In this video I cover charging efficiency as well as differing absorption voltages for LFP. I also, quite by accident, get to show you the effects of sulfation on the AGM battery.
LiFePo4 vs. AGM Charge Efficiency
- Thread starter Maine Sail
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Rod, Great video! Just the other day I was noodling around looking for similar information and could not find it. Great work!
Just a note, equalization voltage range is 15.8 to 16.2 volts. I am not familiar with the "battery savers" you mentioned - but if they aren't running in that range - they can't work. Plus, during equalization, the power supply used must at least have current control.
Equalization cycles are more commonly used with flooded lead acid batteries, not so much with AGM's. I don't really know the why's on that. Last I knew, Lifeline AGM's were the only AGM battery manufacturer with a published equalization cycle for their batteries. I moved to LFP a number of years ago now so I'm both not up to date and relaying on only memory - not a solid foundation. I don't know the current state of AGM's...
dj
Just a note, equalization voltage range is 15.8 to 16.2 volts. I am not familiar with the "battery savers" you mentioned - but if they aren't running in that range - they can't work. Plus, during equalization, the power supply used must at least have current control.
Equalization cycles are more commonly used with flooded lead acid batteries, not so much with AGM's. I don't really know the why's on that. Last I knew, Lifeline AGM's were the only AGM battery manufacturer with a published equalization cycle for their batteries. I moved to LFP a number of years ago now so I'm both not up to date and relaying on only memory - not a solid foundation. I don't know the current state of AGM's...
dj
Glad to see the myth of 14.4-14.6v charging for lifepo4 exposed!
The one spec that users must also consider is at what voltage their cell balancer kicks in. At 13.8V, we should have 3.45 V per cell. If the balancer only kicks in at 3.50 V (per cell), 13.8V would not be a suitable charge voltage.
With cheap cells or packs with mismatched cell impedance, it's beneficial to charge at lower voltage as it reduces or eleminates the possibility of a BMS shutdown due to high cell voltage. (ie: cells at 3.8V, 3.4V, 3.5V, 3.6V = 14.3V, but BMS would shut down the charge mosfet because one cell reached 3.8V).
The other element that is often missed is that when parelleling (spellling??) Lifepo4 packs, they should be fully discharged and then fully recharged individually, then paralleled while sitting at the exact same voltage. Otherwise, some packs might reach full charge first. If the voltages are very different, it could trigger the BMS discharge MOSFETs.
The fusing choice is also one that is often missed by DIY. The formula isn't clear cut if someone only applies it once in their lifetime. Some installations required individual pack fuses, others can get away with a single fuse for the whole bank. Some installations will require class T fuses, other's wont. Some pack manufacturers publish their gear's AIC rating, others don't... It's not as easy as just going to Wall Mart, buy 2x group 31, top them off twice a year and you're good for 4-6 years.
I think a video on Lifepo4 fusing, to ABYC standards, would be a great help to the community! Keep up the good work.
The one spec that users must also consider is at what voltage their cell balancer kicks in. At 13.8V, we should have 3.45 V per cell. If the balancer only kicks in at 3.50 V (per cell), 13.8V would not be a suitable charge voltage.
With cheap cells or packs with mismatched cell impedance, it's beneficial to charge at lower voltage as it reduces or eleminates the possibility of a BMS shutdown due to high cell voltage. (ie: cells at 3.8V, 3.4V, 3.5V, 3.6V = 14.3V, but BMS would shut down the charge mosfet because one cell reached 3.8V).
The other element that is often missed is that when parelleling (spellling??) Lifepo4 packs, they should be fully discharged and then fully recharged individually, then paralleled while sitting at the exact same voltage. Otherwise, some packs might reach full charge first. If the voltages are very different, it could trigger the BMS discharge MOSFETs.
The fusing choice is also one that is often missed by DIY. The formula isn't clear cut if someone only applies it once in their lifetime. Some installations required individual pack fuses, others can get away with a single fuse for the whole bank. Some installations will require class T fuses, other's wont. Some pack manufacturers publish their gear's AIC rating, others don't... It's not as easy as just going to Wall Mart, buy 2x group 31, top them off twice a year and you're good for 4-6 years.
I think a video on Lifepo4 fusing, to ABYC standards, would be a great help to the community! Keep up the good work.
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