sizing solar panel

[Udo Rumpf]

If I want to maintain a 12 volt 7amp/h Battery with a solar cell panel
what rating would I need during flight, if after 4 hrs I wanted
to have a usable, not full, charge in my 12 Volt battery.
Right now, my as good as new battery is useless after 4 hours.
and what size would the panel be?

Udo

[Udo Rumpf]

just did a search and I think I got it covered, still if some with
experience would like to comment please do.
Udo
"Udo Rumpf" > wrote in message
. ..
> If I want to maintain a 12 volt 7amp/h Battery with a solar cell panel
> what rating would I need during flight, if after 4 hrs I wanted
> to have a usable, not full, charge in my 12 Volt battery.
> Right now, my as good as new battery is useless after 4 hours.
> and what size would the panel be?
>
> Udo

[Udo Rumpf]

> Udo Rumpf wrote:
>
>> If I want to maintain a 12 volt 7amp/h Battery with a solar cell panel
>> what rating would I need during flight, if after 4 hrs I wanted to have
>> a usable, not full, charge in my 12 Volt battery.
>> Right now, my as good as new battery is useless after 4 hours.


> This suggests you are drawing about 1.5 amps from your battery, which is
> very high, even for a glider with a transponder. Is that right? Can you
> reduce the drain safely by turning something off?
>
>> and what size would the panel be?
>
> It would have be about a 1 amp maximum output panel just to be sure of
> getting 0.5 amps on average, which would leave ~2 amphours to the battery
> after a 4 hour flight. About 1+ hours of use would remain at your 1.5 amp
> drain. That's a rather large solar panel to mount on glider, or a rather
> expensive one.
>
> If you are really drawing 1.5 amps and can't reduce it, I'd suggest first
> putting in another (or bigger) battery. Cheaper and easier, I think.

Eric,
As per manuals I draw about 1.1 amps without talking on the radio
I can fly for about 4 hours and I drop to 12 volts from fully charged
7 amp/h battery. Add an other 1.4 amps for transmit.
Regards
Udo

[Eric Greenwell]

Udo Rumpf wrote:

>
>> Udo Rumpf wrote:
>>
>>> If I want to maintain a 12 volt 7amp/h Battery with a solar cell panel
>>> what rating would I need during flight, if after 4 hrs I wanted to
>>> have a usable, not full, charge in my 12 Volt battery.
>>> Right now, my as good as new battery is useless after 4 hours.
>
>
>
>> This suggests you are drawing about 1.5 amps from your battery, which
>> is very high, even for a glider with a transponder. Is that right? Can
>> you reduce the drain safely by turning something off?
>>
>>> and what size would the panel be?
>>
>>
>> It would have be about a 1 amp maximum output panel just to be sure of
>> getting 0.5 amps on average, which would leave ~2 amphours to the
>> battery after a 4 hour flight. About 1+ hours of use would remain at
>> your 1.5 amp drain. That's a rather large solar panel to mount on
>> glider, or a rather expensive one.
>>
>> If you are really drawing 1.5 amps and can't reduce it, I'd suggest
>> first putting in another (or bigger) battery. Cheaper and easier, I
>> think.
>
>
> Eric,
> As per manuals I draw about 1.1 amps without talking on the radio
> I can fly for about 4 hours and I drop to 12 volts from fully charged
> 7 amp/h battery. Add an other 1.4 amps for transmit.

I seem to recall your radio stopped working properly at 12 volts, even
though the battery still has half it's capacity left at that point. The
easiest thing might be to go to a 14 volt system by adding a 2 volt
battery instead of a solar panel. That assumes the radio is working
correctly and it is incapable of working below 12 volts.

Before putting a lot of money into a 1 amp or so solar panel, I'd
consider getting a new radio, which will draw less current, and work
until the battery is exhausted (not to mention the other advantages).

--
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

www.motorglider.org - Download "A Guide to Self-launching Sailplane
Operation"

[[email protected]]

www.batteryweb.com/powersonic12vsla.cfm Look for a PSH-12100, ITS
12v AND 10.5 AMPS. Its the same size as a 7 amp and a 8.5 amp, just
slightly taller. # 711.

[Graeme Cant]

Udo,

When our Club's Orion arrived it apparently chewed through batteries at
a high rate. After some time, we found that the spec sheet for the
diode installed to protect against reverse polarity had a huge 1.2V drop
across it.

As a result, the charger wasn't charging to anywhere near full capacity
because the battery only saw 12.6V when the charger saw 13.8V.
Accordingly, it appeared as though the instruments were drawing much
more current than they were. It took quite a while to find the real
problem.

Does this fit your case?

In the course of troubleshooting, we also found the interesting fact
that the cheap $20 SLA chargers (usually a sealed black plastic box from
China) have target voltages which varied from 13.3V to 15.8V for the
sample we tested. 3 out of 5 were around 15V.

My DG has a factory fitted diode in the system with a 0.3V drop. The
manual specifies that a charger charging to 14.1V is needed to charge
the batteries completely. I suspect that a number of the debates on
batteries on this forum are related to diode voltage drops. My
electronic guru pointed out that ALL diodes had a forward voltage drop
and some are quite large.

Graeme Cant

Udo Rumpf wrote:

> If I want to maintain a 12 volt 7amp/h Battery with a solar cell panel
> what rating would I need during flight, if after 4 hrs I wanted to have
> a usable, not full, charge in my 12 Volt battery.
> Right now, my as good as new battery is useless after 4 hours.
> and what size would the panel be?
>
> Udo

[HL Falbaum]

"Eric Greenwell" > wrote in message
...
> Udo Rumpf wrote:
>
>
> This suggests you are drawing about 1.5 amps from your battery, which is
> very high, even for a glider with a transponder. Is that right? Can you
> reduce the drain safely by turning something off?
>
>
> If you are really drawing 1.5 amps and can't reduce it, I'd suggest first
> putting in another (or bigger) battery. Cheaper and easier, I think.
>
> --
> Eric Greenwell - Washington State, USA
>
> www.motorglider.org - Download "A Guide to Self-launching Sailplane
> Operation"


If you measure your actual current draw, and it really is 1.5 amps, consider
testing for a "partially" shorted wire somewhere!
A few strands could make a difference.


Hartley Falbaum
Georgia USA

[COLIN LAMB]

To reduce voltage drop from a charger, when a diode is inserted, the diode
should be a shottky type diode. If 3 amps maximum current is sufficient, a
1N5822 will work fine. Those diodes are available at Radio Shack. Voltage
drop is about .3 volts.

In many cases, a "protection" diode is not needed when charging a system.
They simply prevent current from going the wrong direction when the charger
is not connected.

Solar panels may or may not require them. Many circuits show a diode in
series with a solar charging panel. The theory is that it prevents current
from reversing direction during darkness. In many cases, the diode is not
necessary and the instruction books are guilty of simply copying a circuit
without understanding it. The reason diodes are often not necessary in
solar panel charging systems is that the panel itself is a diode. I always
check with a ma meter, just to make sure.

I installed a 100 ma (.1 amp) panel on a friend's motorglider (no electrical
charging system or starter) and it has charged the battery for over a year
with no problem. He is an occasional user and not a contester, nor does he
fly many hours at a time.

If you consider a 12 volt storage battery as being fully charged at about
14.2 volts and unusable for your purposes at 12 volts, you can consider the
stored power available pretty much as a straight line with 14.2 as 100% and
12 as 0 %. That means that when the voltage is 13.1 volts, you have 50%
power available. Batteries, both rechargeable and non-rechargeable may
expect the voltage to go below 12 volts to achieve the rated amp hours, so
if 12 is your minimum, you may need to de-rate your battery. The
manufacturer should have a graph showing the actual capacity
available with the maximum and minimum voltage you have in your electrical
system.

Colin

[COLIN LAMB]

>In many cases, a "protection" diode is not needed when charging a system.
>They simply prevent current from going the wrong direction when the charger
>is not connected.

Not connected to the AC power that is. When the charger is not connected to
the battery, current would not flow because there is no completed circuit.
Still early.

Colin

[01-- Zero One]

"Udo Rumpf" > wrote in message
:

> If I want to maintain a 12 volt 7amp/h Battery with a solar cell panel
> what rating would I need during flight, if after 4 hrs I wanted
> to have a usable, not full, charge in my 12 Volt battery.
> Right now, my as good as new battery is useless after 4 hours.
> and what size would the panel be?
>
> Udo



Udo,



Most battery manufacturers consider their battery to be depleted at
around 10-10.5 volts. I usually switch to my secondary battery when the
primary depletes to around 11.2 - 11.5V. I also agree with other
posters here that unless you have a transponder or something you should
not be drawing anywhere near 1.1 amps typically. In situ measurements
may be called for.



Larry

[Birdbones]

Eric Greenwell wrote:
> It would have be about a 1 amp maximum output panel just to be sure of
> getting 0.5 amps on average, which would leave ~2 amphours to the
> battery after a 4 hour flight. About 1+ hours of use would remain at
> your 1.5 amp drain. That's a rather large solar panel to mount on
> glider, or a rather expensive one.


Using PowerFilm PT15-75 thin film flexible modules rated at 50ma, 15.4
volts, it would take 20 units to get 1 ampere. Cost $800 ($40@). These
would use 5 square feet plus of surface area. They are 10.6" x 3.9".
There were several of these or similar units on gliders at the SSA
convention. The edges were taped to mount them and at that size they
seemed to form well to the compound curve of the fuselage. Only two or
three on a glider which indicates to me that they were mostly for the
wow factor..
Randy

[Udo Rumpf]

I have been flying with the set up for three seasons.
Since my power supply is adequate for all my instruments but for the radio
which is an old 1980 ATR 720 and it appears to work well if adequate power
is provided. I will go with Tom's suggestion of packing a larger battery.

The routine at a contest would be as follows.
We get our tasked. It will be entered. The radio and the L Nav is switched
off, the GPS and PDA will be on from this time on.
If you are in the middle of the pack it could take 25 minutes till launch.
Radio and L Nav is turned on at launch. Waiting for an other 25 minutes to
get started, maybe more plus a three hour task. Total over 4 hours.

Base on what I can figure the idle radio uses .4 amp, the L Nav, the PDA and
the GPS uses .35 amp combined, as per CAI. Borgelt uses ~.15 amp

I would say a normally charged 7 amp battery with the surface charge taken
off and reading about 12.7 volts to start with, it would not surprise me if
I would see 12 volt or slightly less on the meter after 4 hours.

As it is now all works well but at the end of the flight I should not forget
to
switch batteries and I been known to forget it. If the ground guys have a
good radio my radio will be ok for the normal operation even if I do not
switch batteries certainly air to air was never a problem unless I had the
radio turned off.
Udo

> Eric Greenwell wrote:
>> It would have be about a 1 amp maximum output panel just to be sure of
>> getting 0.5 amps on average, which would leave ~2 amphours to the
>> battery after a 4 hour flight. About 1+ hours of use would remain at
>> your 1.5 amp drain. That's a rather large solar panel to mount on
>> glider, or a rather expensive one.
>
>
> Using PowerFilm PT15-75 thin film flexible modules rated at 50ma, 15.4
> volts, it would take 20 units to get 1 ampere. Cost $800 ($40@). These
> would use 5 square feet plus of surface area. They are 10.6" x 3.9".
> There were several of these or similar units on gliders at the SSA
> convention. The edges were taped to mount them and at that size they
> seemed to form well to the compound curve of the fuselage. Only two or
> three on a glider which indicates to me that they were mostly for the
> wow factor..
> Randy
>

[Eric Greenwell]

Birdbones wrote:

> Using PowerFilm PT15-75 thin film flexible modules rated at 50ma, 15.4
> volts, it would take 20 units to get 1 ampere. Cost $800 ($40@). These
> would use 5 square feet plus of surface area. They are 10.6" x 3.9".
> There were several of these or similar units on gliders at the SSA
> convention.

The "or similar" units were Strobl units, and are not similar at all.
It's a different type of cell (crystalline) that provides several times
the current for a given area compared to the Powerfilm (amorphous)
units. They are also several times more expensive, about 4 times
thicker, and are the panel supplied by the German glider manufacturers.

> The edges were taped to mount them and at that size they
> seemed to form well to the compound curve of the fuselage.

I think they are glued on, and the taping is part of the fairing and
sealing, not mounting. On the ASH 26 E (and probably the other
Schleicher motorgliders), they are flush mounted on the engine bay
doors, an elegant way to do it.

> Only two or
> three on a glider which indicates to me that they were mostly for the
> wow factor..

Not true for the Strobl units, which were capable of 1+ amps on the
gliders I saw at the convention.

I've looked at the Powerfilm units for my glider as they are less than
half the price per amp and easier to mount, but they require so much
area for the amps I require, I decided against them. I think they would
be a good choice for someone looking for 200-300 milliamps.

--
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

www.motorglider.org - Download "A Guide to Self-launching Sailplane
Operation"

[Eric Greenwell]

Birdbones wrote:

> Using PowerFilm PT15-75 thin film flexible modules rated at 50ma, 15.4
> volts, it would take 20 units to get 1 ampere. Cost $800 ($40@)

This site

http://store.sundancesolar.com/powulflexthi.html?page=viewall

offers them for $26, which would make them much more attractive.


--
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

www.motorglider.org - Download "A Guide to Self-launching Sailplane
Operation"

[Birdbones]

Eric,
I downloaded your manual, excellent. Currently I only fantasize about a
self launcher.
I then went to the Strobl-solar.de website but my Deutsch ist nicht so
gut. Google was unable to translate it or find a site in english. Do
you know of a U.S. source on the web for these Strobl panels?
Randy

[Udo Rumpf]

Strobl- Solar
Beschreibung:
Artikel Nr.800328
SFL 7,5 monokristallines, flexibles Solarmodul
Leistung: 7,5 Watt, 400m Amp.
Abmessung:L x B x H 660 x 108 x 1,3mm
Gewicht: 145 gr

Einzelpreis: 378,95 EUR

that one is a narrow strip for one doors only, like the DG 800
one strip = 375.95 Eur
The other unit is similar but different dimension.
If you want to know more about the product I can help translating
Udo

[COLIN LAMB]

Although I have never measured it, I recall the average current drain for my
Becker transonder is only a couple hundred ma. The reason is that only
pulses are sent out and the average power consumed is pretty low.

Colin

[Mottley]

Hi
I can only confirm that the Strobl units are far superior to many other
units as I am using them on my DUO. 1to1,5 hrs in the sun in the
morning usually recharges the 7amp Batterie completly (which you use to
start flying with) you switch to charge the other batterie during
flight and you can keep on switching them like this and you usually end
up a long day with 1 Batterie fully charged and the second one down to
about 12.5V. This is especially handy if you are using the transponder
as well. Sofar never switched more than
once during a flight. A Strobl Solarpanel on the Trailer to charge a
portable Buffer Batterie is the Cherry on the Cake. We fly with
Solarpower so lets charge our Batteries with Solarpower.

[Marc Ramsey]

COLIN LAMB wrote:
> Although I have never measured it, I recall the average current drain for my
> Becker transonder is only a couple hundred ma. The reason is that only
> pulses are sent out and the average power consumed is pretty low.

Not everyone has (or can afford) a Becker transponder. A Terra will
happily consume several times that amount. And, try measuring the drain
from the encoder at altitude, particularly if it's one with a heater...

Marc