Solar charging question

I have a G103 SL with a 28Ah SLA main battery and a Rotax 505A engine.
Over the years I've had some intermittent problems with ground
starting the engine, and the pattern has only recently been more
obvious to me. The engine has a reputation for being a bit finicky to
start, however, air starts are nearly instantaneous and reliable, and
windmilling alone will bring it to life without fail. My starter has
been overhauled recently, and first starts of the year after having
been on the AC charger in the trailer are usually crisp. I keep the
aircraft tied down and covered during the more mild months of the
year, but this is usually when the engine gradually gets a bit more
challenging to start. I have been told that the Rotax uses a CDI
ignition that is sensitive to minimum threshhold RPM levels, and I'm
beginning to suspect that the battery is not being fully topped off.

I've had a solar trickle charger set up that thought would work, but
now I'm not so sure. I use a Powerfilm rollable R15-300 ( 0.3 A, 15.4
V ) with a Morningstar Sunguard controller. The reason I use the
rollable is that I can bungee it onto the top/side of the glider so
wind doesn't become too much of a problem since it shapes itself to
the fuselage and has a fair approximation to the angle needed for
direct sun exposure.

I bought a new battery last year, but this doesn't seem to keep it
topped off enough to get the full cranking RPM I need. Before I start
blaming losses in the charging system, I was wondering if any of the
electrical engineering types might have some words of wisdom about the
adequacy of my setup. The 0.3 A is only achieved in full sun with
direct alignment, and given the curve of the Powerfilm on the fuselage
and the periodic cloudiness of the Pac NW I'm wondering if this setup
is just underpowered. Even after several weeks of summer sun I usually
find that the battery is only about 12.4 volts or so, and not at the
12.7 volts I need. I haven't found much on the web about solar
charging batteries of this size.

Alternatively, are there other strategies for tie down charging such
as DC to DC or inverters to enable the AC charger? The battery is not
easy to replace, so swapping it out is a bit of a hassle, but
possible. If nothing else, I thought this might encourage a thoughtful
discussion on battery care and maintenance in the field. Any words of
wisdom?

On 1/16/2011 5:00 PM, Ed wrote:
and I'm
beginning to suspect that the battery is not being fully topped off.

I've had a solar trickle charger set up that thought would work, but
now I'm not so sure. I use a Powerfilm rollable R15-300 ( 0.3 A, 15.4
V ) with a Morningstar Sunguard controller. The reason I use the
rollable is that I can bungee it onto the top/side of the glider so
wind doesn't become too much of a problem since it shapes itself to
the fuselage and has a fair approximation to the angle needed for
direct sun exposure.

I bought a new battery last year, but this doesn't seem to keep it
topped off enough to get the full cranking RPM I need. Before I start
blaming losses in the charging system, I was wondering if any of the
electrical engineering types might have some words of wisdom about the
adequacy of my setup. The 0.3 A is only achieved in full sun with
direct alignment, and given the curve of the Powerfilm on the fuselage
and the periodic cloudiness of the Pac NW I'm wondering if this setup
is just underpowered. Even after several weeks of summer sun I usually
find that the battery is only about 12.4 volts or so, and not at the
12.7 volts I need. I haven't found much on the web about solar
charging batteries of this size.

Alternatively, are there other strategies for tie down charging such
as DC to DC or inverters to enable the AC charger? The battery is not
easy to replace, so swapping it out is a bit of a hassle, but
possible. If nothing else, I thought this might encourage a thoughtful
discussion on battery care and maintenance in the field. Any words of
wisdom?

Your current (a little battery pun, hehe) solution is totally
inadequate. You should have about 13.2 volts on the battery, measured
soon after you remove the charger.

You don't say how many amphours you use in a flight, and if you want to
fly several days in a row. Amusing you fly several days in a row, and
the drain is 5 amphours or less, a 20 watt panel (aligned with the
morning sun) with a good regulator would be enough. Using more amphours
- use a bigger panel.

A DC/DC converter can work well, also. I use a Multiplex LN5014 hobby
charger, run by a 12 amphour SLA battery to replace the 6 or so amphours
I use in flight. My solar panel can be plugged into the glider at the
same time, in parallel. The LN5014 plus battery charges the glider
overnight; the solar panel takes over in the morning. The LN5014 should
be disconnected in the morning and it's battery put on charge, so it's
ready to charge again that evening.

You can also use a 12 volt battery to run an inverter, then plug your AC
charger into the inverter. The inefficiencies in the setup mean you
probably need a battery twice the size you did for the LN5014 DC/DC
charger. You still need to show up at the airport to put the inverter
battery on charge.

Some people use a "hybrid" system. One example: a solar panel on the
trailer charges a deep cycle 12 volt RV battery (typically around 120
amphours); the RV battery runs an inverter; the inverter runs your usual
AC charger. This system is elegant, but it's inexpensive, it's big
battery lets it coast through cloudy spells, and since the solar panel
is charging it, you don't have to tend to it. Because the panel charges
it all day long, the panel can be horizontal and not aimed in a
particular direction. Plug the charger output into the glider whether
it's in the trailer or tied down (yes, long extension cord!) and forget it.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

Thank you, Eric, this is a good start knowing that I have to upgrade a
bit.

The complicating factor is that the glider is tied down on the flight
line in the summer, far from the trailer. Whatever I come up with has
to be a self-contained, compact and secure solution which will either
fit in the glider or is weatherproof and resistant to wind. Most 20 W
panels make excellent weathervanes, and the only securing mechanism I
have is the tie down cable and eyes. Since I live an hour from the
airport I need a "set it and forget it" solution that charges while
I'm away. I don't often fly on back to back days, and I do get some
recharge from the alternator on launch as well, so I probably need to
make up only about 6-8 Ah.

You've given me an interesting idea. I wonder if I could construct a
small aux battery box with a LN5014 DC/DC converter which I leave in
the glider to top off the battery after I leave. On return to the
airport I could remove the unit and charge it on the AC charger in the
hangar while I'm flying. If that few hours of recharge cycle time were
not enough it would be easy just to buy a second battery and swap them
out so that a fully charged one is always ready when I leave the
airport.

So this leads to two more questions....

Is the LN5014 ok to leave attached for that long (ie., is it like a
charge controller which will shut the current off when the main
battery is recharged)? If so, is it possible to do what you do with
respect to connecting my existing 300 mA solar panel and Morningstar
controller in parallel?

I can't help but feel that the obvious solution is to look at ways of
making removal and refitting the battery in the glider easier. Then take
it home and charge it. As you live so far from the flying ground it would
be a real disappointment to arrive and find that the battery is flat
because something wasn't quite right.

Best wishes

John

At 04:55 17 January 2011, Ed wrote:
Thank you, Eric, this is a good start knowing that I have to upgrade a
bit.

The complicating factor is that the glider is tied down on the flight
line in the summer, far from the trailer. Whatever I come up with has
to be a self-contained, compact and secure solution which will either
fit in the glider or is weatherproof and resistant to wind. Most 20 W
panels make excellent weathervanes, and the only securing mechanism I
have is the tie down cable and eyes. Since I live an hour from the
airport I need a "set it and forget it" solution that charges while
I'm away. I don't often fly on back to back days, and I do get some
recharge from the alternator on launch as well, so I probably need to
make up only about 6-8 Ah.

You've given me an interesting idea. I wonder if I could construct a
small aux battery box with a LN5014 DC/DC converter which I leave in
the glider to top off the battery after I leave. On return to the
airport I could remove the unit and charge it on the AC charger in the
hangar while I'm flying. If that few hours of recharge cycle time were
not enough it would be easy just to buy a second battery and swap them
out so that a fully charged one is always ready when I leave the
airport.

So this leads to two more questions....

Is the LN5014 ok to leave attached for that long (ie., is it like a
charge controller which will shut the current off when the main
battery is recharged)? If so, is it possible to do what you do with
respect to connecting my existing 300 mA solar panel and Morningstar
controller in parallel?

On Jan 16, 8:35*pm, Eric Greenwell wrote:
On 1/16/2011 5:00 PM, Ed wrote:





and I'm
beginning to suspect that the battery is not being fully topped off.

I've had a solar trickle charger set up that thought would work, but
now I'm not so sure. I use a Powerfilm rollable R15-300 ( 0.3 A, 15.4
V ) with a Morningstar Sunguard controller. The reason I use the
rollable is that I can bungee it onto the top/side of the glider so
wind doesn't become too much of a problem since it shapes itself to
the fuselage and has a fair approximation to the angle needed for
direct sun exposure.

I bought a new battery last year, but this doesn't seem to keep it
topped off enough to get the full cranking RPM I need. Before I start
blaming losses in the charging system, I was wondering if any of the
electrical engineering types might have some words of wisdom about the
adequacy of my setup. The 0.3 A is only achieved in full sun with
direct alignment, and given the curve of the Powerfilm on the fuselage
and the periodic cloudiness of the Pac NW I'm wondering if this setup
is just underpowered. Even after several weeks of summer sun I usually
find that the battery is only about 12.4 volts or so, and not at the
12.7 volts I need. I haven't found much on the web about solar
charging batteries of this size.

Alternatively, are there other strategies for tie down charging such
as DC to DC or inverters to enable the AC charger? The battery is not
easy to replace, so swapping it out is a bit of a hassle, but
possible. If nothing else, I thought this might encourage a thoughtful
discussion on battery care and maintenance in the field. Any words of
wisdom?

Your current (a little battery pun, hehe) solution is totally
inadequate. You should have about 13.2 volts on the battery, measured
soon after you remove the charger.

You don't say how many amphours you use in a flight, and if you want to
fly several days in a row. Amusing you fly several days in a row, and
the drain is 5 amphours or less, a 20 watt panel (aligned with the
morning sun) with a good regulator would be enough. Using more amphours
- use a bigger panel.

A DC/DC converter can work well, also. I use a Multiplex LN5014 hobby
charger, run by a 12 amphour SLA battery to replace the 6 or so amphours
I use in flight. My solar panel can be plugged into the glider at the
same time, in parallel. The LN5014 plus battery charges the glider
overnight; the solar panel takes over in the morning. The LN5014 should
be disconnected in the morning and it's battery put on charge, so it's
ready to charge again that evening.

You can also use a 12 volt battery to run an inverter, then plug your AC
charger into the inverter. The inefficiencies in the setup mean you
probably need a battery twice the size you did for the LN5014 DC/DC
charger. You still need to show up at the airport to put the inverter
battery on charge.

Some people use a "hybrid" system. One example: a solar panel on the
trailer charges a deep cycle 12 volt RV battery (typically around 120
amphours); the RV battery runs an inverter; the inverter runs your usual
AC charger. This system is elegant, but it's inexpensive, it's big
battery lets it coast through cloudy spells, and since the solar panel
is charging it, you don't have to tend to it. Because the panel charges
it all day long, the panel can be horizontal and not aimed in a
particular direction. Plug the charger output into the glider whether
it's in the trailer or tied down (yes, long extension cord!) and forget it.

On 1/16/2011 8:55 PM, Ed wrote:
Thank you, Eric, this is a good start knowing that I have to upgrade a
bit.

The complicating factor is that the glider is tied down on the flight
line in the summer, far from the trailer. Whatever I come up with has
to be a self-contained, compact and secure solution which will either
fit in the glider or is weatherproof and resistant to wind. Most 20 W
panels make excellent weathervanes, and the only securing mechanism I
have is the tie down cable and eyes. Since I live an hour from the
airport I need a "set it and forget it" solution that charges while
I'm away. I don't often fly on back to back days, and I do get some
recharge from the alternator on launch as well, so I probably need to
make up only about 6-8 Ah.

For the typical soaring season, laying the panel flat on the ground
works well. It does require a bigger panel, compared to one that's
optimally aimed at the sun, but it's easier to secure. If you aren't
flying consecutive days, a 20 watt panel would probably suffice, but a
30 watt is much more expensive.


You've given me an interesting idea. I wonder if I could construct a
small aux battery box with a LN5014 DC/DC converter which I leave in
the glider to top off the battery after I leave. On return to the
airport I could remove the unit and charge it on the AC charger in the
hangar while I'm flying. If that few hours of recharge cycle time were
not enough it would be easy just to buy a second battery and swap them
out so that a fully charged one is always ready when I leave the
airport.

That plan would work fine. You do need a way to automatically disconnect
the LN5014 from the battery after 10-12 hours: while it will
automatically stop charging the glider battery when it's full, the
LN5014 continues to draw about 50 ma from the battery that powers it. A
12 hour mechanical timer (like you see on bathroom fans or heating
lamps, for example) between the LN5014 and the battery powering it would
do the trick.

So this leads to two more questions....

Is the LN5014 ok to leave attached for that long (ie., is it like a
charge controller which will shut the current off when the main
battery is recharged)? If so, is it possible to do what you do with
respect to connecting my existing 300 mA solar panel and Morningstar
controller in parallel?

Yes, you could use them in parallel. You still need the timer switch to
disconnect the LN5014 from it's battery, or the battery will discharge
too far.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

On 1/17/2011 8:00 AM, Andy wrote:
On Jan 16, 8:35 pm, Eric wrote:

charger, run by a 12 amphour SLA battery to replace the 6 or so amphours


You had me quite puzzled for just a brief moment with "amphours" which
I was assuming was pronounced amfours. Something like an ancient jar
but that would have been "amphora".

Maybe Amp-hour, or Amp hour, would have been less confusing this
early on a Monday morning

What, stretch my pinky all the way to the dash key?

OK, Ah, Amp-hour, ampere-hour, from now on!

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

"Ed" wrote in message
...
Thank you, Eric, this is a good start knowing that I have to upgrade a
bit.

How about a different route. How about adding a small 20 amp alternator to
the engine to charge the battery? You charge it on the way down with a
short engine run, or on the ground, assuming you left enough in the battery
to start the engine.

It has the added advantage of being able to recharge in flight, if the need
arises.
--
Jim in NC

On Jan 17, 10:35*am, Eric Greenwell wrote:
On 1/16/2011 8:55 PM, Ed wrote:

Thank you, Eric, this is a good start knowing that I have to upgrade a
bit.

The complicating factor is that the glider is tied down on the flight
line in the summer, far from the trailer. Whatever I come up with has
to be a self-contained, compact and secure solution which will either
fit in the glider or is weatherproof and resistant to wind. Most 20 W
panels make excellent weathervanes, and the only securing mechanism I
have is the tie down cable and eyes. Since I live an hour from the
airport I need a "set it and forget it" solution that charges while
I'm away. I don't often fly on back to back days, and I do get some
recharge from the alternator on launch as well, so I probably need to
make up only about 6-8 Ah.

For the typical soaring season, laying the panel flat on the ground
works well. It does require a bigger panel, compared to one that's
optimally aimed at the sun, but it's easier to secure. If you aren't
flying consecutive days, a 20 watt panel would probably suffice, but a
30 watt is much more expensive.



You've given me an interesting idea. I wonder if I could construct a
small aux battery box with a LN5014 DC/DC converter which I leave in
the glider to top off the battery after I leave. On return to the
airport I could remove the unit and charge it on the AC charger in the
hangar while I'm flying. If that few hours of recharge cycle time were
not enough it would be easy just to buy a second battery and swap them
out so that a fully charged one is always ready when I leave the
airport.

That plan would work fine. You do need a way to automatically disconnect
the LN5014 from the battery after 10-12 hours: while it will
automatically stop charging the glider battery when it's full, the
LN5014 continues to draw about 50 ma from the battery that powers it. A
12 hour mechanical timer (like you see on bathroom fans or heating
lamps, for example) between the LN5014 and the battery powering it would
do the trick.

So this leads to two more questions....

Is the LN5014 ok to leave attached for that long (ie., is it like a
charge controller which will shut the current off when the main
battery is recharged)? *If so, is it possible to do what you do with
respect to connecting my existing 300 mA solar panel and Morningstar
controller in parallel?

Yes, you could use them in parallel. You still need the timer switch to
disconnect the LN5014 from it's battery, or the battery will discharge
too far.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

Again, thank you Eric for your thoughtful replies. I think I may have
found just what I need. I'll post the details in case someone else
might benefit.

If you go to http://www.powerstream.com/DC-input-chargers.htm and
click on the PST-BC1212-15DCDC Charger you can see this option. It
costs about twice as much as the LN5014, but I spoke with the engineer
who built it and he seems to think it will work well. We devised a
system where I can keep a source battery on the floor of the aircraft
which becomes the input of this converter. It needs to be about 1.5
times the Ah deficit that needs to be replaced (so for a 10 Ah boost
it needs to be at least 15 Ah). It doesn't run hot, so I can keep it
in the aircraft and not worry about weatherproofing. Interestingly,
this setup, run in reverse, allows me to take the source battery and
leave it in my car while I am flying, charging the source battery from
my car battery. The advantage I see to this product is that is it a
smart controller which will keep topping off the main aircraft battery
as needed and then stay in the background until the main battery needs
topping off again. If the source battery is large enough, even if I
don't get a complete recharge from my car I can always take it back to
the the hangar and bring it all the way back up with an AC charger. I
think I'm going to go in this direction since it was specifically
designed to do the very thing I am trying to accomplish. It does not
need to be attended while charging, so it looks as though it is the
'set it and forget it' solution I was looking for.

Andy, thanks for your post as well. Yes, the ultimate solution is
battery removal if all else fails, but the designer of this aircraft
made that difficult to do. It isn't just popping open a small battery
box -- it requires some disassembly of the front instrument panel and
the removeal of some tight clearance attachment hardware for the
terminals. I've done it enough times to know that it will be my
desperation solution if all else fails.

On 1/17/2011 12:09 PM, Morgans wrote:

"Ed" wrote in message
...
Thank you, Eric, this is a good start knowing that I have to upgrade a
bit.

How about a different route. How about adding a small 20 amp alternator
to the engine to charge the battery? You charge it on the way down with
a short engine run, or on the ground, assuming you left enough in the
battery to start the engine.

I don't know the Grob 103 details, but most self-launchers do have an
alternator. If not, finding a way to mount an alternator in what is
usually a very cramped location, and making it sturdy enough to keep the
two-stroke engine from vibrating it to pieces, and integrating it into
the electrical system would be a major project.

The recharge current is limited by the battery size, and the 28 Ah
battery means a limit around 5 or 6 amps. Since the current drops off as
the battery charges, replacing 6 Ah means an engine run of at least 1.5
hours. Nobody wants to put an hour and a half on their engine to top off
a battery - the noise alone is enough to seek other solutions!

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)