Alternators and Charging Systems
B–2
Charging System Requirements
Your charging system should be capable of delivering a charging current
equal to 25% of the amp-hour capacity of your battery. For example, if
you have a 200 Ah battery, the charging system should be able to deliver
50 amps. The charging system must also be able to charge each 12 volt
battery up to approximately 14.4 V and then drop back to a “float”
voltage of 13.5–14 V (or shut off).
Charging With an Engine Alternator
Read the following information to determine whether your vehicle’s
standard alternator will be adequate by itself, whether you should install
an alternator controller, or whether you need a high-output alternator.
Using a Standard Vehicle Alternator
A typical engine alternator (12 volts) may not be able to meet the
requirements outlined above if your system uses large capacity batteries.
Alternators are typically rated for the current they can deliver when they
are cold. In use, alternators heat up, and their output current capability
drops by as much as 25%. Therefore, standard alternators with ratings of
40–105 amps only deliver a maximum of 30–80 amps in actual use and
deliver even less as battery voltage rises. Many alternators cannot
produce more than 13.6 volts when they are hot. As a result, a standard
alternator may not be able to charge a large battery quickly and
completely.
Two solutions are to install an alternator controller or to install a high-
output alternator.
CAUTION
Never operate the PROwatt 3000 directly from an alternator. To
work properly, the inverter must be connected to a battery or a
well-regulated, high-current DC power supply.
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