Just a bit of a thread revival.
I'm still using my E-cig but after problems with my variable voltage "Smok" battery unit not lasting all that long I decided to upgrade as I'm not going back to cigarettes now.
I decided to buy an "Itaste MVP V2.0" battery unit which I have to admit is fantastic so far. Not a cheap unit at £40 but well worth it for all it's great features (listed below).
This is what it looks like below.
This is one of the largest, if not the largest capacity batteries you can buy at 2600 mAh.
It features: variable voltage (3.3-5 volts), variable wattage (6-11 watts), an ohms meter, puff counter, battery level indicator, 10 second auto cutoff (in case accidentally switched on), built in illuminated display, remembers last set voltage/wattage, compatible with most clearomizers, over discharge protection, short circuit/atomizer protection, passthrough, includes charger, choice of clearomizers, beauty ring and it can be used as a mobile battery unit for charging MP3 players, cameras, phones & basically anything that charges using a mini USB unit.
So in summary if you're looking to upgrade your battery then this is well worth considering imo.