On Fri, 23 Apr 2004 03:07:18 +0000 (UTC), Richard G Amirault wrote:

: I am thinking of replacing the power supply with a 20 amp marine
: battery charger that will automatically drop to float charge, charging
: a 105AH flooded deep-cycle battery. The battery would feed a "battery
: booster" -- a DC-to-DC converter that will maintain 13.8 volts at 85%
: efficiency. The booster would feed my equipment.

: Are there any drawbacks to this arrangement -- other than it requires
: a battery? The advantage is it won't boil the battery and will be
: immune to outages and brownouts. Also, it will do a fast recharge
: after an outage.

As I said above .. I think you should look into the possiblity of damaging
your charger if battery voltage is put into it the "wrong way"

The best solution is much simpler than those that I've seen here.

I use dual switching p/s through a dual-diode isolator onto a 100 AH
deep-cycle marine gel-cell. Both supplies are set to deliver 13.5 V
to float-charge the battery. Two supplies are used in case one goes
down for overload or any other reason such as my kicking the on-off
switch to "off" accidently as I did once.

All devices are rated for 50 A. Make sure that you use sufficiently
large wire and adequate overcurrent protection (I use marine-rated
circuit breakers) to protect the supplies, the battery, and the
load(s).

The only thing unusual about the setup is that the isolator has to be
one made for positive-ground vehicles (yes, auto supply stores sell
them on special order, same price) because the standard ones for
negative-ground vehicles are for two batteries charged by one supply
(alternator) rather than one battery charged from two supplies. If
you only want to use one supply, you can use one side of a standard
isolator.

Be sure that the supply is a regulated constant-voltage supply, not
a "battery charger" whose output is really semi-filtered DC. If you
can operate the radio on the supply with no hum problems, it will be
OK for float-charging.

The bottom line -- keep the battery on line at no more than its
rated float-charge voltage, and all the isolator is -- is a big
diode on a big heat sink.

--
73 de K2ASP - Phil Kane

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon