This would be a bad approach, because you are essentially trying to brute force your way around a roadblock (no supported open data format) the supermarket intentionally designed. It would be easy for them to block your bot with Captchas, rate limits or IP blocking or just sue you.
The CMOS battery has maybe 100mA and lasts 5 years. A laptop battery has at least 400x the capacity, it would not drain in a few days.