4100 Battery voltage range

Does anyone know what the battery voltage range is for the 4100 series core module?

I’m assuming the upper limit is 3.6V (same as the primary power limit).

The Rabbit 4000 itself supports battery input voltage down to 1.65V, but the 4100 board has various regulators and diodes which will alter the external voltage limit.

Also, what is the minimum voltage for the SRAM to retain its memory? Perhaps this is the limiting factor?