LIFEPO4 charging and capacity

Fred

Solar Enthusiast
I think most people are charging their banks to a capacity of 80 to 90 percent in order to extend the number if cycles the bank will last for. In order to measure capacity, a shunt/coulomb meter is typically used to count amps in and out and display state of charge. These systems require a periodic full charging of the bank to reset the amp counter and calibrate the state of charge value.

I am wondering if anyone is doing a full charge once a week (or month or...?)

One thought I had to automate this was to set up my charge controllers to charge the bank daily to 90% using a standard bulk/absorb cycle and then use the equalize function to periodically bring the bank to 100%. (EQ voltage would be set to the same voltage as the absorb voltage) Basically, the EQ cycle would just be additional time the bank is charged at the constant voltage stage.

Thoughts?
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
I think most people are charging their banks to a capacity of 80 to 90 percent in order to extend the number if cycles the bank will last for. In order to measure capacity, a shunt/coulomb meter is typically used to count amps in and out and display state of charge. These systems require a periodic full charging of the bank to reset the amp counter and calibrate the state of charge value.

I am wondering if anyone is doing a full charge once a week (or month or...?)

One thought I had to automate this was to set up my charge controllers to charge the bank daily to 90% using a standard bulk/absorb cycle and then use the equalize function to periodically bring the bank to 100%. (EQ voltage would be set to the same voltage as the absorb voltage) Basically, the EQ cycle would just be additional time the bank is charged at the constant voltage stage.

Thoughts?
LiFePO dos not use EQ and if you have a solar controller which cant be properly programmed you can very easily destroy your battery pack ! I know what your thinking because I have a Midnite Classic Controller which is not smart enough for LFP so you have to program around the issues (luckily they can do that). You could in theory do it if programmable and set a schedule but would that hep anything ? not really. The BMS handles the majority of the issues, it isn't like dealing with any Lead Acid type of battery.
 

Fred

Solar Enthusiast
My thought was to set the absorb voltage to 3.65 per cell (x16 cells). And figure out by some trial and error how much time of constant voltage absorb is needed to hit 90%. Once that time is determined it would be programmed as the absorb time. That would be the daily charge routine.
I would set the controller equalize setting to act once a week. This “eq” voltage would be set to 3.65v per cell also and the eq time would be an hour or so (again trial and error to determine the amount of time to now hit 100%) The BMS of course will provide the safeguards.
 
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