Battery question

RedNeckSolarMan
RedNeckSolarMan Solar Expert Posts: 34 ✭
in Solar Beginners Corner #1
Hello everyone, I have question on batteries. Reason for question is, actually a debate with my cousin (car mechanic). He seen my small solar system and I told him my little problem with battery being too big for system. He recommend since I am running only DC rope lights is use a motorcycle battery. They are low amp batteries that are used for motorcycles. Plus since he stated that my charge controller looks like a small slow charger, and the motorcycle battery will handle it. But he said if I put in another solar panel (currently running 80 watts total), I may have to put back my small marine battery in.

I trust my cousin with my car but with solar system, I don't know about it. So I thought I get you guys opinion about it. Thanks


FYI, also thanks to everyone who as responded to my threads in past. You guys are a big help, thanks.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #2
    Re: Battery question

    Some of us have poor memories (don't remember the details of your previous posts) and are lazy (don't feel like doing a search). It would help if you remind us what you have when you start a new post, better yet is to make a sig line. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34 ✭
    #3
    Re: Battery question

    The battery talk was from a problem I had.
    http://forum.solar-electric.com/showthread.php?16226-Need-Help-on-Solar-System



    But I have posted threads in past but most of time, I just come to this website and read and get ideas or/and learn.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #4
    Re: Battery question

    In that other thread you were advised that 80 watt panel would charge a 50 AH battery. So whats the AH capacity of the motorcycle battery that you are thinking of? Also, the motorcycle battery is not a deep cycle battery and will have a short unhappy life in your system. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #5
    Re: Battery question
    vtmaps wrote: »
    Also, the motorcycle battery is not a deep cycle battery and will have a short unhappy life in your system. --vtMaps

    Exactly, you need a deep cycle battery.

    I wouldn't worry about having a battery that is "too big", as long as you are replacing the amps you are withdrawing within a day. The problem comes when you draw the battery down too far and your PV is too weak to recharge it on most days.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #6
    Re: Battery question
    techntrek wrote: »
    Exactly, you need a deep cycle battery.

    I wouldn't worry about having a battery that is "too big", as long as you are replacing the amps you are withdrawing within a day. The problem comes when you draw the battery down too far and your PV is too weak to recharge it on most days.
    A battery can indeed be too big if the charging current from the charge controller is too low to overcome the self discharge of the battery.
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #7
    Re: Battery question

    Implied in "the amps you are withdrawing within a day", but stating that explicitly doesn't hurt either. Bottom line, it doesn't matter how big your battery is as long as it is being fully charged on most days.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34 ✭
    #8
    Re: Battery question

    Ok, pretty much I need low amp battery. I did some pricing on 50 amp hour battery. holy smokes, almost 175 dollars. my other idea is another solar panel. but that idea is not available at this time (due to room on balcony). Can i get away with lawnmower battery until go get overpriced battery or get another solar panel.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #9
    Re: Battery question
    techntrek wrote: »
    Implied in "the amps you are withdrawing within a day", but stating that explicitly doesn't hurt either. Bottom line, it doesn't matter how big your battery is as long as it is being fully charged on most days.
    Well, yes, of course, but there is a point where the battery is so big relative to the PV that the PV can't provide the minimum charging current it needs.
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