car batterie question

cizzi
cizzi Solar Expert Posts: 109 ✭✭✭✭
in General Solar Power Topics #1
Are car batteries similar to the deep cycle batteries i'm familiar with for my solar application? Being winter here in canada I get around 12.5V with my voltmeter when the car is not running. I tried using a car charger at 2A charge rate and it would not maintain a 12.7 (fully charged) reading after sometime of charging. Is this due because of the cold climate or the type of battery? I don't know if car battereis are AGM, GEL, lead acid..I did notice it says cold cranking amps on the label. Anyways I was just wondering what the method to keep them 100% especially in winter would be? Just like I like to keep my solar battery banks topped off I'd like the same for my cars. thanks.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: car batterie question

    If the car starts and you use it regularly don't worry about it.
    You'd only need to add a 'trickle' charger if the vehicle sits unused for long periods of time (weeks).
    Car batteries are flooded lead cells, but do not function like deep cycle types: they are meant to deliver a lot of current for short period of time (cold cranking amps) then be quickly recharged once the motor starts. Modern vehicles 'syphon' off power to keep their electronic gadgetry going, which results in a dead battery if the engine isn't periodically run. Yes the voltage does go down in the cold, but as long as it starts there's no problem.
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  • cizzi
    cizzi Solar Expert Posts: 109 ✭✭✭✭
    #3
    Re: car batterie question

    thank you for your answer.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    Re: car batterie question

    Car batteries are "nearly" the same as deep cycle, but they are optimized for high current for starter motor, and quick recharge from the alternator, spending little time at less than 100%. "Deep cycle" use will quickly kill them.
    An "ordinary" $30 battery charger, is only designed to charge a battery enough to start a car, it will seldom be able to fully charge a battery. For a full charge, you need a 3 stage charger.
    As to the voltage, the chart here
    http://www.windsun.com/Batteries/Battery_FAQ.htm#Battery%20Voltages
    will help some. Lower temps = lower voltage
    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

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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #5
    Re: car batterie question

    A 2 amp charger should be able to bring a car battery to full charge, unless something is wrong with battery.

    I would be more likely to suspect the accuracy of voltmeter.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: car batterie question

    as was said it is a lead acid battery meant for quick high discharges/recharges like that in car starting and not the kind of drains one might see in solar applications. the battery being cold is at it's full charge with 12.5v i'm sure. if you worry about keeping it topped because of the weather then buy one of those small pvs you can plug into the cigarette lighter keeping the window clear of snow so it can charge during the day. (keep pvs inside the car to prevent theft and damages from the weather) of course this doesn't help at night or if you fail to clear the window (assuming the car is outside) then you could make provisions to use a standard utility type trickle charger in about the 1 amp range. this can add more available power for starting as this small charge will help to warm the battery in addition to keeping it full. this presents a set of wires going to the car with the charger usually under an unlatched hood. one may forget and start the car possibly damaging the car and the charger.
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