Just desoldered the Tempest battery, and hardwired the SOL to the + side of the battery connector on the PCB…and the SOL - side to the ‘spare’ GND on the PCB.
I had stare at the card-view of the Battery (3.31v). . .for a couple of moments; thought I was dreaming! That’s very impressive to see that kind of voltage on a Tempest (with the aid of the swapped-out batteries). So used to seeing 2.64v ; 2.82v etc. . . 3.31v was very refreshing!