LiFeP04 vs Flooded Lead Acid batteries

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Post from Simon, Karrak Farms, Australia

Creeky says: I thought this was interesting, so I bring this to the attention of those who are interested in LFP batteries for offgrid power storage.

LFP compared to FLA
LiFePO4  Flooded Lead Acid
Total Operating Voltage Range 14.4 – 11.2 15.5 – 10.5
Normal Operating Voltage Range, No Load 13.8 – 12.8 (90%-20%SOC) 15.5 – 12.0 (100%-50%SOC)
Normal Operating Voltage Range, C/8 Load 13.8 – 12.4 15.5 – 11.0
Normal Operating Voltage Range, C/2 Load 13.8 – 12.0 15.5 – 10.5
Max sustained charge rate 1C C/8
Recommended sustained charge rate N/A C/10
Sustained discharge rate 1C C/8
Peukert Coefficient ~1.02 1.2-1.6
Current efficiency >95% <90%
Lifespan ~10 years ~6 years
Warranty 5 year prorata (balqon) 5 year prorata (trojan)
Cost per kWh ~US$340 ~US$130
Cost per usable kWh ($/kWh/cycledepth) ~US$523 ~US$325
Cost per usable kWh per year ~US$52.30 ~US$54.20

What does it mean

What the specs show is a considerably higher charging efficiency for LFP. A longer life span. A smaller range of operating voltages (less sag, no need for high voltage to charge). Wider range of usable depth of discharge (this means LFP packs are usually sized 60-70% the amp hrs of FLA for the same usable power storage).

Also note LFP can handle much higher charge currents and deliver much greater discharge currents. Neat.

Costs over the long term seem pretty equal as well.

Thanks Simon.

Background data derived from:

Trojan T105-RE from NAWS assuming 2000cycles@40% charge/discharge…ata_Sheets.pdf

Winston LYP cells from Balqon assuming 3650 cycles @65% charge/discharge…ttery_2013.pdf

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