Solar charging question

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)

"Eric Greenwell" wrote

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!

I see your points, but still am not sure that some increased charging system
could not provide a good answer.

Most engines like that have a flywheel magnet and stator system, and are
pretty anemic in the amount of current they put out. One of the small
alternators from something like a small tractor could be mounted, and a
larger battery installed, probably a wet cell, or other type that could
handle more charging current. If not able to fill the larger battery in a
20 minute run to altitude, it would be darn close, and the larger capacity
would have more than enough to run your electronics all day, even at only
1/2 or 2/3rds capacity. I agree about not running an engine a long time,
just to charge, but if you ran the battery down one day on a marathon
flight, a little run would keep your electrons zinging around the
microcircuits!
--
Jim in NC

On Jan 18, 3:17*pm, "Morgans" wrote:
Most engines like that have a flywheel magnet and stator system, and are
pretty anemic in the amount of current they put out. *One of the small
alternators from something like a small tractor

After suffering for years with motorcycles that could barely light a
decent headlight, it was fantastic to get my current bike, a 1995 BMW
R1100.

It has an 800W alternator. That's a lot of amps at 12V!

I don't know how many of those amps it can put into the battery. It
has power outlets for both rider and passenger intended to plug
electrically heated clothing in to for winter riding. (not necessary
in NZ, so I've never investigated properly)

On Jan 17, 6:17*pm, "Morgans" wrote:
"Eric Greenwell" wrote



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!

I see your points, but still am not sure that some increased charging system
could not provide a good answer.

Most engines like that have a flywheel magnet and stator system, and are
pretty anemic in the amount of current they put out. *One of the small
alternators from something like a small tractor could be mounted, and a
larger battery installed, probably a wet cell, or other type that could
handle more charging current. *If not able to fill the larger battery in a
20 minute run to altitude, it would be darn close, and the larger capacity
would have more than enough to run your electronics all day, even at only
1/2 or 2/3rds capacity. *I agree about not running an engine a long time,
just to charge, but if you ran the battery down one day on a marathon
flight, a little run would keep your electrons zinging around the
microcircuits!
--
Jim in NC

Last time I checked we were talking about an aircraft and associated
weight and balance, saftey and regulatory concerns. Adding a larger
generator and a flooded battery is not something more practical people
would even consider to solve a problem that can practically be solved
with a larger solar panel or a DC-DC charger.

Darryl

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 1/17/2011 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)

Old but good thread.

Found these Imac B6 and Imac B6AC of ebay. This may be a good alternative to consider given that the Multiplex charger mentioned about is now apparently discontinued (I believe). The B6 model only runs off 12V, the B6 AC runs on either 115vac or 12v. It looks like Imax came out with the new plastic enclosure so the previous models are going for $35...

http://www.ebay.com/itm/iMAX-B6-AC-B...ht_2631wt_1206

In addition to charging multiple type of batteries (including Pb), the charge can be used to run a discharge test.