Making use of that old garden light solar cell

BigDave · Post by **BigDave** » Tue 05 Oct 2010 4:49 pm

Just my tuppence on this...

I have done some testing with solar cells in the past, and one thing to be careful of is to ensure that you DO fit a diode in the circuit. Failure to do so, will allow current to flow FROM your batteries into the solar cell when the sun isn't shining. You probably won't notice this at first, because when the batteries are new, AND you have good sunny weather, the batteries recover what little charge is lost, but NiCd batteries do suffer with "memory effect" more than somewhat, so with time you'll find that you need to replace the batteries sooner than you might have thought you would need to.

If you want to see if this is happening, you could connect an ammeter between your batteries and your PV cell. During the day, you should see current flowing from the PV to the batteries, but look again at night (briefly covering the cell won't work) and you'll see a negative reading (or positive depending upon which way round you've connected your meter!).

A low power diode will do the job nicely. Shouldn't cost more than a few pence.

nking · Post by **nking** » Tue 05 Oct 2010 5:00 pm

I should give an update, which is there is no update. I decided that as the kit is still in warranty it wouldn't be wise to start moding the transmitter with solar power. I have everything ready to make the mod in January - not the sunniest time here of course

sanramonrover · Post by **sanramonrover** » Thu 23 Dec 2010 3:07 am

Well, I finally got mine all together and tested.

Here's the unit with solar cells on top of the pastille box, screwed to one of the arms.

,

and here is the pastille box opened showing the battery holder for 2 NICADs, and the wire to the transmitter unit.

.

Still measuring 2.75 volts at the batteries. As my unit is only 10 degrees off the equator, I left the solar cells horizontal.

enry · Post by **enry** » Thu 27 Jan 2011 4:45 pm

hi...
very beautyfull work.
i have one station weather wh1081pc.
Have you a material list and photo and circuit for realizing?
(screen solar, battery and component)
I hope you can help me.
Enry

Orion · Post by **Orion** » Thu 27 Jan 2011 6:36 pm

You should always fit a diode when charging battery's from a solar cell
normally an IN4001

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Making use of that old garden light solar cell

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