Tellermate T-ix Battery Varta Ezpack EX We have customers who have used the same battery for over a year. The optional Lithium-Ion battery is similar to the battery in your mobile phone and how long it lasts can be determined by how to you use it. Rechargeable batteries degrade with use. Li+ batteries last longer if not deeply discharged (depleted) before recharging. The smaller the depth of discharge, the longer the battery will last. The best practice to get the maximum life out of your battery is to plug in your Tellermate unit to charge each day when you finish using it.