I replaced a contactor in the upper battery. I have the write up on the Facebook group for the Focus EV. Anyway, the individual contactors are a Kilovac EV200A1ANA. You can find them used on eBay for $50. I got mine new on eBay for $130 or so. I don't know if they are all the same because I didn't pull apart my lower pack, but I'd bet they are. There are some cheaper new ones from China, but I was a little hesitant to go that route. Retail, they are about $250 each. If you have forscan, it will likely say that the positive contactor is stuck open or closed. P0AA0. I would clear the error and retry starting the car a few times to make sure you get just that code. I think I also got a P0A95. At times I got more errors, but I think that sometimes other error codes can get thrown. But the positive contactor in the upper battery pack is the one that usually fails.