battery charger to get through Piper power port?

I bought a cheap SLA trickle charger at a ham fest awhile ago thinking
I might use it with a cable I made for my Aztec. On a warm (but not
warm enough) day last week I tried start the plane without heating the
engines. I failed. I thought it would be a good time to try the
charger.

I knew my bigger charger wouldn't work because it requires a battery
with *some* power to trigger it to start charging. That fails with the
Piper power port because the charger has to supply enough current to
trip the relay before connecting to the battery. It's a standoff.

Well, this trickle charger apparently works the same way. It wants to
sense a charge before it puts out.

Anyone know of a small charger that is safe for extended use and will
produce a charge without first sensing a battery? I'm about ready to
take my inverter and voltmeter to the auto parts store for testing.

Thank you.

--kyler

1. Simplest solution is a dumb charger that doesn't know whether it is
attached to a battery or not... That will put out DC power, no matter
what, which will provide the Piper solenoid with current to operate...
Of course, a dumb charger will over charge to 15 or 16 volts and boil
off the electrolyte over time...
Now, the solution here is to reduce the primary voltage to the charger
so that the charging voltage does not exceed 13.4 volts DC in trickle
mode... This can be as simple as a light bulb socket from the hardware
store wired to a duplex plug in SERIES, so that the 110 volt current
goes through the bulb and then through the 110v cord to the charger...
By selecting a small enough wattage bulb you will limit the voltage and
current to the charger which will hold down the battery voltage to 13.4
v under trickle conditions... You can play with the bulb size at home
using your car as the airplane battery until you get the correct
wattage bulb..
2. Next solution is to have a small battery attached to the output of
the charger which will supply the load to activate the charger and also
to operate the solenoid in the plane..

3.. Best solution! Have your mechanic change the Positive lead from
the Piper plug so that it goes around the solenoid and directly to the
battery... This is how I have Fat Albert The Apache wired (and every
airplane I have ever owned) for charging and jump starting...

denny

"Denny" writes:

1. Simplest solution is a dumb charger that doesn't know whether it is
attached to a battery or not...

That's where I was headed but, as you described, it wouldn't be good for
long-term use and that's what I really want. I'd like to just plug it
in when I put away the plane, just as I do for the engine heaters. That
way I'd be able to run the cabin heater for awhile when I'm getting
ready for the next flight without worrying so much about the battery not
handling it.

Stepping down the voltage is certainly an option. I'm not looking for a
fast charge.

2. Next solution is to have a small battery attached to the output of
the charger which will supply the load to activate the charger and also
to operate the solenoid in the plane..

I finally stumbled on to that yesterday. I have a portable "jump start"
battery (with a handy inverter attached). I realized that if I connect
that to the power port and then plug its charger into it, I have
basically what I want. It would also be handy for helping to run the
heater after I pull the plane out of the hangar, especially on trips
away from home (where I could charge it at a hotel or in a rental car).

3.. Best solution! Have your mechanic change the Positive lead from
the Piper plug so that it goes around the solenoid and directly to the
battery... This is how I have Fat Albert The Apache wired (and every
airplane I have ever owned) for charging and jump starting...

You had no problem with that?! Cool! I wanted this anyway because I'd
like to make a 12VDC tug and the power port is sitting right there just
begging to be used. (Having my tug not start recently makes this even
more enticing.)

Sidenote: I didn't realize the small airplane tug was invented right
here at Purdue...in 2003 (well after I bought my PowerTow).
http://news.uns.purdue.edu/UNS/html4...fi.towbar.html

Otherwise, pilots have to muscle their planes into place with
a manual towbar or have someone at the airport use a tractor-
like towing vehicle,

There must have been some reason to have the port "protected" by the
relay. Are we sure that this is safe and not (more) likely to rankle
any FSDO types? I sure don't see the harm in it other than producing a
signficant reaction if a conductor is jammed into the port. I wouldn't
mind replacing the solenoid with a manual switch inside the nose
baggage compartment.

Thanks!

--kyler

Kyler Laird writes:


{Switched power port}


I'm trying to grok how this works. What comes to mind is a 3-ping
connector: Hot, Ground, Control. Put +13v on the third pin by having
it jumpered to Hot WITHIN the cable's plug and that will do it.

You can then put a diode in series with the control lead so as to NOT
close the relay if the polarity is backwards. (Doing so would result
in what a former cow orker called "Big Sparky-Do's"... as the two
13.8 v sources would be in series with the only resistance being the
wiring and contactor..) A diode in series with the main lead with a) need
to be BIG... b) introduce unwanted voltage drop.

But is this how they did it? Suspect not...


3.. Best solution! Have your mechanic change the Positive lead from
the Piper plug so that it goes around the solenoid and directly to the
battery... This is how I have Fat Albert The Apache wired (and every
airplane I have ever owned) for charging and jump starting...

You had no problem with that?! Cool! I wanted this anyway because I'd
like to make a 12VDC tug and the power port is sitting right there just
begging to be used. (Having my tug not start recently makes this even
more enticing.)

Err. reverse polarity protection? And a short at the external cables
may start a fire inside....


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Kyler Laird writes:


3.. Best solution! Have your mechanic change the Positive lead from
the Piper plug so that it goes around the solenoid and directly to the
battery... This is how I have Fat Albert The Apache wired (and every
airplane I have ever owned) for charging and jump starting...

You had no problem with that?! Cool! I wanted this anyway because I'd
like to make a 12VDC tug and the power port is sitting right there just
begging to be used. (Having my tug not start recently makes this even
more enticing.)



I'm an EE, not an A&P, but your plan really scares me.

The external power jack is unfused so you can jump-start from it.
That's why the solenoid has that scheme to keep a "dead face" aka
no power on the exposed pin.

I don't suggest this lightly, knowing the BS and $$, but have you
considered adding a 2nd jack, smaller in size? That COULD be fused
at say 60A, and always live. That could accommodate both a charger,
or your power-tug, with no risk to your aluminum friend...or you
while in it.


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

David Lesher writes:

I don't suggest this lightly, knowing the BS and $$, but have you
considered adding a 2nd jack, smaller in size? That COULD be fused
at say 60A, and live. That could accommodate both a charger, or your
power-tug, with no risk to your aluminum friend...or you while in it.

Standing at the plane a few nights ago, I considered the same thing.
I've been working on blending a small charger and some old batteries
(from my electric lawn mower) to make a compatible charger.

I decided that I should add some resistance just in case one of the
batteries (plane or charger) gets really low. I don't want a sudden
rush through it. Then I realized that if I'm going to do that I might
as well just use small connectors and wire. And if I'm going to do
that I don't really need to use the high-power port.

However...using the existing power port is handy. The best thing about
it is that it's externally accessible. I can put a charger on it
without leaving the nose open. I leave expensive stuff (headsets) in
the nose so even in my (shared) hangar it's worthwhile to keep it
locked, but it's especially advantageous if I'm on the ramp somewhere
leaving the cabin and engine and heaters on.

Perhaps the answer is to bridge the relay contacts with a low-current
toggle circuit breaker? That would allow me to easily control whether
or not trickle charging or discharge can occur through the port but if
I happen to leave it enabled and a short or reverse polarity condition
occurs the circuit would be broken.

See any problems with that?

Thank you.

--kyler

Kyler Laird writes:

I don't suggest this lightly, knowing the BS and $$, but have you
considered adding a 2nd jack, smaller in size? That COULD be fused
at say 60A, and live. That could accommodate both a charger, or your
power-tug, with no risk to your aluminum friend...or you while in it.

Standing at the plane a few nights ago, I considered the same thing.
I've been working on blending a small charger and some old batteries
(from my electric lawn mower) to make a compatible charger.

What you want is a trickle charger; it need furnish only say 100mA
or so. (This assumes you religiously plug it in while hangared, of
course. Same scheme as most firetrucks.) A common source is the
residential alarm industry; they use a small PCB with a regulator
and a wallwart transformer. {I'll give you one if you need it.....just
to do it safely..}

I decided that I should add some resistance just in case one of the
.....
Good!

However...using the existing power port is handy.

My point was: "using AN external port is handy.."

Perhaps the answer is to bridge the relay contacts with a low-current
toggle circuit breaker? That would allow me to easily control whether
or not trickle charging or discharge can occur through the port but if
I happen to leave it enabled and a short or reverse polarity condition
occurs the circuit would be broken.

If you do that; the "ground power" contactor will close and stay closed;
costing you your protection. Hmm, you'd need a SPDT switch I think but
I'd want to draw it out. Not undoable, and perhaps cheaper than a 2nd
hole in the skin, etc.
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

: I decided that I should add some resistance just in case one of the
: batteries (plane or charger) gets really low. I don't want a sudden
: rush through it. Then I realized that if I'm going to do that I might
: as well just use small connectors and wire. And if I'm going to do
: that I don't really need to use the high-power port.

I would think a circuit breaker would be a better idea than a resistor. If
you go through the trouble of making a well-thought-out bypass for the interlocking
mechanism, why limit yourself to a trickle charge?

: Perhaps the answer is to bridge the relay contacts with a low-current
: toggle circuit breaker? That would allow me to easily control whether
: or not trickle charging or discharge can occur through the port but if
: I happen to leave it enabled and a short or reverse polarity condition
: occurs the circuit would be broken.

I think that this could be done well, but I would try to add some interlocking
to the bypass. Probably some diode logic to the coil of a relay. Then you could
protect yourself from reverse polarity on the plug, and overcurrent protect the large
solenoid bypass. Without schematics I can't say for sure the best way, but as I said
before, I'd try to think of every possible failure mode. I'm sure that Piper did.

Along the same lines, I've notice a significant difference in the later
PA-28's from my '69 model. Mine has a 60A breaker in the ALT feed line and the later
ones don't. All I can say is if mine ever tripped, it could put a big load dump
transient on the bus. That could cook a lot of avionics in a hurry.

Be careful,

-Cory


--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

What you need is a REGULATED lab power supply that has adjustable
voltage and current adjustments. I use a 0 to 33 volt at 0 to 30
amp power supply that has digital readouts for voltage and current
that I bought surplus.
Set the charge voltage and max charge current and plug it in. As the
battery charges the supply will switch from current limit mode to
voltage limit mode automatically.

You cannot feed the power into the APU port for a long time (more than
10 minutes) or it will generally fry the APU port relay because most
are not rated for continuous operation.
Install a charging jack on an inspection panel and wire it direct to
the battery with a FUSE at the battery that will support the expected
charging current from your power supply.
For 12v systems set the power supply to 14.00 to charge overnight or
13.45 for long term float charge. Double these voltages for a 24 volt
system. These voltages need to be adjusted some what if the
temperature is not close to 70F. This voltage verses temperature data
can be found on the internet for the type of battery you are using.

You do NOT want to use a low cost common UNREGULATED trickle charger
or you will surely fry your expensive battery by over charging.
Don't take the battery caps off unless you intend to charge at very
high rates or the acid will cover everything near the battery.
John

On Thu, 17 Mar 2005 15:08:05 GMT, Kyler Laird
wrote:

David Lesher writes:

I don't suggest this lightly, knowing the BS and $$, but have you
considered adding a 2nd jack, smaller in size? That COULD be fused
at say 60A, and live. That could accommodate both a charger, or your
power-tug, with no risk to your aluminum friend...or you while in it.

Standing at the plane a few nights ago, I considered the same thing.
I've been working on blending a small charger and some old batteries
(from my electric lawn mower) to make a compatible charger.

I decided that I should add some resistance just in case one of the
batteries (plane or charger) gets really low. I don't want a sudden
rush through it. Then I realized that if I'm going to do that I might
as well just use small connectors and wire. And if I'm going to do
that I don't really need to use the high-power port.

However...using the existing power port is handy. The best thing about
it is that it's externally accessible. I can put a charger on it
without leaving the nose open. I leave expensive stuff (headsets) in
the nose so even in my (shared) hangar it's worthwhile to keep it
locked, but it's especially advantageous if I'm on the ramp somewhere
leaving the cabin and engine and heaters on.

Perhaps the answer is to bridge the relay contacts with a low-current
toggle circuit breaker? That would allow me to easily control whether
or not trickle charging or discharge can occur through the port but if
I happen to leave it enabled and a short or reverse polarity condition
occurs the circuit would be broken.

See any problems with that?

Thank you.

--kyler

: 3.. Best solution! Have your mechanic change the Positive lead from
: the Piper plug so that it goes around the solenoid and directly to the
: battery... This is how I have Fat Albert The Apache wired (and every
: airplane I have ever owned) for charging and jump starting...

I haven't really been following this thread too closely, nor have I looked at
the schematics, but it sounds like it's wired from the factory with a safety
interlock that you are proposing to bypass. When I worked on the HEV project at UIUC,
we had a similar setup with the big charging plug... basically in order to charge the
car, there had to be 14v present *in the car* to close the relay to enable the
high-voltage contactor. There were also diodes present in the HV line to make sure it
was impossible to discharge the battery out the charging port. Granted, a lot of
safety issues are reduced when both sides have a max of 15v, rather than the 350 I was
working with, BUT...

The way it was wired from the factory no doubt was pontificated upon a great
deal. I suggest you consider *ALL* possible failure modes and do the appropriate
official paperwork approved. Making big sparks in an aluminum plane is not good for
its structural soundness. Even if "Cooter the Airplane Mechanic" has done it 100
times before, it only takes one error to have a 1" hole burned in the side of the
plane.

-Cory

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************