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Thread: Help needed with solar panel for emergency generator battery maintenance

  1. #1
    Join Date
    Nov 2001
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    Chesapeake, VA
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    Default Help needed with solar panel for emergency generator battery maintenance

    During the last hurricane I had a need to use my emergency generator. The battery (12V small AGM) was dead but it pull started OK. The battery was dead because the solar maintenance charger was dead and had been for some time. I want to get a new one, and am looking at some on BangGood.com,

    One is rated at 18V 5.5Watts .19Amp. for $13 ( https://www.banggood.com/DC-18V-5_5W...r_warehouse=CN )
    Will this be OK for a 12V battery? I know charge voltage should be 14.4V or so, what should it taper off to?

    Do I need a charging controller for this charger? I don't know what they do exactly.

    There is another one for $25 ( https://www.banggood.com/Waterproof-...r_warehouse=CN ) that is listed as a trickle charger, it is 12V 5.5W .3A rated and stated as waterproof, it sounds better.

    Any thoughts on these questions?

  2. #2
    Join Date
    Jan 2003
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    On the Oil Coast,USA
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    19,683

    Default

    If the panel will be outdoors at all,then you need one that is water proof.Just morning Dew condensing on the "water resistant" ones will ruin them in short order.

    No,you won't need a charge controller,but you may need to pay attention to sizing.If your generator has anything digital on board(meters,power monitors etc) it will take more wattage than if you just need to make up for normal battery losses.

    I've been using this type to keep vehicle batteries up for years-

    https://www.amazon.com/POWOXI-Portab...102081&sr=8-12

    And this one for keeping equipment up that has multiple batteries or large singles-

    https://www.amazon.com/POWOXI-Portab...9102519&sr=8-7
    I just need one more tool,just one!

  3. #3
    Join Date
    Oct 2006
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    Ivins, Ut
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    Default

    At first I thought maybe the 18V unit was for a lithium pack, but looking at the 12V link, it also puts out 18V. From the description alone I'd think they both are for 12V batteries, the second one listed seems a bit more robust.

  4. #4
    Join Date
    Nov 2008
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    SF East Bay.
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    Default

    Quote Originally Posted by Steve Steven View Post
    One is rated at 18V 5.5Watts .19Amp. for $13 ( https://www.banggood.com/DC-18V-5_5W...r_warehouse=CN )
    Will this be OK for a 12V battery? I know charge voltage should be 14.4V or so, what should it taper off to?

    Do I need a charging controller for this charger? I don't know what they do exactly.
    You should use a charge controller. An unregulated 5 watt supply will slowly boil away your electrolyte. A plain solar cell (some designs) can drain your battery if the panel is shaded or partially shaded. I use one like the first one Wierdscience listed. I've had batteries last twice their normal life. It's a real battery saver on cars that are seldom used.

    Dan
    At the end of the project, there is a profound difference between spare parts and extra parts.

  5. #5
    Join Date
    Nov 2007
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    Woodinville, WA
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    You can get away with not using a charge controller with a low powered panel. But why take the chance?

    And why solar - can't you just plug it into a real 3 stage charger? Mine's plugged it and I get 9+ years out of junk lawn tractor battery.

  6. #6
    Join Date
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    Tai Tokerau - NZ
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    Low wattage panels will be "pulled" down to the voltage of what they're connected to, and should have reverse-blocking diodes. It would be a good idea to fuse it.
    A charge controller never goes a miss.
    Generally the high crank-amp and frequent cycle batteries will be run at 14.4-14.9, standby 12.6-13.8.

  7. #7
    Join Date
    Jun 2004
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    N.J.
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    Buy a Battery-Pal, hook it up, forget about it.

  8. #8
    Join Date
    Jul 2018
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    SE Michigan
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    I used to have a boat and the best reliable trickle charger was a marine charger. I think I got it at Boaters World, but they may be out of business now. West Marine now probably has trickle charges more advanced than I had. You pay a little more, but your battery is up and not fried when you need it.

  9. #9
    Join Date
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    I have had a harbor freight 1.5 watt solar charger feeding a 12 volt, 7 ah SLA battery in my storage shed for 10 or 15 years. The battery provides light via a 3 watt LED. I sealed the seams with silicon calk after the first one flooded and shorted.


    https://www.harborfreight.com/15-wat...ger-62449.html

    The only down side is that, like all solar panels, it heats in the sunlight. Various critters have cuddled up to the panel at various times and some of them are quite unsanitary. I wash the poop off the shed's roof periodically.

    Dan
    At the end of the project, there is a profound difference between spare parts and extra parts.

  10. #10
    Join Date
    Nov 2001
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    Chesapeake, VA
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    Thanks for all the comments, I hadn't thought about a plug-in charger, I think thats the way I will go. I was stuck on the solar since that was the only way when I installed it, but since then I ran power out to the shed and can use a plug-in. Now to research a plug-in trickle charger-maintainer.

    Thanks again!!

    Steve

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