Large Scale Central

Solar path light help

Electronics
#1

So the dollar store and Walmart always have the little solar path lights for about a buck. I know a lot of you use them. I bought one in hopes of using it on my MIK. Since we are doing a building I get to. I took it apart and its pretty straight forward. Single LED hooked up to a 2/3 AA battery hooked to the solar cell. There is a board in there but thats neither here nor there I think. Since my recent education on LEDs I am pretty sure I have my answer but want to run it by the experts.

Here is what I would like to accomplish with it if possible. It is meant to run 1 LED. I would like to run the one that came with it as well as a couple of the picos that I have. I am assuming that I don’t need to do anything special other than wire them in parallel. Since the voltage and mAmps should work for a couple more without the need for a resistor or anything else. I assume that the added LEDs won’t cause it to not work at all since voltage doesn’t change but shorten the life of the battery before needing to be recharged because of the increase in current demand.

My proposal then is to separate all the components so that I can remotely mount the solar cell. I want to run that down to the battery keeping it external in case it needs to be changed, add a switch after the battery (so the solar cell and battery can still charge even with the switch off) so that I can turn it off when not in use and then finally run it to a set of say 3-5 LEDS (one larger one and 2-4 picos) ran in parallel. I also have the option of increasing battery size at this point as I have some full AA size tenergy batteries. I am not going to switch that out unless I find the 2/3AA doesn’t last long enough.

Any problem with this plan?

#2

de-fuser

lighting test

Devon, have been using them for about 3 years, with one LED they last for about 3hours with 2 LED’s they last about 25% longer but are not quite as bright. I have one for my city water tower blinking red LED that I have 2 solar panels and 3 AAA batteries and it lasts all night. De-soldering can be a little tricky specially the re-soldering but not impossible, I screw up about 1 of 10 and at .98c hard to beat. Getting the solar panel out can be a pain just depends how much glue the china man used. I some times use the whole fixture and just remove the solar panel as the light defuser spreads the light well, it is a little bright white and you can tone it down using a yellow magic marker. When I’m lazy I just cut a 1 3/4" hole in the top and silicon it in place, and also have glued them whole into windows just don’t usually recharge as much. solar panel in roofIt’s funny the LED is in the 3vdc range and the battery is a 1.2vdc the way it works is that on that board there is either a converter or a jewel thief which boosts the voltage to 3vdc so that the LED will work, if you have any questions feel free to ask, Bill

house solar panel

#3

Thanks Bill,

Interesting that with more LEDs you get a longer life but not as bright and I am also thinking that is actually a good thing. You pretty well answered my question. I had considered mounting the whole contraption but I can’t bring myself to do it. Especially on this build it really would work of look good. Not where I would need to mount it anyway. But I think I have a plan.

#4

In my mill grist I mounted it in the chimney worked great, get you a picture if you want

#5

That’s exactly where I am thinking of putting the solar panel for this build.

#6

LEDs will light at less then their rated voltage/current, but they will not be as bright. 2 1.2 volt cells will give you 2.4 volts (in series) and a 3 volt LED should light fairly bright with that.

#7

Bill must have put the 2 LEDs in series, not parallel.

Is the battery a nimih or a li-ion? My guess is nimih (measure the voltage to tell)

if it is nimih, then the circuit board is a “joule thief” that bumps the voltage up.

Adding more LEDs in parallel will probably not hurt much, but it might draw too much current.

Adding more LEDs in series will make them less bright, and you might not be able to have 3 in series.

Greg

#8

I will have to play with it and see what I can get away with. I also have other rechargeable batteries if I need it. But really if I can get them to look decent for three hours or so that would be ample. I mean I can’t see me being out there to long in the dark. So I am not to worried about getting a long time out of them before needing to be recharged. And with a switch they will only draw down when I want them too.

#9

I have already misplaced the battery that came with the light. But that is fine as I was really thinking of ditching it for a full size “AA” tenergry rechargeable 1.2v 2000 mA battery or two. Now this brings up a question. If I wnt to wire two of these together would it be better to run them in series and have 1.2v and 4000 mA or 2.4v and 2000 mA. If I understand this whole thing correctly 1.2v/4000mA would mean dimmer LEDs for a longer period of time whereas 2.4v/200mA would give me brighter light but for a shorter period of time. That’s with a given # of LEDs in parallel.

Also with the little solar cell is that a voltage specific deal meant to charge 1.2v or will it charge 2 batteries at 2.4v? This might be a mute point after experimenting because I am thinking I don’t need bright and likely would be better if they were a bit dimmer.

Now about my only experience with charging multiple batteries hooked together is an electric trolling motor set up for 24v operation. I know that even though they are wired in parallel to give 24v, they can be charged with two 12v chargers hooked to each battery in the usual manor. If this is the same principle can I use one solar cell and wire split the pos and neg leads sending one each to the respective batteries? That is if I choose to increase the voltage. If I choose to run them in series and increase the mAH I assume then that I run the pos lead to the pos side of my series and the neg lead to the neg side of my series.

I am thinking I’d like to have a total of 4 LEDS. 0ne larger in the building and three picos for outdoor lanterns. I did this for the black smith shop and love the look.

So the question is what is the best way to wire up the solar cell, the battery/batteries, switch, and the four LEDs.

#10

Devoin, your question is way too complicated for my retired brain, but I can tell you that the first thing I do after one season of using a solar-powered light system is to ditch the battery and install a Tenergy rechargeable. You will note on Tenergy’s website page that it says “great replacement for cheap chinese batteries in solar systems”.

#11

Pete,

i think I am going to ditch the stock battery and use the tenergy ones I have.

#12

Devon, I think you missed my point…

There is a special circuit there that is called a “joule thief” and it basically raises the voltage of a single cell to enough to run an LED (below a certain voltage they do not light)

So, you can leave the circuit as is, and try more LEDs, but I did comment on series and parallel and the expected effects.

If you try to add batteries, then you need to discard the special circuit and solar cell and just use batteries and probably a resistor, although the LEDs MIGHT light with 2 cells, but now you have given up the solar recharging.

Hope this is clear.

Greg

#13

No I got your point Greg its just too many chiefs and not enough Indians. Everyone is being very helpful and giving me a lot of good information which has served to complicate this more than it needs be.

I do not want to give up solar charging. That’s the whole point of this endeavor. So with that said sticking to the 1.7v or what ever that little battery is putting out (that I seem to have lost) and using all the circuitry that came with the light so that it will increase the voltage and make the thing work is fine by me. I guess my real question then is increasing battery size to a 1.7v 2000 mAh. It would be the same voltage as the stock one so it should charge with the solar cell. So it should be a matter of just wiring in that battery instead of the stock one. While this will not give me more voltage it will give me more the desired current for a longer period of time or run a few more LEDs at that voltage for not as long.

#14

OK, so the battery is most certainly a nickel metal hydride battery, nominal voltage 1.2 volts… when charging they will go to about 1.41 volts or so, no battery has a 1.7 volt rating.

Increasing the mAh will just make it take longer to charge, and I would guess the charging rate and the size of the solar cell means getting a much larger (amp hour) won’t do much.

But experiment, and you could just put 2 batteries in parallel and see how well they charge. My guess is the charging rate and capacity is pretty matched to the solar cell output.

Will be interested to see what you learn.

Greg

#15

Thanks Bill, Greg, and all.

I think I messed up the one I had. I broke the wires off of the solar cell and also of the little board. At any rate I am scraping all the pieces off the old one and going and buying another one and starting over. The solar cell I have was puting out voltage but now in direct sunlight I am getting nothing. I will set it aside for later.

I am going to get another one and just start small an learn and experiment as I go. If I can get it to all be remotely located like I want and work one LED with the stock components I will call it good for the MIK. Then I can play with adding other batteries and other LEDS at another time.

#16

Side track Question: How many micros equal one solar LED?

Thanks

#17

I hope you are asking the someone else. Cuz i don’t know

#18

Okay so after ruining my first solar path light I went to the dollar store and got another. Its a little different beast than the Walmart one. For one it has a bigger battery and also a larger solar cell. I was able to get it all apart without ruining it. I cut off the stock LED since I am remote mounting the working bits. I soldered on longer leads and attached a single warm white LED. That worked. So then I got brave and cut each of those leads and wired in a single pico LED in parallel. It worked without much of any diminished brightness. I got even more brave and wired in a second pico in parallel and it worked, again without much of any diminished brightness. And finally got seriously brave and cut the positive lead before the first LED and wired in a switch. Holy #^%%^$& it worked!!!

If there is any real diminished brightness I can’t tell enough to care and it will serve it purpose.

#19

Devon, thanks for the up date I’ve never added more than 2 LED’s extra to the circuit but if the battery has enough capacity it should work never mind how many but was wondering why the switch? thanks Bill

#20

let it run until the battery gives up or the lights stop working to let us know how it all works. I am going to try something like this as soon as I get some supplies, and a soldering iron