When you look for a battery, look for the rated 'mah' of the battery. The mah stands for milliamp/hours, and speaks of the capacity of the battery. You will probably want to find a battery with a higher mah rating. This will, though, mean you have a physically larger battery. Any of the ego-style
batteries will work, as long as they have the 808 threading. You can use batteries such as the ego batteries, the e-power batteries, or any other, as long as they have the proper threading. You may have to use an adapter, such as a 510 to 808 adapter for the ego batteries. Just look for more battery capacity and you will have longer battery life. Now, you are open to many types; you leave the realm of stick-type batteries.