Yamaha EF2600FW Owner's Manual page 32

Operating range of DC power supply
(exclusively for charging 12 V battery)
This power source is designed to charge batteries up
to 40 Ah that are half-discharged.
Do not charge batteries of a higher capacity than 40
Ah.
12 V battery
The time required for recharging a battery varies
depending on the discharge level of the battery. When
the specific gravity of the battery reaches 1.26 to 1.28,
charging is complete.
When charging, check the battery's specific gravity
once an hour.
The average time for charging a half-discharged 40 Ah
battery is approximately 5 hours.
Be sure to check the battery fluid level before charg-
ing.
NOTICE
9 Do not connect any load to the battery or use
the engine starter motor while charging.
This causes high current to flow through the
generator which will burn out the coil.
9 Do not connect a VRLA (Valve Regulated Lead
Acid) battery.
To charge a VRLA battery, a special (constant-
voltage) battery charger is required.
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