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Thread: how to take care of sealed lead acid rechargeable flashlights?

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    Default how to take care of sealed lead acid rechargeable flashlights?

    Hey guys, I was wondering how do you take care of the sealed lead acid rechargeable flashlights? I have bought 2 and they both broke .. the million candlepower kind. Well I now bought another one but this is a work light and is a fluorescent rechargeable light with a sealed lead acid battery in it. I would like for this one to last and wanted some advice. All I think it has is a charge indicator and I bet there is nothing really inside that controls how the battery is charged other than a simple resistor or something inside it as I found in one of the other million candlepower flashlights I broke open. Any ideas or simple charging circuits that I can build for lead acid batteries?

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    Flashaholic* MrAl's Avatar
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    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    Hi there,

    A simple way to charge is with a wall wart of a higher voltage in series
    with a power resistor to limit current. You then monitor the battery
    voltage with a meter and stop charging when the voltage gets up to
    the right point for your battery.
    You'll have to check the specs as to what the max charge current is
    and float voltage.
    Take care,
    Al
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    Administrator Norm's Avatar
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    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    If your looking for a charger there are some very good plug pack fully automatic SLA chargers for not much money. The one I have was only about $20 Australian.
    Google search http://www.google.com.au/search?hl=e...e+Search&meta=
    Norm

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    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    One key thing about any lead-acid battery is that they always like to have a full charge. Even a 90% charge will cause some accelerated aging. After use recharge as soon as possible, and charge it every month or sooner when not in use. Never run it all the way down if you don't have to, NiMH batteries like this - Lead-acids hate it.

  6. #6

    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    How do lead acid batteries deal with overcharging? There is no way to tell if the battery is fully charged or not as the LED only tells you if it is plugged in or not. I can't really open the flashlight all the time and check the voltage. I do know however is that the wall charger outputs 6V 300ma. But when I checked the voltage with a voltmeter it was about 11.9V and I just connected a little computer fan rated at 12V in to see what the voltage is under load and it was about 7.9V under load. I don't know if this makes a difference or not.

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    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    Quote Originally Posted by OhMyGosh View Post
    One key thing about any lead-acid battery is that they always like to have a full charge. Even a 90% charge will cause some accelerated aging. After use recharge as soon as possible, and charge it every month or sooner when not in use. Never run it all the way down if you don't have to, NiMH batteries like this - Lead-acids hate it.

    It's not good to run NIMH down past 1.1V.

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    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    Quote Originally Posted by johnny13oi View Post
    How do lead acid batteries deal with overcharging? There is no way to tell if the battery is fully charged or not as the LED only tells you if it is plugged in or not. I can't really open the flashlight all the time and check the voltage. I do know however is that the wall charger outputs 6V 300ma. But when I checked the voltage with a voltmeter it was about 11.9V and I just connected a little computer fan rated at 12V in to see what the voltage is under load and it was about 7.9V under load. I don't know if this makes a difference or not.

    I have a $9 1MCP Spotlight. I don't know how much your flourescent one cost, but I generally just plug in the charger for a few hours every month or so if I don't use it. Other than that I don't really worry about it. I haven't used it a whole lot though. It usually sits on my desk with a 4D Maglite sitting on top of it that never gets used either.

  9. #9

    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    Quote Originally Posted by ampdude View Post
    I have a $9 1MCP Spotlight. I don't know how much your flourescent one cost, but I generally just plug in the charger for a few hours every month or so if I don't use it. Other than that I don't really worry about it. I haven't used it a whole lot though. It usually sits on my desk with a 4D Maglite sitting on top of it that never gets used either.
    Well it was 20 bucks and I could probably buy another one but I feel like it would be a waste if it just broke. I really wanna make this thing last as long as it can as my other two spotlights have broken only after about 10 uses at most and it felt like a waste even though it wasn't worth much.

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    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    Quote Originally Posted by johnny13oi View Post
    Well it was 20 bucks and I could probably buy another one but I feel like it would be a waste if it just broke. I really wanna make this thing last as long as it can as my other two spotlights have broken only after about 10 uses at most and it felt like a waste even though it wasn't worth much.

    I really wonder if lead acid batteries are that sensitive to overcharging. I know on most spotlights they say only to charge it for so long and no longer, but when you think about it the lead acid battery in your car is getting overcharged all the time while you are driving around.

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    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    Hello Ampdude,

    Car charging systems have this wonderful thing called a regulator. It insures that the battery is kept fully charged and protects against overcharging.

    Lead acid batteries are sensitive to overcharging.

    Tom
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    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    Quote Originally Posted by SilverFox View Post
    Hello Ampdude,

    Car charging systems have this wonderful thing called a regulator. It insures that the battery is kept fully charged and protects against overcharging.

    Lead acid batteries are sensitive to overcharging.

    Tom

    I was wondering about that! Thank you.

  13. #13
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    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    Lead-acid is generally more tolerant of overcharge than any other type. Often they are used with float-charge at about 2.2-2.3 volts per cell (6.75 to 6.9v for 6v). They can last a couple of years floating, so a few days is unlikely to hurt it. Just be sure to limit the voltage. (A simple resistor is not enough - you need a resistor + 3-terminal regulator). That is assuming room temperature. A sophisticated charger needs to adjust the voltage for temperature. Lots of info available on the net if you look around.

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    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    Quote Originally Posted by OhMyGosh View Post
    One key thing about any lead-acid battery is that they always like to have a full charge. Even a 90% charge will cause some accelerated aging.
    On the flip side, I've heard numerous times that it's not good to fully charge an SLA. Care to comment?
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    Default Re: how to take care of sealed lead acid rechargeable flashlights?

    If you really want the nitty gritty details check out Battery University. It seems there are different kinds of lead-acid and you should read the manufactures spec sheet. That being said, They say you can float it at 2.25v per cell indefinately.

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