On Sat, 20 Aug 2005 21:06:12 GMT, Ed wrote:

Not meaning to get this tread off on a tangent, but the above comment
prompts me to point out that even "maintenance free" batteries AREN'T,
necessarily.

Some of us refer to such batteries as "maintenance resistant".

With regard to three-stage charging:

I use at Size 31 - 100 AH - gel-cell battery as the main power
source for my radio equipment. Gel-cells are REALLY sealed and can
be operated in any position. They do not have vent caps, hidden or
exposed, and as the name implies, has a gelled electrolyte rather
than a liquid electrolyte. Truly maintenance-free discounting the
need to check the connections for tightness and corrosian from
outside sources.

I recently put a new charger designed for gel-cell charging into
service. This is a professional type charger, not an automotive
charger (with price to match), and it has a specific setting
(dip-switch on control board) for gel-cells. It was recommended as
the proper companion to the battery by the local industrial battery
supplier.

In addition, if the current drawn by the load while the battery is
being charged is greater than 2A (which it is here) a jumper has to
be added on the control board to change it to a two-stage charger
or else the control circuitry will see the load current as charging
current and adjust the voltage upwards to compensate.

I have also found that when in "charge" mode, the DC output has a
60 Hz component which needs to be filtered between the battery-charger
junction and the load. One more thing that "they" don't tell you
in books or teach in courses.

--
73 de K2ASP - Phil Kane
(Regsitered Professional
Electrical Engineer)