Having 4 of these scopes sometimes working on projects and then they are not being used for
a few month, the batteries never lasted really long for me. I don't think I ever got fifty
cycles out of a new TEK battery.
I used to buy the original TEK batteries from Allied electronics in the US, since they had the best price.
But even that got too expensive and finally I modified mine to hold 4 Type C rechargeable batteries.
There is a company on ebay Germany that offers the modification.
But I have no idea how good they are or hwo they do it in detail.
ebay auction number: 171053081107