June 26, 20206 yr 22 minutes ago, Solaris said: I had this very same idea before these protection cards came along. My idea was to use a 48v relay that would open (cutting power from the PV to the MPPT) as soon as the battery disconnected. I went so far as to do it with a solid state relay. It worked for about 20 mins, it got so hot I couldn’t touch it and then burned out. 😩 I then learned that solid state relays are not designed for constant use. My next idea was to use a 48v golf cart relay. I found some, but when I heard that they were about R1500 each I hesitated. You need something like this https://m.littelfuse.com/products/dc-solenoids-and-relays/high-voltage-dc-contactor-relays/dcnev150.aspx it's 150amp 900v.
June 26, 20206 yr Author 16 minutes ago, Gerlach said: You need something like this https://m.littelfuse.com/products/dc-solenoids-and-relays/high-voltage-dc-contactor-relays/dcnev150.aspx it's 150amp 900v. I was also looking into something similar from a supplier over in China, but then decided to rather find something local for guarantee purposes. Even though I have now installed these protection boards I still would like some added protection, something physical like a relay.
June 30, 20206 yr Author I asked Wouter at Microcare how the high voltage protection works and here is his answer: It makes use of components that can handle the voltage spike and steps down the high voltage to display.
June 30, 20206 yr 1 hour ago, Solaris said: I asked Wouter at Microcare how the high voltage protection works and here is his answer: It makes use of components that can handle the voltage spike and steps down the high voltage to display. That aligns with my (later) suspicions that it sits in the supply line to the main SMPS (the one I marked 2 in the image). So the "blowing up" could be because the stock SMPS used cannot take the resulting voltage spike. I remember trying to find out what chip is on that little board but I could not figure out what it is. The protection board could just be a simple power supply, possibly even linear, that just chops the top off.
June 30, 20206 yr Author This is making sense now. When the battery is disconnected the transient power spike hits the display board. This protection board is a voltage arrester of sort, smoothing out the voltage spike. It is quite possibly a linear power supply, looking at the size and simplicity.
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