Volvo 2007 S80 Owner's Manual page 202

Never disconnect the battery when the engine is running (for example, when replacing the battery).
The service life and function of the battery is influenced by factors such as the number of starts, discharging, driving
style, driving conditions, climatic conditions etc.
Never use a quick charger to charge the battery.
WARNING
Never expose the battery to open flame or electric spark.
Do not smoke near the battery.
Battery fluid contains sulfuric acid. Do not allow battery fluid to contact eyes, skin, fabrics or painted surfaces. If
contact occurs, flush the affected area immediately with water. Obtain medical help immediately if eyes are affected.
NOTE
The life of the battery is shortened if it becomes discharged repeatedly.
208
06 Maintenance and specifications
Battery
Maintenance
Regularly check that the electrolyte level is correct
Check all cells. Use a large screwdriver or a coin to remove the cell caps. Each cell has its own maximum and
minimum level mark.
If necessary, top up with distilled water to the battery's maximum mark.
Tighten the cell caps thoroughly.
CAUTION
Always use distilled or deionized water (battery water).
Never fill above the level mark in the cell.
Changing
and never fill above the level mark.