Hi,
Your Varta battery is of 1.5v instead of 1.35v.
As analox suggested, you may try to check the accuracy of the shutter at 1/15 and below.
Else, for cheaper option you may need to self compensate the f-stops during low light or night shots.
Example if you night shots is constantly over by 2 stops, then you need to reduce by 2 stops to have correct exposure.
Note :
Anyway, for film the tolerance for over expose is pretty good compared to under-expose.
Even up to 2 stops should not be of any issue unless you are using slides.
Your Varta battery is of 1.5v instead of 1.35v.
As analox suggested, you may try to check the accuracy of the shutter at 1/15 and below.
Else, for cheaper option you may need to self compensate the f-stops during low light or night shots.
Example if you night shots is constantly over by 2 stops, then you need to reduce by 2 stops to have correct exposure.
Note :
Anyway, for film the tolerance for over expose is pretty good compared to under-expose.
Even up to 2 stops should not be of any issue unless you are using slides.