For hot-swapping Talentcells, I use a Y cable into the recorder. That way the two Talentcell simply run in parallel for a bit until the 1st one is disconnected.
That way, even if the internal batts are drained, the recorder remains powered during the swap. I then disconnect the spent battery to keep it from drawing current from the fresh one due to the voltage differential between the two.
But if I know I'll be recording all day long I sometimes run two fresh Tallent cells in parallel the entire time, effectively doubling the runtime of a single one alone and avoiding the need to make the swap at all, That only works effectively if they both start out with the same state of charge.
Generally I use larger capacity Talentcells to avoid the need for swapping or paralleling in most cases, but also because I figure if I drain them less fully each time they're likely to have longer effective lifespans.