So I'm curious if there's someone who may know what's going on here. I have a 2010 Zero DS electric motorcycle which I love but it developed a glitch/cutout at times at 1600 miles. If I let the bike sit for 3 minutes or so it would work. I narrowed it down to what I believe is the contactor which I pulled the battery pack out to access. The stock contactor is rated for 48v and 200AMPS continuous. I called ALLTRAX since I was doing some tuning on their controller and they recommended getting a 400AMP contactor. When I took the contactor apart I could see arching and pitting on the disc which would cause resistance. I ordered a 48V 400AMP contactor but I just took a voltage reading from the pack and the pack is reading 56volts @75% SOC. So why would Zero put a 48V contactor in on a bike where the battery has higher V's? The next contactor up in V's is 72V. Is it better to run a 72V contactor or am I find with the 48V contactor? Update: Looks like if you have a contactor that's rated lower than your battery voltage the contacts can weld and the contactor will then always be on, if the contactor is over your voltage it then may disengage when the voltage drops below the required amount to make the contact. From the Alltrax website and pdf on contactors: "The coil voltage rating is important – use the correct contactor voltage rating! Using 24 volts to drive a 48 volt coil does not generate the required force necessary to hold the contacts in place during operation. Too much voltage will burn – or cook - the coil wiring of which the contacts may not separate when turned off. Contactor plunger binding or self arcing will cause controller failure. Choosing the correct current rating of a contactor is just as critical as choosing the right size wire for the motor and battery connections. The carrying current is determined by the size and plating of the contacts inside of the contactor. "