PV Solar System: Lightning and EMP?

A few weeks back we had a typical Florida thunderstorm including lots of typical lightning. During the storm, there was one bolt/flash of lightning with a simultaneous, wall rattling BOOM which told me it was very close to home like less than 50 yards. Nothing appeared to be damaged from that one so all was thought to be good.

It wasn’t until a couple days later I noticed my solar charge controller display was ‘nervous’ where the display wasn’t steady like normal. The voltage display digits would constantly bounce around from .1 to .5 volts!

After a couple weeks nothing changed. I checked the battery water level and it was extremely low, like almost empty in EVERY CELL. The water has been boiled out of BOTH my RV/Marine 12v batteries, very odd for my system. In the 7½ years I’ve had this system running 24/7 I have added water only one time several years ago and it was a very small amount, actually didn’t need any, just felt guilty that it must need some! The controller has worked perfectly all that time.

So what happened to what has been a bullet proof solar system????

I’m guessing the nearby lightning damaged the controllers upper charge limit of 14.4volts and with that limit not working it overcharge the batteries and subsequently boiled out the water. There was a diagnostic feature in the controller that told me the controller was set properly to 14.4 volts. So to test the controller I reset the float charge to 14.2 volts, replaced all the water and watched to see if the batteries and controller could attain and maintain a ‘float charge level’. It never did reach a float level mode just kept on charging with all the power the panels delivered and boiled the water out again. Obviously the controllers float charge limiting function was toast and so were my two, 15-month-old RV/Marine batteries.

In summary:

I have since replaced the batteries and controller and all is well now. I would have to guess that if a CME or an EMP pulse were to strike a solar system that uses a controller component it will probably be killed. Maybe because there're only two electronic items in the solar system I need to have a backup Controller and Inverter stored in a Faraday Cage? That may be very smart as I feel EMP would be the weapon of choice of our adversaries.