LABC1 • 17
ADJUSTING YOUR LABC1 BATTERY CHARGER
Now that you have finished the assembly stage there is only one more step
before you start charging your batteries. The necessary alignment is to adjust
R2 for the proper ‘Float’ voltage with reference to the current air temperature
around diodes D5 to D14. In order for the temperature compensation network
to function properly and automatically adjust the ‘Float’ voltage as needed,
you will need to know the air temperature in the room you are in. Note that this
adjustment only needs to be done once. When R2 has been set, the unit will
automatically track as needed from there on out.
To adjust R2, take a temperature reading for the current room temperature
with a thermometer. Set your voltmeter on the 20VDC scale and attach the
probes (Red = +, Black = -) across the output of J2. Trim the pot (R2) to get a
reading of 13.4 VDC (+- 0.01 VDC) at a room temperature of 25°C (77°F) with
no battery attached. If your room temperature is above or below 25°C, you will
need to account for the difference by offsetting the alignment voltage by 22mV
(10 x 2.2mV/°C for each of the sensor diodes) for every 1°C of difference. See
Table 2 for examples.
If you do need to adjust for any temperature differences, here are a few
helpful hints to point you in the right direction:
· If the temperature is higher than 25°C (77°F), reduce the alignment
voltage at J2 by 22mV for each 1°C difference.
· If the temperature is lower than 25°C (77°F), increase the alignment
voltage at J2 by 22mV for each 1°C difference.
Handy formulas: °F = (°C x 1.8) + 32 or °C = (°F – 32) x 0.556
Temperature J2 Terminal Voltage
12V Battery
27°C (81°F) 13.356 VDC
25°C (77°F) 13.400 VDC
23°C (73°F) 13.444 VDC
‘Float’ Mode voltage settings of R2 for
different example temperatures
Table 2.