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  • overloading MPPT questions. help

    So, I am in the process of converting a school bus into an rv and its time to hook up solar panels.
    I have 5 fiamm 12UMTX180FT telecom batteries that i happened upon that were in great shape for only 75 bucks a piece all of which were holding at 13.2-13.3v 983amp hrs at a c20 rate
    anyway i have since purchases an EPSOLAR 40 amp mppt charge controller model no. Tracer4210A specs listed below
    basically what my question is, is that i found a great deal on three 295 watt solar panels at 36v 885 watts. the specs for the controller say that its capable of handling a max of 520 watts on a 12v system (43 amps) but the input amperage from the solar panels would be about 25 amps at 36v. id like to have the extra wattage so i can charge at full power even in less than optimal conditions, provided that the controller wont fry because its connected to a bigger solar array than it can convert to 12v and 40 amps. will the controller blow or will it just only draw enough current to process the 43 amps thats its rated at. i know i should have gone to a 24v but i already had my 3000 watt inverter and that thing was expensive. thanks for the help guys
    Last edited by Radtech86; 04-24-2017, 01:25 AM.

  • #2
    heres the specs on that controller
    Attached Files

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    • #3
      Those telecom batteries are made for about 6 deep cycles, and then they sell them on the surplus market. You just saved someone their HazMat disposal fee.

      The better controllers with heat sinks and active cooling, can be over paneled and not cook themselves. Smaller controllers without good thermal protection, may fail.

      You may be better off going to 24V, and staying within the controller limits - BUT your PV won't properly charge 24V from 36V panel via MPPT controller.

      You are in a bind.
      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

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      • #4
        well after speaking with the company who manufactures the controller they say that it will not burn up. i also have an external temp control fan and attached it to an additional heat sync also i do not plan to discharge these batteries below 11.8 - 12.2 volts i have a low voltage alarm setup to alarm at 12.2 volts and a generator backup just incase my power demands exceed what my batteries can handle to keep the battery voltage high. i dont think any 12v battery deep cycle or not is designed to be cycled to 10.5v or so more than a few times without crapping out, which is the low voltage cutoff for a lot of inverters

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        • #5
          Originally posted by Radtech86 View Post
          well after speaking with the company who manufactures the controller they say that it will not burn up. i also have an external temp control fan and attached it to an additional heat sync also i do not plan to discharge these batteries below 11.8 - 12.2 volts i have a low voltage alarm setup to alarm at 12.2 volts and a generator backup just incase my power demands exceed what my batteries can handle to keep the battery voltage high. i dont think any 12v battery deep cycle or not is designed to be cycled to 10.5v or so more than a few times without crapping out, which is the low voltage cutoff for a lot of inverters
          Most 12volt batteries don't like to go as low as 11.9volts without getting hurt. Even that 12.2v low limit is taking a chance.

          And as Mike stated those batteries were not designed for numerous deep cycles at any low voltage.

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          • #6
            On the topic of the original question, the max PV input power is telling you the maximum input that corresponds with the 40 A output rating. If you read the manual carefully, you can see that if you meet the Voc and Isc requirements, they state that state that an array rating of up to 3X the input rating is allowed, 1560 W in your case. You won't ever *use* more than 520 W of the available power instantaneously, but with an 885 W array, you will get more production on cloudy days, and increase the amount of time you are can charge at 40 A on sunny days. See page 10.
            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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