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Alternators and Charging Systems
C–2 975-0128-01-01
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 V) 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. When in use, alternators heat up, and their output current
capability drops by as much as 25%. Therefore, standard alternators with
ratings of 40–105 A only deliver a maximum of 30–80 A in actual use
and deliver even less as battery voltage rises. Many alternators cannot
produce more than 13.6 V 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.
Using an Alternator Controller
If your regular alternator is inadequate, you can install an alternator
controller that bypasses the voltage regulator and boosts the alternator’s
output voltage during charging. This will increase the alternator’s
charging rate at higher battery voltages and ensure more rapid and
complete charging.
Using a High-Output Alternator
Heavy-duty alternators rated from 100–140 A can replace standard
alternators and produce the higher current and voltage required to charge
multiple battery systems. They are available from RV and auto parts
suppliers.
XPower3000.book Page 2 Wednesday, December 10, 2003 6:52 AM