Convert solar lights to electrical with transformer?

wynswrld98February 18, 2010

I have some very cool solar lights that are VERY unique that don't do very well as solar lights due to too many trees providing shade.

I wanted to find out if it's practical to convert these to electric with a transformer so I can run them as low voltage.

I've looked everywhere for 12v lights anything like these and came up empty so I would like to convert them from solar to electricity if possible.

I have about 15 of them spanning 150' with the power source at the center of that 150' run.

Each solar light has its own solar panel on top of the light and contains 2 AA batteries so is 3 volts.

I know very little about electrical regarding if they could be wired in series (which would be the most practical), would they be run with a 3 volt transformer? or due to 15 of them being connected it's really 45 volts? I'm a total newbie to electrical believe me! Also am curious what gauge wire I'd need to use.

My preference would be to connect the wiring to the output of the "case" that the AA batteries are in to bypass the solar panel and batteries altogether.

Any tips greatly appreciated.

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It would be really helpful to know the specifics of the bulbs that are in these lights...for instance are they incandescent or LED? The batteries indicate that there's some form of power storage...are they rechargeables? Do you have a make and model number for the lights?

In general, if they're 3V incandescent bulbs, you could probably wire them in series with a 45V transformer, or in parallel with a 3V transformer. Please be aware that like Xmas tree lights, if you wire these in series, and one of the bulbs fail, all of the lights will go out. But more information is necessary before a new power source can be properly configured.

    Bookmark   February 19, 2010 at 9:46AM
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bulb is incadescent. Yes, the AA batteries are rechargeable, the solar panels recharge them.

What I'm confused about is for malibu lights, you run them on a 12v transformer and seemingly how many are run in series doesn't seem to matter (within reason) so why for my situation is the proper voltage to run completely dependent on the number of lights run in series vs. with the malibu lights it is not?

    Bookmark   February 19, 2010 at 1:50PM
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Most likes aren't run in series. It may look that way because the lights are lined up in a row, but if you look at the wiring, it is in parallel.

    Bookmark   February 19, 2010 at 2:16PM
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and all of those Malibu lights use 12v bulbs.

    Bookmark   February 19, 2010 at 2:27PM
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Just to add to Bill's note, in series, the voltage drops across each bulb must be added together to figure the total amount of voltage needed. When wired in parallel, the voltage that is delivered to each bulb is the same.

What is the voltage rating of the bulb, and how many watts is each bulb? If they're incandescent, it should be fairly straight-forward to re-wire each fixture to accept an external power source. The voltage and wattage of each bulb will determine what size transformer and wire is needed.

    Bookmark   February 19, 2010 at 2:38PM
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I have no idea what wattage the incadescent bulb is, the box doesn't mention it and the lights are discontinued.

I need to read more about wiring in series vs. parallel because I'm totally confused now since I thought 12v Malibu lights were wired in series, not parallel...

    Bookmark   February 19, 2010 at 2:45PM
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Most of the time the voltage and wattage are marked (or stamped) on the base of the bulb. At my age, a magnifying glass is often helpful. Of course, if you have a meter, you should be able to measure the voltage and the resistance of the bulb, which could be converted into the wattage.

Malibu lights are all wired in parallel, and as mentioned are typically 12V. BTW, it might be expensive to purchase a 3V exterior-grade transformer. Most outdoor/pool lights are 12V, so their transformers are more common and thus less expensive.

    Bookmark   February 19, 2010 at 3:11PM
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It simply is not practicle to wire unwired solar lights to be run by a 12V transformer. Period!

    Bookmark   February 19, 2010 at 9:49PM
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I'm not suggesting running these solar lights with a 12v transformer. Good point about exterior-grade vs. interior-grade transformers. I've seen inexpensive transformers online that let you select the voltage including 3 volt but they're really interior transformers.

    Bookmark   February 20, 2010 at 2:04AM
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Trying to wire a sting of lights with a 3V transformer means the wires will be HUGH... not very practical IMHO.

    Bookmark   February 20, 2010 at 8:25AM
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Solar lights use very low power lamps, so it may not be all that impractical to power them with a transformer. For a lamp to run 8 hours on a 1600mah battery (about the size of the battery I've seen in these solar units), the lamps can't draw more than 200ma (about half a watt in this application).

Your 15 lamps would thus draw about 7.5 watts. I don't know of any lighting transformer that would even break a sweat at that power level.

Note that two NiMH or NiCd cells in series will provide about 2.5 volts nominal, not 3 volts. Five lights in series should thus work just fine powered by a 12v transformer, IF it really produces 12 volts.

You'd make up three strings of 5 lights in series, then parallel the 3 strings across the transformer output. Try to keep the runs to the strings about the same length, though at 200ma only the smallest, longest wire will have much voltage drop to speak of.

One warning - you're probably getting into a fair bit of work here. You'd have to REALLY want to do this.

    Bookmark   February 21, 2010 at 9:59PM
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It sounds like a plan. What gauge wire should I use? Thanks!!

    Bookmark   February 21, 2010 at 10:52PM
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