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Thread: Solar light AA's

  1. #1
    Flashaholic
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    Default Solar light AA's

    I need a recommendation for some AAs that can handle a 12 hour or more low current charge to be used in solar lights. My brother has 24 solar lights that are about 3 years old. He told me that they are only running at about half the time that they used to when they were new. I told him to pull out one battery take a pic and text it to me. Its an 700mAh no name NiCd. When I went to visit him last weekend I took 4 Tenergy NiCd AAs to try as a test and they ran all night. I would prefer buying NiMh batteries but I need non LSD, low capacity 1000mAh more or less and can handle low current charging.
    Thanks
    Frank

  2. #2
    *Flashaholic* ChrisGarrett's Avatar
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    Default Re: Solar light AA's

    Quote Originally Posted by fmc1 View Post
    I need a recommendation for some AAs that can handle a 12 hour or more low current charge to be used in solar lights. My brother has 24 solar lights that are about 3 years old. He told me that they are only running at about half the time that they used to when they were new. I told him to pull out one battery take a pic and text it to me. Its an 700mAh no name NiCd. When I went to visit him last weekend I took 4 Tenergy NiCd AAs to try as a test and they ran all night. I would prefer buying NiMh batteries but I need non LSD, low capacity 1000mAh more or less and can handle low current charging.
    Thanks
    Frank
    I put 30+ in at my dad's place three years back and used different sets. If they're all of the same type, just use what they originally used. Honestly, they're cheap enough to buy new, that buying NiCADs might not even be cost effective.

    Chris
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  3. #3

    Default Re: Solar light AA's

    Quote Originally Posted by fmc1 View Post
    I would prefer buying NiMh batteries but I need non LSD, low capacity 1000mAh more or less and can handle low current charging.
    I don't see how LSD cells can be any liability for such an application, except they are usually more expensive. The low capacity is what makes a cell resiliant, not whether it is LSD or HSD. My recommendation are the lower capacity IKEA LADDA 1000mAh cells. The price is right, and they're probably relabeled Eneloop Lites. Another radical option is to use 14500 LifePO4 cells, though the full length 14500 is not easy to find in the giant local hardware chains, they usually have 18500 or cells the same diameter as AA but shorter enough (14430?) to prevent mistakes being made that they are typical AA voltages or chems. 14500 LiFePO4 cells can be found inexpensively domestically, Exell for instance. I got Exell 14500 LiFePO4 off eBay, experience positive, but for another application (lower lumen incan flashlighting). The LiFePO4 capacities are of course at least half of what low cap NiMH provide, but they are reasonably resiliant, and should give 3x the brightness, if the units can handle the higher voltage and recharge the cells.
    Last edited by night.hoodie; 08-12-2018 at 07:23 PM.

  4. #4

    Default Re: Solar light AA's

    Problem with solar lights is heat. They sit in the sun for hours daily. Nimh die early from heat, nicad not so much if you get the right ones

  5. #5
    Flashaholic* Timothybil's Avatar
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    Default Re: Solar light AA's

    I see two main interrelated problems. If I remember correctly, one can charge a NiCd cell in a NiMH charger, but not an NiMH in a NiCAD charger. Second has two parts. Unless there are three AA cells in series, any LiIon cell is going to burn out the electronics. Also, again unless there are three AA cells in series, the charging voltage will not be sufficient to do anything for a LiIon cell. And even if the voltages matched, the charging algorithm for LiIons is significantly different than that for NiCds.

    I understand the desire to make it better, but there are times it just doesn't work. Find a reasonably priced replacement NiCd cell and just swap them in. If they last another three years it is more than likely that all the solar heating during the day will have fried some other part of the system by then anyway.
    Remember, Two is One, and One is None!.

  6. #6
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    Default Re: Solar light AA's

    I've replaced AA cells in solar lights. I just used whatever older cells I had laying around. In my case, I swapped out the worn-out 600mAh cell, and replaced them with 1800mAh NiMH cells. They worked fine, and lasted a few more years.

    You don't need NiCad cell, and you don't need really low-capacity cells. Just stay away from any really high-capacity cells, because they aren't built to last very many cycles. Moderate or low capacity cells will last hundreds to thousands of cycles. One advantage of using a moderate capacity cell (something 2000mAh or less) is that it will take a long time before its capacity drops to 600mAh. You don't have to worry about the high internal-resistance that builds up over time, because solar lights are very low drain.

  7. #7

    Default Re: Solar light AA's

    Quote Originally Posted by Timothybil View Post
    I see two main interrelated problems.... Second has two parts. Unless there are three AA cells in series, any LiIon cell is going to burn out the electronics.
    Possibly, and possibly probably. But not necessarily.

    Quote Originally Posted by Timothybil View Post
    Also, again unless there are three AA cells in series, the charging voltage will not be sufficient to do anything for a LiIon cell.
    Untrue. You can charge the largest Li-ion with the smallest voltages, just takes longer. But one kind of dumb charger will stop charging at NiCad termination voltage, another kind of dumb charger will just keep charging indefinitely.

    Quote Originally Posted by Timothybil View Post
    And even if the voltages matched, the charging algorithm for LiIons is significantly different than that for NiCds.
    I'm not sure this is relevant, even if true. It may not be an ideal algorithm for LiFePO4... but so what?

    Quote Originally Posted by Timothybil View Post
    I understand the desire to make it better, but there are times it just doesn't work.
    Agreed, sometimes increasing voltage will not work, will just fry electronics. I am not up to date on the advancements in the electronics in solar charging lawn lights. But last I looked they were primitive and I can't think of any reason to advance the tech for usually surprisingly inexpensive outdoor solar lighting. If they're NiCad cells to begin with, chances are at least decent the charger is as dumb as they get, has no termination, and there may be no LED driver to burn out, just an LED that can be overdriven and itself burned out. It was just an idea others (not I) have been successful with, not any recommendation, just a possibility. So use your head, OP, and caution, and test it if the idea interests you. Please do not blow yourself up, or burn down your property, or Timothybil is going to haunt me with "I told you so!"

  8. #8
    Flashaholic* Timothybil's Avatar
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    Default Re: Solar light AA's

    Quote Originally Posted by night.hoodie View Post
    Please do not blow yourself up, or burn down your property, or Timothybil is going to haunt me with "I told you so!"
    I wouldn't do that! I just send some smirking emojis if I can find them though.
    Remember, Two is One, and One is None!.

  9. #9
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    Default Re: Solar light AA's

    Quote Originally Posted by night.hoodie View Post
    I don't see how LSD cells can be any liability for such an application, except they are usually more expensive. The low capacity is what makes a cell resiliant, not whether it is LSD or HSD. My recommendation are the lower capacity IKEA LADDA 1000mAh cells. The price is right, and they're probably relabeled Eneloop Lites. Another radical option is to use 14500 LifePO4 cells, though the full length 14500 is not easy to find in the giant local hardware chains, they usually have 18500 or cells the same diameter as AA but shorter enough (14430?) to prevent mistakes being made that they are typical AA voltages or chems. 14500 LiFePO4 cells can be found inexpensively domestically, Exell for instance. I got Exell 14500 LiFePO4 off eBay, experience positive, but for another application (lower lumen incan flashlighting). The LiFePO4 capacities are of course at least half of what low cap NiMH provide, but they are reasonably resiliant, and should give 3x the brightness, if the units can handle the higher voltage and recharge the cells.
    I concur with the LADDA's!

    I used to get the Tenergy AA NiMH 2000mAh batteries to replace the 250 and 500mah solar light cells... but now use the IKEA Ladda 1000's.. they are perfect and inexpensive!

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