Fancy a bigger battery? We currently stock the eGo 900mAh battery which will suit your eGo/Tank/510 atomisers and cartomisers.
This battery gives around 1 day of use to the "average" user. Obviously this varies hugely and someone using 10ml e-liquid per day is likely to get a lot less time out of the larger batteries.
One thing you can be sure of is that they will provide a longer charge than the standard eGo and 510 batteries.