On Wed, 25 Feb 2004 22:48:04 -0000, Dave Platt wrote:

First thing I'd do is check your battery-charging circuit. If you're
trying to charge them from a 12-volt regulated source, then this could
be the root of your problem... a "12-volt" gel cell won't accept a
useful amount of charge at this voltage. You'll need around 13.8
volts to slow/float-charge the battery, and perhaps 14.3 - 14.4 volts
(with an appropriate current limit) to fast-charge it.

Read the label on the gel-cell. 14.4 volts will cook the battery in
no time flat. I learned that the hard way several years ago.

My power panel uses two regulated power supplies (a 50 A unit and a
35 A unit) operating through an isolation diode block to float
charge the Size 31 (100+ AH) marine deep-cycle gel-cell. The 50A
supply is set to deliver 13.5 V to the battery bus by itself, and
the 35A supply is set to deliver 13.3 V by itself - so I can tell by
the digital voltmeter readout as well as the LED on-line indicators
if the big supply goes off-line and the small supply has picked up
the load. The steady-state load on the bus is 7A which goes up to
25A when all transmitters are firing.

In designing the panel it helped that both my wife and I are both
electrical engineers trained in power distribution and that she
spent a few years in large-scale UPS design. She did insist,
however, that the installation be done to UL and USCG 12-V marine
safety standards, not "hamshack haywire". Expensive but "right".

The installation will run for about four hours in UPS mode after
which various boxes drop off line when the voltage goes much below
11.8 V. My next investment is a small natural-gas-powered gen-set
to supply the 120 VAC for the chargers and the computer installation
when commercial power fails. I'd love to put the whole house on
standby power, but who has a 50 KW gen-set or better yet fuel cell
hanging around that needs a good home? ggg

--
73 de K2ASP - Phil Kane

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