Capacity Testing a Pack

[Dr. Dickie]

Okay, finally putting together the 14 packs of 160 cells each for my powerwall build--got the connecting wires (28 AWG tinned copper) for the negative side all welded and soldered in and just got the 32 AWG tinned copper wire for my positive side fuses.
As I make these packs, I would like to capacity test them before final assembly into the battery. I have an icharger X8 and a variable 30V 10A bench top power supply--so I think charging it will not be problem, just a very, very long time; however, I do not have a battery that I can regeneratively discharge the pack into. Since it will only be 3.7 V nominal, I don't have a inverter or anything I can run to discharge the pack into. I know the icharger has the ability to discharge without regenerative, but is that realistic? I haven't seen anyone use that so I don't know how well it can discharge such a large pack.
Do you guys test your packs before assembly into the large battery?? If so, how do you do it?
Thanks

 

[OffGridInTheCity]

I've used my iCharger X8 regeneratively and in 'regular' mode many times.

Normal mode (50w) - It takes about 6hrs to discharge my 130ah base-packs (90-120 cells) from 4.2 -> 3.7 (storage). A little less than double that for a full discharge... say 11hrs. By extrapolation (11hrs / 100cells) in regular mode would be (aprox) 33hrs for a 300cell pack.

Regenerative mode (100w+) - This can be used to cut in half a full discharge to aprox 16hrs - e.g. 1 day. This is pretty reasonable for $/convenience of iCharger X8 auto cut-off features etc in my opinion. Of course you can always DIY something with load meters and achieve faster discharge tests - and it may be worth it for you.

Note: In the beginning, I tried to use the cheap discharge testers with large fans that you see - and they were a disaster. Mine burned up after a few hours and the auto cut-off was not good. This is what lead me to go with iCharger... (X6 or X8) level equipment - which has been reliable enough that I let it run thru the night without worry it will overdischarge the pack.

For iCharger X8 regenerative operations I made a 7s7p pack in an APC UPS 1500 with an adjustable halogen lamp as my load. The 7s7p powered the APC and the iCharger X8. By adjusting the lamp I could match the burn to the power being dumped into the 7s7p pack by the iCharger X8 to sustain the discharge test. A little bit kludgy but the 'battery charge level' lights on the APC helped me adjust the load so I could keep it balanced... and this worked for me

 

[Dr. Dickie]

I've used my iCharger X8 regeneratively and in 'regular' mode many times.

Normal mode (50w) - It takes about 6hrs to discharge my 130ah base-packs (90-120 cells) from 4.2 -> 3.7 (storage). A little less than double that for a full discharge... say 11hrs. By extrapolation (11hrs / 100cells) in regular mode would be (aprox) 33hrs for a 300cell pack.

Regenerative mode (100w+) - This can be used to cut in half a full discharge to aprox 16hrs - e.g. 1 day. This is pretty reasonable for $/convenience of iCharger X8 auto cut-off features etc in my opinion. Of course you can always DIY something with load meters and achieve faster discharge tests - and it may be worth it for you.

Note: In the beginning, I tried to use the cheap discharge testers with large fans that you see - and they were a disaster. Mine burned up after a few hours and the auto cut-off was not good. This is what lead me to go with iCharger... (X6 or X8) level equipment - which has been reliable enough that I let it run thru the night without worry it will overdischarge the pack.

For iCharger X8 regenerative operations I made a 7s7p pack in an APC UPS 1500 with an adjustable halogen lamp as my load. The 7s7p powered the APC and the iCharger X8. By adjusting the lamp I could match the burn to the power being dumped into the 7s7p pack by the iCharger X8 to sustain the discharge test. A little bit kludgy but the 'battery charge level' lights on the APC helped me adjust the load so I could keep it balanced... and this worked for me

Thanks OffGridInTheCity. I probably should rig up something that would be able to discharge off faster (I have the cells that did make the cut--only due to low cap testing. And I got about 200 LGM26 cells I got in ebike packs that I just haven't had time to break out and test. I am just so burned out right now, but work it getting to relax a lot, so..
First pack I get done I will try the icharger in regular mode and see how bad it is
Eh, I have to be able to say I did it once!!

​

 

[Dr. Dickie]

Wait, the icharger doesn't come with a connector for the sensing leads?? WTH?? That is crazy.
Wonderful, something else I have to order and wait for it to come in.

 

[OffGridInTheCity]

Wait, the icharger doesn't come with a connector for the sensing leads?? WTH?? That is crazy.
Wonderful, something else I have to order and wait for it to come in.

A while back I bought some of this stuff - https://www.amazon.com/gp/product/B07GD3SHG6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 - and these have been incredibly useful for random DIY. For example, I just peeled off 2 of the wires and used them with iCharger X8 for sense leads to a pack - e.g. female to iCharger and soldered aligator clips to the other end. The sizing of the female connector is such that it will fit nicely side-by-side on most sense lead connection pins such as iCharger X8 for BattGo(s) etc so you can create 2 or 4 or 8 wire sense lead connections as needed by simply plugging in 2 or 4 or 8 wires as needed.

 

[Dr. Dickie]

A while back I bought some of this stuff - https://www.amazon.com/gp/product/B07GD3SHG6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 - and these have been incredibly useful for random DIY. For example, I just peeled off 2 of the wires and used them with iCharger X8 for sense leads to a pack - e.g. female to iCharger and soldered aligator clips to the other end. The sizing of the female connector is such that it will fit nicely side-by-side on most sense lead connection pins such as iCharger X8 for BattGo(s) etc so you can create 2 or 4 or 8 wire sense lead connections as needed by simply plugging in 2 or 4 or 8 wires as needed.
View attachment 24632

Mm looks good, thanks.
I ordered some JST-hX or whatever those connectors are. I have the wire I got of the Batrium BMS so I have that.
I will likely get this too.
DAMN, I am ordering enough stuff to do this for a living!!

 

[floydR]

The 1S balance lead I use just a 2 wire jst of some sort. This one I think came with an amp meter. I had to cut off a couple pieces to get it to work and the red is now ground and black is positive. I have a pair of alligator clips on the two end s which I hook to <harbor freight>jumper cables I cut off and soldered a xt60 connector to. So if you have a cheap watt/amp meter like this one https://www.ebay.com/itm/DC-100A-10...879021?hash=item41ada0eced:g:ysgAAOSwU3VbLz0a the red and black connector should work as the sense leads. Dupont connectors work well too but I didn't have any dupont connectors and had extra 2 wire connectors.

just another option
later floyd

 

[Dr. Dickie]

The 1S balance lead I use just a 2 wire jst of some sort. This one I think came with an amp meter. I had to cut off a couple pieces to get it to work and the red is now ground and black is positive. I have a pair of alligator clips on the two end s which I hook to <harbor freight>jumper cables I cut off and soldered a xt60 connector to. So if you have a cheap watt/amp meter like this one https://www.ebay.com/itm/DC-100A-10...879021?hash=item41ada0eced:g:ysgAAOSwU3VbLz0a the red and black connector should work as the sense leads. Dupont connectors work well too but I didn't have any dupont connectors and had extra 2 wire connectors.View attachment 24633 just another option
later floyd

Thanks.

 

[Dr. Dickie]

Oh carp! It requires 9V input minimum. So I will have to test 4 packs put in series! That will take a week to discharge and charge.
I am going to have to discharge through a 12V inverter, then regeratively discharge another 4 packs at a time.
Only have 4 more packs out of 14 to go before I got all 14 packs done. June is approaching and still have to get the shed fan system done and dig the trench (150") to run the power to the off-grid panel.

 

[floydR]

Get a 3s bms hook 3 packs up to uses as a power source for the x8 uses that to text individual packs. (lithiumSolar) did a video on testing his big 300p pack that way. will take less time to test 1 pack at a time than to try to test 4s packs also you want the power supply battery to have enough Ah space to hold all the Ah in the battery being tested. you need something larger than a 3s pack can hold ~4617Wh while a 1s pack only holds ~1539Wh so if the 3s starts 11.1v it shouldn't be full by the time it regenerative discharges the 1s pack.
later floyd

 

[Dr. Dickie]

Get a 3s bms hook 3 packs up to uses as a power source for the x8 uses that to text individual packs. (lithiumSolar) did a video on testing his big 300p pack that way. will take less time to test 1 pack at a time than to try to test 4s packs also you want the power supply battery to have enough Ah space to hold all the Ah in the battery being tested. you need something larger than a 3s pack can hold ~4617Wh while a 1s pack only holds ~1539Wh so if the 3s starts 11.1v it shouldn't be full by the time it regenerative discharges the 1s pack.
later floyd

Thanks FloydR.
I am not known to be the sharpest pencil in the pack, so don't be surprised if I have more questions.
I do have an electrodacus BMS just sitting around, I think it does 1-8 S--although I have no manual for it and have never used it--I guess this might be the time to learn.
Funny, I went to the LithiumSolar video and it shows that I already watched more than half of it before (mind like a steel sieve).
I will watch the vid and see if I can figure it out.
Thanks again.

 

[floydR]

Been there usually my mind only records useless information. Worse is when it only remebers part of the information. I probably watched that video 2 or 3 times and still came here and asked How to do a regenerative discharge with an x8.

later floyd

 

[Dr. Dickie]

Okay, just watched the video--gave me great info on running the Icharger.
But I don't really need a BMS, I can just take a 3S pack, hook to a 12V inverter and run it down to about 10.5 volts then use that for regenerative discharge and recharge.
Cool, I will probably give this a try this weekend!!
Thanks again (and thanks LithiumSolar).

 

[OffGridInTheCity]

Okay, just watched the video--gave me great info on running the Icharger.
But I don't really need a BMS, I can just take a 3S pack, hook to a 12V inverter and run it down to about 10.5 volts then use that for regenerative discharge and recharge.
Cool, I will probably give this a try this weekend!!
Thanks again (and thanks LithiumSolar).

If you burn off the 120w the regenerative discharge is putting into the iCharger power source battery as the test is underway - the iCharger power source battery will retain its voltage and you don't have to discharge/charge it much between tests. The iCharger will show you the watts being discharged (maybe 120w in regenerative mode) so you know how much to pull. Maybe a 12v inverter + 100w light-bulb or even a variable AC source if you have one for fine tuning.

 

[Dr. Dickie]

If you burn off the 120w the regenerative discharge is putting into the iCharger power source battery as the test is underway - the iCharger power source battery will retain its voltage and you don't have to discharge/charge it much between tests. The iCharger will show you the watts being discharged (maybe 120w in regenerative mode) so you know how much to pull. Maybe a 12v inverter + 100w light-bulb or even a variable AC source if you have one for fine tuning.

Yeah, my plan is to drop a four-pack down to about 120% of what I think the capacity of the one-pack is (the packs are all at 4.154 V right now). Then I can discharge the one-pack into the four-pack, and re-charge the one-pack back from the four-pack--should only lose a bit of a charge from original in the four-pack. After I do that about five times (that is, after testing 5 one-packs), I may have to do a little touch up on the four-packs with the power supply.
I only have 3 packs left to weld up, so I expect to start testing Monday.
Biggest thing I want to see is use the FLIR the backs during discharge and re-charge and make sure everything is okay, I do not expect (as of right now) to discharge at greater than a 30 A rate--since I am only powering a 3 kW inverter (which would be 25 amps at 120 V--with losses, should be less than 30 Amps).

 

[Dr. Dickie]

If you burn off the 120w the regenerative discharge is putting into the iCharger power source battery as the test is underway - the iCharger power source battery will retain its voltage and you don't have to discharge/charge it much between tests. The iCharger will show you the watts being discharged (maybe 120w in regenerative mode) so you know how much to pull. Maybe a 12v inverter + 100w light-bulb or even a variable AC source if you have one for fine tuning.

Used a 100 watt light bulb and a heating pad, going on 30 hours to get a 3 pack from 12.4 volts to 10 volts. The heating pad does turn itself off after an hour or two, so it has not run continuously.
Getting close.

 

[Dr. Dickie]

Okay, the manual for the icharger wins to award for most useless manual I have every seen (I see no difference between the one written in Chinese and English--and I DON'T read Chinese).
I put together a 3s 160 P pack to power the icharger (since it wants 9 to 48 V). I then drained that pack down to 10.5 V--the inverter I used gives alarms at 10.5 v. So far so good-this is why I had to go 3s rather than 4 as the max input was 16V.
I set the icharger to regenerative discharge, and hooked up a 1S pack to the output (with a sense cable). I set the discharge info and start the run (it IS in regenerative discharge as the green light is showing).
The icharger starts throwing off hot air and is discharging the 1S pack, but it is NOT charging into the 3s pack, it is just discharging the pack as heat and blowing it out the icharger.
Am I missing something? Stupid question, clearly I am. Does regenerative discharge mean that the 3S pack will be used to charge the 1S pack after
ischarged?? Or does it mean it will flow back and forth between the two packs depending in discharge or charge.
Since the cells in the 3s are already at 3.6 V, I cannot use it to recharge the discharged pack. Not a problem, i can use bench power supply, but just what the hell does regenerative discharge mean?

 

[Wolf]

Several things.
Did you setup a new Liio regen workflow in the main workflow selection screen ?
This is where you select 30A discharge and enable regen. It is somewhat confusing but once you get it it works great.
Also when you select the previously set up workflow and then select discharge you should get a screen that asks you are you sure?
Once that workflow is setup properly you should be regen discharging the pack at 30A and charging the 3s battery at 30A

what the hell does regenerative discharge mean?

It means you can charge from a 3s pack to a 1s and discharge from a 1s to a 3s at whatever amps you desire up to the max of 30A. The iCharger is acting as a buck/ boost power supply and basically just is a go between the different voltages of the packs. Be very sure your sense wires are working and showing the 1s voltage accurately.
If you want when I get home I can post screenshots of the setup.

Wolf

 

[OffGridInTheCity]

Agree with @Wolf and I would take him up on his offer
Its tricky to get used to the iCharger... but eventually it get's easier and you can even admire that the easy clicks/twists are pretty efficient.

 

[Dr. Dickie]

Several things.
Did you setup a new Liio regen workflow in the main workflow selection screen ?
This is where you select 30A discharge and enable regen. It is somewhat confusing but once you get it it works great.
Also when you select the previously set up workflow and then select discharge you should get a screen that asks you are you sure?
Once that workflow is setup properly you should be regen discharging the pack at 30A and charging the 3s battery at 30A

It means you can charge from a 3s pack to a 1s and discharge from a 1s to a 3s at whatever amps you desire up to the max of 30A. The iCharger is acting as a buck/ boost power supply and basically just is a go between the different voltages of the packs. Be very sure your sense wires are working and showing the 1s voltage accurately.
If you want when I get home I can post screenshots of the setup.

Wolf

Well, I went through the one in there. I it was in regen mode, like I said the little green i was lit green (which is says indicates that it is in regen mode). Yep, got the screen asking if I was sure to discharge. Could not get 30 amps. I set it to 30 amps, but the best I could get it to do was 12 or so. I am going to check everything again.


Okay, I stopped it and checked everything. Could see nothing wrong. Started regenerative discharge, and now it does seem to be charging the 3 pack.
Mind you, I had stopped and started it a half dozen times this morning, and it was not putting anything into the 3 pack. But letting it run for a few hours and then stopping and restarting it seems to have it working.
Still can't get 30 A--that is what it is set to--all it get is about 12 amps out. It says 30 amp discharge, so I know it took what I put into it, but it only does about 12 A.
Fine by me, as long as it works. of course I will have to top this pack back up to 4.1 V before getting the correct cap, but that is fine.
Thanks