Hach-Lange DR 2800 eco - Manual (Page 112)

110
Maintenance
7.2.1.4 Loading the battery/Operating time
The time required to charge a newly installed battery is about 3.5
hours.
Operating time of a fully charged battery:
Charge: If a battery is charged to 100% capacity, and the user
carries out 10 measurements per day, and the instrument is left on
after each measurement for the full 15 minutes before it
automatically switches off, the battery can be used for 6 to 7 days
before it needs recharging.