32 Cell 48v 400 ah Battery questions

[Blahplunger]

Hi.I just purchased 32 12v 200 ah cells and have some questions.I plan to build a 48v 400 ah battery.In the future,I would like to add another 400ah for a total of 800 ah.Im worried that if I use these 32 cells for awhile,and then buy 32 more,that I will have issues,since they will have been in use for awhile,and have different resistance and capacity.Is there any way around this problem?What happens if Im unable to purchase the exact same cells?Can I use other cells of the same voltage and capacity from a different manufacturer?Here is the diagram that the manufacturer gave me for the 48v 400 ah battery.Should I make a different battery with the new cells I will purchase in the future,and then connect the two batteries together?Or can I just add them in and create one large battery,mixing used and new cells?I bought a BMS that is large enough to handle the 48v at 800ah.The cell manufacturer did tell me that it was recommended to make just one battery and not use two different batteries with different BMS.Thanks for the help.

Also,the manufacturer says they balance and match the cells.I will check them when I receive them.Do I need to do anything else before I begin building the battery?

 

[zorlig]

You need to confirm cells are balanced at a minimum the first time you charge it (regardless of what you were told), but you could do that by charging the cells and seeing what happens. If they all top out together at the same voltage fully charged then you are good, otherwise you need to top balance them. If you have no way to monitor individual cell voltages then you might want to get that, or just top balance first. If you gave us more information about they cells/vendor/price we would be able to guess if they are actually balanced or not.

Cells all have sightly different charge/discharge profiles, putting cells in parallel causes uneven usage unless they are correctly matched. A new batch of cells would probably not be matched to the existing but it isn't a significant issue for most people.

Most people here use unmatched cells + top balance them and have great success. I would expect the same for you.

 

[Blahplunger]

You need to confirm cells are balanced at a minimum the first time you charge it (regardless of what you were told), but you could do that by charging the cells and seeing what happens. If they all top out together at the same voltage fully charged then you are good, otherwise you need to top balance them. If you have no way to monitor individual cell voltages then you might want to get that, or just top balance first. If you gave us more information about they cells/vendor/price we would be able to guess if they are actually balanced or not.

Cells all have sightly different charge/discharge profiles, putting cells in parallel causes uneven usage unless they are correctly matched. A new batch of cells would probably not be matched to the existing but it isn't a significant issue for most people.

Most people here use unmatched cells + top balance them and have great success. I would expect the same for you.

Thank you.I wasnt sure how closely matched they had to be.Here is a link to the cells I bought.....

1992.0US $ |OYE 16Pcs 3.2v 200ah Lfepo4 NOT 135ah 150ah battery Lithium iron phosphate cell batteries 48V for solar RV pack EU US TAX FREE|Rechargeable Batteries| - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

They are supposedly calb cells.Not grade A,but new.

 

[Steve_S]

Looked at the advertisement, looks really good, then I spotted a wee detail. They are using a YR1035+ battery tester... even in the test docs, it says it's not accurate above 100AH. I can attest to that, I own & use a YR1035+ and have cells above 100AH. Everything else does appear to look like they are actually batching them.

Cell Configurations for 12V 24V and 48V LiFePo4 Batteries

This short deck shows 1P and 2P cell configurations for 12V, 24V & 48V LiFePO4 batteries. To get the deck, click on the orange button at the top of this page. Note: Reviews, Comments and corrections are welcome Document Revision History...

diysolarforum.com

 

[Blahplunger]

Looked at the advertisement, looks really good, then I spotted a wee detail. They are using a YR1035+ battery tester... even in the test docs, it says it's not accurate above 100AH. I can attest to that, I own & use a YR1035+ and have cells above 100AH. Everything else does appear to look like they are actually batching them.

Cell Configurations for 12V 24V and 48V LiFePo4 Batteries

This short deck shows 1P and 2P cell configurations for 12V, 24V & 48V LiFePO4 batteries. To get the deck, click on the orange button at the top of this page. Note: Reviews, Comments and corrections are welcome Document Revision History...

diysolarforum.com

It wont measure voltage accurately above 100 ah?I wouldnt have thought capacity would affect a voltage measurement,but Im new to this stuff.

 

[Steve_S]

It wont measure voltage accurately above 100 ah?I wouldnt have thought capacity would affect a voltage measurement,but Im new to this stuff.

I did not know that about that tester either until after I had it in my hand and was reading the manual (which I scanned & posted in the resource section). In their case I highly doubt that is how they are batching & matching, I suspect they are likely doing a decent job of it. But that is ONLY Supposition! Ideally, it would be good to do a proper set of tests against them to make sure what exactly you have there. There are many ways to determine the capacities of cells and assembled packs, as Will has put out quite a few vids on.

 

[Blahplunger]

I did not know that about that tester either until after I had it in my hand and was reading the manual (which I scanned & posted in the resource section). In their case I highly doubt that is how they are batching & matching, I suspect they are likely doing a decent job of it. But that is ONLY Supposition! Ideally, it would be good to do a proper set of tests against them to make sure what exactly you have there. There are many ways to determine the capacities of cells and assembled packs, as Will has put out quite a few vids on.

Yes,I have seen them,I bought the small capacity tester he recommended,but at 185 watts,it will take a long time to test the capacity of a 48v 400 ah battery bank.Im not sure what Im going to do yet.Is there a charger you can recommend for a 48v bank?Im not sure which one to buy.I appreciate the help.

 

[Steve_S]

My 180W / 20A tester takes 14 hours +/- a bit doing 280AH cells from 3.550-3.600 deep charge to 2.500.
By deep charge, I mean CC-CV charging until cell resistances reduces amps taken to 1.5-2.0A and stays there, then allowed to settle for one hour.

The CALBS will take 100A Charge & discharge without a blink, per the specs there they apparently can do 1C or 200A charge/discharge.
This means you can charge a cell at 3.65V/100A or a full battery pack at 100A (0.5C) without concern.

Charger ?
Solar ? Inverter Charger ? Independent AC to DC Charger ?
What is your setup design ?
How fast do you want to be able to charge your complete bank ?

If charging at 56V/100A, it would take at least 4-1/2 hours with 2-stage charging from 10% to a full 90% IF the cells and packs are cooperative.

 

[Blahplunger]

My 180W / 20A tester takes 14 hours +/- a bit doing 280AH cells from 3.550-3.600 deep charge to 2.500.
By deep charge, I mean CC-CV charging until cell resistances reduces amps taken to 1.5-2.0A and stays there, then allowed to settle for one hour.

The CALBS will take 100A Charge & discharge without a blink, per the specs there they apparently can do 1C or 200A charge/discharge.
This means you can charge a cell at 3.65V/100A or a full battery pack at 100A (0.5C) without concern.

Charger ?
Solar ? Inverter Charger ? Independent AC to DC Charger ?
What is your setup design ?
How fast do you want to be able to charge your complete bank ?

If charging at 56V/100A, it would take at least 4-1/2 hours with 2-stage charging from 10% to a full 90% IF the cells and packs are cooperative.

Just a charger to charge my battery bank so I can do a capacity test.Doesnt matter how long it takes.Slower is better from what Ive read,but I will not be using it much,so I doubt it will make a difference in battery life.Maybe something that will charge my battery,but then be useful for something else in the future.First time doing this,so Im not too sure what I need yet.Or what kind of problems I will run into in the future that will require me to use the charger again.This is a off grid solar setup with 9kw worth of panels.I plan to use 800 ah at 48v,charging to about 85-90% with a DoD to around 30%.

 

[MisterSandals]

Just a charger to charge my battery bank so I can do a capacity test.

I personally think capacity tests are overrated. They take specialized equipment, take a long time to perform and the results are sometimes open to interpretation.
The downside is that many folks have destroyed cells doing capacity tests. Its not hard to overcharge or discharge a cell and accidents to happen! Also, you'll be connecting and disconnecting the cells quite a few times which can result it stripping out the threads (fairly drastic, especially since you have 32 cells and the chances of replacing one with an equivalent are less than optimal).

Do you have a plan for what you would do with the results of your capacity test(s)? Or is it to feel good about your purchase?

 

[Blahplunger]

I personally think capacity tests are overrated. They take specialized equipment, take a long time to perform and the results are sometimes open to interpretation.
The downside is that many folks have destroyed cells doing capacity tests. Its not hard to overcharge or discharge a cell and accidents to happen! Also, you'll be connecting and disconnecting the cells quite a few times which can result it stripping out the threads (fairly drastic, especially since you have 32 cells and the chances of replacing one with an equivalent are less than optimal).

Do you have a plan for what you would do with the results of your capacity test(s)? Or is it to feel good about your purchase?

Well,Its mostly to make sure that Im getting close to what they say I am getting.I purchased 2 extra cells in case theres any bad ones.That way I dont have to wait months for the replacements.If any are bad,or not close to the rated capacity,I will contact the manufacturer and be refunded for them.Most of the time,they dont require me to return it because its costs too much for them to pay the shipping back to them. The capacity will be tested one way or the other.Wether its while in service,or before I put them into service.The problem is,I have 15 days from when I receive them to make a claim.So if I dont test them right away,I may be stuck with them,if the manufacturer decides they dont want to replace them,or refund my money.

What else can I do other than a capacity test?I thought that was standard.

 

[Javalord1]

Hi.I just purchased 32 12v 200 ah cells and have some questions.I plan to build a 48v 400 ah battery.In the future,I would like to add another 400ah for a total of 800 ah.Im worried that if I use these 32 cells for awhile,and then buy 32 more,that I will have issues,since they will have been in use for awhile,and have different resistance and capacity.Is there any way around this problem?What happens if Im unable to purchase the exact same cells?Can I use other cells of the same voltage and capacity from a different manufacturer?Here is the diagram that the manufacturer gave me for the 48v 400 ah battery.Should I make a different battery with the new cells I will purchase in the future,and then connect the two batteries together?Or can I just add them in and create one large battery,mixing used and new cells?I bought a BMS that is large enough to handle the 48v at 800ah.The cell manufacturer did tell me that it was recommended to make just one battery and not use two different batteries with different BMS.Thanks for the help.

Also,the manufacturer says they balance and match the cells.I will check them when I receive them.Do I need to do anything else before I begin building the battery?

Hello @Blahplunger from Idaho! May I ask how you what charger you used to top balance your batteries? I have 32 basen 272ah. Currently have a 20amp PS. Thanks, Jerome