Is it ok to change out batteries mid roll on Pentax 645 and Bronica ETRS?

Pentax 645 bodies use lithium battery(CR1220?) that goes into a separate compartment at the bottom of body.
The manual says CR1220 is for remembering the film speed and # of shots taken in case the AA batteries in the grip needs change mid roll.
But I haven't installed this lithium battery and started shooting using the main AA batteries.
Does anyone know what happens if I take the AA batteries out mid roll when the lithium battery haven't been installed?
Film speed can be reset but I thought the exposure count might get messed up.
I was also curious about the same thing on Bronica ETRS.

No problem on a Bronica ETRS; the battery is only for the shutter.

I have never had a problem changing batteries mid roll with any camera. I have do this many times when I worked as a camera salesman.

Of course one gets what one pays for with this website.

hsandler said:

No problem on a Bronica ETRS; the battery is only for the shutter.

Click to expand...

… and -in some cases- for the metering finder prism - no problem at all.