Ok. Spring loaded pins in the tube? That would be very difficult to manufacture inside the tube of the light. And I'm not talking about lights with battery carriers. I'm just talking a simple tube with a switch at the tail and a head at the other end. I think you're over worried about cell balance though. I use almost exclusively Incan lights. Some draw a lot of power. Never a problem of cell balance. A tenth of a volt or so doesn't matter. And I don't even have low voltage protection. With incans it's easier because I can see when the batts are dead. If an led light takes 2x18650 and lvp of 6v. If one cell is 2.9V and the other is 3.1V it's still not a problem