Daly BMS gone crazy..Update Opinions

pianotuna wrote:
From the search suggest by FWD

https://www.sciencedirect.com/science/article/abs/pii/S0378775310014898

If I am reading that correctly LI are not well suited to cool temperatures and the loss of capacity is permanent?

Details are important - the study was looking at LiFePO4 for Electric Vehicle use, and was cycling to 100% DOD at 3C and then recharging at 3C. To put this in context for a typical 100Ah RV battery, this would be discharging at 300A (!) in 20 minutes, then turning around and charging again at 300A in 20 minutes then repeat 600 times.

Even under those extreme conditions the battery only lost 25% of it's capacity when charged/discharged 600 time at -10C, and lost 15% capacity at room temperature. It would be impossible to do this test even once with any of the lead-acid chemistries.

An interesting quote from the paper:

Excellent long-term cycling stability was demonstrated for C-LiFePO4/graphite prismatic cells with capacity loss of only 14% after 6000 charge–discharge cycles, where the cells were cycled at 20 °C and around 1C rate.

If you reduce the charge/discharge to 1C (still 100A for a 100Ah battery!) the capacity fade is only 14% after 6000 cycles. Imagine what the lifetime would be at a more typical RV use of 0.05C?

More surprisingly after 300 100% DOD charge cycles at -10C at a 3C charge rate there was almost no loss in capacity. So occasionally charging at absurdly high rates at -10C (14F) has very little impact on your battery, and even doing it 600 times in a row is only slightly worse (25% capacity fade vs 15%) than room temperature charging. As I have been saying all along, the cold temperature charging of LiFePO4 is completely overblown.