What's the best 18650 charger/tester?

[okrobie]

I am about to acquire a large quantity of used 18650's and I want a good instrument to do quality control with. One that will report the mA/hr capacity of the cell etc.

I have been told that the OPUS is very good
https://smile.amazon.com/Universal-Battery-Charger-Tester-Anazlyer/dp/B076P52TMH/ref=sr_1_20?dchild=1&keywords=18650+tester&qid=1591054987&sr=8-20

But this MiBOXER looks like similar specs and it has 8 bays
https://smile.amazon.com/Universal-Battery-Automatic-Rechargeable-Prevention/dp/B07QXP6XT3/ref=sr_1_15?dchild=1&keywords=18650+tester&qid=1591047389&sr=8-15

Does anyone wish to offer an opinion? Or are there other options? Thanks, Jim

 

[markz]

iChargers are one of the best, but the best for what, in your case you want to individually charge each individual 18650 cell quickly. You could make something for the iCharger to hold 18650's but you'd be stuck with one or two 18650 cells. The iChargers are good for testing the Internal Resistance and graphing dis/charges plus a multitude of other features, I am not familiar with iChargers beyond casually reading others efforts here on ES. Icecube57 member did a lot of Lipo testing on his iCharger. Search username for his posts under advanced search.

https://www.icharger.co.nz/

Your selections look good for what you want to use it for.
I wouldnt trust their build quality in terms of safety cut off, grounded, temp sensor cutoffs, charge cutoff or whatever they claim in their specifications, so keep an eye on them while they are is use. Remember that keeping a cell charging can creep higher and higher well beyond safe limits.

 

[pwd]

I've used a Littokala li500S and a Zanflare C4 for their "testing" capability. They both work fine but I found the "touch" function on the li500S to be a bit buggy (occasionally turns on at random). There is the regular Littokala li500 (non-touch) version as well.

Be aware that these type of charges have their inaccuracies. I found that each bay/slot had it's own variance that you need to take into account. Example: Slot 4 would always be 2-3% higher mah reading than the others. The internal resistance measurement doesn't appear to be very accurate at all on the C4 but I've read that is true for most "18650" charges/testers.

I would have preferred to use the iCharger 206B I had but it was more convenient to purchase the chargers mentioned above. I suppose if you could build/buy a 6 slot holder to use on the iCharger as a 6S pack, that would be more accurate than most of these cyclindrical cell tester/chargers.

 

[okrobie]

Thanks pwd and markz, I went ahead and ordered the MiBOXER. I wanted to get the Littokala but ithe MiBOXER had a quicker delivery date, and of course it has the 8 bays. It'll be here tomorow and I will be sure to give it an informal review sometime over the weekend.

 

[okrobie]

Hi all, My MiBOXER Charger/Tester arrived today and the re4sults are even better than I expected. Not only is thedevice working well, but the batch of batteries I ran, had much better specs than I had hoped for. More detailed information tomorrow.

 

[okrobie]

Sorry folks, but I'll be sending this MiBOXER 8 cell Charger/Tester back to Amazon. Much to my surprise, I found that this product does not have temperature control. MiBOXER does have a 4 bay unit with temperature control, and I think I "assumed" that all of their products would have it.

I have an infrared laser temperature sensor and it is showing temperatures as high as 130°F on the battery surface. Some of the cells were too hot to touch with my fingers. I made a small video of the experiment which is linked beloe

http://thewebplace.com/images/VID_20200606_064600860.mp4

 

[okrobie]

This unit works so well in every other way, I have decided to try it for a while using the manual current setting option. I'll let you know how that works out. Thanks, Jim

 

[okrobie]

I'm finding that if I keep the charging current below 600 ma. the cell temperatures will stay below 90 deg. F. I think what happened yesterday was that I allowed the charging current to go on automatic. If I hadn't caught it in time I may have been dealing with the infamous thermal runaway that can cause spontaneous combustion.

Some feedback and dialogue would be nice folks. Either my topic is un-interesting or I'm talking to myself here.

 

[john61ct]

Pingback, we hear you.

"The best" will of course cost thousands, maybe millions so better to qualify that question with your intended budget or it seems silly.

Cheap gear like that will likely not give accurate results, but maybe $100+ is more than you want to spend, or you only need consistency in comparing cells rather than actual accuracy.

It would be valuable for the community if you do upgrade, to compare the cheap device accuracy against the more expensive, presumably more accurate ones' readings.

Yes, charging above 0.3C or thereabouts is stressful, really for longevity should be at a rate where you cannot detect any temp rise.

You also need to use much lower rates if you are testing mAh capacity against vendor's "optimistic" rating.

But for Y/N testing matching dubious cells, just pick a consistent current rate and stick to it, realizing you will never get rated capacity.

 

[goatman]

what was the starting voltage of the cells that went to 130f?

 

[okrobie]

Thanks john61ct, you are very perceptive. You realized right away that my budget was not in the millions or even the thousands. Actually, for my first effort in this area, I didn't want to get over $50. I was working with an unknown factor and that was, do my newly acquired batteries work at all? And you are correct to say that my goal is more like seperating them into general categories. 0-1000 mA/hr 1000/2000, 2000/3000, 3000/4000 etc. etc. If this project can provide usable battery packs for my 48V TaoTao 500 Watt scooter and the 2-1000 Watt bikes I am currently building, I will be happy. If this ever becomes a commercial venture, I won't expect the free forums to provide me with valuable answers. And thank you for the "ping"

goatman: I'm not being scrupulously scientific about this whole thing so my data collection has gaps. The "as-found" is missing and hopelessly irretrevable. Thanks for the "ping"

 

[okrobie]

Yes, charging above 0.3C or thereabouts is stressful, really for longevity should be at a rate where you cannot detect any temp rise.

john61ct, I was just re-reading your post and wondered if you could elaborate on the statement about "0.3C" as I don't understand what you meant.

There is some concern about productivity so I have gone above the level of "cannot detect any temperature rise" I am currently charging at a rate of 600 ma. and it has raised the average cell temperature to about 90°F where the ambient room temperature is about 75°F. This is admitedly a production motivated compromise, but unless I hear otherwise I will be comfortable with it. Thanks, Jim

P.S. This MiBOXER seems to have some undocumented features. Wheras I set the charging current manually to 600ma. a recent check reveals that the charging current has been "automatically" reduced to the vacinity of 300ma. So it seems that the manually set charging current may be actually a high limit.

 

[pwd]

"0.3C" means 0.3 multiplied by the cell's rated capacity. So if you are working with a 3000 mah cell, 0.3C is 0.3 X 3000 = 900ma

 

[goatman]

heres a graph of how a charge happens. the red line is Amps and blue line volts.

this battery was 5amp charge, what happens is the battery gets the full 5amp charge til the volts reach 4.2 volts. then the amps start dropping to a selected cut off amp. so if you've programmed for 0.6amp charge but then see 300ma youre probably just seeing the last of the charge cycle where the amps are dropping.

 

[john61ct]

my goal is more like seperating them into general categories. 0-1000 mA/hr 1000/2000, 2000/3000, 3000/4000 etc. etc. If this project can provide usable battery packs

Set your sights higher.

Say you have 500 cells all the same make and model supposed to be 2000mAh when new.

Which at a high C rate means your device shows 1700 at best.

The "buckets" you're grouping into should really be as closely matched as possible.

Truly worn out past Eol not worth messing with IMO would be 1000mAh and below (please dispose of responsibly).

Between that and 1400mAh maybe good for portable powerpaks, charge phones, camping, jumpstarting engines.

Then 1400-1500 grade C, 1500-1600 grade B, 1600-1700+ grade A.

There are online tools to try to get all the parallel groups to a similar capacity with a mix, but given enough supply, the better goal would be all the cells in a pack the same grade, finer "resolution" the bands the better.

I would also much prefer a solderless no-weld pack building technology, if one is reliable enough, so every say 50 cycles you toss out the weak links and replenish with better ones.

 

[john61ct]

And **many** members smarter than me have said, just don't waste your valuable time on scrap garbage

buy top-notch cells, brand new so you **know** your packs will perform well for a reasonable period of time.

Of course someone whose time is worth little, is third-world poor, and just want to fool around learning about this stuff, different story. . .

 

[okrobie]

"0.3C" means 0.3 multiplied by the cell's rated capacity. So if you are working with a 3000 mah cell, 0.3C is 0.3 X 3000 = 900ma

Got it John. Thanks.

Set your sights higher.

My sights are going higher by the minute, but I was taught to learn to walk before I can run. and don't count my chickens before they are hatched. I have found these axioms to serve me well. It was only a week ago that I cracked my first laptop battery and found these beautiful jewels inside and today I have over 50 jewels laid out on my table in groups. Some "groups" have only one cell because they are outliers or just don't have any cousins yet. I'm seeing as the groups get more populated.

As I continue to process more batteries, I have, for one thing, stopped calling them "Jewels". I have realized the need for more charging/grading capacity so I decided to buy another MiBOXER 8 bay charger and I'll continue to set an upper charging current limit. But mainly I have realized why you stated that my sights were too low. My earlier established groups were filling up quickly and I soon found the need to re-sort those groups into finer divisions and I can envision even finer divisions to come.

goatman: thanks for the chart. It helped me to visualize the process better.

"0.3C" means 0.3 multiplied by the cell's rated capacity. So if you are working with a 3000 mah cell, 0.3C is 0.3 X 3000 = 900ma

Thanks for the explanation.

 

[okrobie]

A question on internal resistance. Most of my battery experience is with Lead Acid. In that world high internal resistance is deadly. You can charge it up to a nice voltage, but if the internal resistance is high it will pull down quickly with a load.

What is the pattern with Lithium Ion? My charger shows internal resistance as soon as I pop the cell into it. Would that be a good time to toss cells with a high reading directly into the recycle bin rather than wasting 4-5 hours on it? I don't know if internal resistance will ever improve with LI cells.

This might be off topic, so if it is let me know. But it's based on readings I'm getting from my charger.

Thanks, Jim

 

[goatman]

high resistance is heat like the 130f heat you saw and if you have a cell with really low voltage like 0v id be very wary of it. ive brought some back from 0v, I had 52 of them and saved 35 but I don't trust them at all and some were getting ready to go thermal while bringing them back up= garbage.

average joe on youtube plays with batteries

https://www.youtube.com/channel/UCwHeIzOoLgSXHwxTSNSaKXA

 

[okrobie]

I bought a new charger analyzer this week. This one is an "OPUS" BT-C3100 V2.2. It seems to work very well, but it has raised a question. The internal resistance values given by the OPUS are way higher than the IR values measured by the MiBOXER's. The values given by the OPUS are nearly 200 milli Ohms higher than the measurements from the MiBOXER's. Looks like I will have to break out Kirchoff's law and see if either is correct. Naturally, I will report the results here.

P.S. If you do the math, you can see that using the OPUS will wipe out my entire inventory.

 

[john61ct]

ESIR is not an objective absolute, so do not try to find different devices that give similar results

IOW there is no "accuracy" best to strive for is consistency, especially wrt temperature.

Just come up with your own systematic protocol with a given device that yields **consistent** results.

And then use **relative** test results to compare different cells.

 

[pwd]

ESIR is not an objective absolute, so do not try to find different devices that give similar results

IOW there is no "accuracy" best to strive for is consistency, especially wrt temperature.

Just come up with your own systematic protocol with a given device that yields **consistent** results.

And then use **relative** test results to compare different cells.

That was my experience/findings exactly. ^^ Because each cell slot on my testers had its own variance, I had to just look for inconsistencies or larger than normal variations while trying to keep everything else consistent.

 

[john61ct]

If you want consistency

https://www.rcgroups.com/forums/showthread.php?1323465-ESR-IR-Meter-fo-Lipos


But no hope of "accuracy" unless cells are at exactly 72°F every time.

 

[okrobie]

Folks, I mentioned Kirchhoff's law. "Kirchhoff's voltage law (2nd Law) states that the sum of all voltages around any closed loop in a circuit must equal zero."

In practical terms this means that by putting a resistor, of known value, across the terminals of a cell, and measuring the voltage drop across the resistor, you can then subtract that voltage from the original unloaded voltage of the cell and you will then know the voltage drop across the Internal resistance. By Ohm's law I=E/R (voltage & resistance of the external resistor) you can calculate the current in the loop. Again, using Ohm's law R=E/I you can then know the EXACT internal resistance of the cell. Therefore you can conclude that Internal Resistance IS an objective absolute.

Therefore, if my instrumentation does not reflect a reasonable approximation of the objective absolute...it's going back to the store.

 

[john61ct]

“In theory, there is no difference between theory and practice. But in practice, there is.”

How can something be called objective if it varies **a lot** with even slight variations in temperature, or SoC? which is not well represented by voltage. . .

Good cells ESIR is so low internally you need expensive gear to get accuracy, 4mOhms can in some cases be a very high result lead to rejected cells.

Don't forget you really have no access to the **internal** materials, lots of external ones getting in between, different for different cells and measurement tools.

And the exact temperature standardization perhaps the biggest variable, how are you solving for that in your quest for "absolute objective" measurement.

Being on a low budget is not conducive to achieving what you are fantasizing about.

And it's overkill anyway, not at all required to achieve very useful results in your actual practical goals.

Just buy the Wayne Giles device
https://www.rcgroups.com/forums/showthread.php?3364193-The-official-new-ESR-IR-Mark-II-meter-thread-%C2%96-NB-READ-THE-FIRST-10-POSTS
and benefit from their experience. Or FMA PL8 or iCharger units, not yielding the same absolute numbers, but all fantastic if used properly - controlling for the important variables, and only for **relative** comparisons

You'll waste more money on return postage or reinventing the wheel.