Noob here. I need to add overvoltage protection to a small, portable solar power system I'm putting together. The solar PV array has a loaded voltage in the 23-26v range and an open circuit voltage that can be as high as 45v. The PV array is connected to a solar charge controller to charge a couple of deep cycle batteries. The "load" output of the charge controller is connected to a voltage regular that has a maximum input voltage of 30v.
The load is a 10A max circuit. I need to limit the voltage to 28-29v to prevent damaging the voltage regulator.
I started my research to solve the problem and have read about crowbar circuits, zener overvoltage protection circuits and TVS diodes, etc. I think that a basic zener+PTC is a good fit for my needs, but I'm absolutely stumped on the values. The problem I'm finding is that my circuit needs to operate at 10A so I need at least a 10A PTC fuse. When I check digikey for 10A PTC fuses they are all VERY slow which from my initial understanding means I will fry my zener before the fuse has time to blow.
I'm stuck. The 10A PTC fuse (or any fuse) will current protect my voltage regulator and downstream parts but the 10A fuse won't blow fast enough to save the Zener and if the zener fails I lose my voltage protection. - Ahh!
How do I overvoltage protect a 10A, 30v DC signal?
Edit: I just realized that I think this is fundamentally flawed: If the batteries are low or disconnected the solar PV can't produce enough current to blow the PTC. I'd have a maybe 1-2A of 50v shunting through the zener and it would fail.