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I have an EPEver 3210A MPPT connected to my solar panel and a battery to charge. I'm initially experimenting with a small size battery (12 V, 7 Ah) before I upgrade. The MPPT pulls 100 mA from the battery to operate. There is no on/off button on the MPPT.

I don't want to drain the battery too much with the MPPT on inclement days (which often happens during this time of year), so I added a DC switch that kills the connection between the MPPT and the battery. I'm not sure if the manufacturer intended for the MPPT to be under constant use and I'm afraid that using the switch would often put too much stress on the system.

Will a switch that periodically turns the MPPT on and off damage it?

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  • \$\begingroup\$ While it seems unlikely that turning something on and off could be a problem, this is a question that only the manufacturer can answer. Everything else is just speculation. \$\endgroup\$
    – crj11
    Commented Mar 23, 2018 at 11:16
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    \$\begingroup\$ Some charge controllers insist you connect the battery before connecting the solar panel. If yours does, then it might be damaged with the battery disconnected, so don't do that. \$\endgroup\$
    – user16324
    Commented Mar 23, 2018 at 13:12
  • \$\begingroup\$ If it really uses 100mA in standby, it is a piece of junk. However, maybe it will transition to a lower power mode after some period of time elapses. So I suggest you do some more measurements to make sure. But if it really uses 100mA in standby, then I suggest that you simply get rid of it. \$\endgroup\$
    – user57037
    Commented Mar 24, 2018 at 23:47
  • \$\begingroup\$ @mkeith The accuracy on the MPPT are in increments 0.1 V, so I measured the current draw and it's actually around 35mA. Does that still qualify as a "piece of junk"? \$\endgroup\$
    – Mr. Cheezits
    Commented Mar 25, 2018 at 20:56
  • \$\begingroup\$ Maybe not. I mean, it would not be hard to do better. But 0.035A * 12hr = 0.42Ah. That is around 6% of battery capacity lost every night (if the night is 12 hours). Considering that the power loss is less than you expected, do you still even want to use a switch? \$\endgroup\$
    – user57037
    Commented Mar 25, 2018 at 22:31

2 Answers 2

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On bigger commercial off grid systems being sold they have a shut down procedure that alows you to turn off/on the system safely. So in your setup if you add breakers or switches in between batteries, charge controllers, panels, inverters and even after inverters you can control your system the way you want safely.

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To manage the solar system, install a switch across the solar panel input on the MPPT controller to short-circuit the input. This method is also effective for testing your solar panel by measuring the short-circuit current (Isc).

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