Update November 9, 2008
After a couple weeks of assembly and and waiting for a battery charger module to arrive by mail, the
Porta-Power unit was completed this weekend.I spent an hour or two a few nights each week and had it not been for a mis-wire
on my part, I would have completed it a couple hours sooner.
The mis-wire involved
reverse polarity with the charger module. The real head scratcher was due to the fact that this unit has reverse polarity
protection, so even though it was connected improperly, the power LED was just glowing green, waiting for me to properly connect
it. The confusing thing about the operation of this device is that when the battery is fully charged, it's green; when
not connected it's green as well. There was also a problem with panel meter which also had to be investigated and repaired.
With all that behind me, I finished wire-tying things up, trying to make the unit look reasonably good
for the camera.
How It Works
There
are two "sides" to the unit. The left side is a 12 volt, 14 amp hour battery source. Output jacks include a cigarette
lighter socket and 3 sets of banana jacks to power anything requiring portable power at the flying field - or wherever
it's needed. The output bus is protected with a fast acting 10 amp fuse, so use of electric starterswon't work on
this unit due to the small fuse size. I was concerned about having the unit equipped without an over-current protective
device. A 4 amp automatic switch mode charger handles recharging the pair of 7.2 amp hour batteries when battery condition
warrants. Voltage is monitored through the use of a small meter module connected to the battery bus.
Another feature of the unit is the ability to switch the charger and metering to a separate set of
banana jacks to permit charging of an external battery. This is accomplished by flipping the yellow switch down, disconnecting
the charger from the internal battery and connecting it to the dedicated jacks. Metering is toggled between the two with a
dedicated switch. Flipping the switch up disconnects the external battery and connects the internal battery.
The right side of the unit is a 12 volt, 4 amp DC power supply equipped with a DC power switch, pilot
indicator and 2 pair of banana jacks. The supply can be used to power whatever is needed as long as the current requirement
does not exceed 4 amps. The right side power source is also monitored with its own panel meter.
A single pole switch handles AC power control for both the charger and DC supply AC switch status is monitored
with a red pilot lamp. DC output is monitored with a blue pilot lamp. The AC input is fuse protected.
Parts Sources and Cost
Most of the parts used to build
this unit came from my junk box of stuff I've had for years including the DC supply, switches, enclosure, meter modules,
AC cord and banana jacks. I bought the batteries about a year ago for other uses.
I
spent $35 on the charger, having found it from Gruber Power Servicesvia Ebay; the single largest purchase for the project. A couple pilot lamps were purchased at about $5 each from my newly
found electronics store. Quality electronic parts don't come cheap in the retail world.
To buy allthe parts for this project would have been cost prohibitive, so unless you have a lot of spare cash,
it's not worth it.
Quality Electronics Parts in Columbus
If you're reading this and are interested in good quality electronic parts and are fed up with the
junk Radio Shack sells, check out Esco-Ohio. They have a location in Clintonville at 4672 Indianola Ave., as well as a Lancaster store. Ron in Columbus has
a good selection of parts, tools and supplies. Take note, the stock is not second hand nor bargain basement type items and
are first quality commercial grade. If you are looking for Radio Shack prices, this is not the place. Esco is a purveyor of
quality merchandise.
The gallery of photos below illustrates the finished unit, now
fully operational.
