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33. BATTERY TEMPERATURE COMPENSATED VOLATGE SET POINT
The temperature of a battery has an impact on the recharging process—in higher ambient tempera-
tures, the regulation set points (Absorb and Float) need to be reduced to prevent overcharging of
the batteries. In lower ambient temperature conditions, the voltage regulation set points need to be
increased to ensure complete recharging of the batteries.
The default charger settings of the FLEXmax 80 are based on typical lead acid battery systems. Always
ensure the Absorb and Float voltage regulation set points are set to the recommended battery manufactur-
er’s recharging regulation voltages.
Non-Battery Temperature Compensated System
If a battery remote temperature sensor is not available the Absorb and Float voltage regulation set
points can be adjusted for the expected weather conditions. The following table shows the appropri-
ate adjustments for both Absorb and Float voltage regulation set points for weather conditions above
or below 77˚F / 25 C
EXPECTED TEMPERATURE ADJUST SET POINT 12V 24V 48V
Average = 95˚F / 35˚C Subtract 0.30V 0.60V 1.20V
Average = 86˚F / 30˚C Subtract 0.15V 0.30V 0.60V
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Average = 68 F / 20˚C Add 0.15V 0.3 V 0.60V
Average = 59˚F / 15˚C Add 0.30V 0.60V 1.20V
Battery Temperature Compensated System
A battery remote temperature sensor (RTS) will automatically compensate the Absorb and Float
voltage relative to the Absorb and Float set points in the Charger menu. Please reference page 49 of
this manual for adjusting the upper and lower battery compensated limits.
Battery temperature compensation with other slopes
The FLEXmax 80 uses a 5mV per degree C per cell (2V) compensation slope required by UL. For other
slopes, you may be able to pick a dierent battery voltage and change the charger Absorb and Float
voltage settings to achieve a more or less aggressive slope. If going lower in voltage, reduce the Float
voltage rst, since the Absorb voltage will not be adjustable below the Float voltage setting. If going
higher in voltage, increase the Absorb setting rst before raising the Float voltage above the present
setting. Here is a table of FLEXmax 80 compensation based on system voltage for reference:
12V system -30mV/degree C
24V system -60mV/degree C
36V system -90mV/degree C
48V system -120mV/degree C
60V system -150mV/degree C