.
Sorry for waffling! :-)
With the simple current regulation the current is constant through the whole circuit. So the current being measured by the mAh counter is exactly the same as is passing through the lithium cell. It's only on some more sophisticated power banks like potentially the Duracell one that buck regulation skews the result.
bigclivedotcom To add to Clive’s comment, that is true during DISCHARGE as most power banks use only a simple linear voltage/current regulator during charging for simplicities sake - this means that the mA-hr reading you read when charging a depleted battery will ordinarily match that of the battery to within better than 1%...and if you want battery Watt-hours you would multiply that mA-hr figure by the battery nominal voltage of 3.6-3.7V.
But during discharge you must account for not only the added power draw the battery sees from the boost regulator boosting 2.8-4.2V up to 5VDC but also for the 85-90% efficiency of that boost circuit plus whatever load your USB power monitor may add - so determining native native battery capacity during discharge is more complex, but determining such during charge is usually trivial and since the efficiency of Li-ion batteries is better than 99% you may as well use the charging figure since it will be off by less than 1%.
However, there are a few charge banks out there (particularly those with fast charge support) that use more efficient buck regulator’s during charging in which case the best you can do, short of removing the battery and measuring directly, is to measure the Watt-hours used during charging and then multiplying that figure by 0.85 to 0.9 to compensate for the inefficiency of the buck regulator since, in this case, the Watt-hours figure is the most trustworthy number to go by with a switching regulator and then derive the battery mA-hr rate based upon its nominal 3.6-3.7VDC (so, real Watt-hours equals measured W-hr multiplied by 0.875 and to get Ah figure you would divide the real W-hr figure by 3.7V).
Back again. So I measured my one phone, a Nexus 5X, from flat to full and it came out around 2300 mAh. Supposed to be 2700mAh new. Makes sense to me. I think I used the mWh reading and converted it down to mAh @ 3.7V
I know that normally this would be difficult to measure at all since usually you charge a phone while it's on, so I did it while it's off, hopefully keeping the draw down.
That's not my Daily phone though. It's one of the models that had a widespread bootloop issue, so now it's really slow to use.
The replacement was a Doogee S60. A brick of a phone. I noticed a lot of lies in their advertising. Like they say it has stereo speakers, it's only got one for media playback. They say the charger's capable of 12v 2A (so 24W) charging, I can only get 9v1a, or 5v1.4a out of it.
They say the Battery is 5580mAh. So of course I want to measure that.
Ran it flat. charged it to full while it's off. The numbers are confusing. It started at 5.12v 1.4a and went down to 5.02v .25a by the end.
Ruideng says it used 3080mAh. Being generous and using the max voltage to convert that to mWh, 15769. Down to 3.7v, 4262 mAh.
The Ruideng also said it used 23835 mWh, which I think is what I used to measure the 5X before, and THAT converted down to 3.7v is 6442 mAh.
Since neither of these are close to the stated capacity, and I've had the Doogee for a year, would you think the mAh -> mWh -> mAh reading is more accurate or the flat mWh -> mAh?
If you read all that, thanks a ton! Also never buy a Doogee phone, Clive.
is there an app that can use to determine actual mah of a power bank?
I remember when nickle cadmium was the thing before Li+ existed. I would trickle charge a battery until I knew it was fully charged (a few days, doesn't hurt them). I had a modified analog travel alarm clock. Instead of it having a battery, I installed a resistor and some wires. I would set the clock to 12:00 and hook up the charged battery to it through an ammeter. I would write down the current at the start and finish of the discharge and take the average (close enough) of that current and divide it by the hours the clock ran to get the AH of the battery.
hi what are the names of the usb testers he uses and the name of the big tester thanks
Rui Deng (Sp?) makes great stuff like their line of CC/CV DC PSU's The display gave it away :-)
I guess Watt hours (Wh) would be more accurate when comparing the bare cell to the 5V bank output ?
da-Share
Yes, it would. As an example, what Clive started near the end could confuse people: a 3.7 V cell capable of outputting 1 A for three hours is absolutely not going to be able to output that same 3 Ah at 5 V. Shifting the discussion to the energy capacity in Wh would make this far easier to understand.
(Photography review websites always use the Wh ratings, for example, as this lets the reader know how much energy is available in a given cell or battery - and this is what people really want to know.)
da-Share LOL, at 13:15 Clive says Watt else...
da-Share Not really as W-hr is skewed by the linear regulator during charging and you will need to compensate for the 85-90% efficiency of the 5V boost switching regulator circuit during discharge and both of those will require compensation to determine actual battery capacity (though either would be an acceptable measure of actual powerbank capacity as a complete unit). Since nearly all of these powerbanks use a linear regulator charge circuit the easiest figure to work with is the mA-hr capacity input to the battery during charging (from fully depleted cutoff voltage) then if you want an estimate of W-hr capacity multiply the mA-hr figure by the nominal 3.6-3.7V of the Li-ion cell to get the battery’s native capacity. Since you will get better than 99% of what you put into a Li-ion battery back out of the battery the discrepancy between input and output power is less than 1%, hence it is easiest to work with the mA-hr figure you put into charging the dead battery to figure actual capacity if the internal battery.
There are advantages and disadvantages when using Wh, the same as there are advantages and disadvantages when using Ah.
If there are no buck or boost converters, Ah is a more useful unit to use.
If there are buck or boost converters, Wh may be a more useful unit to use.
It all comes down to what and where you are measuring, or what the load is on the cell/battery.
For example, if using a high capacity lead acid 12V battery that is directly supplying a 12V load, as no conversion circuitry is involved, Ah is the more useful unit, as that tells you how long the load will run for at a near constant current.
All cell/battery manufacturers use Ah to state capacity (including primary and secondary cell types).
Can you explain what are the disadvantages of using Wh?
I am not aware of any. There only are advantages.
(except when you want to count "impossibility to confuse the customer" as a disadvantage, of course)
The "tight" power bank is only meant to take a cell that doesn't have a protection circuit. The protection adds a little bit to the length of the cell. Most things that receive 18650s can fit both lengths. Considering thats a "DIY" style USB battery its pretty much a defect of design not to accommodate both lengths.
Good video. 👏🙌👍👌
Can I give you some of my old electrical test equipment to tear down? Thanks
Interesting, I'm surprised you get capacity from charging.
I used to test 18650's like that but I've had lots of batteries that are old that must be internally failing as they take quite a bit more to charge than you get back out.
Now I use an Mc3000 charger though as it gives me charge and discharge characteristics on the PC/phone which is pretty sweet.
If those cells are taking longer to charge than their capacity suggests then monitor their voltage over time with no load. If it drops significantly then recycle the cells as they may have internal shunts.
I don't like any of the displays on those USB-testers. What happened to the nice blue Keweisi branded one with an OLED?
The new Ruiden one is a lot clearer to read.
@@bigclivedotcom that may be but the LCD display of the UNI-T is just awful.
Ruideng should sponsor you, lol. Bought a um34c because of this.
Any info about 9volt USB type C units?
Did you get the Ruideng UM34C with blue-tooth? A couple of months ago I purchased a cheap android phone from China so I could load all sorts of dodgy apps without worrying (separate gmail account w/pre-paid credit card). The app for the UN34C is well worth checking out.
I didn't. I'm always cautious about downloading apps like you describe. It really does require a separate account and system.
I'll buy you one. I am a Patreon supporter, so you may be able to get hold of me through them.
I can recommend the Imax B6 charger or one of its many clones for people who play around with LiPos. It will show the capacity while charging and discharging. It is also very hackable for someone tech savvy. I have a homebuilt case with 3 of these powered from an old, hacked 203W Xbox 360 powersupply, which is just enough for my use.
if you want to test a charge, you can use UM34C to check the voltage , then you use usb load to adjust the max current to test the load output . this way can judge the quality of charger
Bigclivedotcom Clive, can I get the make, model, and supplier of your yellow USB meter, please? Thanks!
m.banggood.com/RUIDENG-UM34-UM34C-For-APP-USB-3_0-Type-C-DC-Voltmeter-Ammeter-Voltage-Current-Meter-Tester-p-1297185.html?gmcCountry=US¤cy=USD&cur_warehouse=CN&createTmp=1&ID=511646&gclid=EAIaIQobChMIvKCqs7DO3wIVAgNpCh09LAAgEAQYAiABEgIdRvD_BwE
@@alphatexltd7040 Thank you!
@@alphatexltd7040 Thgank you, Happy New Year
didn't you have a keweisi 5$ tester as well Clive?
I do somewhere, but I like the Ruiden unit. It's got a very clear display.
I have an adapter than lets me hook up various things to one of those fancy model chargers, then just run the "discharge-charge cycle" (at limited current, like 500mA) and look at the display.
Interesting that you say the Uni-T metres are fairly good. AvE seems to have a differing opinion.