12v 4S (320ah) array not getting full output capacity

[Rumbaar]

I purchased 4 x 3.2v 320ah cells via AliExpress (tried to find a high rated seller with a good score). I've gotten a Daly 250a BMS.

On initial setup, I put into 4S and charged to capacity with a 14.6 40a charger. I did a capacity test and via a shunt recorded only ~289ah of capacity. I then when back to the order and have now seen that when I click through to the item, the store has change it to 280ah cells. The QR codes on the cells aren't in a format that can be used to determine build, date or capacity.

I've since charged again, setup in a 4P configuration and top balanced them to 3.6v. Reconfigured back to a 4S configuration performed a load test (10-13a draw) and gotten ~290ah of capacity till the BMS shut down at ~10v.

I've gone back to the seller, for a please explain.

But my question, is there something I am doing wrong and should I expect to get 320ah capacity for the type of test I'm running?

I had gotten a Daly 5a active balancer, and now have connected that up and trying a 3rd capacity test to see if that'll help (currently charging the array).

 

[Solar_Mann]

If you top balanced (all 4 in parallel) till amperage was down to .0Xv then you should have gotten an accurate capacity and an active balancer won’t make any difference.

 

[wpns]

But my question, is there something I am doing wrong and should I expect to get 320ah capacity for the type of test I'm running?

Not if they actually shipped you the 280AH cells. Tell them you want a 50% refund.

 

[Rednecktek]

As I understand it, 320a cells don't technically exist. The largest are the 314's so you probably got sold 280's and just got lied to.

 

[Suijkerbuijk]

I will charge and discharge a time.
See what go up and down.
It need some use for it really have it max Ah .
So i will do that first .
Than if not you can prove it

 

[Rumbaar]

Thanks for the responses. I've done a number of cycle tests and gotten ~290ah on average. Have been in back and forth with the seller, that at one point said ~300 is close to 320ah, so good enough. To which I said 290 is 30ah less and closer to the cheaper 280. AliExpress support has been good, and working with the seller for a 'credit' for the difference. Which they've initially offered $18 as compensation. The 280 was between 50-80 less (their prices fluctuate). So awaiting their 'need to talk with manager' response.

I had tried to find a good score seller, but seems the top level capacities are lies.

 

[wpns]

Occam’s Razor says you got 280s.

 

[Suijkerbuijk]

Occam’s Razor says you got 280s.

I agree
If its class a cells than it go over that 280s and that is the reason it hit 290 and up.

 

[Yurtdweller]

Probably hoping no one does a cap test. I must admit that I never did. I got 16 cells for a 4s4p 12v bank, and even though I never did a cap test, any possible discrepancy will never be noticed in my use case. But if you want to run a set device for a set amount of time (e boat or something) then you want to get what you paid for. For what it's worth, I purchased from Amy Wan at Shenzhen luyaun. I hope you can get it worked out to your satisfaction. If I required a specific capacity, and did not get that, I would be upset, and a partial refund would not satisfy me. If I was just gonna use it for occasional lighting or tailgating, then a refund would be acceptable.