Electronics

Monching · Joined: 17 Oct 2007 Posts: 5

Hi, all! I have 12 solar lights with 2 LEDs in each light. They originally came in 3 sets of four lights. Each set has a solar panel charger containing 3 AA NiMh batteries (2300mAh each battery). The lights have 20 feet of wires between them.

I don't think buying the 2650mAh batteries will make a big difference. And since the lights quickly fade in only 2 hours after turning on, I was wondering if there is an ideal power supply to run some or all the lights.

Considering it is for outdoors, I wouldn't mind drilling a hole into the house to keep the power supply indoors if the Wisconsin climate (Cold winters) would damage the power supply. Thank you.

neon · Joined: 25 Feb 2006 Posts: 570

yes i converted them to transformer type .I live in the desert and day time can get to 120 degrees and inside those boxes even higher temperatures. to replace batteries means $$$$ so i got a cheap old telephone charger transformer $2.00 and plug the damn thing to ac. hint if you have one LED add another in series more brighter that way use AC or DC no difference since they are diodes add a resistor for each STRING/led so that 20+-5ma flows into the LED that is all to it . defenetly put the transformer inside the house.

Monching · Joined: 17 Oct 2007 Posts: 5

Thanks, Neon!

What current rating would be sufficient for the 12 X 2 LEDs? Is there a formula for this? I'd like to be on the safe side and wouldn't want to burn out the LEDs. I only know basic electronics from a long time ago. Thank you.

neon · Joined: 25 Feb 2006 Posts: 570

you may use any ac wall transformer that you may find or might have. here is the trick it will work on ac also provided that the applied voltage does not exceed the diodes reverse breakdown a telephone transformer charger usualy 5 to 12v is just fine. these diodes LED will show light at a level of a couple of volts or less. The current trough them are variable by limiting the current by using a resistor i usualy choose 0.020 ma per unit. So now asuming i got a 9.74v DC transformer how to choose the resistor is the question.If you bought the LED you have choosen the forward voltage drop of let say 2.12v each so now divide 9.74 by 4 2.12=8.48v that leaves 1.26 volts to be dropped by the series resistor or 1.26v/0.02=63 ohms well they don't make 63 ohm so buy a 62ohms 1/4watt that makes one lamp of 4 LED want one per lamp then 9.74v-2.12v=7.62v the resistor that you will need becomes 7.62v/.020ma=381 ohm or 380ohms 1/2watt.usualy a telephone charger is good for 500 ma so by definition you may hang on 25 series LEDS on it. or using 4 for string a total 4x25 or 100 LEDS. I leave my lights on at all times my power consumption is 200mw for 37 LEDS can't see them in the sun but who cares

Monching · Joined: 17 Oct 2007 Posts: 5

Thanks again, Neon! I wasn't able to check back on your answer right away coz my computer crashed. I'll do some computations based on your advise and see how they work out. Very Happy

neon · Joined: 25 Feb 2006 Posts: 570

ON A FINAL NOTE SAMS stores sells the whole setup for $100 the claim is for 98% savings in power from the anchient system of malibu lights. No i did not buy my lights there because the lights are a set of 12 i needed 30. so i bought them at harbor freights individualy.

Monching · Joined: 17 Oct 2007 Posts: 5

I've seen the set you're talking about at Sam's. But I have the Malibu Outdoor Metal Bollard Four-Light Solar Powered Light Kit #LZ635RP4. I have now 6 sets x 4 lights (24 lights total). Still on the hunt for the perfect DC transformer. I know I have a lot of chargers gathering dust somewhere Smile

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neon · Joined: 25 Feb 2006 Posts: 570

24 lights 2 each means 48 LED RIGHT? asume a 2.5v each then you need a transformer of 2.5v at 48x.020ma=.96 amps or 1 amp. what i try to tell you any 2.5 watt transformer can work for you. maybe what you got allready is good enough don't give me model no: just give me volts out and current out of what you already have.

Monching · Joined: 17 Oct 2007 Posts: 5

The Max voltage of solar panel is 5V (based on manual), but the 3 NiMH batteries x 1.2 = 3.6V operational. 48 LEDS x 0.020 mA = 0.96A or 1A of 3.6V to 5V: I think I do have one of these DC adaptors/chargers! I'll try it out! Thanks again, Neon! Very Happy

neon · Joined: 25 Feb 2006 Posts: 570

i tink you are missing the point
. there is nothing that you can do at this point in time to make the lites last longer not to fade except to change all those battery to new ones. the cycles time of those guys are in times and lets face it 365 days means cycles for the battery the battery are not new and will not retain performance as new. you might bench charge them for peak performance but then how long? it reverts back to this state. i told you dig up the dirt install wires like a malibu lites and use any transformer that you can buy using the previous formula. any cheap old cell phone tranformer can do that by serial parallel connections

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