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  • 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?
    4 Kyocera KD135 in series, Tristar 45 MPPT, Exeltech XP600 24
    volt, 4 - 6 volt 210AH AGM's in series, Iota 25 amp/24 volt charger, 6kw cheap noisy generator.

  • #2

    Re: Charge batteries from charger and solar at once

    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.

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    • #3

      Re: Charge batteries from charger and solar at once

      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.

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      • #4

        Re: Charge batteries from charger and solar at once

        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.
        4 Kyocera KD135 in series, Tristar 45 MPPT, Exeltech XP600 24
        volt, 4 - 6 volt 210AH AGM's in series, Iota 25 amp/24 volt charger, 6kw cheap noisy generator.

        Comment


        • #5

          Re: Charge batteries from charger and solar at once

          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

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          • #6

            Re: Charge batteries from charger and solar at once

            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.
            4 Kyocera KD135 in series, Tristar 45 MPPT, Exeltech XP600 24
            volt, 4 - 6 volt 210AH AGM's in series, Iota 25 amp/24 volt charger, 6kw cheap noisy generator.

            Comment


            • #7

              Re: Charge batteries from charger and solar at once

              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.

              Comment


              • #8

                Re: Charge batteries from charger and solar at once

                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?
                4 Kyocera KD135 in series, Tristar 45 MPPT, Exeltech XP600 24
                volt, 4 - 6 volt 210AH AGM's in series, Iota 25 amp/24 volt charger, 6kw cheap noisy generator.

                Comment


                • #9

                  Re: Charge batteries from charger and solar at once

                  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.

                  Comment


                  • #10

                    Re: Charge batteries from charger and solar at once

                    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.

                    Comment


                    • #11

                      Re: Charge batteries from charger and solar at once

                      Re: Charge batteries from charger and solar at once

                      The practical rate of charge for a lead acid battery bank works out to around 5-13% times the 20 Hour rate.

                      Below 5%, for flooded cell you have self discharge and electrolyte mixing issues.
                      For all types of lead acid batteries, you want to recharge them quickly above ~75% state of charge. If you have a low charge rate, it could spend days below 75% state of charge and tend to sulfate the batteries (for an early death).

                      For flooded cell, standard storage batteries charged >~13% rate of charge, can over heat (with quick charge industrial chargers). For solar panels, they are expensive and >13% rate of charge--they are not going to charge at that high of rate very long before the battery voltage rises and charge rate tapers off.

                      For Concorde AGM, they can charge at less than 5% rate of charge (no electrolyte to mix, lower self discharge). And they can charge over C*4 rate of charge (check vendor manuals).

                      For standard utility powered charger (and gensets to a degree), you can have a charger rated upwards of ~25% rate of charge without concern.

                      Basically, the way many chargers work:
                      • Bulk (less than 80% state of charge): Charger outputs rated current into battery bank
                      • Absorb (~80-90% to 100%): Battery reaches charger set point (such as 14.5 volts) and charger will taper off on current to keep 14.5 volts
                      • Float (100% state of charge): When charging current falls to a few percent of battery AH capacity and/or a timer (~2-6 hours) is reached in absorb mode--The charge controller will cut back to ~13.2-13.6 volts to keep the battery charged (self discharge--also differing forms of corrosion occur in a battery depending on voltage of battery--13.x volts is a compromise for long life between the various failure mechanisms--and to reduce water consumption).
                      • Equalize: Done on 100% charged battery. Increase voltage to ~10-16 volts and 5% rate of charge. Done for flooded cell batteries roughly when needed / once every couple months. Hold ~5% rate of charge and monitor specific gravity of each cell until SG no longer rises in any of the cells (check every 1/2 hour).
                      • Equalize AGM: In general, many vendors do not recommend equalization--other recommend a "light" equalization (14.2 volts or so held for a few hours?) to equalize the level of charge among all cells perhaps 1-2x per year. AGM's, if over charged can overheat and release pressure (gas+electrolyte)--which will shorten their life.
                      I think I got the above correct... As always, read the manuals for your battery brand/type for their recommendation.

                      -Bill
                      20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

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                      • #12

                        Re: Charge batteries from charger and solar at once

                        Re: Charge batteries from charger and solar at once

                        And FYI:

                        The Iota IQ/4 module is okay for AGMs because it doesn't actually equalize. What the IQ/4 does, is after 7 days as float, it triggers bulk stage and does a quick run-through of the bulk and absorb stages and then it's back to float.

                        They call it equalize, but it really isn't.

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