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Solar charging 2400 mAh batteries - Part 2

Discussion in 'Power Electronics' started by mkuehlok2, Nov 28, 2020.

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  1. mkuehlok2


    Dec 16, 2014
    Well, simply swapping a 2400 mAh NiMh battery for the smaller one (I think it was a 600 and it might have been a NiCd but I can't be sure because I disposed of it) that originally came with it didn't really do much for my outdoor post light. In my previous post, one of the contributors mentioned the material surrounding the solar cell would probably be cloudy, and it clearly was, so I suppose it is useless (I tried to attach a picture, but for some reason I can't). I'm probably just going to buy another light, but that won't really teach me anything, and besides where's the fun in that? So I have a number of questions:

    1. Can the solar cell be replaced with one that is higher quality? Something maybe in a glass medium that isn't going to get cloudy?
    2. In my last post somebody mentioned something about using a lithium battery. I think he said he had a 3v which I don't think would work because what is in there now is only 1.2 v and 3 would probably fry the bulb and the circuitry. But is there any option for using a lithium battery?
    3. Another problem is with the design of unit. The solar cell is mounted on top of the light housing. It is flat, parallel with the ground. It seems to me that having a solar cell that is mounted on an angle would catch more sunlight for charging. Is it possible to just mount a solar cell outside of the light housing so that it could be angled toward the sun and run a couple of wires into the light?
  2. Audioguru


    Sep 24, 2016
    Old cheap solar garden and post lights used a solar panel and LDR with plastic covers that got sunburned and cloudy so they soon became useless.
    They also used a very cheap low capacity Ni-Cad battery that rusted and failed soon.

    Modern ones use a solar panel with a glass cover and a higher capacity Ni-MH cell that lasts a long time. They are designed to have plenty of charging power at different angles and even when it is cloudy.

    Kiss your old lights goodbye and buy new replacements.
  3. Bluejets


    Oct 5, 2014
    The angle of the cell with regard to your latitude would make next to zero difference.
    They are a 2 bob light so expect 2 bob performance.
  4. dave9


    Mar 5, 2017
    If it has a plastic lens you can try polishing it with plastic polish and put a coat of wax on to slow down degradation, but probably not a lot of work is worth bothering with because this type of light can often be bought for under $3 (at least in the US).

    Yes you could swap in a better solar panel, which will probably cost as much as the whole light does, and then you may have to carve up the housing and/or use sealant to keep water out.

    Yes you could remotely locate a separate panel and run wire to it, but the complexity/durability/cost will continue to rise.

    Yes aiming the panel a bit more towards the sun (a moving target) will improve it a small amount.

    Conversion to lithium battery means basically abandoning all the electronics inside and shoehorning in a charge circuit, a protection circuit, and an LED driver circuit. If all that will even fit in the available space.

    Personally, I just run outdoor path lights from a 12V PSU that came with the set, the old school type with a wire running to all of them, then the incan bulbs were swapped out to LED bulbs. Now they can't melt ice and snow in winter, but the set has lasted nearly 20 years with a few repairs needed over time to reconnect and weatherpoof the infernal insulation displacement type connectors.
  5. Technomaniac


    Oct 31, 2020
    I had a good run with a solar garden light when the plastic coating fogged up, polished up the coating with cutting compound and gave it a coat of clear epoxy. Lasted several summers until it became redundant.
    I have a motion detecting outdoor light in the toilet. The original AA cells (NiCd) were low quality and lost capacity and failed, replaced with NiMH and still working after a couple of years. The solar panel is a separate plugin which I have mounted inside the window, so it gets morning sunlight.
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