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Anyone using Lishen 202 AH prismatic cells?

Gazoo said:
I have asked for a refund and Mr. Tim agreed. I simply can not accept the batteries with milliohm readings that high and with the wide range readings.

Having said that I would still highly recommend billion. Mr. Tim replied to all of my messages promptly. Just make sure to check the milliohm readings when they send the videos. The readings should be less than .4 milliohms and should be almost the same for each battery no matter who one orders from.
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Thank you for relaying all your dealings and impressions, sorry the deal didn't work out for you, but glad you caught it before it was too late to turn back. From everything you have reported, it sounds like Mr. Tim and Dongguan Billion have integrity and good customer service.

What method were they using to check internal resistance? I'm still not clear on the best method to accurately measure this.
 
Dzl said:
Thank you for relaying all your dealings and impressions, sorry the deal didn't work out for you, but glad you caught it before it was too late to turn back. From everything you have reported, it sounds like Mr. Tim and Dongguan Billion have integrity and good customer service.

What method were they using to check internal resistance? I'm still not clear on the best method to accurately measure this.
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Yeah it's a shame this didn't work out. When I placed the order my Chase card went through within 10 seconds...lol. I was surprised since I have read about so many people having problems getting their CC to go through. I am going to wait until my refund is processed before ordering from some where else.

I am not sure about the best way to measure internal resistance either. I hope @Will Prowse will post a video dedicated to to this. However after searching the internet and reading the posts here from other members that had the IR tested, I am confident I made the right decision cancelling the order. If not for this forum I would have not known any better.

The IR resistance of the cells is very important to look at. If not matched the batteries will not balance. The individual cell voltages being very close to each other doesn't mean squat if the IR is bad and varies as much as it did with the cells I had ordered.
 
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I connected my pack in series and performed a crude load test and a rough calculation of internal resistance under load. I didn't have my BMS connected yet, but I hooked up my 2000W inverter and ran a 1500W hair dryer. The front panel of the inverter and my kill-a-watt meter were both reading about 1.54 kW, and my pack voltage sagged from 26.0 volts down to 25.6 volts. I calculate the internal resistance of the pack around 6.2 milliohms. At first I was crestfallen as I thought it should be somewhere in the vicinity of 1 milliohm. Then I remembered I had 8 cells in series, so my internal resistance per cell is around 0.8 milliohms, which is a bit lower than the vendor measured, but still higher than spec. Assuming it holds up at my inverter's maximum load of 2000W, the largest voltage sag I should see is about 0.5 volts. But for my main application - running two freezers which each pull 120watts each when compressors are on, plus a surge whenever the compressors are starting up, I think I will be fine for now. But I recognize that this is probably as good as it gets, and I should monitor internal resistance as my pack ages. I also checked the voltage of each individual cell while under the 1.5 kW load, and they were all very close to equal so that indicates the internal resistance of all the cells are close to the same. Quiescent current of my Giandel 24V 2000W pure sine inverter is 0.7 Amps, so I'm reasonably happy with that. I didn't run the hair dryer longer for a few minutes, but I didn't notice any of my connections or inverter cables getting warm so that is good. I didn't bump it up to 2000W load because I'm using the cables it came with that I think are about 6AWG, and I have some 2AWG cables on order, but not here yet. I want to wait until I have all the connections the way I want them before I do a max load test.
 
Thanks for taking the time to test. I would be very curious to know what the IR would test on your cells with a meter. But I don't think it's necessary since the voltage remained equal under the hefty load you put on the cells. I am curious if your cells remain in balance after you get your BMS hooked up and everything.

The manufacturer spec for Lishen is less than .4 milliohms. The readings of the cells I was going to get was between .613 and 1.042 milliohms. The posts I have read from forum members that had the vendor test their cells showed the IR was way lower than what mine tested at. Also their IR readings for the cells were within a few milliohms of each other. There are Alibaba sellers with videos on their sales pages testing cells and they all show normal readings.

It's possible the IR meter they were using to measure my cells was flakey. I was very tempted to take a chance on that and ask the seller to ship them with the understanding if they did not balance I would be asking for a resolution....since they claimed the cells are new. But then that may have resulted in a bunch of headaches. Anyways thanks again for your testing and please keep us updated when you get your BMS.
 
Gazoo said:
It's possible the IR meter they were using to measure my cells was flakey.
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Is it really possible to get an ohm reading to 4 decimal places with a meter like that and simple alligator clips?

Even with a good dmm, measuring voltage drops to hundredths of a volt, calculating parts of a milliohm is statistically insignificant. Right?
 
MisterSandals said:
Is it really possible to get an ohm reading to 4 decimal places with a meter like that and simple alligator clips?

Even with a good dmm, measuring voltage drops to hundredths of a volt, calculating parts of a milliohm is statistically insignificant. Right?
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So if one of the batteries measure .600 milliohms and the other battery reads 1 milliohm measured with the same meter will they balance?
Why is it all the other readings I have seen are in the .13 -.16 milliohm range?
Did you watch the video I posted in this thread of my batteries being tested?
Knowing the Lishen spec sheet rates the internal resistance of the cell less than .4 milliohm would you have accepted them?

I don't mean to be snarky or anything. I look forward to your reply. I think the subject could use more attention.
 
MisterSandals said:
Is it really possible to get an ohm reading to 4 decimal places with a meter like that and simple alligator clips?

Even with a good dmm, measuring voltage drops to hundredths of a volt, calculating parts of a milliohm is statistically insignificant. Right?
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They are AC impedance readings (same as ESR meters for capacitors) so yeah, not a classic ohmmeter, that would require 4 wires kelvin connections and a meter almost as expensive as a car...

The DC IR should be relatively close tho. The more important part is for the readings to be close to each other for all the cells and to be within datasheet spec.

Gazoo said:
Why is it all the other readings I have seen are in the .13 -.16 milliohm range?
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Higher capacity cells will have a lower IR. Do you compare identical (or near enough) capacities cells?

Gazoo said:
Knowing the Lishen spec sheet rates the internal resistance of the cell less than .4 milliohm would you have accepted them?
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Nop, unless they are super cheap, like 1/3 of the cost.
 
Gazoo said:
Knowing the Lishen spec sheet rates the internal resistance of the cell less than .4 milliohm would you have accepted them?

I don't mean to be snarky or anything. I look forward to your reply. I think the subject could use more attention.
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>would you reject them?
Maybe/probably if i knew as about this as you do!
It seems like an awfully small difference to me.
I tried testing my cells with quite a few gadgets and got numbers in the 1ohm to 10 ohm range. These crappy gadgets only worked thru a loom on a battery. I found that certain cell positions had higher IR values regardless of how i arranged the cells.
My Battgo 8S shows IR in the 1.3 ohm range for 6 month old 206 ah LiFePO4 cells.
My dmm showing only hundredths of a volt was meaningless trying to calculate ten-thousandths of an ohm.
I still have no idea what the IR is but i do know they capacity tested full value and evenly across 13 cells. That was where i stopped testing.

Its good to know someone knows about this and was willing to share.
I learned something today. Thanks!
 
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@MisterSandals If you want to know your cells IR precisely it's pretty easy; you need a voltmeter, a current clamp (or a shunt, or any other means to measure the battery current) and a constant load, ideally close to 1 C but even 0.5 C is plenty enough.

Measure the rest voltage with no load.

Load the cell/battery with the load. Measure the voltage right at the cell terminals and the current.

IR = (no load voltage - loaded voltage) / current ;)

Repeat for the next cell (of course the simplest is to measure first all the no load voltages in one go and then the loaded voltages but don't take too much time to avoid errors due to the cells discharging).

You can also do it at the battery level if you want to know the whole pack resistance (it includes the busbars, connections, etc... of course) for other calculations like short circuit current or voltage drop for a given load ;)

Also it's best to do that at a SoC around 50 % to be on the flatest part of the curve and avoid introducing errors due to the cells discharging.

The accuracy is very high as it's directly dependent of the voltmeter and ammeter accuracies even if it's in the µOhms. For example with a 1 % voltmeter and a 3 % ammeter you'll have a 4 % accuracy on the IR.
 
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I found a Youtube video of a guy demonstrating how to measure internal resistance of 18650 cells using a Turnigy Accucel 6 charger. He also did the determination manually using a discharge load test. Generally normal laptop type 18650's are around 100 milliohms, and power tool 18650's are usually lower - around 50 milliohms. So, since your average laptop cell is around 2000 mAh with an IR of 100 milliohms it stands to reason that a 202 AhLiFePO4 has 100x the capacity and also around 100x less internal resistance. I think these Lishen cells are OK (at least I hope so since that's what I got). But the EVE cells are reported to have quite a bit lower internal resistance with respect to their capacity.
 
Hum, not sure you can apply a ratio as large as 100x and still be accurate enough. But the laptop 18650s are NMC which is not the same as LFP so you can't really use their data anyway.
 
Metalophile said:
I found a Youtube video of a guy demonstrating how to measure internal resistance of 18650 cells using a Turnigy Accucel 6 charger. He also did the determination manually using a discharge load test. Generally normal laptop type 18650's are around 100 milliohms, and power tool 18650's are usually lower - around 50 milliohms. So, since your average laptop cell is around 2000 mAh with an IR of 100 milliohms it stands to reason that a 202 AhLiFePO4 has 100x the capacity and also around 100x less internal resistance. I think these Lishen cells are OK (at least I hope so since that's what I got). But the EVE cells are reported to have quite a bit lower internal resistance with respect to their capacity.
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Why not get a meter and measure your cells? Like the one @snoobler recommended in this thread.

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Internal Resistance Meters. Any recomendations?

I had been trying to use my icharger to measure internal resistance but it doesn't seem very reliable. I found this in stock with some decent reviews so I'll let you guys know what I find once I get it. My guess is it will only be good for binning cells not checking full pack resistance...
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I know it's more money to shell out and you might not feel the need to.

A resistance meter will be on my list of things to get but it's at the bottom of the list. I need to get cells ordered again.

If you do get a meter please measure the IR resistance on the cell studs and directly on the cell terminals. I am curious if the studs being welded on changed anything as Mr. Tim implied. In other words is there any resistance between the cell stud and the terminal? There shouldn't be. I also wonder if the cell stud is made of the same material as the terminal.
 
The 2 vendors I am looking at to place a very large order with both indicate that the EVE 280ah cells will be less than .25 milliohms.
 
BiduleOhm said:
Hum, not sure you can apply a ratio as large as 100x and still be accurate enough. But the laptop 18650s are NMC which is not the same as LFP so you can't really use their data anyway.
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Of course I know they're different chemistries. I just want to know that the 0.8 milliohm reading I got on my cells is in the right ballpark. If anything it might be an overestimate because my measurement includes busbar connections and post weld connections.
 
Just a quick update. I have been charging my pack at a low rate using one 260 Watt, 60-cell panel and a cheapo PWM solar charge controller. I wanted to see whether there is enough voltage overhead using the 60-cell panel that has a Vmp of 30.7 volts to charge my pack. So far so good. Even on a hot summer day the pack is just about full. Three cells are triggering the BMS to stop charging at 3.65 volts, so today I am trying to carefully bleed those 3 cells down to the rest of the pack using a 1-ohm hefty power resistor. This is my attempt at top balancing. After I get it balanced I intend on doing a capacity test at 0.2C or about 40Amps ~ 1000 watts.
 
I finally got around to doing a capacity test. I top balanced, not in the recommended way first. I was too lazy to disassemble my pack and parallel all cells - I don't have enough bus bars made for that. I have a small buck converter which I set to 3.65 volts, up to 3A. My pack was already in a high state of charge, so one-by-one I connected my 3.65 voltage source (which draws power from my existing smaller 12V solar system) to each cell until it was at or very close to 3.65volts and drawing almost no current. That process itself took a day and a half. So this afternoon I connected my shunt meter, inverter, space heater, 65W incandescent lamp, and Ryobi 40V lawnmower charger. Turned it all on. All told my loads drew ~730 Watts from the battery at first, short of my 1000 Watt target. But I didn't find any other convenient loads around to add. So I know that is less than a 0.2C discharge rate. I also began the test a day or two after I had top balanced the battery, so cell voltages started at ~3.45- 3.50 volts, not 3.65V. I also had the BMS set to cut-off when the first cell dropped below 2.8V. And the result was 198AH, just a bit short of the 202AH rating. That's probably close enough considering the less than ideal measuring conditions, also I don't know how accurate the shunt meter is. And there might be some measureable capacity between the 2.8v cutoff I used and 2.5v, but I want to take it easy on my batteries.
 
Well, my off-grid system is basically functional, but not in its final form just in time for Hurricane Laura. Batteries are charged back up to about 80% before clouds moved in today. We're expecting Hurricane Laura to pass very close to us after it makes landfall near the LA-TX border. Will likely get 40 MPH winds, about 6" of rain, and scattered brief tornadoes here in Central Arkansas. If the power goes out, I'll have some backup power from my new system and from my older 12V system.
 
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