Hi David
,
7S and 8S refers to 7 or 8 series cell. Sometimes you see a battery pack.
referred to as 3S2P meaning 3 cells in series and 2 in parallel. (3x 1cell voltage.
And 2x 1 cell AH capacity. LFP or Lithium Iron Phosphate (LiFePO4) is.
the kind i have and the voltage needs to stay between 2.6v/cell minimum to 3.6v/cell.
maximum. I have mine set to run from 3.1v to 3.5v but im not concerned about.
capacity. I'm usually only using top1/2 of capacity sometimes a lot less. My needs
are mainly concerned with leveling the variableness of clouds so my AC output watts
stay even to run loads without switching loads on/off. In your application if you have.
a large AH bank then you may want to use more of the usable range. You can do it by
using voltage triggers for full/empty battery but its critical. You absolutely must keep.
All cells above 2 volts or the cell will be junk. There isnt much capacity left below 2.8v
So better to stay away from 2 v as far as possible. The Full mark isnt as critical but 3.5v is
mostly full. Ive read that LiFePO4 chemistry is more forgiving about overvoltage than under.
Either one should be avoided. The tricky part is you are using these cells in a series configuration and the capacity of each cell is slightly different they always will be. If one cell gets full before
the other 7 and you are monitoring bank voltage, that cell can reach 4 volts in seconds with 60Amps of charge current, (ive watched it on bar graph) . So you have 2 choices, either top balance and stay away from bottom or bottom balance and stay away from top. You cant really do both though racers and vehicle applications do this with fancy circuitry but they also have higher failure rates. Balancing allows all cells to reach the full or empty threshold at the same time which allows the use of bank/pack voltage to indicate charge level. Even after balancing and calibrating voltage triggers its best to have a monitor that can detect a problem and shut off chg/dischg.
The CellLog8S unequal drain has 2 possible fixes that i know of, one is to connect a switch with lead wires to board. (jumper works too if you dont need to connect to computer) or you make buffer with 2 quad op amps configured as unity gain. I will post details.
I really like the record feature as i dont have balancer boards yet, i do it manually. The celllog allows me to see how each cell is performing through the day and if a balance problem exists. I also use it to (teach/program) my controller voltage setpoints.
Best of luck to you sounds like you have a great setup. As oztules said, pj will allow 30v for a few beeping seconds before shutdown without modification he refers to. Ive not had to modify mine but it seems many have.
Lighthunter