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  1. #1
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    Solar Powered Lights: NiCAD vs. NiMH Batteries

    I need to replace the batteries in one of my solar lights. The manual says to use NiCAD. I can't find any. NiMH are common. Will they work, or is the charging circuity specific to NiCad?

    I've searched all over for the answer to this question. Lots of sites on the advantages of one type over the other, but nothing specific on whether or not charging circuity designed for NiCAD will work OK with NiMH. Apparently, NiMH chargers work fine with NiCAD batteries....

    TIA

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    I would think that the nicad charger will charge both types of batterys, I think the NiCad comes up to voltage before others as I know that it holds a higher voltage until it is about dead before it drops voltage to unusable levels.
    Do you know the voltage of the charging circuits, Anything less than 16 should be alright for a 12V battery.

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    Thanks BG. The lights use two AA's in series, so just under 3 volts.

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    I bet those batterys would work as the charger we have for NI-MH batterys we use in our digital cam is a 2.8 V and those batterys last a long time and are fully rechargable.
    But are spendy..

  5. #5
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    if it's the same factors (AA) then you can use either (as they long as they are all the same, 2xNiCAD or 2xNiMH), but make sure they have enough "power drain", some are 800nmh, others 1600nmh, I would recommend taking a high version, maybe 1000nmh would be enough

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    Which are better, NiCd batteries or NiMH batteries?
    For most electronic devices it is better to use NiMH batteries than NiCd batteries. NiCd batteries use Cadmium, a highly toxic heavy metal, that can damage the environment if not disposed of properly. (They should be recycled not discarded). NiMH batteries usually have a higher capacity than NiCd batteries of the same size. Some people argue that NiCd batteries deliver faster discharge rates than NiMH batteries. While this may be true under certain circumstances, the difference is not relevant when considering power sources for electronic devices like digital cameras or portable music players. (If you are choosing a battery to drive a high torque power screwdriver, then NiCds can outperform NiMH). NiMH batteries require more sophisticated chargers than those typically used for NiCd batteries. But smart chargers designed especially for NiMH batteries are now readily available

  7. #7
    Member More Volts Igor's Avatar
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    There is no doubt that the charge circuit of your solar lights will charge NiMH batteries, indeed the minimal amount of power available from the small solar cells probably means that the charge circuit consists simply of a diode to prevent the batteries discharging through the solar cells when the sun goes in.

    As to your replacements, examine the existing cells, they will have a capacity marked on them in mAh (milliamp hours), the replacements should be of the same or greater capacity.The higher the capacity the longer the illumination time may be. However this is subject to the solar light fixture being able to charge a higher capacity battery and also subject to there being enough solar energy. Therefore a higher capacity battery is not always the best choice if it will only ever partly charge.

    EDIT If you do decide to use larger cells (like twice as large), charge them fully with a mains charger before installing them to give your solar array a chance to keep them full.
    Last edited by More Volts Igor; 05-04-2008 at 09:24 PM.

  8. #8
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    Yes, you can use NiMH.


    Save the NiCads; many/most can be 'resurrected'. If you are a hobbyist, I can send you link to a circuit that does so.

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    I think the NiCADs are finished. They got wet and corroded. I've cleaned them up and they work, but the charge lasts less than half the time of the ones that didn't get wet. (The drain hole in the solar light assembly got plugged....)

    I went looking for NiMH batteries at Lotus yesterday. The largest capacity they have is 1000 mAh. The ones I have for my camera are 2600. Need to keep looking.

    Thanks for all the info and suggestions.

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    ^ An easy experiment to conduct: Put the old NiCads in a plastic jug or metal can, with some pebbles. Rattle the container at a medium tempo so that the batteries are getting bounced and banged, but not dented.

    You might find that some or all the cells will hold a charge longer now. Depending on the corrosion damage, a cell whose electrolyte is leaking or is no longer air-tight, won't work.

    [NiCads grow fine 'whiskers' between the poles, and the whiskers, once broken, will resurrect the battery. The circuit I mentioned will burn off the whiskers with a short duration over-voltage. Actually, any electrolyte-based battery can be resurrected for a short time by banging it around.]

  11. #11
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    the best way to restore batteries, is to put them in the fridge for a few days, or even the freezer,

    I was able to restore capacity for an old NiCAD laptop battery with this,

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    Member More Volts Igor's Avatar
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    I've done a bit of poking around on the web, and found the following issues.

    High capacity NiMH batteries have a very high self-discharge rate possibly sufficient that the solar array won't be able to charge big cells.

    I still think that NiMH of similar capacity to the original NiCd calls will be fine but I would not attempt to use cells more than say twice the original capacity.

    NiCd batteries are still available, Amorn for example will likely have them.

    A couple of sites that advise against NiMH in solar lights:-
    Use NiMH batteries instead of NiCd in outdoor solar lights? - Yahoo! Answers
    Batteries for solar lights on Squidoo

    and a site that says they are ok:-
    Solar Light Batteries

    So it's now UP2U Do let us know how you get on, real experience is useful.

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    Quote Originally Posted by More Volts Igor
    Do let us know how you get on, real experience is useful.
    Last night the light with the corroded batteries stayed on as long as the rest. So, I'm not going to do anything for the moment. However, I'm sure the batteries will need replacing sooner or later. I'll post some photos at that time.

    Thanks again for all the suggestions.

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    adding to this thread with a slight change (now that it is sorted)

    any recommendations as to the best solar lights to buy, and where from please?

    Chiang Mai area preferred

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    The Pikey Hunter
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    Quote Originally Posted by buad hai
    Last night the light with the corroded batteries stayed on as long as the rest. So, I'm not going to do anything for the moment. However, I'm sure the batteries will need replacing sooner or later. I'll post some photos at that time.
    Do you really stay up at night watching your solar lights to see which one dies first?

  16. #16
    The Pikey Hunter
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    Quote Originally Posted by DrAndy View Post
    adding to this thread with a slight change (now that it is sorted)

    any recommendations as to the best solar lights to buy, and where from please?

    Chiang Mai area preferred

    I bought some from Tesco's a while back. Some idiot had put the wrong price label on them - 160 baht for a pack of 4! I bought 8 packs.

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    Quote Originally Posted by Gerbil
    Do you really stay up at night watching your solar lights to see which one dies first?
    What I should say is that when I went to bed at 9 PM all three were still 'on'. Since that's all the solar light I need, I didn't bother to see which one died first.

  18. #18
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    Quote Originally Posted by Gerbil
    Originally Posted by DrAndy adding to this thread with a slight change (now that it is sorted) any recommendations as to the best solar lights to buy, and where from please? Chiang Mai area preferred
    Quote Originally Posted by Gerbil
    I bought some from Tesco's a while back. Some idiot had put the wrong price label on them - 160 baht for a pack of 4! I bought 8 packs.
    You bought 8 paks of Solar Lights?? and they come 4 to a pak?? thats a lot of lights..

  19. #19
    The Pikey Hunter
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    ^ Yep.

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    are they any good though?

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    Well they don't produce much actual 'light', they more act as lanterns - good for marking out garden paths, etc.

  22. #22
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    that's no good then

    I want some reasonably bright lights. I did see some with LED bulbs, which looked very good, at some restaurant but forgot to ask about them

  23. #23
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    The ones I have use three LED's behind lenses that focus the light into a reasonable spot:



    These made-in-China solar lights were purchased at Price-Costco in the States by my Dad and sent over here as a Christmas gift. US importer is the Brinkmann Corp.

  24. #24
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    Brinkmans makes a kick ass smoker, their Professional model is the cats meow..
    Sumbitch stold my plans and now getting rich, rotten bastards

  25. #25
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    Quote Originally Posted by buad hai View Post
    The ones I have use three LED's behind lenses that focus the light into a reasonable spot:



    These made-in-China solar lights were purchased at Price-Costco in the States by my Dad and sent over here as a Christmas gift. US importer is the Brinkmann Corp.

    yep, they look the type I want; not for sale in Thailand?

    as Christmas does not exist, maybe I will try to find some in UK

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