Yamaha RX10K Assembly Manual page 61

Charging method using a constant voltage charger
YES
Charge the battery until the battery's
charging voltage is 15 V.
Measure the battery open-circuit voltage
after leaving the battery unused for
more than 30 minutes.
12.8 V or more --- Charging is complete.
12.7 V or less --- Recharging is required.
Under 12.0 V --- Replace the battery.
Measure the open-circuit
voltage prior to charging.
Connect a charger and
AMP meter to the battery
and start charging.
Make sure that the current
is higher than the standard
charging current written on
the battery.
NOTE:
Set the charging time at 20 hours
(maximum).
This type of battery charger cannot
charge the MF battery. A variable
voltage charger is recommended.
3-36
NOTE:
Voltage should be measured 30
minutes after the machine is stopped.
NO