Early arrival capacity test/discharge/storage advice

[Gurusi]

Hey, my X32 docan eve 280ah cells turned up earlier than predicted and I don’t have my array built. It’s likely I won’t put them into commission for prob about 3 months.



So far, I have checked them externally, confirmed each voltage (all are around 3.29v) and am building a spring compression pack for them (X2 16 cell packs).

I have a EBC-A40L and plan on capacity test on them all individually (parameters to be confirmed on the charge/discharge settings).

So I am considering whether to:-

Capacity test them individually and discharge them to 30% SOC and then leave them until I’ve built the array.

Capacity test individually, discharge them to 30% SOC, connect in parallel and leave them for a while to equalize, put them in series, hook them up to my inverter and BMS so they are setup, balanced and ready to go.

Capacity test individually, leave them fully charged, connect in parallel and leave them for a while to equalize, hook them up and test some loads on the inverter to bring them down to 30%.


I can see benefits in all the options, but as this is a first time process I’m unsure of the best plan or pitfalls or difficulties I may have.

I have read the top balancing resources and had a search around as regard similar scenarios.

 

[Gurusi]

I'm guessing all options are good? Battery Compression build took longer than I thought!
I guess I could also hook them up in parallel and top balance before capacity testing (as individual voltage ranges are similar) .

 

[Lt.Dan]

With the EBC-A40L, you can program it to fully charge the battery to 3.65v, then discharge at 40a to 2.5v. This will give you your capacity results. If you are not going to build your pack for a while, then I would fully charge back up to 3.65v, then discharged at 40a for 30min. This will pull 20ah out of the cell, leaving it at a perfectly fine resting voltage (whatever that ends up being, probably somewhere around 3.37v~). No need to go down all the way to 30%.

Then, whenever you do connect them in series, they are all at the same Stage of Charge, which in theory, means they are all "Top Balanced", and will be perfect to throw together in series and start using them.

No need to parallel connect them and let it equalize. It takes way too long and is unnecessary so long as they are all at the same state of charge.

 

[WindWizard]

It sounds like you want to capacity check them since you have your EBC-A40L. I thought about purchasing one but then after the pack is all together, would I ever use it again? Testing all of the Cells will take some time to do and since your are not in a hurry then why not? One reason not to is it will take at least 28kw of electricity to test them all, and a whole lot of your time. Make sure you mark each cell and make a spreadsheet for future reference. After you run your test them then charge them up to 3.65 volts each and then connect them all in parallel. Let them be for a few days and they should all be top balanced.

When you put together your pack, make sure that you clean the contacts and torque the nuts down to spec.

I am just giving you advice that I do not follow myself. When I purchased my Cells, I connected them all up into a battery pack and started to use them. I had to watch the Cells that were creeping up to 3.4 volts + and then discharge them before they tripped the BMS. It has worked great for me.

 

[rhino]

I think the 30% to 50% comes from the data sheet which states for "long term" storage to leave the cells at that %:

 

[Gurusi]

With the EBC-A40L, you can program it to fully charge the battery to 3.65v, then discharge at 40a to 2.5v. This will give you your capacity results. If you are not going to build your pack for a while, then I would fully charge back up to 3.65v, then discharged at 40a for 30min. This will pull 20ah out of the cell, leaving it at a perfectly fine resting voltage (whatever that ends up being, probably somewhere around 3.37v~). No need to go down all the way to 30%.

Then, whenever you do connect them in series, they are all at the same Stage of Charge, which in theory, means they are all "Top Balanced", and will be perfect to throw together in series and start using them.

No need to parallel connect them and let it equalize. It takes way too long and is unnecessary so long as they are all at the same state of charge.

Thanks for confirming I'm on the right track. Ah so discharge for time/amps as opposed to a certain voltage?

 

[Gurusi]

It sounds like you want to capacity check them since you have your EBC-A40L. I thought about purchasing one but then after the pack is all together, would I ever use it again? Testing all of the Cells will take some time to do and since your are not in a hurry then why not? One reason not to is it will take at least 28kw of electricity to test them all, and a whole lot of your time. Make sure you mark each cell and make a spreadsheet for future reference. After you run your test them then charge them up to 3.65 volts each and then connect them all in parallel. Let them be for a few days and they should all be top balanced.

When you put together your pack, make sure that you clean the contacts and torque the nuts down to spec.

I am just giving you advice that I do not follow myself. When I purchased my Cells, I connected them all up into a battery pack and started to use them. I had to watch the Cells that were creeping up to 3.4 volts + and then discharge them before they tripped the BMS. It has worked great for me.

I'm currently on the grid until my array is built, so usage isn't an issue and as you said I have the time.

Thanks for the info, I do have a excel spreadsheet, torque amounts, alcohol to clean etc.

If i had the array built I would consider just hooking them up as well!

 

[Gurusi]

I think the 30% to 50% comes from the data sheet which states for "long term" storage to leave the cells at that %:
View attachment 146716

Yep that's what I was going by, not sure if 3+ months is considered long term storage though.

 

[Lt.Dan]

I think the 30% to 50% comes from the data sheet which states for "long term" storage to leave the cells at that %:
View attachment 146716

I have seen this before as well, but I don't see any damage occurring from a LiFePO4 battery resting at 3.35-3.4v. Everybody freaks out about voltage being over 3.5 and looses there minds about 3.6v. Under 3.4v you aren't in the knee.

Can anyone explain how staying at 80% can damage a cell?

Thanks for confirming I'm on the right track. Ah so discharge for time/amps as opposed to a certain voltage?

Yes because you might discharge to 3.1v per cell and SOC could be widely different at that voltage. If you remove the exact same Ah from each cell, they are all at the exact same State of Charge still.

 

[rhino]

Can anyone explain how staying at 80% can damage a cell?

@RCinFLA would probably know.

 

[Alkaline]

Hey, my X32 docan eve 280ah cells turned up earlier than predicted and I don’t have my array built. It’s likely I won’t put them into commission for prob about 3 months.



So far, I have checked them externally, confirmed each voltage (all are around 3.29v) and am building a spring compression pack for them (X2 16 cell packs).

I have a EBC-A40L and plan on capacity test on them all individually (parameters to be confirmed on the charge/discharge settings).

So I am considering whether to:-

Capacity test them individually and discharge them to 30% SOC and then leave them until I’ve built the array.

Capacity test individually, discharge them to 30% SOC, connect in parallel and leave them for a while to equalize, put them in series, hook them up to my inverter and BMS so they are setup, balanced and ready to go.

Capacity test individually, leave them fully charged, connect in parallel and leave them for a while to equalize, hook them up and test some loads on the inverter to bring them down to 30%.


I can see benefits in all the options, but as this is a first time process I’m unsure of the best plan or pitfalls or difficulties I may have.

I have read the top balancing resources and had a search around as regard similar scenarios.

Sounds good test witht he EBC-A40L, also be sure to test at 40 amps as 30 amps may not show the true condition of the cell. Many people swap out the aligator clamps with lugs for a better contact to the cell termianl.

post results and upload your csv file (in a zip file) for fellow diyers. Thanks

 

[Saltyoldcruiser]

Hey, my X32 docan eve 280ah cells turned up earlier than predicted and I don’t have my array built. It’s likely I won’t put them into commission for prob about 3 months.



So far, I have checked them externally, confirmed each voltage (all are around 3.29v) and am building a spring compression pack for them (X2 16 cell packs).

I have a EBC-A40L and plan on capacity test on them all individually (parameters to be confirmed on the charge/discharge settings).

So I am considering whether to:-

Capacity test them individually and discharge them to 30% SOC and then leave them until I’ve built the array.

Capacity test individually, discharge them to 30% SOC, connect in parallel and leave them for a while to equalize, put them in series, hook them up to my inverter and BMS so they are setup, balanced and ready to go.

Capacity test individually, leave them fully charged, connect in parallel and leave them for a while to equalize, hook them up and test some loads on the inverter to bring them down to 30%.


I can see benefits in all the options, but as this is a first time process I’m unsure of the best plan or pitfalls or difficulties I may have.

I have read the top balancing resources and had a search around as regard similar scenarios.

If there's a compression fixture in your future I'd hold off on any charging or testing until you get them compressed. There are a lot of opinions out there but I think it's important to compress before monkeying around with them. IMHO

 

[Gurusi]

Oops Double post

 

[Gurusi]

Cells are all compressed (with the lb’s/springs).

Tester is all setup.

Does this appear correct?

 

[Lt.Dan]

Looks good to me. Run it!

 

[Gurusi]

Looks good to me. Run it!

Sweet! Let the fun begin.

 

[MarcoWasRight]

Cells are all compressed (with the lb’s/springs).

Tester is all setup.

Does this appear correct?

That cutoff level on the charging looks very very low as in it will absorb for a very long time. If charging at 40A I would cut off at 2A or somewhere in that neighborhood.