Sun Yoba MPPT Solar Charge controller.

Discussion in 'Van Accessories' started by mikedjames, Oct 13, 2017.

  1. I bought one of these as a quick cheap stop gap solution for solar cell charge controlling after getting hold of two 100 watt flexible solar cell panels.

    The panels are about 1100 x 550 mm so I fitted them side by side towards the front of the pop top.

    Glued down with beads of polyurethane sealant.

    I chose to connect the panels via separate wiring fron each panel to the controller, the solar panel wiring was isolated from earth on both positive and negative sides of the panels.

    I used Halfords OFC 1.5mm2 speaker cable as this is flexible and silicone insulated. Threaded through some 10mm ID pond fountain hose it bends and flexes with the Devon pop top hinges and springs.

    Just before the controller I connected a 10 amp Schottky diode in series with the positive wire from each panel then connected the two diodes to the controller.
    This is to stop losses caused by current flowing back when there is shadowing on one panel.

    The controller claims to be MPPT tracking but it does not have any energy storage components so the maximum current output is the same as the solar cell output.

    So it is NOT a true MPPT controller.

    The back panel of the controller is an isolated heatsink.

    It features an output switch feature which will disconnect the output load if the battery voltage is too low and reconnect it when the battery is recharged.

    You can also program switch on and off based on delay from sunrise and sunset. But there is a catch.... see later..

    You can also set the full charge voltage for disconnecting the solar cell from the battery.

    Unfortunately because it is so cheap there is a major flaw.

    The switching transistors are all on the negative side as N channel MOSFETS are cheaper and more efficient.

    This means it only works properly if you do not have a ground connection to the battery negative, only grounding the output negative.
    In a camper van with other charging arrangements the negative of the leisure battery is grounded.
    This means the output switch transistor is permanently shorted by the chassis of the bus. So it does nothing.

    On the input side the switching only works because my solar cells are not connected either side to the chassis.
    If you grounded the solar cell negative you would short out the controller switch and boil the battery.

    Also the positive terminals of the solar cell, the battery and the output are all connected together ... which I discovered when I turned off the output then accidentally dragged the positive wire over the chassis of my inverter and there was a crack and the solar controller turned off.
    I soldered up the blown PCB in the controller and it still works.

    Conclusion : OK as a basic cool running charge controller. Not MPPT and the output switch facility is useless. Do not earth either side of the solar panel and all will be well.
    Reasonable value for about £23.

    I will be replacing mine with something more professional costing 3 to 4 times as much . As my panels were free I wanted to keep the cost down. If they were new , an £80 controller would be about 5% of the installation cost.

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