Regarding capacity testing on the Lii-500 Engineer.
When doing NOR testing, selected current = 1000mA or 700mA, the discharge current is just 500mA.
When selected current in NOR test is 500mA or 300mA, the discharge current is 250mA.
I think capacity test for a 3400mAh battery are usually 0.2C (ie. 20% of 3400mAh or 0.68A discharge current). 500mA discharge current should be close enough. using a 250mA discharge current probably won’t be that truthful… You are using the NOR test instead of the Fast test, right?
Thank you for your response. Yes I only did NOR tests, as you can see in the link to my results.csv . The issue with 4 slots 1000mA NOR test (so 500mA discharge) is that it heats up, that’s why my reasoning was to do 250mA discharge (so 500mA NOR test). Why wouldn’t a 250mA discharge current be “truthful” ?
Btw for my use case, if I suppose my 2W constant load application, it makes (2,000/3.7/18) around 30mA constant load for each cell (in theory).
I saw the HKJ’s review of the Lii-500 Engineer, and don’t quite understand everything, but it’s strange his resistance tests are much more cohesive than mine (maybe because PCB?).
I’ve had 3 Lii-500. On all of mine the resistance test was worthless. Frankly, I wouldn’t believe it. You have a superior resistance tester anyway.
I’m surprised at the extreme spread of capacity on new Panasonic cells, unless they are fake. There have been some problems with fake cells at AliEx. There’s a thread somewhere on that issue.
I have seen cells that have been sitting around a good while need a few cycles to ‘wake up’ for want of a better term.
FWIW if you are building/soldering a pack together you don’t need protection. That will be provided by the external protection circuit you will add, or by a balance tap-unless you have some kind of holder you are able to put cells in and out and still get the pack configuration you want. I haven’t seen anything of that configuration that would work. Maybe in the E-bike realm?
Just built a 3S4P pack with balance tap for a friend. Largest pack I’ve ever built. Original pack/cells came out of a dive light. Simply would not perform, it was pathetic. Pulled the pack apart and tested all cells. Every one was OK. Likely the PCB board went bad, not the first one I’ve seen that way. Getting so I don’t trust those things. Got my early lithium experience with RC lipo cells, so am accustomed to balance taps.
Soldered them all back together, this time with the balance tap > works fine. But, I did have to give him one of my hobby chargers to charge it now.
I’ve found the Li-500 capacity (NOR) test to be fairly consistent. It might give a difference of around 2% from one test to another, but not anything like the 8% you describe. Perhaps your unit isn’t working properly.
However, I usually do my testing at the 250mA drain rate (running the NOR test at 300mA or 500mA). As you mentioned, it gets too hot when testing 4 cells at the 500mA drain (700mA or 1000mA setting). Perhaps the 250mA rate is more accurate.
As others have mentioned, ignore the Li-500 internal resistance values. They’re really inaccurate.
@flydiver:
The “wake up” you are talking about seems very relevant, the first test I did on my 4 “first” (labelles 1 2 3 4) cells had very bad (around 2800mAh) results for cell 1 and 2. I didn’t include the first test (one NOR test for cell 1,2,3,4) in the csv because I thought I had made a mistake in the test somehow since it was so far off.
My reasoning behind the protected cells was that if one cell goes bad, at least it will shut itself down before catching fire or other catastrophic event since I want to be able to use those batteries for like 100 cycles over 3 years. I will be using a BMS (not hobby charging, too inconvenient on the long run since I will be charging like 15 packs at the same time after each use) for each pack but I thought adding the individual protection included in each cell was safer. On a side note I made the acquisition of a great spotwelder (kweld) which is working great on all the tests I did. I will therefore not damage the cells with hot solder heating up the cells too much during assembly.
I’m sorry to hear about your bad experience with BMS, I heard quite a lot about the no-bms “trend”
(for example How to build a safe and better lithium battery WITHOUT a BMS. - YouTube) and they make a good poitn but usability is a big factor, my batteries being enclosed in a box with a xt60 female plug to charge from the outside.
Yes perhaps my unit is bad, I have 4 extra Lii-500 I ordered last week that should arrive in the next weeks, I will be able to test if it was my unit that was bad or simply the model. And also test at 250 and not 500. It is also in theory possible that the PCB in each cell is so unprecise it cuts the power prematurely sometimes (wild guess though).
Can’t comment on the reliability of the ‘double’ protection methodology. Something about it doesn’t feel right though.
What the defective BMS seems to do is take unbalanced cells, and starts corralling them in at the top and bottom. They don’t “balance”, though you can get more expensive ones that do apparently. What they do it prevent any single cell from getting over or undercharged. Since you always have some level of imbalance it seems the swings from charged to discharged get smaller and tighter with each cycle until the pack effectively has no top or bottom end.
I don’t know if this is a characteristic, a defective BMS, or just a lousy design on a cheaper pack. The experience I’ve had has been people bringing me by packs that were not working right and wanting someone with at least a bit more expertise than they had (essentially none), to help them out. I don’t have tools to check BMS, nor the knowledge to do so. So, I take the pack apart and test the individual cells. So far, in my small sample, the individual cells have always been good, all of them, when the pack was performing badly.
@BlueSwordM : Getting back on your first point. After reading the thread it is indeed horrifying. I “dissasembled” one of the cells ( I ordered 40 at the time, I didn’t use one of the 20 I already “tested” but one of the others, so I can test the first 20 again with the other lii-500 that are expected to arrive soon).
Nothing is written on the cell, here is a video of the top of the cell I case the “form factor” can reveal a bad cell : dissasembled18650protected .
Yes your capacity testing spreads out too much crevettedragon. This can of course be caused by slot variation, but is also cut-off influenced by inconsistent rail contact resistance. To fix the latter you should insert and wiggle the cells in the rails a bit to seat 'em properly, then power up the Lii-500 and check all IR readings. They should be within a narrow marging, e.g. ±10%, or as close as possible (cell internal resistance variation counts too).
Ok I am doing two consecutive 500mA NOR tests with the lii-500 with the cells well seated, on the same slot, and without touching them between two tests.
Will keep you posted with the results.
In the meantime, I am considering buying a EBC-A20, but need some research to confirm and also look for compatible cables (seems to be aviation connectors) for xt60(to test the assembled battery) and compatible cables+battery holder for testing individual cells.
So measured capacity stays roughly the same across the 3 tests (max deviation being 2.5). But as you can see the resistance test is nonsense: not only is the value absurd compared to what is measured with the much more trustworthy SM8124 but it also goes from simple to double with the cell staying at exactly the same place (I even unplugged the sector side after full charge before a new NOR so it stays still between tests) so I’m not sure how one could be expected to have the IR be withing a 10 narrow margin unfortunately.
I will test cell 2 at 1A using the CC load tester I ordered before which just arrived.
I take great care to minimize variation and even then it occurs to some extent (check here for example), this is normal. Contact resistances are normally high by themselves even when the surfaces are clean and tightly coupled to, let alone if they're not.
The order of magnitude of a cell's internal resistance is close to that of a contact, expecting to measure it this way is rather tall order.
While it may be consistent, I find that my Lii-500 underestimates Li-Ion capacity during NOR test by about 5-6. That’s just by comparing my results when using 500 mA discharge rate to values tested by HKJ for various cells. HKJ may be using slightly lower cutoff voltage, but that in itself couldn’t explain the 5-6 difference I am seeing.
For example, using Samsung 35E cells, I get about 3175 mAh, while HKJ got 3379 mAh.
Does anyone else’s Lii-500 behave the same way?
Can anyone who owns both Lii-500 and some other analyzing charger (such as Opus 3100) comment on differences they’re seeing when performing discharge capacity tests on the same cell?
First of all let me say the Lii-500 scores a mAh when it is 100% done. If it were to measure cells with less than a full mAh of capacity, it will never score a single mAh point. This causes all capacity measurements to err down by half a mAh. To solve this let me say the capacity counter should update half a lapse before. Whether this is common in analyzing charger capacity tests or independent reviewer tests I do not really now, and in any case it does not make it or them exact. It is good to know in any case, and henceforth my capacity measurements will show 0.5 additional mAh.
First of all I will say that as early adopter I ordered a couple Lii-40A cells in early 2018. That 3rd of March I got 3865.5 and 3898.5mAh for them in my Lii-500, slots 1 and 4 as you may understand. It was a tight fit, both cells ended up slightly arse dented. This is a different slot and cell 3882mAh mean, while Henrik got 3960mAh.
Since every slot in a Lii-500 operates independently, all of them display measuring differences. I made a small test to get slot deviation info by testing the capacity of a couple old, laptop pulled Samsung ICR18650-26C cells. Since cell capacity theoretically degrades with each cycle, to cancel this effect I tested each cell two times per slot in a pendulum swing motion arrangement, 1 - 2 - 3 - 4 - 4 - 3 - 2 - 1 and 4 - 3 - 2 - 1 - 1 - 2 - 3 - 4. Between parenthesis is the slot and cell measured DC IR, in mΩ:
So, it seems your unit is about as accurate as mine. About, +/- 2%.
In addition, I don’t think it’s necessarily giving the correct absolute value, but if it reads a bit high all the time or low all the time, that allows me to compare cells to one-another, or in the future.
IMO, that’s good enough, considering the Li-500 is a budget charger/analyzer. I’d expect more accurate and consistent readings in an expensive analyzer.
Got my early lithium experience with RC lipo cells, so am accustomed to balance taps.
But, I did have to give him one of my hobby chargers to charge it now. 
