Disabling biometrics to save power (Android7)

My Android 7 phone has the power saving feature. The max setting extends battery life by a huge amount and a lions share is saved when biometrics are disabled. Prefer a model-agnostic answer for older pre-v8 android phones, but if not possible, I have a Samsung from about 2016 iirc, with a fingerprint sensor built into the power button. The battery life estimate jumps from 9.5h on MID power save to 29h on MAX, with the contribution from disabling biometrics being +8h (only exceeded by the speed limiter at +9h) If I don't use biometrics how can I disable them permanently ? I can't find any settings entry to allow this directly. I don't want to set max power saving mode all the time to achieve this because that's very intrusive on my daily use (it stops background processing and limits which apps I can use...) So is there another way to switch off biometrics on an old android7 version? I'm thinking via developer options or via an app? I searched the settings for biometrics but it didn't turn up anything I could switch off.