Crimp Daddy
Member
- Joined
- Feb 21, 2018
- Messages
- 973
This thing was a bit of a pain... but I got it done.
thunderheart said:Crimp Daddy, thanks for that battery porn! Love it!
P.S. Why did you discharge down to 2.5V/cell when ANR26650M1B's discharge cut-off voltage is 2.0V? And why did you use 10A (10A : 8 = 1.25A/cell i.e. 0.5C) for checking capacity instead of 4A (0.5A x 8).
I think 37% capacity loss is kinda unreal.
CrimpDaddy said:thunderheart said:Crimp Daddy, thanks for that battery porn! Love it!
P.S. Why did you discharge down to 2.5V/cell when ANR26650M1B's discharge cut-off voltage is 2.0V? And why did you use 10A (10A : 8 = 1.25A/cell i.e. 0.5C) for checking capacity instead of 4A (0.5A x 8).
I think 37% capacity loss is kinda unreal.
Because in real world operational scenarios most 12v equipment would not operate down in the 8v range (2vdc per cell), 10vdc is a more realistic operating range.
Plus, when you look at the discharge curve of the battery itself, going from 2.5 to 2.0 offers VERY LITTLE in terms of additional capacity, and increases cell degradation at an expedited rate.After 2.5v the fall off curveis STEEP, which is typical for most LiFePO4 chemistry... curves are flat until they start to roll off then dive.
Two, these are very high drain cells... capable of 70 amps discharge each. The test preformed at 1.25a each vs 0.5a each literally makes zero difference. In addition, these would not be used in low drain applications, higher discharge rates give a better real world use case for testing. Higher rates are preferred so I dont have to wait around all day, and my charger is capable of doing it without an external load.
My testing methodsyield pretty accurate results with this charger... 37% loss at the module / pack level is actually the better of the 12v chunks I evaluated.