How do I temperature compensate my voltmeter readings?

If you are using a digital voltmeter, make the adjustments in the table below. For example, at 30° F (-1.1° C), the voltage reading would be 12.53 for a 100% State-of-Charge. At 100° F (37.8° C), the voltage would be 12.698 for 100% State-of-Charge. For sealed batteries, measure the Open Circuit Voltage across the battery terminals with an accurate digital voltmeter. This is the only way to determine the State-of-Charge on sealed, non-accessible batteries.

Table 3 - Voltmeter Temperature Compensation

Temperature Add or Subtract to Hydrometers Reading Add or Subtract to Voltmeter Reading
0°F / -17.8°C -.032 -.192
10°F / -12.2°C -.028 -.168
20°F / -6.7°C -.024 -.144
30°F / -1.1°C -.020 -.120
40°F / 4.4°C -.016 -.096
50°F / 10°C -.012 -.072
60°F / 15.6°C -.008 -.048
70°F / 21.1°C -.004 -.024
80°F / 26.7°C 0 0
90°F / 32.2°C +.004 +.024
100°F / 37.8°C +.008 +.048
110°F / 43.3°C +.012 +.072
120°F / 48.9°C +.016 +.096
130°F / 54.4°C +.020 +.120
140°F / 60.0°C +.024 +.144
150°F / 65.6°C +.028 +.168
160°F / 71.1°C +.032 +.192