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How many amps will my MPPT put out to battery

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  • How many amps will my MPPT put out to battery

    Hello! Thank you for whatever info you may help me with. I'm completely new to solar and learning, from Puerto Rico, post-hurricane Maria (a total cataclysm). Before, I used to hook a Windynation VertaMax 1500W 12V inverter to my running car's battery and had a pretty good generator for all those months without power. Eventually my father lended me a small 12V PV system from my sister who moved out, and I liked the convenience of flipping a switch and not having to pop my car's trunk and do all that. Grid in PR is shot even worse than before post hurricane, so I get very frequent power outages.

    Current materials are 3 335W GCL 38V 8.82A panels, 2 Trojan T-105 6V, Epever Tracer 10420AN 100A 150V MPPT. Max power draw (load from inverter) will be 7-8A for washing machine cycle (family of 3), 700W microwave oven. Other than that, 0.8A standard AC 120V fridge (most important), 85W LCD TV (grandma, looking for a more efficient one), 12V DC fan (.5A, 6W). Inverter eats 9.6W for operation. All lights are solar, other fans are Li-battery 10,000mAh fans, so no problem there. Main TV set is 50W 120V AC, maybe charge phones / laptop, small stuff.

    The question's in the subject: how much amps (at most) will my MPPT put out to batteries? Charge controller manual states 2AWG to battery (altough I see max current for that size wire is 94A). My guess the answer is depends on how much PV you're feeding it / charging specs of the battery (at float charge of 13.5V, 1005W / 13.5V = 74.4A). This is why it's always recommended to use higher voltage systems... but in the former, am I correct?

    Reason I did not go 24V / 48V (original plan) or over was money and low power requirements on load. A) Already had 1500W inverter, saved $ there ($250+), B) from ceiling to location 15ft at most, C) would have had to purchase 2 additional T-105's ($300 more). But orig. plan *was* 24/48... at least MPPT will accommodate for future. Do know lots of people here hate 12V systems and braced for harsh criticsism from so much reading as lurker xD

    All my limited experience has been with PWM's. I understand MPPT's will change the output amps to the battery from what my PV system is capable of sending in series (9.41A Isc).

    Epever manual: https://www.epsolarpv.com/upload/fil...MS-EL-V1.1.pdf
    Solar panel specs: http://sepbatteries.com/media/add_info/gcldatasheet.pdf
    Inverter: https://www.windynation.com/Inverter...440?p=YzE9NDg=

  • #2
    335w x 3 = 1005w possible with well aimed, cool panels. Knock off 20% for hot panels in sun, and you should see 800W or 57 amps with good sun and batteries accepting the charge. (at 14V)

    Because your panels are 38V, you need not wire them in series, that could over-voltage your controller.
    Powerfab top of pole PV mount (2) | 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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

    Comment


    • #3
      Originally posted by Mike90250 View Post
      335w x 3 = 1005w possible with well aimed, cool panels. Knock off 20% for hot panels in sun, and you should see 800W or 57 amps with good sun and batteries accepting the charge. (at 14V)

      Because your panels are 38V, you need not wire them in series, that could over-voltage your controller.
      Thanks Mike! I thought series as the system is 12V (batteries, inverter) to keep the amperage / wire gauge down and 46Voc x 3 = 138V, so I'm under the 150V limit on the controller.

      Comment


      • #4
        Originally posted by serialteg View Post

        Thanks Mike! I thought series as the system is 12V (batteries, inverter) to keep the amperage / wire gauge down and 46Voc x 3 = 138V, so I'm under the 150V limit on the controller.
        Wiring panels in series is correct; the higher the voltage from the solar array, the easier it is to reduce line losses. Generally speaking, you would only need to put all the panels in parallel if you have a PWM charger.
        You're in PR, so this (probably) doesn't apply to you, but it's worth knowing: solar panels have a temperature coefficient, and the colder they are, the higher their voltage--and by a potentially significant amount, too. The panels' Voc rating on my system is 37.30--so four in series = 149.2v...really close to the 150v limit, but why not? Well, if we apply a -10F temperature coefficient to the array, the possible Voc of four panels in series becomes 160.2vDC. *POOF*.

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        • #5
          Originally posted by NochiLife View Post
          Wiring panels in series is correct; the higher the voltage from the solar array, the easier it is to reduce line losses. ........
          Not every install is the same. This is only 3 panels, in parallel, less than 30A from the PV. But the other thing you are not seeing is, as the input/output voltage spread gets wider, the MPPT converter efficiency starts going down as you transform 114VDC down to 14V for battery charging. This causes the controller to run hotter than needed.
          so just because things can sometimes be done one way, does not always mean that's the best or only way to do it. If the user's system was 48V, that would be a very different story but a 12V system does not need 114V from the PV to make the MPPT work

          Powerfab top of pole PV mount (2) | 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

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister

          Comment


          • #6
            Originally posted by Mike90250 View Post

            Not every install is the same. This is only 3 panels, in parallel, less than 30A from the PV. But the other thing you are not seeing is, as the input/output voltage spread gets wider, the MPPT converter efficiency starts going down as you transform 114VDC down to 14V for battery charging. This causes the controller to run hotter than needed.
            so just because things can sometimes be done one way, does not always mean that's the best or only way to do it. If the user's system was 48V, that would be a very different story but a 12V system does not need 114V from the PV to make the MPPT work
            I get your point; it would be interesting to see if the controller's increased loss with a big voltage drop, has any relation to the reduced line losses (especially if the panels are a large distance from the charger). At least on a Morningstar Tristar MPPT, their chart shows a 3.7% loss at 98vMPP over 14vMPP for a 12v system (didn't see an equivalent chart in the Epever Tracer 10420AN manual). I suppose whether that would balance out would be determined by the length and gauge of the solar lines...

            Comment


            • #7
              In a system like the posters, with a small battery bank, and a mid-size 45A controller, wiring parallel is the way to go, because a small controller is less likely to be able properly manage a large, high voltage array feeding 12v batteries. Both line loss and conversion loss will be irrelevant mostly.
              Powerfab top of pole PV mount (2) | 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

              solar: http://tinyurl.com/LMR-Solar
              gen: http://tinyurl.com/LMR-Lister

              Comment

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