Try to talk you out of it
Never heard of it but cool idea. If they are cheap its an option and I want TWO!
Problem is I bet they going to be expensive. They probably ganged a bunch of SCR's in parallel. SS relays of high amp rating cost the better part of $100. If it can really handle +350 amps (says 600 amp surge) long enough to get a plane started, that's cool thing to do with solid state. Solid state means its going through some silicone semi-conductor. Weight savings? A regular relay is about .5 lbs may be .75 lbs. They say the super switch is .3 or .5 lbs. Not a big wt. savings.
Sorry I can't help you more. The following is a rant and rave, suggestions, wild ideas and guessing.
I don't like the master contactor sucking almost an amp. The starter relay seems redundant as well. They are mechanical, but gosh they cheap and reliable. Kind of a necessary evil. There are some deluxe super high capacity (steady and surge) electronic/magnetic latching high end relays made by Electrovolt, that only take milliamps to stay latched.
LINK They cost about $200 and boat supplies have them. The tired $20 old contactors are looking pretty good.
The EV200 is pretty awesome but do you need it? Its so powerful, rating wise, it could be used for master and starter relay, but one is cost prohibative, much less two.
In theory you can do away will both battery (master) and firewall starter contactors (relays/solenoids). From the battery you go from the POS direct to the starter. The starter has its own solenoid, right? Just like a car. The down side is the BIG starter wire/cable is always HOT. As far as the master, if you route the starter cable as I say, the master does not have carry starter current. Now you can use a small relay with a 50 amp rating, like a Bosch black cube. They are light with low cost. Again this is how cars do it. You get rid of ALL big contactors for ONE little contactor. You could even afford (cost and weight) to put two relays in parallel for redundancy. Most find the idea of not using BIG fat contactors too radical, but you will save about 2 pounds and reduce the cowl clutter. Just ideas. Still the standard way is buy two relays from Van.
What about a crash or electical fire and you want to disconnect the battery?
There is always the manual method?
You have the RV-4 and the battery is in the cockpit? GREAT, mount a battery disconnect switch right there on or near the battery box with in reach of the pilot. Here is a popular selection of switches from Flaming River
LINK. In theory you could mount the battery disconnect in reach and use it like a manual master switch. It takes no juice to latch close, just wrist action. It's light and cost about what a solenoid contactor cost. You can even buy remote handles to actuate it with a lever if you like. There available at race part suppliers for about $60.
Just food for thought. I went through the same process but came to the conclusion "resistance is futile".
Have fun and create but the tried and true has some charm and utility. I am not sure $200 relays are the way to go. However with RV-4's and RV-6's, with the BAT on the cockpit floor, near you feet, I would not hesitate to consider a manual battery disconnect switch. Even the RV-7/9 could use it if you mount the disconnect on the firewall. A torque or push-pull tube from the switch to an easily accessible handle would work. Old planes had manual BAT switches. What's old is new again. What will you save? May be not weight (they weigh 17 oz) but you'll get that 1 amp back and super reliability. You could also use this one just for emergency shut down
LINK. Make the push switch accessible by foot for emergency shut down only. Mounted the switch in the firewall for RV's with the battery fwd of firewall. There would be no routing of a big battery cables through the firewall.
As for the starter, if you decide to go with a firewall starter contactor, I don't think there's a substitute to the cheap old solenoid contactor we always have used. As I said you can just forget the firewall contactor and use the one on the starter, but the starter cable is hot when ever the master is on. May be not a big deal.
