Originally Posted by xrated
A LFP battery cell is considered to be fully charge at 3.45V per cell or 13.8V for the entire 12V battery. Anything over 13.8V will simply charge the battery at a faster rate than if the maximum output of the charger were at say....13.8V or 14.0V And of course the 14.6V number is the maximum voltage that a LFP battery should ever get....or 3.65V per cell, without the risk of damage to a cell or cells.
kind of but not really. that voltage is resting voltage which works out to 13.6V like I mentioned.
3.65V is the maximum voltage you should subject the cell to, but it is also the correct voltage to charge to for 100% capacity and rated life.
This is right out of the EVE data sheet, who are the manufacturer of high quality Prismatic cells and the cells I bought to make the battery for my camper.
"4.2 Standard Charge
The standard charge means charging the cell with charge current 0.5CA and constant voltage 3.65V at (25Ī2)℃, 0.05C cut off"
Just like a regular battery, there is an adsorption phase for LFP. It's just shorter and done at the same voltage as bulk charging, so we can't tell when it is there by the changes in the charge. This is where the voltage of the group of cells are taken to 14.6V (3.65V/cell) and then after the charge is removed and it sits for 15 20 min the voltage will measure 13.6V. do we have to do this every time no, but most BMS inside these bought LFP batteries don't start doing there balancing until the battery its self is over 14V (quite a few have to be closer to 14.6V for the balancing to start ) so if your never getting up there or not staying up there for long enough, then you will never get a proper top balance on your cells.
when I am camping, I only charge to 13.4V which means the maximum charge I am ever going to get works out to 90% of my capacity and I set the cut out at 10% so that's my maximum working range I use, but every week I do a full charge so my BMS can ensure my top balance is good. I probably would be good with once every 2 weeks or once a month, but I just picked a week. I use my BMS to control this charging profile as I can adjust all m y cut offs and cut ins with my phone, so it makes it easy to say charge to 90% then turn the charge off and don't start charging again until the battery is at 78% capacity. My battery will last me 10 days in the early spring/late fall running the furnace at night, so I do shallow discharges to increase the cycle life.