BE99 Pilot reported they inadvertently turned the starters on in flight which resulted in an electrical failure.

Narrative

I lost all electrical and communications during flight. I took off on Runway XX on runway heading then was told to fly 245 before contacting departure. At this point the flight was normal. I reported that I was 7;100 ft. for 9;000 ft; and was almost immediately given 16;000 ft. to climb to and a heading of 275. At this point I noticed the generator annunciator lights came on. I had also turned off the auto feather at this point. I monitored the electrical and began to toggle the generators on and off to try to reset them. I attempted to toggle everything one at a time so that I wouldn't accidentally turn off something that I needed. Everything continued to operate normally at this point and was giving me no indication that the annunciator lights were not false which unfortunately; I've had the experience with other aircraft. As I climbed through 17;000 ft. things started to fall off line. First my fuel gauges; then my fuel flow indicators. At this point I decided to tell approach I needed to go back to ZZZ but they called me first to ask me to recycle my transponder. That's when I noticed the red x through my transponder. I was able to turn my back up on to altitude and they did verify that it worked and that's when I requested a vector to head back. They gave me 6;000 ft; and I was at 18;000 ft. at this point. I was still able to use the GARMIN; but it was fading and I was beginning to wonder about its validity. I started using my backup instruments and at that point everything faded to black and I lost comms. I also lost trim and autopilot; flaps and the ability to put my gear down; which I confirmed with ZZZ Tower before I landed. I continued flying my assigned heading and altitude for what seemed like forever. Once I got back over the front range I decided that I was going to turn toward ZZZ1; an uncontrolled airport that would keep me out of any other airspace. Just as I began my descent and began a very shallow turn toward ZZZ1; Approach was able to contact me through XXX.X. I told them my intentions and they told me that they could allow that or they could get me on the ground at ZZZ2 or Runway YY at ZZZ; which I ultimately opted for. I had to make one low approach to verify my gear wasn't down; then flew a normal pattern and landed uneventfully on Runway YY after pumping my gear down. The cause of the electrical issue had to be a starter relay blocking the generators. There are two big takeaways that I have from this incident. First; trust my annunciator lights. It's not that I didn't action them; but when my troubleshooting didn't work I didn't escalate properly until things began to fail. I still might not have been able to get back to ZZZ before everything failed but I would have at least had a clearance to follow through with. The other takeaway is the technical part of how you lose all electrical in the Beech 99. If the starters are on the generators will not work. This is something that I'm keenly aware of. Of course; you turn the starter off when the engine has started. I know I did this and I verified this. I did a current limiter check; to ensure that a current limiter hadn't fallen offline. I also verified on take-off that I had no annunciator lights on. There was some discussion that I might have turned the starters on instead of the auto ignition; and this thought did pop into my head; but I do know that that's not the case. I turned the auto ignition off while I was holding short of a taxiway after landing. I remember it well because it was far out of my normal flow. I also know that when I shutdown the starters were not on. The probable cause that I was given is that somehow I knocked the starters on during climb; perhaps when I turned auto feather off. I don't recall that. But; whether or not I engaged the starters or if the relays were engaged another way; I should have paid attention to the starters as the number one possible culprit. I was so busy flipping on the battery; generators; and avionicsand changing the inverter that I didn't mind the starters.