LiFePo4 voltage under load
Hi all, This is the first chart (stage left graph when looking at the image) I've been able to find that shows voltage under load. I may be reading it wrong.
Forum Discussion
The OP LFP graphs seem to use 10v as the "end voltage", which is 0% SOC.
Trying to compare the LFP in the OP with SiO2 discharge table (which is all I have to compare with) for how that all works, and I think I see something but not sure. Maybe it makes sense to some others who can help?
The SiO2 table seems to show how you can pick a time say 60 minutes, and then if you run ever- higher loads in amps you have to go lower in "end voltage per cell". Nothing like that in the OP info for LFP?
The thing is SiO2 resting voltage for 0% is 11.1v (1.85 per cell), but the discharge table goes down to 1.6 per cell or 9.6v
So apparently the SiO2 times include going well below 0% SOC! (confusing!) but the LFP times do not. Is this because LFP cells get damaged if you do that? BMS cut off?
As to the times themselves it seems the LFP is 60 min for 1C but the SiO2 is more like 30 min, and then at 0.5C the LFP is 120 min vs about 60 min for the SiO2. However at 0.2C it is 305min LFP vs about 240 min for SiO2?
IMO the real LFP figures in the OP graph should only go to the "knee" and use about 12.5v as the "end voltage". That would make the times approx:
1C- 40 min, 0.5C 100 min, and 0.2C 270 min
It all seems difficult to make a comparison. I don't have a comparable discharge table for AGMs or FLAs. Maybe because they can't do that at all except once or twice?
Trying to compare the LFP in the OP with SiO2 discharge table (which is all I have to compare with) for how that all works, and I think I see something but not sure. Maybe it makes sense to some others who can help?
The SiO2 table seems to show how you can pick a time say 60 minutes, and then if you run ever- higher loads in amps you have to go lower in "end voltage per cell". Nothing like that in the OP info for LFP?
The thing is SiO2 resting voltage for 0% is 11.1v (1.85 per cell), but the discharge table goes down to 1.6 per cell or 9.6v
So apparently the SiO2 times include going well below 0% SOC! (confusing!) but the LFP times do not. Is this because LFP cells get damaged if you do that? BMS cut off?
As to the times themselves it seems the LFP is 60 min for 1C but the SiO2 is more like 30 min, and then at 0.5C the LFP is 120 min vs about 60 min for the SiO2. However at 0.2C it is 305min LFP vs about 240 min for SiO2?
IMO the real LFP figures in the OP graph should only go to the "knee" and use about 12.5v as the "end voltage". That would make the times approx:
1C- 40 min, 0.5C 100 min, and 0.2C 270 min
It all seems difficult to make a comparison. I don't have a comparable discharge table for AGMs or FLAs. Maybe because they can't do that at all except once or twice?
