My second Fandyfire UV-S5….ie skyking from FastTech just arrived and it was D.O.A .First one worked well and was given away as gift.One of the springs in the battery holder was 2-3mm higher than the others,making the one battery make contact first.I have a Sky-Ray King around also so I tried screwing its battery compartment unto the led/emitter of the UV-S5 thinking that may work ,but nothing.If someone could tell me something to try or how I could check the led of the UV-S5 to see if they might be bad I would appreciate it.I’m not even sure how to take one apart to check it.
Thanks 
how to do the paperclip thingy. i’m using a wire on a Sky-King.
Ok, place the positive part of the battery on the ring in the middle. Then you take the wire from the negative end of the battery to the body of the head.
light…it does not!! No spark either,pushed on/off button no difference.Actually when i tried this on a working “King” ,nothing happened either.
Just email them, I am sure they will send you a replacement. They seem to be on top of their game. Just got an email follow up on an order that I placed. They wanted to know how my purchase was working out for me. Nice touch of customer service!