Imhotep's Lab Interactive FAQ

Hi. i am new to the forum.i have a question.
i have two solar cell,they are for garden light, nothing is mentioned on them,but each
one is for single LED.Now i have attached the solar cell in series and then to relay everything is working perfectly,both cell show 7 volts in sunny day.End of the day charged batteries come to where i started.i also tried different diodes on +ve side of
cell but no charging.Can any body tell me what is the problem. Thanks

If the solar cells are 7v, now measure the amps directly across the solar cells (like shorting the cells with the ammeter) this will give you the maximum peak rating of the solar cells. multiply the volts by the amps the multiply the answer by 0.66 and this will give you the continuous rating in watts.

I suspect the rating of your solar cells is too small. but if you put a small electrolytic capacitor in parralel with solar cells it may help a little. This is because the relay is taking short pulses of electricity allowing a little charging of the capacitor between pulses.

I don't understand what you mean about the diode on the cells. the diode should be on the output side of the coil feeding to the +ve of charging battery.

Will your solar cells power a computer fan? If so maybe a Bedini fan would be better, small computer fans draw less power than a relay.

NADEEM, if your relay has a diode parallel to the coil, it will not charge very well, or at all.
Check that too. Your relay will not pull much current if properly set up, I measured 30 mA
in most all my setups. My relays operated at 6.00 volts, so maybe if your cells cannot supply
enough current, try running the relay at 7v and the current will be doubled. Parallel hookup.

Rob

PS: All this is in addition to what Mr. Brown says above...
He's the true expert in most areas around here

PPS: 6.00 volts is where the relay STARTS to work, it is OFF at 5.99v.
What type of relay are you running?