Alternators and Charging Systems
A good charging system is important for the health of your batteries.
Poor recharging methods can quickly damage your batteries. When possible,
recharge your batteries when they are about 50% discharged. This will
give you much longer battery cycle life than recharging when the batteries
are almost completely discharged.
The charging system should be capable of delivering a charging
current equal to 25% of the ampere-hour capacity of your battery.
For instance, if you have a 200 ampere hour battery, the charging
system should be able to deliver 50 amperes. The charging system
must also be able to charge each 12 volt battery up to approximately
14.4 volts and then drop back to a float voltage of 13.5 to 14 volts
(or shut off ).
A typical engine alternator (12 Volt) may not be able to meet these
requirements if large capacity batteries are used. Alternators are
typically rated for the current they can deliver when they are cold.
In actual use, alternators heat up and their output current capability
drops by as much as 25%. Thus standard alternators with ratings
of 40 amperes to 105 amperes will only deliver a maximum of 30 to
80 amperes in actual use and will 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.
One solution is to install an alternator controller that will bypass
the voltage regulator and boost the alternators output voltage during
charging. This will increase the alternator's charging rate at higher
battery voltages and ensure more rapid and complete charging. Alternator
controllers are available from marine product dealers.
Another solution is to install a high-output alternator. Heavy-duty
alternators rated from 100 amperes to 140 amperes are available
from RV and marine dealers, and auto parts suppliers. These alternators
are designed to directly replace standard alternators but produce
the higher current and higher voltage required to charge multiple
When recharging from AC power, use a good quality marine battery
charger or RV converter that meets the requirements specified above.
Do not use chargers intended for occasional recharging of automotive
starting batteries; these chargers are not intended for continuous
Your batteries may also be recharged from alternative energy sources
such as solar panels, wind, or hydro systems. Make sure that you
use the appropriate battery charge controller for your energy source.
Do not operate the 2500W INVERTER directly from a charging source
such as an alternator or solar panel. 2500W INVERTER must be connected
to a battery or a well regulated, high-current DC power supply to