iONic

I'd like to charge a 12V 35AH Lead-Acid Battery using Solar a panel.
In full sun lets assume that I have enough light to keep he charge cycle working
at it's max.

I have read somewhere, not remember now where, that there is a way to keep charging the battery even when the sun is diminished(Cloudy). Somehow the circuit collects enough voltage to give the battery intermittent pulses of charge.

Does anyone know how I would accomplish this?

audioguru

When it is cloudy then the amount of light power is so much less than sunlight that it is worthless.

My solar garden lights shine brightly for about 4 hours following a sunny day.
After a cloudy day they shine dimmly for 10 minutes.
When it is very cloudy then the LED turns on because the solar cell can't develop enough voltage even when it has hardly any load.

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Uncle $crooge

iONic

I understand what your saying, but since the battery will not be used until it is completely charged one can not waste a day or two with only 1/4 full sun waiting for the next perfect day for charging. Let us say that the solar panel is large enough to re-charge battery in one full day of sun. If what I hope is possible the two full days of "half sun" can charge the battery... we just need a
circuit that allows for some sort of pulse charging. That's the circuit I am looking for. Maybe if by charging a cap till the voltage is high enough to discharge a pulse charge will do something.

Anyone know how a "trickle charger works?" This may shed some insight on how
to harness the days of limited sun and make them work to my advantage.

Nigel Goodwin

The battery will trickle charge anyway, under low light conditions, assuming there's enough light for the output voltage to exceed that of the battery.

There's recently been a thread about solar power, which gave a link to a website for maximising power transfer, it's probably this that you're thinking of?. Essentially it used a PIC controlling a SMPS, that transfers the maximum amount of power under varying conditions.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

iONic

I know it wasn't a forum where I read about it but what your saying sounds exactly like what I was looking for...

audioguru

Have you tested your large solar panel to charge the battery in one full day of sun?
Or did you just look at the exaggerated numbers of the solar panel?

The numbers are at noon on the equator with the solar panel pointing straight up at the sun. Its output power is much less at other times of the day and at an angle. Turning the panel and changing its angle throughout the day to follow the sun increases the low average daily output power.

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Uncle $crooge

iONic

The 1 day battery complete charge on a good days was just an example. I'm sure that given my location I would need a pretty big solar panel to do a complete charge in a day. But since I have a backup battery I will not be in need of it for 3-4 days.

audioguru

There is a big advertising sign in a field beside a busy street in my city. Instead of paying the electrical utility a fortune to run electricity to the sign, the owner installed a big solar panel and a battery. Its lights lasted about 1 hour.
Then the owner installed a windmill. Now the combination of the solar panel and windmill allow the lights to shine for 2 hours following a windy sunny day.

I don't think the lights work following a calm cloudy day.

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Uncle $crooge

Nigel Goodwin

Solar/wind road signs are commonplace in the UK, but they are LED and presumably have fairly modest power requirements? - they are usually warning signs for your speed or for a sharp bend, and only come on when a vechicle approaches at a suitable speed. I've never seen one fail to work, so presumably they happily work 24 hours a day?.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

audioguru

We have roadside solar powered (battery charged) school zone reduced speed limit signs, lights at the end of docks on the lake and machines that print parking coupons. The signs for road construction are huge and also have huge solar panels.

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Uncle $crooge