My Harbor Freight Panels died
 

I was out in my shed and noticed that may battery voltage was 12.3 volts. Should have been 13 something as it was in the middle of the day. Checked each panel with a multi-meter and nothing. I don't see how all three died at once. Did have some lightning a couple of nights earlier, but no physical damage and the little charge controller was still indicating battery voltage. I did have a circular saw laying right next to the charge controller though. Maybe the magnets in the saw motor did something to the charge controller to kill the panels? Strange....

Did you check each panel at the panel terminals? It almost sounds like there is a wiring problem. You mention lightning- was there rain with it? Maybe there's a connection that has gotten wet repeatedly, and enough corrosion and oxide have accumulated to finally open the circuit. Is there a fuse hidden in a connector somewhere? I can't imagine that a skilsaw sitting close by could have that much infuence. Let us know how it works out!

Coulda got a surge. Disconnect the battery from the controller after dark for a few minutes and reconnect. Go out tomorrow and check 'um again..

Mine screws up when I key up my 2-way radio. I have a C-40 but the r.f. makes it do weird stuff..

How do you know that they all died at once?
First tip off was that they are from harbor freight...
On really basic set ups like it sounds like you have it's really common to have a basic amp meter as well as a volt meter so you can see how many amps you are getting off the panels, that way you can tell right away that something doesn't look right because on a clear day or whatever, you should be getting a set number of amps if all the connections are good and there aren't any issues with the panels, get to much shading or something and your numbers will start dropping quickly.

Check for diode issues.

I agree with this... Corrosion on terminals will kill voltage. Just a little loss here and a little loss there pretty soon you have several volts lost due to poor connection. For electrical connections I use stuff called deox-it. Great stuff. It also protects electrical connections so it doesn't happen in the first place.

Checked voltage at the batteries, and was 13.6 volts with the charge controller display still indicating 12.3 I probably will slave in a different meter and see what happens. Just lighting the shed and occasionally use a power tool on the 1200 watt inverter.