Car battery charger/maintainers

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JetMech
JetMech Solar Expert Posts: 71 ✭✭✭✭
Solar car battery charger/maintainers...are any of them worth buying? Do they help AT ALL?

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
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    Re: Car battery charger/maintainers

    I can verify the "cheap" battery maintainers will boil a battery dry in a few months... I have purchased a couple and they all can cook an 80 amp car battery (even with loads for GPS, On-Star, Lojack, etc.).

    My trick is to purchase a cheap electronic or mechanical timer (like those used on lamps) and set them to charge for an hour a night (or what ever you believe the minor loads/self discharge require).

    I did this on my In-Laws car which has a 0.185 amp drain (above electronics) for their car which sits for a month or more at a time:

    24 hours * 0.185 maps / 1.0 amp "charger brick" = 4.4 hours per night on timer

    No problems since (battery water stays OK--maintenance free battery, car starts first time, no jumping/charging). Only problem--trunk gets left unlatched (key fob unlock?) and nobody sees the trunk light on for a week -- kills battery. I should probably just take the trunk lights out of all of their cars and give them an LED flashlight. ;)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JetMech
    JetMech Solar Expert Posts: 71 ✭✭✭✭
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    Re: Car battery charger/maintainers

    I'm thinking of the kind that sit on the dash and plug into the cigarette lighter, I don't think those put out enough to worry.

    Come to think of it, it would have to be a "constant-on" lighter wouldn't it? Rather than those that only et power in ACC or ON.

    Yeah those trunk lights have got me more than once too.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
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    Re: Car battery charger/maintainers

    The small chargers I used are just 1 amp. And a 1 amp charger running 24x7 is more than enough to destroy a couple 100 amphour batteries unless they are refilled with distilled water monthly (ask me how I know :roll: ). Actually, it was a battery maintainer which cycled on and off at a set voltage (this was before I came here and learned the details of battery maintenance).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Car battery charger/maintainers

    I have a couple of 5 watt, 15 volt Pv panels sold by coleman. I got them from that weird site that sells just one thing every day. I paid ~$10 each for them. The trick is that it puts out less than 1 amp while the sun is out, and the voltage is limited to a max of 15 vdc. It never gets to that 15v so it doesn't need a controller of any sort. I have one on a genset that runs only rarely, another on a tractor and another I put on a bush truck that we rarely use.

    It has kept these batteries fully charged for a couple of years. Pretty simple.

    Tony
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    Re: Car battery charger/maintainers

    They should be OK, heck even VW uses them in the new cars shipping over on boats, they have a 10W panel on the dashboard. You can often find them on ebay.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
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    Re: Car battery charger/maintainers

    The thing is that a 1 amp solar panel only runs 2-5 hours a day... Its own automatic timer.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
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    Re: Car battery charger/maintainers

    Charger/maintainers like BatteryTender are okay.

    They should be used for a battery that sits for more then a couple of months unused.

    The only problem you can get into is when their maximum current won't get the battery past the initial bulk stage (14.4 vdc) and into their float voltage of 13.2vdc.

    It is usually not a problem for a car battery, small boat battery, riding lawn mower, or electric start generator. I would rather they just do a current limited 13.2 vdc float.

    They are definitely better then letting a battery sit and sulfate.

    Now if you want 'snake oil' get a battery desulfator.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Car battery charger/maintainers

    watch out that the current isn't going backwards during nights or cloudy times as some may skip the blocking diode. i prefer to use some kind of regulation, but the diode would be a must have if no controller is present to stop the back-flow of current.
  • JetMech
    JetMech Solar Expert Posts: 71 ✭✭✭✭
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    Re: Car battery charger/maintainers

    Good point. Thanks for the info fellas.