Photovoltaics vs. vehicle charging

[archerships]

Photovoltaics are an extremely expensive way to produce
electricity, and they simply do not work under many RVing
circumstances. For a big rig, that spends extended periods,
for most of the year, parked in one sunny place, without
moving, they can be a viable source of quiet power. It is
basically a way to avoid the noise of a generator, unless
you have to run the air conditioning, which is much more
likely when parked at a good sunny Solar site. However,
for us who use smaller vehicles, that we are likely to be
driving, at least a little bit every day, there is a cheaper,
more convenient, and more dependable alternative.

That alternative is to modify our vehicle's engine charging
system to efficiently charge a bank of deep cycle batteries
while we drive. This means replacing the standard automobile
regulator with a special multistage regulator, designed to fast
charge deep cycle batteries. It may also mean that you need
to replace your factory alternator with a larger heavy duty
one, from the boating industry, or salvaged from an ambulance
or limousine. You will also need a large battery bank, if you
want fast charging. For fast charging, your battery capacity
will need to be 3-4 times the amount of electricity that you
will typically use between charges, instead of the minimum of
double. Depending on how you set up your system, you will be
able to put a pretty good charge into your batteries in only
20 minutes to an hours of driving time. The system will also
be able to charge while idling.

Photovoltaics will only help you when you have a lot of sun,
for a lot of time, and have put a lot of money into the system.
You will still have much of your time, when you will need to
charge you batteries from another primary system. Our small
vehicles can rarely afford the space that a generator takes
up, so converting our engine's charging system, to rapidly
charge our deep cycle batteries, is our best option, after
we do what we can to reduce our electrical needs. PVs
should be in addition to that.

These high efficiency charging systems are fairly common
in large sailboats. There are quite a few good books, which
go through all aspects, and explain in reasonably good detail,
how to design a successful system.

One book, which I have found very informative is:

"Managing 12 Volts: How to Upgrade, Operate,
and Troubleshoot 12 Volt Electrical Systems"
by Harold Barre (under $14 on Amazon)

-Laren Corie-
Passive Solar Building Design Since 1975