Re: Using a Solar Panel for 12V battery
Bill
> I have one of those 12 volt solar panels. It was on a electronic
> solar fence charger for farms. The rest of the fence charger was
> dead, but the solar panel works. I want to connect it to a 12V car
> battery. Do I just connect it directly, or does there need to be a
> diode or other parts in between, so the battery dont fry the solar
> panel?
>
> Thanks
>
> please reply on newsgroup - no valid email
First thing off you need to know that a 12 V car battery is actually a
13.2 volt battery. The cells are 2.2 colts each so do the math. It takes
about 13.5 - 13.7 to keep the batteries on float charge, just enough to
keep them from self-discharging over time. I have 2 batteries in my
office room and they are at 13.5 and still good after 2 years.
Also, don't believe that old mechanics tail that concrete sucks the
charge out, total B.S. to cover their own butts for not keeping them
charged.
Bill Baka
Kendra Weissbein
<hpit...@none.com> wrote in message
news:3jci74t524d2trb8s...@4ax.com...
>I have one of those 12 volt solar panels. It was on a electronic
> solar fence charger for farms. The rest of the fence charger was
> dead, but the solar panel works. I want to connect it to a 12V car
> battery. Do I just connect it directly, or does there need to be a
> diode or other parts in between, so the battery dont fry the solar
> panel?
>
> Thanks
>
> please reply on newsgroup - no valid email
Maybe you need to actually put the solar panel in the sunlight, holmes.
Franc Zabkar
keyboard and composed:
>I have one of those 12 volt solar panels. It was on a electronic
>solar fence charger for farms. The rest of the fence charger was
>dead, but the solar panel works. I want to connect it to a 12V car
>battery. Do I just connect it directly, or does there need to be a
>diode or other parts in between, so the battery dont fry the solar
>panel?
>
>Thanks
You need a diode with a low forward voltage drop, eg a 1N5817 Schottky
rectifier. The open circuit voltage of the solar panel can be quite
high but you might get away with not using a voltage regulator if the
short circuit current in maximum sunlight is below the continuous
charging current that your fully charged battery can tolerate. Be
aware that solar panels are really only useful for keeping your car
battery topped up. A 100mA panel would take 400 hours to charge a flat
40Ah battery. That's at least a month of sunny days.
- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
Caesar Valenti
> >> The cells are 2.2 colts each so do the math.
If I assume about 3 colts = 1 horse, then the battery should supply
about 2 horsepower or about 1500 watts.
But for how long? .... lets see.....1500 watt drain (125 amp) on a 65AH
battery is about 30 minutes.
Charlie Bress
"Caesar Valenti" <cae...@email.com> wrote in message
news:487a464f$0$17191$742e...@news.sonic.net...
Seems to me your just horsing around.
(sorry, the devil made me say that)
Allodoxaphobia
> "Caesar Valenti" <cae...@email.com> wrote:
>>
>>> >> The cells are 2.2 colts each so do the math.
>> Cool....how many colts = one horse? If I assume about 3 colts = 1 horse,
>> then the battery should supply about 2 horsepower or about 1500 watts.
>> But for how long? .... lets see.....1500 watt drain (125 amp) on a 65AH
>> battery is about 30 minutes.
>
> Seems to me your just horsing around.
Just colt not resist, I see.
Yukio YANO
>
> Also, don't believe that old mechanics tail that concrete sucks the
> charge out, total B.S. to cover their own butts for not keeping them
> charged.
> Bill Baka
That's because its got to be a COLD (-20" ~30' Celcius) concrete floor
in a heated room to set up a temperature gradient in the battery where
the Specific Gravity at the bottom of the cell is higher than the top
of the cell.
The battery then tries to come to an equilibrium with the S.G.
difference between the top and bottom of the Cell, powered by the
Potential Difference caused by the different S.G. between the warmer top
and colder bottom of the Cell.
Yukio YANO
Bill
That is a believable temperature gradient effect, but much the same, and
more, happens under the hood of a car. Concrete may make a faster
self-discharge, but as I said most of it is the mechanics tossing them
in a spare parts area and forgetting to charge them once in a while.
In a car, most lots/shops remember to start the car at least about once
a month to make sure it will start when a customer wants to buy it.
Not always true with the used junker fixer uppers, and there are plenty
of dim mechanics here stateside.
Bill Baka
Even a Ni-Cad will corrode after a year or 2 in a drawer.
I haven't got any old NiMH or Lithiums that old yet.
mike
> I have one of those 12 volt solar panels. It was on a electronic
> solar fence charger for farms. The rest of the fence charger was
> dead, but the solar panel works. I want to connect it to a 12V car
> battery. Do I just connect it directly, or does there need to be a
> diode or other parts in between, so the battery dont fry the solar
> panel?
>
> Thanks
>
Depends on the ratings of your panel and battery.
A solar panel sized to charge a battery in reasonable time
can easily cook a battery.
We could make assumptions about all that, but you know
what happens when we assume...
alt.energy.renewable, alt.solar.photovoltaic, alt.energy.homepower
might have answers.
mike
Dave Plowman (News)
<hpit...@none.com> wrote:
> I have one of those 12 volt solar panels. It was on a electronic
> solar fence charger for farms. The rest of the fence charger was
> dead, but the solar panel works. I want to connect it to a 12V car
> battery. Do I just connect it directly, or does there need to be a
> diode or other parts in between, so the battery dont fry the solar
> panel?
If the panel is large enough to produce a meaningful charge into your
battery it will need some form of regulation to prevent overcharging the
battery.
--
*Lottery: A tax on people who are bad at math.
Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.
N_Cook
Germanium one , so only dropping 0.2V or so
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/