Yamaha 2011 WR250FA Owner's Service Manual page 122

• The charge state of an MF battery can be
checked by measuring its open-circuit voltage
(i.e., the voltage when the positive terminal is
disconnected).
• No charging is necessary when the opencir-
cuit voltage equals or exceeds 12.8 V.
b. Check the charge of the battery, as shown in
the charts and the following example.
Example
Open-circuit voltage = 12.0 V
Charging time = 6.5 hours
Charge of the battery = 20–30%
A. Relationship between the open-circuit
voltage and the charging time at 20 °C
(68 °F) (These values vary with the tem-
perature, the condition of the battery
plates, and the electrolyte level.)
B. Open-circuit voltage
C. Charging time (hours)
D. Time (minutes)
E. Charging condition of the battery
F. Ambient temperature 20 °C (68 °F)
a. Charging
b. Check the open-circuit voltage
5. Charge:
• Battery
(refer to the appropriate charging method il-
lustration)
Do not quick charge a battery.
• Never remove the MF battery sealing caps.
• Do not use a high-rate battery charger
since it forces a high-amperage current
into the battery quickly and can cause bat-
tery overheating and battery plate dam-
age.
• If it is impossible to regulate the charging
current on the battery charger, be careful
not to overcharge the battery.
• When charging a battery, be sure to re-
move it from the machine. (If charging has
to be done with the battery mounted on the
machine, disconnect the negative battery
lead from the battery terminal.)
• To reduce the chance of sparks, do not
plug in the battery charger until the battery
charger leads are connected to the bat-
tery.
• Before removing the battery charger lead
clips from the battery terminals, be sure to
turn off the battery charger.
• Make sure the battery charger lead clips
are in full contact with the battery terminal
and that they are not shorted. A corroded
battery charger lead clip may generate
heat in the contact area and a weak clip
spring may cause sparks.
• If the battery becomes hot to the touch at
any time during the charging process, dis-
connect the battery charger and let the
battery cool before reconnecting it. Hot
batteries can explode!
• As shown in the following illustration, the
open-circuit voltage of an MF battery sta-
bilizes about 30 minutes after charging
has been completed. Therefore, wait 30
minutes after charging is completed be-
fore measuring the open-circuit voltage.
3-47
ELECTRICAL