"gojamo" wrote in message
ps.com...
I installed an electric gate opener which came with a
transformer to be
operated from house current but was specifically made to
allow a 12v
battery for power outages. Because of the gate's
location, I removed
the transformer and put in a 7 amp hour gel cell with a
"1.8 watt"
trickle solar charger. The battery ran down over a couple
of weeks,
even without using the gate opener. I suspect the the
constant battery
drain from the receiver may have something to do with
this, along with
the fact that I live in cloudy Oregon. I bought a 5 watt
solar panel
to replace the smaller one. It too is indicated to be a
trickle
charger, although this is probably meant for an auto
battery, not a
much smaller gell cell. I noticed the battery is at about
14volts when
not operating the opener, and I am concerned about over
charging. I
thought about getting a charge controller, but with such a
small
battery, could the charging current still be too high? I
believe the
charging current curve for the controller is likely meant
for larger
batteries. I also thought about connecting a power zener
diode of
about 13.5 volts across the battery. Is this a bad idea?
My last idea
is to get an auto battery, put it in a plastic case, and
connect it to
the solar panel without any charge controller. Are any of
these
solutions good or are there other ideas? Thanks

Measure the current from the cell to the battery after it
has reached "full charge" condition. (In full sun, etc) if
that current is low enough for your battery, you should be
fine. One reference I found suggested trickle charging at
1/100 the battery capacity, which would be .07 amps for your
battery. You might find a spec for your particular battery
with proper searching. Or, you could adapt someone elses
charging circuit perhaps.

http://www.google.com/search?hl=en&q...trickle+charge

Bob