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
BFL13 wrote:
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?
the do and they don't go below SOC,the volatge SOC is based on a resting battery not a battery under load. the under voltage sag as I call it can be hard on a battery, this is why GC batteries are better then say optima batteries, and also the difference between cheep GC batteries and expansive ones. the ability to recover from a heavy load. this is usaly due to plate thickness and manufacturing process.
I think this is where the "only use the top 50% of capacity came from so your not dipping into that low point all the time.
also you cant stop the LFP at the knee "for comparison" as this is the feature of the LFP, the rated life is based on 100% dischargeso 3000 to 3500 cycles depending on the manufacture and battery size so by making it easier for comparison you are handy caping one of its features.
