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Thread: Charge batteries from charger and solar at once

  1. #1
    Join Date
    Sep 2010
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    Muscle Shoals, AL
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    88

    Default Charge batteries from charger and solar at once

    Can you have batteries being charged from a battery charger (Iota) and solar charge controller (Morningstar SunSaver) output at the same time? My battery cable +, charge controller batter +, and Iota charger + are all tied together on the line side of the main DC breaker. The - of each are also all tied together at the shunt. May be a silly question, but can you mix the different output voltages together?

  2. #2
    Join Date
    Mar 2009
    Location
    Los Angeles, Ca.
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    1,332

    Default Re: Charge batteries from charger and solar at once

    You can think of it like an air compressor. The battery is the tank and you have two different compressors connected to it. One puts out 13.6 psi and the other puts out 14.4 psi.

    As long as the tank pressure is below 13.6 psi, then air will flow from both compressors into the tank, but once the pressure in the tank gets to 13.6 psi, then air is only flowing from the 14.4 psi compressor.


    The problem to watch out for, is not the voltage (psi) it's the current (cfm). If the battery is below 13.6v, then you could have full output current (bulk stage) from both, which might be more than is good for your battery.

    For example, if your battery recommends 30a max charge current and both of your chargers are rated at 15a, then no problem - but f your chargers are both 30a units, then you could hit your battery with 60a which would be double what is healthy for the battery.

  3. #3
    Join Date
    Mar 2011
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    just south of Seattle, Wa
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    49

    Default Re: Charge batteries from charger and solar at once

    An option, put the Iota on a timer that turns on at night only. Solar charge during the day.

  4. #4
    Join Date
    Sep 2010
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    Muscle Shoals, AL
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    Default Re: Charge batteries from charger and solar at once

    The charger is a 45 amp and the solar is 15 amp max. I have 220 AH of AGM's. I will have to see what amperage the agm's can take or do as SolarT says and use the charger at night if needed and solar in the day.

  5. #5
    Join Date
    Sep 2006
    Location
    Willits, CA
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    5,647

    Default Re: Charge batteries from charger and solar at once

    If you have a place to plug the charger in, why are you using batteries.
    Generally, your best bet is to use the charger/generator in the AM, and bulk the batteries early, and let the sun do the slower part of the charging. saves fuel, unless you need to run the genset at night to cook with the microwave.
    http://tinyurl.com/LMR-Solar
    http://tinyurl.com/LMR-BigLug
    http://tinyurl.com/LMR-NiFe

    Grundfos 10 SO5-9 with 3 wire Franklin motor (1/2hp 240V 1ph # 214505 ) on a timer for 3 hr noontime run - Runs off PV
    Powerfab poletop PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe battery | 15, Evergreen 205w "12V" PV | Midnight ePanel || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT

  6. #6
    Join Date
    Sep 2010
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    Muscle Shoals, AL
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    Default Re: Charge batteries from charger and solar at once

    My setup runs lights and small items in the shed and a dusk to dawn light at night outside. Solar keeps up most days. I use the charger to keep it up on heavy use days. I will also use it on the home to power lights, clock, satellite and tv during an outage. The main senario for the question was: I run the batteries down during the overnight during and outage and either the power is back on by morning or hook up the generator to charge the next morning. If the sun is shining next day and the solar kicks in, what happens with both of them charging together. I just didn't want to have to "babysit" it if both charging at the same time wasn't ok.

  7. #7

    Default Re: Charge batteries from charger and solar at once

    I have a 75A Iota charger connected to my battery bank, along with 630W of solar panels (900 by the weekend).

    There's no problem having multiple chargers (and types) connected to the battery bank. They each are self regulating, and will taper off as the battery voltage increases. One charger will also not back flow into the other.

    But leaving the charger connected and powered up means any battery energy used, will be replaced by grid power. Especially when using battery power at night. By the time morning rolls around, your battery bank will already be at 100%, and the solar panels will have almost nothing to do.

    My solar array is large enough to keep up with my loads most of the time. If we have a major outage, and I end up running both fridges on battery power overnight, or have bad weather for a few days, I'll need to plug in the Iota charger to bring the bank back up to 100%. FWIW, the 75A Iota charger works great with my Yamaha EF2400iS generator.

    Details about my setup here: http://2manytoyz.com/iotacharger.html
    Robert
    Central FL
    http://www.2manytoyz.com
    900W of solar panels, 860 AH 12V battery bank (8 6V Golf Cart Batts), Xantrex Prosine 1800W inverter, Xantrex Prowatt SW2000 inverter, 2 Prostar 30M controllers, 1 Morningstar Sunlight 10L controller, Iota 75A charger (for rainy days), Furrion 30A automatic transfer switch, Yamaha EF2400iS generator.

  8. #8
    Join Date
    Sep 2010
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    Muscle Shoals, AL
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    88

    Default Re: Charge batteries from charger and solar at once

    Thanks for the info. I was afraid if one with higher voltage or I guess amperage, may try to backflow to the wrong location.. not the batteries. My solar almost always keeps up with my small needs. Its the occasional outage that will drain the batteries. I have a secondary motive for having the charger that I have not yet asked here in the forum and have been researching instead. But since I am on the subject, can someone tell me the relationship between amps and voltage into the battery bank to fully charge and possibly equalize on the agm's. I would love to have twice the battery bank for an outage. I currently have 220 ah. I can justify the cost of the batteries, but not the thousand or so for more solar and larger charge controller that would be capable of that size battery bank. I was hoping to use the Iota charger to bring the larger bank back up to full charge and then let the Morningstar controller once again keep up with daily use. Is that possible, or would I need twice the amp input capacity?

  9. #9

    Default Re: Charge batteries from charger and solar at once

    I'd advise against expanding your battery bank without some significant increase in charge capacity. The reason being that at 15 Amps max you're at about 7% charge rate of the existing bank. Unless your usage is low and you spend a lot of time in 'float' daily, you really don't have much capacity for charging and handling loads as is.

    You could use the Iota for bulk charging and then 'finish off' with the solar, but it would be a real pain in the anatomy to do so every day.

    BTW, you don't equalize AGM's unless the manufacturer specifically says so. Just leave them be and use a battery monitor if you have one.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  10. #10

    Default Re: Charge batteries from charger and solar at once

    Post Scriptum;

    You could separate the two banks with a battery switch, and leave the "emergency" bank alone - giving it a boost charge now and then with the Iota. AGM's have a fairly low self-discharge rate and can be left to their own much longer than an FLA.

    Still a nuisance, though, as you would have to look at the Voltage level of the "emergency" bank periodically or else set it up so that whenever you run the generator it automatically gets recharged.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

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