I've had a vamo v3 for a long time -- that thing is a tank man i keep it as my backup in case one of my higher wattage mods break and I need to wait on a replacement -- The battery showing low when its not could mean a couple things maybe you want to try some troubleshooting?
1) the battery is bad -- try getting a couple new batteries that are rated well and don't have the protection board built in to them
2) the spring isn't making a good connection -- try pulling it apart slightly so it has a better connection
3) is there a sticker, wrap, dirt, or something keeping the extension tube from connecting well? scrape it around the threading a bit to clean it off.
1) the battery is bad -- try getting a couple new batteries that are rated well and don't have the protection board built in to them
2) the spring isn't making a good connection -- try pulling it apart slightly so it has a better connection
3) is there a sticker, wrap, dirt, or something keeping the extension tube from connecting well? scrape it around the threading a bit to clean it off.