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Awesome new MPPT controller with bluetooth control for $99

Discussion in 'Power Systems' started by JCruse, Feb 19, 2017.

  1. george_tlc

    george_tlc SILVER Star

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    Firstly, I assume you mean Bluesolar controller (not bluesea...).

    With the 75/15 I've done several tests with constant load (electronic load) and power supply as the battery and have not seen any 'jumping around' issues.

    cheers,
    george.
     
  2. bj70_guy

    bj70_guy

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    No remote temp sensor? :(

    I ordered one of the 75-15s w/dongle today to use with 2 mono 50W panels in series on my 24V BJ74.
    My HDJ81 has a 100W mono panel and a Morningstar Sunsaver MPPT, so it should be interesting to compare the 2 systems.
     
  3. diver1498

    diver1498

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    so I finally broke down and bought one (actually the smartsolar. same controller but has built in Bluetooth) and now I fully understand why mppt is so much better than pwm.
     
  4. bj70_guy

    bj70_guy

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    I picked mine up today. One of my winter projects is throwing the (2) 50W mono panels I scored off craigslist in series on the roof of my 24V BJ74.
    Looking forward to getting it up and running.
     
  5. iptman

    iptman

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    I know it was mentioned earlier the controller should be mounted as close electronically to the battery it's charging so would the rear inside quarter panel of am 80 be too far away? I have some 6 awg wire leftover from another project I was planning on using to run from the deep cycle battery up front. Is this overkill? I assume I shouldn't hang a distribution block off this run so as to not mess up the readings of the controller to the battery?
     
  6. george_tlc

    george_tlc SILVER Star

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    Distance from charge controller to battery from a voltage perspective is just to do with voltage drop and voltage measurement accuracy.

    So, lets assume 10g and having say 20' from a rear deployment back to a front mount aux battery. Lets assume battery is fairly discharged and the solar is pushing out 150W. So, let's call that 12A into the battery.

    10g wire has nominal 1 ohm per 1000'. So, for our 20' (lets assume x 2 for both a red & black wire run from controller to battery).

    So, that's 40' total wire length.

    So, our wire resistance is 1 / 1000 x 40 = 0.040 ohms.

    Now, 12A is flowing and we have 0.040 x 12 = 0.48V drop from the solar controller back to the battery. The charge controller will think there's say 13.8V (battery charging nicely) but the battery is at 13.8 - 0.48 = 13.32V. Not really a big deal. Even less of a deal since the battery will draw less and less current as the voltage heads up to 14.4V (or whatever you have set the max to). Less current, less voltage drop and this more accurate sensing of actual battery voltage.

    6g is about 0.4 ohms per 1000'. You can do the math :)

    I wouldn't sweat it either way since all it means is that the battery voltage will be a bit lower than what the controller thinks. You won't risk overcharging the battery and that's the bigger issue.

    Myself, well, I'd mount the charge controller high up in the passenger side footwell (that's about 12' total cable length)... But that's the EE in me wanting to optimise things...

    cheers,
    george.
     
    thelal, bluesquirrel and iptman like this.