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Electrical Systems
For accuracy, test the auxiliary battery voltage using a volt-ohm
meter. A fully charged auxiliary battery will read 12.7 volts DC
and 1.265 specific gravity at 80°F (32°C).
The auxiliary battery is considered discharged at 11.8 volts,
and dead at 11.65 volts. When voltage drops below those
levels, permanent damage may occur. Typically, a deep cycle
battery has an amp-hour rating of 75-100 amps.
If the furnace and refrigerator are operating simultaneously,
approximately (12.0 + 3.0) 15.0 amps per hour are used. This
does not include any 12-volt lights, water pump or any other
12-volt component.
In the above example, if the furnace and refrigerator
operated constantly, a 75 amp-hour battery would
become fully discharged in 5 hours (75ah /15a = 5h).
The auxiliary battery should be installed in parallel with the
battery in your tow vehicle. When the 7-way trailer plug is
connected, both batteries power the RV so it is important not
to discharge your tow vehicle battery below the level required
to start the engine. To prevent this from occurring, disconnect
the 7-way trailer plug or install a battery isolator. When the tow
vehicle engine is operating with the RV connected, the tow
vehicle charging system will charge both batteries.
Replacement and maintenance
Some equipment in your RV will draw small amounts of cur-
rent even when turned OFF. To prevent the auxiliary battery
from being discharged when your RV is not connected to
shore line power, disconnect the auxiliary battery negative
cable at the battery. During storage, it is important to check
the voltage monthly and recharge the auxiliary battery as
needed. If you remove the auxiliary battery from your RV,
store it in a dry, cool area per the manufacturer’s instruc-
tions.
When it is time to replace the auxiliary battery, replace it with
a Group 24 or Group 27 deep cycle battery only. Contact the
battery manufacturer for further information. Do not reverse
the positive and negative battery cables (doing so will blow
the reverse polarity fuse(s) that protect the converter)
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