RG Battery Charger by Jim Weir in Kitplanes

[Kevin O'Brien]

Hi,

As an 8-year (or longer) Kitplanes subscriber, and longtime electronics tech
(Army Aviation-trained), I read with interest the articles Jim Weir wrote
about building your own RG battery charger (Kitplanes: March, April, & May
2004). This looks just like the ticket for my application, but I did have
two questions:

First, would sealed reghargable lead-acid batteries (such as the Yuasa
NPH5-12 12V 5Ah) be an applicable model to recharge with this charger (is a
gel-cell a gel-cell a gel-cell, etc.), and what would be the best way to
reduce the charging current to the c/100 that is recommended? Secondly, is
there an easy way to provide a parts list (with quantity, type, current
capacity, and tolerance) for the components in these circuits? These would
be a HUGE help!

As I still rent from my local FBO, and they have apparently had a few acft
returned in the past with dead batteries, they have summarily disabled all
of the cig lighter sockets in all of their acft. I fly with a PDA-based GPS
which requires a 12V source for power, but only drains 250mA during
operation, so I keep a small gel-cell battery in my flight bag with a cig
lighter socket pigtailed to the terminals. It works great, but I'm afraid to
attach that little battery to my auto batt charger, and don't think a 13.8V
wall-wart charger has enough current to push into the battery. The RG
Charger in Jim's article looks like the ticket, but I wanted to be sure that
I was using the right tool for the job, and needed a shopping list to take
to Radio Shack.

Thanks.

Kevin M. O'Brien

Seffner, Florida.

[Dave]

"Kevin O'Brien" > wrote in message
om...
> which requires a 12V source for power, but only drains 250mA during
> operation, so I keep a small gel-cell battery in my flight bag with a cig
> lighter socket pigtailed to the terminals. It works great, but I'm afraid
to
> attach that little battery to my auto batt charger, and don't think a
13.8V
> wall-wart charger has enough current to push into the battery. The RG
> Charger in Jim's article looks like the ticket, but I wanted to be sure
that
> I was using the right tool for the job, and needed a shopping list to take
> to Radio Shack.
>
> Thanks.
>
> Kevin M. O'Brien
>
> Seffner, Florida.
>

Kevin, if you want to charge from a regulated source of similar voltage such
as your car battery, the solutions are cheap and easy. Just put a light bulb
in series with the battery on the charge cord. The lamp will limit the
current but still allow a full charge. Total cost, about $2. Make sure the
current does not exceed the recommendations of the battery maker. A 15W lamp
(common) allows a little under 1 amp into a discharged cell.

[[email protected]]

FBOs find batteried dead because people leave the master on.
Too tired or distracted to complete a proper shutdown checklist. As for
the cig lighter socket, Cessna and the FAA issued an AD years ago to
have them disconnected as they presented a fire risk; there was no
breaker for the socket. They did allow the owner, if he desired, to put
an inline fuse in the line to the socket if he needed it for other
things like intercoms and such.

Dan

[[email protected]]

Kevin O'Brien wrote:
<snip
> As I still rent from my local FBO, and they have apparently had a few
acft
> returned in the past with dead batteries, they have summarily
disabled all
> of the cig lighter sockets in all of their acft. I fly with a
PDA-based GPS
> which requires a 12V source for power, but only drains 250mA during
> operation, so I keep a small gel-cell battery in my flight bag with a
cig
> lighter socket pigtailed to the terminals.

Sort of a non-sequitur to your question, but I always ask this:
Do you have a fuse right on the battery?
A really easy way to do this is a short jumper with female connectors
on both ends. (I've actually soldered two back-to-back and put
heat-shrink over them) Slide one end on the battery terminal, the
other end to one tab of an automotive fuse. Your former power
connection then slides on to the other tab of the fuse. Cheap. Easy.
Safe.

I had a setup similar to yours for a handheld radio which I would have
_sworn_ would not short. It did, though. Caused some smoke, burned
through my little custom-sewn denim bag, and gave an enormous shot of
adrenaline.

Tim "once burned, twice shy" Ward

[Model Flyer]

"Kevin O'Brien" > wrote in message
om...
> Hi,
>
> As I still rent from my local FBO, and they have apparently had a
few acft
> returned in the past with dead batteries, they have summarily
disabled all
> of the cig lighter sockets in all of their acft. I fly with a
PDA-based GPS
> which requires a 12V source for power, but only drains 250mA during
> operation, so I keep a small gel-cell battery in my flight bag with
a cig
> lighter socket pigtailed to the terminals. It works great, but I'm
afraid to
> attach that little battery to my auto batt charger, and don't think
a 13.8V
> wall-wart charger has enough current to push into the battery. The
RG
> Charger in Jim's article looks like the ticket, but I wanted to be
sure that
> I was using the right tool for the job, and needed a shopping list
to take
> to Radio Shack.
>

While the normal wet type of battery requires up to 15 volts to
charge it properly if you use a charger designed for them on a
gel-cell it will fry it, had some gel-cell batteries fry for that
reason. Be sure that any charger you use on a 12v gel-cell does not
exceed the recommended 13.6v.
--
..
..
Cheers,
Jonathan Lowe,
Rallye 880b
EI-BFR

> Thanks.
>
> Kevin M. O'Brien
>
> Seffner, Florida.
>
>