Hitachi ZW 310-6 Operator's Manual page 217

Using Booster Batteries
IMPORTANT: The machine electrical system is a 24 volt
negative (-) ground. Use only 24 volt booster batteries
with sufficient capacity.
d
WARNING:
 An explosive gas is produced while batteries are in
use or being charged. Keep open flames and sparks
away from the battery area. Do not continue to use
or charge the battery when electrolyte level is lower
than specified. Explosion of the battery may result.
 Park the machine and a machine with the booster
batteries on a dry or concrete surface, not on steel
plates. If the machine is parked on steel plates, the
machine is equivalent to a continuously grounded
machine so that dangerous unexpected current flow
may result.
 Never connect a positive terminal to a negative
terminal, as a dangerous short circuit will occur.
If the machine batteries are completely discharged so that
when starting the engine using booster batteries is necessary,
do the following procedure.
OPERATING THE ENGINE
3-9
SA-032