solar charging 6volt tractor battery

unisentient
unisentient Registered Users Posts: 5 ✭
in General Solar Power Topics #1
Hi folks : ...newbie here.
I already maintain/charge my 12volt tractor batteries with solar.
Now i would like to have some advice on how to maintain/charge/desulphate my old Massey Harris Pony tractor battery year-round.
Is there a way of using a 12-volt , 5-watt panel and adapting it for the 6-volt use?
I assume that the 6-volt deer-fence/feed chargers are not sufficient for the tractor battery?
Thanks for any clues!
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: solar charging 6volt tractor battery

    How large (Amp*Hours) is the battery...

    You can use a 12 volt panel to trickle charge a 6 volt battery--but it will no longer be 5 watt output panel, but approximately 1/2 that value (panel output current remains the same, but voltage is 1/2).

    Too large of battery (amp*hours)--may need a larger panel. Too small of panel (with respect to the panel), may need a charge controller to prevent battery overcharging.

    Also, need to confirm that the panel has a blocking diode to prevent the battery from discharging back through the panel at night (or add a blocking diode).

    -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 ✭✭✭
    #3
    Re: solar charging 6volt tractor battery

    A couple of notes from an old tractor guy:

    Your Pony is, I believe, (+) ground so make sure your panel connection polarity is correct. You can't rely on the "cigarette lighter" connection type here.

    Since this is a small, gasoline engine the Amp/hr is probably not very high - most likely around 100 +/-. But since it is 6V it needs more current to do a good charge job. The small panels probably won't do much for truly charging or desulphating. A 5W panel would barely be able to stay ahead of self-discharge at best. Two 5W panels, on the other hand, might be more readily available and capable.

    You are perfectly correct that the panels for fence chargers are way too small to make a dent in a starting battery's needs.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: solar charging 6volt tractor battery

    if it's just to maintain the battery this can be 1-2% roughly of the battery ah capacity so be sure the pv itself can deliver the same current as you calculated the 1-2% would be. of course, it can be a higher % of charge if you wish it to be, but it will be a higher wattage pv to do that. the problem i think you will run into is that charge controllers are designed for 12v battery systems minimally.
    one solution may be to utilize a linear ic regular of the variable type like the lm317 to go between a 12v pv and the battery. most 12v batteries like to float charge at around 13.5-13.8v and yours will just be adjusted to half of that if you don't know the proper float voltage. even putting the voltage higher like for normally charging voltages should be fine, at about 7.1-7.2v roughly, as this is a low current application. and like as was said, you will lose about half of the power available from a 12v pv in this application to 6v. no direct connecting of any 12v pvs to your 6v batteries should be done.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: solar charging 6volt tractor battery

    Niel;

    Might this be a case for the "light bulb" solution? Run a 12V 5W panel in series with a 6V 5W bulb to the battery?
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: solar charging 6volt tractor battery

    might work and would be cheap enough for him to try.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #7
    Re: solar charging 6volt tractor battery

    I cannot imagine the need to run a "light bulb" for voltage drop... The solar panel is already current limited and its output will not be affected if the bulb is there or not.

    And the light bulb will not act as a regulator to limit the battery to 6.5 volts for float charging.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
    Re: solar charging 6volt tractor battery

    Not a very elegant solution, but I used to run 12v batteries in my old machines all the time. Sometimes changed the generators (alternators) and coils, sometimes not. If they started easily, the starter didn't really care if you didn't have to crank it long. I just kept the batteries on float chargers since they often didn't get charged by running.

    Tony
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  • unisentient
    unisentient Registered Users Posts: 5 ✭
    #9
    Re: solar charging 6volt tractor battery
    Cariboocoot wrote: »
    A couple of notes from an old tractor guy:

    Your Pony is, I believe, (+) ground so make sure your panel connection polarity is correct. You can't rely on the "cigarette lighter" connection type here.

    Since this is a small, gasoline engine the Amp/hr is probably not very high - most likely around 100 +/-. But since it is 6V it needs more current to do a good charge job. The small panels probably won't do much for truly charging or desulphating. A 5W panel would barely be able to stay ahead of self-discharge at best. Two 5W panels, on the other hand, might be more readily available and capable.

    You are perfectly correct that the panels for fence chargers are way too small to make a dent in a starting battery's needs.

    Right, the Pony is + grnd. which brings the question... onto which terminals should the hot and neg. panel clips fasten ?
    And, do the tractor's cables have to be disconnected from the battery during charging?
    I do have a 15 watt 12 volt panel which i could use after i retire the outhouse fan for the season.
    You mentioned nothing about 12 volts charging a 6 volt system.... do-able? dunnit yourself ? no consequences?
    thanks!
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  • unisentient
    unisentient Registered Users Posts: 5 ✭
    #10
    Re: solar charging 6volt tractor battery

    Neil wrote:
    "one solution may be to utilize a linear ic regular of the variable type like the lm317 to go between a 12v pv and the battery"

    Hi, where would i find such an animal readymade , or would i just look for those components and solder together those flimsy wires and rubber-paint?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #11
    Re: solar charging 6volt tractor battery
    unisentient wrote: »
    Right, the Pony is + grnd. which brings the question... onto which terminals should the hot and neg. panel clips fasten ?
    And, do the tractor's cables have to be disconnected from the battery during charging?
    I do have a 15 watt 12 volt panel which i could use after i retire the outhouse fan for the season.
    You mentioned nothing about 12 volts charging a 6 volt system.... do-able? dunnit yourself ? no consequences?
    thanks!

    (+) to (+) and (-) to (-) ALWAYS. So you have to sort out the panel's polarity.

    Leave the cables hooked to the tractor: nothing draws when the ignition is off (unless someone flicks the lights on).

    12V to charge 6V is doable. It's a matter of current and resistance. The reason I mention the light bulb trick is because the 'resistance' of a 6V battery on charge is low for a 12V source - if the source is low power (like a small solar panel), it'll be dragged down to 0 volts. If it is high power the current will be high and something will fry. Remember that batteries are always charged with higher than nominal voltage: a 6V system will want up to 7.2 volts for charging.

    Yep: been there, done that, but not with solar panels. Standard battery chargers and 12V "jumps" which, if "unballasted" send sparks flying easily.

    A note about the difference between 6V and 12V automotive systems: the only component in common between like versions is the ignition coil. The 12V system uses a ballast resistor or resistance wire to reduce the current strain on the coil. Applying 12V directly to this will burn it up soon enough. The same can be said about frying voltage regulators, generators, and starters.

    Shall I start reminiscing about the days when they sold batteries with the cell connectors accessible on the top? They even sold 12V batteries with 6V center tap posts so you could convert to a "dual voltage system" (which there was really no point to at all).

    Maybe you could find the 12V equipment for your Pony. After which it would also be negative ground.
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  • unisentient
    unisentient Registered Users Posts: 5 ✭
    #12
    Re: solar charging 6volt tractor battery
    BB. wrote: »
    How large (Amp*Hours) is the battery...

    You can use a 12 volt panel to trickle charge a 6 volt battery--but it will no longer be 5 watt output panel, but approximately 1/2 that value (panel output current remains the same, but voltage is 1/2).

    Too large of battery (amp*hours)--may need a larger panel. Too small of panel (with respect to the panel), may need a charge controller to prevent battery overcharging.

    Also, need to confirm that the panel has a blocking diode to prevent the battery from discharging back through the panel at night (or add a blocking diode).

    -Bill

    Thanks Bill : So you seem to state assuredly that i can use the 12volt panel to charge the 6volt battery.
    That's great, though i don't understand why there would not be some downside ...? It sure seems like the easiest solution.
    It only suggests that i'm paying too much for the charge,,, if the same panel would normally charge a 12 volt battery more efficiently...correct?
    Can i just leave it attached all the time i'm not running the tractor?
    (You see, it's away from AC in a remote location)
    I do also have a 15watt panel with a 7 watt? controller inline. ...and i believe i read in the literature that it has a blocking diode.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #13
    Re: solar charging 6volt tractor battery

    A lead acid battery is a "Voltage Source"... Basically, it tries to hold the voltage stable (6.x volts, 12.x volts, etc.).

    A solar panel, once it has sunlight on it and it reaches near full voltage (with no load)--becomes a "current source"... The output current being proportional to the amount of sunlight energy hitting the surface. And, you can connect the panel to a 12 volt battery, a 6 volt battery, or a dead short--and there will be no damage... Just the panel outputting nearly the same current into any of those loads (of course, if you connect it to a 24 volt battery, it cannot generate enough voltage to charge the battery--hence, the Vmp of the panel needs to be at least as high as the load voltage for current to flow).

    The "draw back" to connecting a 12 volt panel (really, Vmp is around 15-17 volts or so)--to a 6 volt battery is that the "power" from the panel going into the battery is less--because of the lower battery voltage.

    Lets take a guess that your 15 watt panel at 15 volts:

    P=I*V
    I=P/V=15 watts / 15 volts = 1 amp (basically, from zero to 15 volts in full sun)

    Now, assume that the controller you use has a 1 volt drop (when passing full current). The maximum available voltage at a 12 volt battery will be:

    15 volts - 1 volt drop = 14 volts @ 1 amp at the battery...

    Power into a 12 volt battery will be:

    P=I*V=1 amp * 14 volts = 14 watts into a 12 volt battery in full sun

    Power into a 6 volt battery (assuming 7 volts when charging):

    P=I*V= 1 amp * 7 volts = 7 watts into a 6 volt battery in full sun

    So--the "drawback" with charging a 6 volt battery with a 12 volt panel is that 1/2 of the charging power is loss (your 15 watt panel is outputting 7 watts useful)...

    You could, disconnect the two 6 volt batteries (and assuming they are the same Amp*Hour rating and level of charge) and put them in series (12 volts) and now the panel could charge both batteries with 1 amp and 14 watts maximum (full sun).

    Now--if the batteries are fully charged and their is no load (small lamp left on, etc.)--you can probably trickle charge them at around 1-2% of their AH rating without a charge controller (but you need a blocking diode to prevent leakage thru the panel in dark--if the panel does not have one installed--see specs.).

    Also--make sure that when you connect the panel--that you know the polarity of the connection. Solar panels when connected backwards become pretty little drink coasters.

    You can use red/black battery clips (and you always connect them correctly) or you can use some sort of polarized connector to ensure proper connection.

    Technically, it is probably impossible to desulfate a battery (although, they do sell desulfinators that some folks believe work). And, a small panel does not have enough power to equalize a battery ("boil" it lightly to cause the electrolyte to mix)--but you sound not need to equalize--just trickle charge.

    Once a month, check the battery electrolyte level... If the solar panel current is on the high side--you could need to add distilled water every month or so (more or less normal).

    You should also check the specific gravity of the electrolyte once in a while to ensure that the batteries are > 75% state of charge--batteries below 80% or so State of Charge will begin to sulfate.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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