The batteries that come wi th the spark plug should not be used :(

[architectus]

beware the batteries that come with the spark plug, I was using mine and it almost blew up on me, so now I have to wait to get some real batteries before I can use it again , if anyone else buys this mod ( I like it by the way), buy protected to use with it, the unprotected batteries it comes with are a little dangerous

 

[oldsoldier]

Yes it is important to use protected batteries or the lifepo4 batteries that have a safer chemistry. Do not use unprotected batteries even in a 3.7v (unstacked) application they can and will explode.

Unprotected batteries are BAD: