# Solar lights to DC

Discussion in 'LEDs and Optoelectronics' started by chur_bro, Dec 12, 2015.

1. ### chur_bro

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Dec 12, 2015
Hi all,

I'm after a little help:
I have 3 sets of solar lights, each set have 6 lights that connect together with plugs/sockets and have a seperate solar panel that plugs in that charges 3x 1.2V 600mAh batteries. On 2 of the sets the solar panel modules have ended up with moisture inside and the components have rusted making them useless.

I noticed that I can add two extra lights to the working chain without affecting the performance but anymore and the batteries drain rather quickly.

What I would like to do is connect all 18 lights together and run them off a low voltage transformer but I'm just not sure what I need.
Do I use a 3.6V (3x 1.2V) transformer or do I need to increase the voltage per set?
How do I calculate how many amps I need?

Cheers

2. ### Martaine2005

3,554
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May 12, 2015
Hi chur_bro,
That should be a fairly simple conversion.
Are the batteries in series? so you get 3.6v.?
I doubt they are parallel to get 1.2v and 1.8A..
I would also imagine the 600mAh is for longer run times rather than required amperage..

First you need to find out how they all connect together. If they connect in a series configuration, then you will need to calculate that in your power supply. 3x3.6v .
600mA will probably be plenty for all of them..LED dependent...

If they are parallel connected, the voltage will be the same but the amperage will be x3..

Martin

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3. ### duke37

5,364
772
Jan 9, 2011
You should not use just a transformer, that will give you AC which is not be desired.
You should use a power supply which gives DC regulated at the battery voltage., Make sure the polarity is correct.

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4. ### Martaine2005

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May 12, 2015
Good point Trevor,
I assumed when the OP said low voltage, he meant a DC brick or "wall wart" kind..

Martin

5. ### chur_bro

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Dec 12, 2015
Sorry for the late reply, things are crazy busy leading up to Christmas.

Hi Trevor, yes I did mean a power supply 240V to ?V DC type thing depending on what is required. Sometimes the term transformer (incorrectly) is used here.

Martin, So just to double check, I am just looking to see if the batteries are connected in series or parallel? Or am I also looking at how the lights are connected? I can check and get back to you (and post a picture if I can't work it out).

Thanks for your responses guys, I really appreciate it.

Cheers
T.

6. ### AnalogKid

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718
Jun 10, 2015
All information is useful. Yes, the connectivity of both the batteries and the LEDs are needed to reverse engineer a power system. part of the problem is that solar panels are inherently self-limiting - as you draw more and more current, the output voltage goes down. A small AC/DC power supply might behave that way, or you might have to add a small circuit.

But if we get a good enough idea of how your stuff is connected, whatever it takes to make the new system safe for the batteries becomes more clear. Another piece of the puzzle - battery chemistry. Are yours NiCad, NMH, or lithium?

ak

7. ### Martaine2005

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May 12, 2015
I was under the impression the batteries were being discarded?
And supplied by a AC/DC power supply only?

Martin

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8. ### davennModerator

13,865
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Sep 5, 2009
yes agreed ... that's the way I see it too
The battery talk is just about determining how they are wired so we can determine what voltage plug pack is needed

D

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