HP-34C external battery charging

[Steve Simpkin]

(12-06-2017 09:16 AM)Frido Bohn Wrote:  To my knowledge, the Spice series is not critical to be operated without batteries that buffer the power coming from an adapter, as it was the case in the Woodstock series. However, I personally favor the workaround of a transplant with an up-to-date battery pack because you are more flexible without the power cord being attached all time.

No, I believe the Spice series has the same type of charging circuit design as the Woodstock series so it shares the same problem of potential damage to the calculator if using the changer without batteries installed.
My HP-33E/33C Owner's Handbook (April 1979) has the following warning on Page 76.

"Note: Do not attempt to operate the calculator from the ac line with the battery pack removed."