|More power to you!
(Supersizing a scope-side portable power source)
As a completely sealed unit, these
Gel-Cells have little likelyhood of leaking or
causing damage, and I'm told they are even
allowed to be shipped via air-freight. The
battery box provides a convenient way of
mounting all the harware though, as well as
supplying a strap to carry it.
I decided to incorporate four individual 12V
power outlets, so as to reduce the tangle of
cables or octopus-style adapters. I also
wanted to protect these via circuit breakers,
but could not get the appropriate panel
mounted CBs on short notice, so used
panel-mounted fuses instead.
With ever increasing demands for scope-side power capacity, and not being overly fond of being tethered to an AC
power line, meeting those needs was becoming quite a challenge. I had "graduated" from a single 17AH 12VDC
|12VDC 17AH Portable "Jump-Start" Gel-Cell Batteries
65AH Battery and a completed unit
JumpStart, only to find that even two were
becoming taxed with my longer sessions.
Granted they were getting quite a workout,
often starting their service-day not much
beyond afternoon, providing power to a 5"
LCD and an AP 900 or 600GTO mount
tracking the sun.
When night arrived, they picked up the
added burden of several dew-heaters and
and an SBIG STV auto-guider, gallantly
giving their best but often not enough! I
would find myself juggling devices and
cords to keep the mounts driven or
auto-guider guiding, and needed
desperately to find a solution.I had
considered going to a 34AH battery, but
even that would only measure up to my
current capacity, and the two smaller units
would still be required as supplements.
I then had the extremely good fortune of
being tasked to perform a systems upgrade
to several large-scale memory arrays with
(drum roll please!) ... a total of ten 12VDC
65AH Gel-Cells that were to be disposed of!
Of that number, although five had difficulty in
maintaining a charge, the remaining five
were in pristine condition. The wheels
started to spin as I thought of how to best
contain, transport, and utilize these 48
pound beasts. Fortune was again on my
side, as being a standard size battery
(group 24), the local marine supply store
had a case that fit like a glove and could
become the basis for a portable power
|Front view showing the fuses and
Side view of power-out ports
The case allows convenient mounting
of the power-out ports on each end,
with a total of four being installed, each
bank having its own fused protection.
The outlet ports are Radio Shack units
which have neat rubber caps and come
equipped with in-line fuses, which were
canabalized in lieu of the panel mount
Radio Shack 12VDC Adapter Outlet PN
Rear-view showing the charging port
The original configuration for charging and
accessing these cells was via a
multi-conductor umbilical that feeds directly
to the Gel-Cell electrodes. This was
retained in an effort to ease the charging
process, and was routed to the rear of the
Normally nestled just inside the top cover
wings, it is extended here to denote its
location. A mating umbilical (not shown)
connects to the charger.
It perhaps would be almost as easy to
simply remove the cover, but what the hey...
I already had the harness!
Top of the unit and power monitor
Here you can see the four power-out
ports (two each on either end), their
associated fuses in the recessed
coves, the master switch (in the lower
right corner), and the voltage monitor.
The master switch applies power to
the fuses, which in turn provide
power to the left and right power-port
Having had much angst with people
striking panel-mounted fuses, I was
quite happy to find these protective
nooks in which to place them.
I wanted something to indicate when the
unit was on, and also to be able to
monitor the voltage level.
While toying with the idea of throwing
together a perf-board mounted LED
monitoring circuit, I discovered Radio
Shack had an "Vehicle Battery Tester"
(PN# 22-112) that would fit the bill for six
bucks (good fortune strikes yet again!)
With such a small current draw, I opted to
keep things simple by wiring it to the
switch leg of the master, rather than use a
separate momentary switch. When the
power unit is switched on the monitor also
Close-up of the power monitor
And the guts....
Nothing elaborate here, as this
"under-cover" shot shows the simple
arrangement used to route power
from the battery to the receptacles,
via the master switch and fuses.
The only surpise that befell me was
that I couldn't find anyone who
wanted these Gel-Cells!!! Eventually,
they all found homes, but I was
amazed that no one wanted these
free (as in no $$$) cells!?!
UPDATE: It worked out so well, that I
just threw together a second one.