Solar landscape lights conversion to low voltage

[efcstfo]

I have some really durable solar lights that I purchased but do not like the short duration of lighting provided. They currently use 2 1.5 volt rechargable batteries and use a single LED light bulb. I want to convert them to a low voltage system and am not sure how to calculate the voltage requirment for these bulbs, since they are not rated by wattage, for purchasing the appropriate size  12V transformer.

[ghurd]

Think 6V transformer.

What color are the LEDs?

G-

[TomW]

Think 6V transformer.

What color are the LEDs?

G-

I am thinking 5 volt USB device power supply. might be even closer match. Seems my USB hub has a 5 VDC supply
Often the batteries are just toast. I got some from Bruce and mine do well when they get enough lite (not February).

Tom

[Bruce S]

Think 6V transformer.

What color are the LEDs?

G-

I am thinking 5 volt USB device power supply. might be even closer match. Seems my USB hub has a 5 VDC supply
Often the batteries are just toast. I got some from Bruce and mine do well when they get enough lite (not February).

Tom

Tom;
 Not February here either ...

[DamonHD]

Hey, not here either?  Is it a global conspiracy?

Rgds

Damon

[TomW]

NOT in FEBRUARY  [/color]

[Bruce S]

Hey, not here either?  Is it a global conspiracy?

Rgds

Damon

 I think we need a globally mandated Blue Ribbon committee to get to the bottom of this 

[Bruce S]

NOT in FEBRUARY   [/color]

TomW:
You're having way tooooo much fun with this new board   <a href="http://" target="_blank" rel="noopener noreferrer" class="bbc_link bbc_flash_disabled new_win">http://</a>

B

[efcstfo]

The LEDs are white.

[Bruce S]

With the unit running white LEDs the voltage can tend to be higher "normally". If they have a slight blue tint to them, then the "turn-on" voltage can still be fairly low.
NiCds & NiMhs both max voltage at rest is 1.25 and your probably uses to in series to get the voltage up to 2.5 at best.
So you'll have a nice LEDs circuit that's right at 2.4vdc 600ma out of the box. The solar circuit that's charging this if anything like others is on the edge of being able to charge fully in best light and will need 4 full light hours to come close to completely recharge the batteries.

How many lights are you planning on running at the same time? I've seen setup with as many as 20 Lights setup in yards for a nice effect.

The LEDS in these really should not be run at their MAX amp (about 20ma), plus at that current rating they'll be as bright as they're going to get without lowering the life span.

Distance of Lights from power source and how many in a string will be the deciding factor of how to wire them up along with power needs.
Hope this helps;
Bruce S
 

[OperaHouse]

With 12V  I would string them in series. Generally for white would be three in series.   You can do a combination of two in parallel and then in series with the next pair for six lights.   Because of peak voltage of transformer four in series is possible.  limit the current to about 20ma with a resistor. .02A X 12V is next to nothing so any transformer would work.  A cell phone switching  charger would be great in this application.

[ghurd]

A cell phone switching  charger would be great in this application.

I like that, and the USB.

Newer cell phone switching  chargers are about 3.8V, but mine is 5V.  USB is about 5V.
Newer white LEDs tend to operate near 20ma with 3.2V.
Meaning not enough voltage for series (easier for this application).

I would suggest calculating the LED at 16ma and 3.2V when choosing the resistor.  Then actually measure the ma.
(5.0V - 3.2V = 1.8V in the resistor.
1.8V / 0.016A = 112.5 ohms, 110 or 120 ohm is a good place to start)

If going through this much surgery, I would also suggest changing the factory LEDs to something brighter (if they are 5mm and Not surface mount).  Solar yard lights tend to have lame LEDs in them.
More light for the same power.
G-

[Opera House]

I've bought a bunch of LEDs for the camp and have yet to install them, 3W star, 1W star, and bare 1W.  The stars are nice for the ease of mounting, but I am leaning towards the bare 1W that I can just mount on some metal with some epoxy.   The 3W are listed 100-130 lumens and the 1W are 60-80.  Been buying from various sellers on ebay when I can get a deal.  Even if their numbers are way off it looks like three 1w are more efficient than one 3W LED.  At least three 1W are easier to configure for 12V.

All the cell phone chargers I have found so far are 5V.  Cell phones do have a limited useful life, but not as many of the 3.2V ones have been thrown out. I literally find them everywhere, walking the dog I found one on the street. 

[DamonHD]

I pity the idiot who thinks that dumping electronics trash on the street is a reasonable thing to do.  I wonder if they yet found out about lifting their string vest before going to the toilet?

Rgds

Damon

[Bruce S]

The car charger unit to look for are the Palm Treo units. They are the same for a great many of their phones and haven't changed since the Palm 650 came out. Will take 12Vdc in and give a loaded 3.7Vdc out, newest ones (Palm Centros & Pixie) have external blade style fuses.

Not sure the wires coming out for the 3.7V side would handle much over 500ma continuous draw, but easy enough to find.

Cheers
Bruce S

[Norm]

I'm having a terriffic time with push button stick up LED lights that I get
from DollarTree for $3 I can put 3 in series to a 12-14 volt source
uses about .035 amp, a 4 amp/hr battery seems to run them about
8 hrs or so ,with as far as I can determine less than 1 volt drop in battery.
then salvage a few solar cells to charge up the battery.
 Each of the PBs has 3- 5mm LEDs in parallel , it's best to leave them as
intact as possible if you're an all thumbs solderer like me, justs soldering
the wire leads to the appropriate battery contact tabs on the battery
side, a short piece of PVC for the stake and a transluscent plastic cone for
each PB completes the solar light.
$12 + salvaged parts from solar lights.....equals 12 solar lights......
can't beat the price.....for $50 you could light up your yard like a Christmas
tree !