Automotive charger and generator

Gregmik
Gregmik Registered Users Posts: 19 ✭
in Solar Beginners Corner #1
I have a 5000w generator that I use for work. I have two banks of batteries, 73AH 12v Gel's, One bank is 6 batts the other is 4. I only have 120W of solar. I have a sunpower non-MTTP 30amp controller. I manually switch the controller between banks when the controller says a bank is fully charged.

My question is, am I hurting the panels or controller by hooking up an Automotive battery charger, that says 15 amp(Puts out 18amps by meter), up to the blocks I have my panels hooked up to and running thru my controller?

Thanks for helping the newbe out,

Greg
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Automotive charger and generator

    Neither the charge controller nor the panel will be harmed if connected to batteries being charged from another source such as a battery charger. The controller will simply see a higher battery Voltage and react accordingly (is in assume the batteries are charged and not allow any current from the panel to pass).

    Can't say the same for the batteries, though. Gel batteries are picky about both Voltage and Amperage. Neither of your banks will mind 15 Amps, as that isn't even 10% of the smallest (292 Amp hours). But the Voltage could be an issue. Leave it on too long and that charging could push the Voltage too high, which can damage the batteries.
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  • Gregmik
    Gregmik Registered Users Posts: 19 ✭
    #3
    Re: Automotive charger and generator

    I think you mis-understand. I am hooking the charger up to the blocks my panels are hooked up to and running the 15amps thru the controller(which is switched to "Gel" vrs "Flooded").

    Thanks,

    Greg
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Automotive charger and generator
    Gregmik wrote: »
    I think you mis-understand. I am hooking the charger up to the blocks my panels are hooked up to and running the 15amps thru the controller(which is switched to "Gel" vrs "Flooded").

    Thanks,

    Greg

    I recommend you do not do this.

    The output from an automotive charger is far from the pure DC that solar panels produce. It could damage the controller. It could damage the solar panel (produce more current than it can tolerate).

    It is okay to connect directly to the batteries, providing the Voltage isn't allow to go too high as I mentioned before.
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  • Gregmik
    Gregmik Registered Users Posts: 19 ✭
    #5
    Re: Automotive charger and generator

    OK, got ya on the panels. I will be disconnecting them when charging the batts. But I would rather ruin my $40 controller than my batteries.

    Greg
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  • Seven
    Seven Solar Expert Posts: 292 ✭✭
    #6
    Re: Automotive charger and generator

    Why not put the charger directly on the batteries and not risk damaging anything? That is how it is supposed to work.
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  • Gregmik
    Gregmik Registered Users Posts: 19 ✭
    #7
    Re: Automotive charger and generator
    Seven wrote: »
    Why not put the charger directly on the batteries and not risk damaging anything? That is how it is supposed to work.

    Because the batts are Gel's and the charger is a regular Automotive Charger. It could damage the batts if the voltage gets too high. The controller will prevent this.

    Greg
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
    Re: Automotive charger and generator

    greg,
    although we generally don't recommend putting a charger to a controller it can work sometimes. most often the problem is with putting it to an mppt controller, but yours is pwm. sometimes the ac ripple from the charger will harm things.

    also in your case you must be sure that the current from the charger and/or the pv will not be too high for your gel batteries for controllers do not usually regulate the current. now some of the better mppt types may regulate the current too.
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  • Gregmik
    Gregmik Registered Users Posts: 19 ✭
    #9
    Re: Automotive charger and generator

    Neil,

    It seems to be working. The cheap controller does not fully charge the batts tho as when it reaches 14.1volts it just shuts the current off. Next investment is a good, or at least better, charger that I can trust. Mine is a 20 yr old Sears 25/15/2. As I said, I would rather ruin a $40 controller than 6-10 batteries.

    The batts are 73AH 12v gel's, one bank is 6 batts the other is 4. I have 4 more batts waiting for me to pick them up. From what Cariboocoot has said, both banks should be able to handle the 15amps. The 25amp setting will not work hooked up to the controller for some reason...

    Thanks letting me pester you all with questions.

    Greg




    niel wrote: »
    greg,
    although we generally don't recommend putting a charger to a controller it can work sometimes. most often the problem is with putting it to an mppt controller, but yours is pwm. sometimes the ac ripple from the charger will harm things.

    also in your case you must be sure that the current from the charger and/or the pv will not be too high for your gel batteries for controllers do not usually regulate the current. now some of the better mppt types may regulate the current too.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: Automotive charger and generator
    Gregmik wrote: »
    Neil,

    It seems to be working. The cheap controller does not fully charge the batts tho as when it reaches 14.1volts it just shuts the current off. Next investment is a good, or at least better, charger that I can trust. Mine is a 20 yr old Sears 25/15/2. As I said, I would rather ruin a $40 controller than 6-10 batteries.

    The batts are 73AH 12v gel's, one bank is 6 batts the other is 4. I have 4 more batts waiting for me to pick them up. From what Cariboocoot has said, both banks should be able to handle the 15amps. The 25amp setting will not work hooked up to the controller for some reason...

    Thanks letting me pester you all with questions.

    Greg

    Shutting the current off at 14.1 Volts is just what it should do.
    The controller probably won't take the 25 Amp setting due to the way automotive chargers work. The "higher Amp" settings change the primary windings on the transformer, resulting in higher Voltage on the secondary and thus the half-rectified DC output. This is fine when you're dumping to a battery, but the charge controller may experience too high a V-in on that setting. A good one will shut down; a bad one will fry.
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