Severe voltage sag under heavy load

[timselectric]

Maybe I misunderstood. I thought that you were saying that cells from Docan were the best they could get. But maybe you were saying that they shouldn't expect full ratings from them?

 

[Alkaline]

after seeing how the "grade a" 280K performs I don't think we can really trust EVE on what the claim...

 

[timselectric]

I don't have any personal experience with anything other than the 18650 280k double terminal cells.
But, they have exceeded expectations. So, all of my future cells will come from them.

 

[sunshine_eggo]

probably pulling too hard, but the spec sheet on these says tehy can burst to 3c so I dunno...

https://cdn.shopify.com/s/files/1/0481/9678/0183/files/LF105_3_2V_105Ah_Product_Specification_Version_F_1.pdf?v=1641491228

<0.5mΩ

His voltage drop measured at the cell is 5X that.

There are places like ECPC that are authorized distributors for CALB and a couple of other brands. You're going to pay a premium, but you're going to get fully compliant cells.

 

[PeSCaLo]

Not really solar but same tech. I have a 72v 105ah pack with a 200a JK BMS I built for a golf cart. Under heavy load approx 250a the voltage will sag to 2.7 or lower at times. This is at full SOC. I’ve tested individual cells with my meter to confirm it’s not something jacked with the BMS. Soon as the load is removed the voltage jumps right back to normal. Even at a full 3C, based on the chart, they shouldn’t be below 3v.View attachment 130489

So, what is the Question?
is the Voltage Sag to 2.7v @ 2.5C Normal?


Well, Asuming you are using 24 Cells, that would give you 64.8v @ 2.7v

In My Experience, yes. completely normal. 64.8v should be ok for a temporary load on the motor.
these cells are meant for <1C discharge. above that they will sag heavily. have tested the same cells.

is this impacting other parts of the build?