The first thing to do is determine the Constant Discharge Rating (CDR) of your battery. This measurement will be in Amperes (Amps for short) and is a measure of how much strain you can place on a given cell.
You can also do the simple equations. But calculators help learn it.
Put 4.2 volts as voltage Coil resistance as ohms/resistance and push calculate
And, just make sure that Amps/current/amperes is lower than the CDR mentioned above.
Mech mods will need maintenance. Basically cleaning up the contacts from the gunk that forms. Products like deoxit gold, or conductive grease (noalax, no ox id) will extend time between maintenance sessions.
Sometimes things wiggle loose etc. If ever you push fire, and nothing happens. Log in here and ask for troubleshooting, and blame fatman