42 Owner’s Manual
Wanco® Metro™ Message Sign
■ To lengthen battery life and prevent freezing, always keep batteries fully charged and
keep cable connections clean and tight.
■ Visually inspect batteries for physical damage, including cracks and leaking. Always
replace damaged batteries immediately. Dispose of old batteries in accordance with
local regulatory codes.
■ Keep the battery box lid closed and latched unless you are performing maintenance,
charging the batteries, or using the touchscreen controller.
Charging
Battery voltage should be checked once a week, to ensure the charging system is
keeping the batteries charged. In northern locales during winter, when sunlight is less
intense, battery voltage should be checked more often. For an overview of the
charging system, see Section 6.3.1, page 40.
If the battery voltage is low because the charging system is not able to fully charge the
batteries, use the external AC-powered charger when the batteries need charging (see
“External AC-powered charger” on page 44).
To determine charge requirements, perform a voltage test as described below.
Voltage testing
Perform an open-circuit voltage test with a DC voltmeter or multimeter. Because the
message sign’s maintenance-free batteries are sealed, an open-circuit voltage test is
the only method for determining the state of charge.
1. Observe battery safety precautions (see “Safety” on page 41).
2. Turn off all electrical loads and halt battery charging from both the solar panels and AC
charger.
3. Ensure battery cables are disconnected and terminals are clean.
4. For accurate voltage readings, wait at least one hour to allow the battery voltage to
stabilize.
5. Using a DC voltmeter or multimeter, measure and record the DC voltage across the
positive and negative terminals of each battery.
6. If the voltage varies between batteries, recharge the batteries and perform the test
again, or obtain appropriate test equipment from the battery manufacturer and follow
the manufacturer’s instructions.
7. Correct the voltage readings to 80°F (27°C). Using ambient air temperature:
■ Add 28 mV (0.028 volts) per cell for every 10°F above 80°F (5.6°C above 27°C)
■ Subtract 28 mV (0.028 volts) per cell for every 10°F below 80°F (5.6°C below 27°C).
■ Each 12-volt battery has two 6-volt cells.
8. Refer to Table 6-1 to determine the battery charge requirements based on the
corrected voltage.
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