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BUILD THE SOLAR
By John Guyer
This article describes
how to build a solar
enables a single solar
panel to charge
multiple batteries of
different sizes and
them isolated from
each other. This
article also covers
how to use a solar
panel and battery to
run a garage door
opener in a building
without access to
utility power. The
provides a maintenance charge to 12 volt lead acid automotive batteries
from a 45W solar panel. My unit has been in operation for three years now.
■ FIGURE 1. Solar sequencer prototype.
The solar panels are from Harbor Freight’s 45 watt
solar panel kit. The panels face due south and are
mounted at 30 degree angles to each other in order to
spread the capacity over as much of the day as possible. If
they are mounted as shown in the kit directions, the
current can be over three amps at noon, but not much in
the morning and evening. The mount was made out of 1"
aluminum angle purchased from the hardware store.
Garage Door Opener
The garage door opener I used is a
Craftsman/Chamberlain belt drive with a battery backup.
It is designed to run from a 12 volt 5 Ah lead acid battery
(included), but only as a backup. Everything but the lights
work with no AC power, and it draws about 40 mA when
will work from the battery afterward. I used a long
extension cord at first, but switched to a cheap 400 watt
modified sine wave inverter to get it started, then
disconnected the inverter. This garage door opener uses
four amps DC to open the door and 3. 5 amps to close it.
Both take about 20 seconds.
The small battery included with the garage door
opener only lasts about six months. It is only intended as a
backup — not a primary power source. I replaced it with a
lead acid battery that was still good but out of warranty,
which I removed from a Jeep Grand Cherokee. It is a size
26 battery which has a standby power number of 150,
meaning it can supply 25 amps for 150 minutes. I plan to
add another opener and this should be more than enough
to power both. It also can run the lights that came with
the solar panel kit. The Jeep's battery is on a shelf in the
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