Sun Xtender Batteries Temperature Compensation

Coach Dad
Coach Dad Solar Expert Posts: 154 ✭✭
I'm using Sun Xtender batteries (four PVX3050T's in series) set up as a 24 volt 305 AH bank.

I've got the Charge Controller set to 28.6V Absorb and 26.6V Float (as per Concord spec)
However, I've noticed that the Charge Controller (and Inverter) display over 29 volts when it is in Absorb mode.

I've been thinking all along that this was due to the Temperature Compensation setting that I entered into the MPPT.

The Concorde site states:
Temperature compensation: 4.00 mV. per cell per degree C [Reference to 25° C (77° F)]. This is for battery temperature (not ambient temperature) and is useful for battery temperatures from 0° C to 40° C. Contact Concorde Battery Corporation for temperatures that exceed this range.

Since I'll be using the batteries in temperatures from -26deg C to 41deg C, I asked Concorde what setting I should use. I was instructed to use:
"For the temperature range of -26 to 41C, a temp. coefficient of 5mV/cell/degC should be used."

Since this states that it is /cell and I have 12 cells, I calculated it in the following manner
0.005V X 12 cells = 0.06V
Is this correct??


  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: Sun Xtender Batteries Temperature Compensation

    -2 mV/degC per cell to -6 mV/degC per cell is the common range of temp comp'g for lead acid batteries. Higher SG batteries are generally toward the lowerer end. AGM's are starved electrolyte, higher SG (which you cannot measure) by design.

    You can use the higher rate of temp comp change for batteries that are cycled regularly and need to replenish the upper 20% capacity in shortest time. Systems that float charge for longer time between discharges are run at low end of temp comp range (-2 mV/cell per degC.)
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Sun Xtender Batteries Temperature Compensation

    couch dad,
    i did address this elsewhere and you did not need to open a new thread for it, but i did overlook that you were outside the normal temp ranges they gave for 4mv. go with their recommendations as this should further reduce the voltages when outside of the normal range making damage less likely.