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  • Maximize 10A Charging Interface

    Sorry if this is a bit lengthy.

    TLDR; how can I maximize two 12V 10A charging interfaces with solar?


    I have a 12V 120Ah LiFePo4 Battery Pack with 2 charging interfaces (DC5521 connectors) that can handle up to 10A each, so 20A total.

    I want my solar setup to get as close to the 10A without causing damage to re-charge the battery as fast as possible.

    I know the safe, straight forward solution would be a 10A charge controller with a 100W panel, but it's never going to get to 10A.

    I could over panel a 10A charge controller with a 130W, but this seems sub-optimal too. (And charge controllers that support over panelling are more expensive.)

    If I increase to say a 160W panel (Isc 9A) or maybe two 100W (Isc 6A each) panels it would charge faster, but now I'm concerned that it will exceed 10A. I could use a 20A charge controller, but what about the 10A limitation on the battery interface?

    From my research, I'm learning towards the 160W panel with a cheap PWM 20A charge controller for each of the two charging interfaces. This should get me pretty close to 10A without going over 99.5% of the time, right?



    What do you think?




  • #2
    Generally, well aimed PV panels only produce about 80% of their rated output, for 20 minutes at solar noon.
    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
      Generally, well aimed PV panels only produce about 80% of their rated output, for 20 minutes at solar noon.
      Right.

      My main confusion is around the solar charge controller's output and the 10A charging interface input. Will a charge controller automatically stay under 10A regardless of the PV wattage? If not, what do you recommend for the PV panels and controller.
      Last edited by doorty; 07-29-2019, 02:38 PM.

      Comment


      • #4
        MPPT charge controllers are usually smart enough to manage their output power and stay within their design & thermal limits.

        PWM controllers either have a fuse, or you just blow the transistors, they cannot limit the current at all. No brains at all.

        Real smart MPPT controllers can be programmed for a max output limit, both of my 60A controllers can be reset for anything less than 60A. perhaps 3A is not within their limits.
        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


        • #5
          Hmm... I think MPPT is going to be over my budget. I'd need two of them.

          What are your thoughts on 20A PWM with a 160W panel (9.27A short circuit)? If my battery can only accept 10A, how likely is it to go over?

          Comment


          • #6
            Most panels need to be within the input voltage rating of the controller. But the controller itself usually does not control current - it merely passes what it was designed to handle. Thus you don't put a 100 w panel on a dinky 2a controller.

            Also be aware that with solar, you can temporarily exceed the standard lab condition current outputs by a natural condition called "lensing", which occurs typically at the edge of cloud formations. Usually this is very brief, and most controllers are designed for to handle these temporary high-output conditions.

            So despite this temporary protection in the controller, most people don't try to match a solar arrays output to the maximum current the controller can handle to give it some breathing room anyway.

            And, the question is if your li-ion battery-pack charging interface can handle even those temporary current lensing affects if you push the envelope too far.

            Unless it was designed for solar, it is probably expecting a stable source of current never to exceed 10a. With the edge-of-cloud effect, even temporarily, I'd just be cautious and be a tad conservative and not try to push it. The batteries might handle it, but the interface, whatever it is, might not.

            Comment


            • #7
              Your panel can only produce 13A, so the 15A sunsaver MPPT should be fine. about $250 I don't have the voltage numbers from your panel.

              prostar MPPT 25A
              https://www.morningstarcorp.com/products/prostar-mppt/
              About $320
              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


              • #8
                Is there such thing as a cheap current limiter that I could use between the controller and battery for 10A? Otherwise it sounds like I'm limited to 100-130W panel and longer charge time.

                Comment


                • #9
                  How are your Li batteries configured ? are they already wired together in parallel, or are you using 2 separate battery banks with 2 separate 10A interfaces ?

                  to get about 10A, @ 13.8V you need a harvest of 130watts. To get that nominal wattage, you need a 155 or 160W PV panel. if that panel is a 18V panel, you use a PWM controller. If the panel Vmp is over 18V, you use a MPPT controller.
                  If you are charging 2 packs, you need double the charging

                  And remember, below 40F, Li batteries start to fade and at freezing 32F. they can no longer be recharged without fatal damage. Whoops, did the dealer forget to tell you that ?
                  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


                  • #10
                    Originally posted by Mike90250 View Post
                    How are your Li batteries configured ? are they already wired together in parallel, or are you using 2 separate battery banks with 2 separate 10A interfaces ?

                    to get about 10A, @ 13.8V you need a harvest of 130watts. To get that nominal wattage, you need a 155 or 160W PV panel. if that panel is a 18V panel, you use a PWM controller. If the panel Vmp is over 18V, you use a MPPT controller.
                    If you are charging 2 packs, you need double the charging

                    And remember, below 40F, Li batteries start to fade and at freezing 32F. they can no longer be recharged without fatal damage. Whoops, did the dealer forget to tell you that ?
                    It's 1 battery pack (with BMS inside metal case) with 2 separate 10A charging interfaces. They can be used concurrently to get up to 20A. If a current of 10A is exceeded I'll have to disconnect the power to reset it, which is something I want to avoid while on the road.

                    The 160W panel has a Vmp of 18.2V and Isc 9.27A. I would use 1 panel & 1 controller for each interface. My concern is the current may exceed 10A due to lensing, as [USER="10928"]PNjunction[/USER] mentioned.

                    Maybe I can install a device that caps current at 10A before entering the charging interface? Suggestions?

                    I'm in Southern California, but yes, I'll need a low temperature disconnect for trips to the mountains.

                    Comment


                    • #11
                      Originally posted by doorty View Post
                      ........
                      Maybe I can install a device that caps current at 10A before entering the charging interface? Suggestions?......
                      That would be a fancy MPPT charge controller you can program with a 10A limit, or nearly any 10A MPPT controller will limit the output to 10A

                      Beware, there is a detection and response time. Hopefully the BMS will allow a few seconds to slightly exceed the 10.00A limit, so the controller can respond and throttle back.

                      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


                      • #12
                        Originally posted by Mike90250 View Post

                        That would be a fancy MPPT charge controller you can program with a 10A limit, or nearly any 10A MPPT controller will limit the output to 10A

                        Beware, there is a detection and response time. Hopefully the BMS will allow a few seconds to slightly exceed the 10.00A limit, so the controller can respond and throttle back.
                        Good point. I just checked, and the Victron has a setting for max charge current. Is there another low-budget option that limits current?

                        I was hoping to use a cheap PWM, but it sounds like I'd be limited to 100W. With a nice MPPT (Victron 75/12), I could double the panels to 2 100W.

                        Comment


                        • #13
                          Can your Li BMS, accept a 20A controller feeding each 10A input, or do you need discrete 10A controllers ? There really is no [I]current limiting circuit[/I] you can buy and throw in, I think a MPPT controller, with a limit set to 10 (or 9.5) amps, is the only way to do it. https://www.morningstarcorp.com/products/sunsaver-mppt/
                          If you want to call Morningstar and ask if the sunsaver-mpp is able to be programmed to some output amp limit.

                          And since I'm asking BMS questions. What does the BMS do to stop charging ? If it simply disconnects the battery from the MPPT charger, you stand a good chance of the MPPT charger being fried because there is no 12V battery for it's brains to run from in that case.
                          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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