Good or best solar panel/charger to keep auto battery topped up....

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alyaz
alyaz Solar Expert Posts: 114 ✭✭✭
in Solar Beginners Corner #1
Sorry, maybe my searching capabilities suck, but couldn't find a link to anything useful.

Does anyone have or has used a solar panel / charger to keep their vehicle battery topped up, that they would recommend? Our vehicle sits at our place for a month or two while we are away working. Although the battery is in good condition, I have seen the wonders of using trickle chargers in the past and would like to find an equivalent solar trickle charger to keep hooked to the battery when we are away.

Is there a good 'all in one' charger available or does one need to look for a separate small solar panel and a small charge controller?

Thanks...
3.3 kW solar.  3 Midnite Solar controllers; 5 lightening suppressors.  Magnum’s inverter; auto gen start, BMK.  Davidson 2 v FLA’s - 24v bank.  Perkins diesel gen.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Good or best solar panel/charger to keep auto battery topped up....

    Other than the fact it really shouldn't be necessary ...
    Canadian Tire actually sells little panels that can plug in to the cigarette lighter (providing its of the type that stays "live" with the ignition off) or can clip on to the terminals. Similar panels can be had from E-bay - originally used on new cars (like VW) in shipment to keep the batteries up until they reach the dealer. These are very small and provide a tiny amount of charge.
    If the vehicle is older and you need to provide a more significant trickle charge, you'd want about 15 Watts of panel and some form of regulator. This gets expensive. It is probably cheaper to buy a small automotive charger and a timer and let it turn on for an hour a day (or even an hour a week if you get a more complex timer).
    Or give the battery a charge prior to starting the vehicle once you return.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
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    Re: Good or best solar panel/charger to keep auto battery topped up....

    i'm with coot on this one as a month or 2 should not hurt the battery if left with a full charge. 3 months may be pushing it as the self discharge can become more prevalent and a larger amount of water present in the electrolyte to possibly freeze. as was said give, it a charge when you return. if no charger is available you can jumper from another vehicle, but that'll waste gas. or you can use a small pv left on it during that time period with at least a blocking diode on it. the big things with a battery are the amount of capacity lost due to,
    1> self discharge which either a small charge be it trickle from solar or from a battery charger should reverse that.
    2> low temps that would improve if the battery is allowed to get warmer.

    of course be sure it has good water levels, good connections, and is fairly clean before its final charge that you'd give it before leaving.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,457 admin
    #4
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    Re: Good or best solar panel/charger to keep auto battery topped up....

    Volkswagen (and others?) use solar panels to trickle charge their batteries when shipping cars. You can find a fair number of them on EBay.

    If you have a fairly modern car, some panels can plug into the vehicle diagnostic port.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: Good or best solar panel/charger to keep auto battery topped up....

    To be fair to batteries, cars these days chew up some power just sitting (maintaining program in various computers and such). This will add to the "self discharge" rate, so to speak. It might actually be worthwhile pulling the negative cable before leaving to prevent this (providing you don't mind losing your radio presets).
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #6
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    Re: Good or best solar panel/charger to keep auto battery topped up....

    In the winter you can get away with 3 months between a charge, but in the summer you need to charge once a month, overnight. Or keep a trickle charger on it. Get one of the ones that Cariboocoot suggests and you'll be fine.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #7
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    Re: Good or best solar panel/charger to keep auto battery topped up....
    Cariboocoot wrote: »
    To be fair to batteries, cars these days chew up some power just sitting (maintaining program in various computers and such). This will add to the "self discharge" rate, so to speak. It might actually be worthwhile pulling the negative cable before leaving to prevent this (providing you don't mind losing your radio presets).


    Some cars use a ton of phantom power,, and couple of months batteries can be totally dead. A small (~15 watt) panel would be great. Alternatively disconnecting th ground strap is a pretty good idea.

    Tony
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