Battery Open-Circuit Voltage Test; Battery Load Voltage Test - BMW 5251 Service Manual

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Battery, Starter, Alternator
Table b. Specific gravity of battery electrolyte at
27°C (80°F)
Specific gravity State of charge
1.265 Fully charged
1.225 75% charged
1.190 50% charged
1.155 25% charged
1.120 Fully discharged
if the specific gravity is at orabove 1.225, butthe battery lacks
Dower for startinq, determine the battew's service condition
with a load volta& test. if the average specific gravity of the
six cells is below 1.225, remove the battery from the luggage
compartment and recharge.
Battery open-circuit voltage test
Before testing, load battery with 15 amperes for one minute
with battery load-tester or turn on headlights for about one
minute without engine running. Connect digital voltmeter
across battery terminals. Open-circuit voltage levels are giv-
en in Table c. Open-circuit voltage and battery charge.
If open-circuit voltage is OK but battery still lacks power for
starting, perform a load voltage test.
If open-circuit voltage is below 12.4 volts, recharge battery
and retest.
Table c. Open-circuit voltage and battery charge
Open-circuit voltage State of charge
12.6 V or more
12.4 V
12.2v
12.0
v
Fully charged
75% charged
50% charged
25% charged
11.7Vorless Fully discharged
Battery load voltage test
A battery load tester is required for a load voltage test. The
test is made by applying a high resistive load to the battery
terminals and then measuring battery voltage. The battery
should be fully charged forthe most accurate results. The bat-
tery cables must be disconnected before malting the test. Re-
place the battery if the voltage is below that listed in Table d.
Battery load test
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minimum voltage.