Battery chargers convert 120 volt power from the utility or a generator
into a form usable by the batteries. There are two common ways of accomplishing
this. The first is a transformer type charger. This type of charger is
by far the most common type, with most chargers conforming to this design.
They work very well with utility power, but the less expensive ones are
very inefficient and can lose performance drastically when operated from
a generator. Some generators affect chargers in this way more dramatically
than others. (When buying a small generator, ask LOTS of questions…….)
In general, generators should be adjusted to produce 125 - 130 volts to
provide satisfactory results, and even then don’t count on more than half
of the chargers stated capacity. The second type of charger is actually
a switching type power supply adapted to charge batteries. These units
are typically smaller and more efficient than their transformer based equivalents,
and are less affected by generator operation. Switching type chargers,
like their transformer laden brethren, should be run at their maximum rated
input voltage for best results when operating on generator power.
A typical system with a generator should have a total charging capacity
of one tenth the battery size if practical. An example follows: a 1000
amp hr battery bank with a DR1512 inverter (built in 60 amp charger) would
require a 40 amp auxiliary charger for an optimal configuration.