BATTERIES
Battery Testing – 8 Volt
16
Interpreting the Results of the Hydrometer Test
The approximate state of charge can be determined from the following table:
SPECIFIC GRAVITY (TEMPERATURE CORRECTED)
APPROXIMATE
STATE OF CHARGE
1.250-1.280
100%
1.220-1.240
75%
1.190-1.210
50%
1.160-1.180
25%
If the difference between the cells is 0.020 or more, the low cell should be suspected. It may require a catch-up
charge or it may be a weak cell. When the variations between cells reach 0.050 or more, the battery with the low
cell should be replaced.
CORRECTED SPECIFIC GRAVITY
VEHICLE
NO.
BATTERY
NO.
ELECTROLYTE
TEMPERATURE
CORRECTION
FACTOR
CELL 1
CELL 2
CELL 3
REQUIRED
ACTION
12
1
20 °F (-6.6 °C)
– 0.024
1.275 –0.024
= 1.251
1.280 – 0.024
= 1.256
1.280 – 0.024
= 1.256
Sound Battery –
Fully Charged
35
6
90 °F (32.2 °C)
+ 0.004
1.155 + 0.004
= 1.159
1.165 + 0.004
= 1.169
1.160 + 0.004
= 1.164
Discharged
Battery –
Recharge
54
3
50 °F (10 °C)
– 0.012
1.260 –0.012
= 1.248
1.200 – 0.012
= 1.188
1.270 – 0.012
= 1.258
Bad no. 2 Cell
69
5
80 °F (26.7 °C)
0.000
1.250 – 0 =
1.250
1.255 – 0 =
1.255
1.230 – 0 =
1.230
Weak no. 3 Cell –
Catch-up Charge
38
2
100 °F (37.8 °C)
+ 0.008
1.200 + 0.008
= 1.208
1.180 + 0.008
= 1.188
1.170 + 0.008
= 1.178
Discharged
Battery –
Recharge and
Recheck
22
4
80 °F (26.7 °C)
0.000
1.240 – 0 =
1.240
1.245 – 0
= 1.245
Float does
not rise
no.3 Cell Dead –
Replace Battery
2009 Electric Precedent Maintenance and Service Manual
Page 16-11