samlexsolar SCC-30AB, Owner'S Manual, Page: 39 / 48

39
6
INSTALLATION & OPERATION
Temperature Compensated Battery Charging
An optional Battery Temperature Sensor (BTS) is available for temperature
compensated battery charging. The BTS consists of a temperature sensing probe that
is installed on the + battery post. A pair of 10 ft. wires (marked
+ & - ) connect the
temperature sensing probe to the 2 terminals marked BTS at the back of the unit. (Fig.
5.2).
As the battery gets warmer, the gassing increases. As the battery gets colder,
it becomes more resistant to charging. Depending on how much the battery
temperature varies, it is important to adjust the charging for temperature changes.
Various voltage set points given in the specifications are indicated at a reference
temperature of 25 ºC / 77 ºF.
There are three battery charging parameters that are affected by temperature:
PWM Absorption
This is the most important part of charging that is affected by temperature
because the charging may go into PWM absorption almost every day. If the battery
temperature is colder, the charging will begin to regulate too soon and the battery
may not be recharged with a limited solar resource. If the battery temperature rises,
the battery may heat and gas too much.
Equalization
A colder battery will lose part of the benefit of the equalization. A warmer battery
may heat and gas too much.
Float
Float is less affected by temperature changes, but it may also undercharge or gas too
much depending on how much the temperature changes.
The Battery Temperature Sensor corrects the three charging set points noted above
by the following values (reference temperature is 25 ºC / 75 ºF):
• 12 volt battery: –0.030 volts per °C (–0.017 volts per °F)
• 24 volt battery: –0.060 volts per °C (–0.033 volts per °F)
The temperature sensed by the BTS at the battery is displayed on the LCD screen
under the screen display “Heatsink BTS” (see Fig. 5.3). As the LCD display is not
capable of displaying negative values, battery temperature below 0 ºC will not be
displayed. Voltage compensation will, however, be carried out below 0 ºC.