BOLT 3895151 - Caterpillar

Machine Charging System Recommendations
In order to limit the alternator voltage to a safe value a voltage regulator is included in the charging circuit. The primary function of the regulator is to provide control of the output voltage to maintain the battery at a proper state of charge.Many voltage regulators are temperature compensated. The system voltage is decreased as the temperature increases and conversely increases as the temperature decreases. Normal settings are adjusted for approximately 25 °C (77 °F) temperature. The purpose of this adjustment is to compensate for the charge acceptance characteristics of the battery, which varies with temperature.The voltage regulator setting can influence the service life and performance of the battery.Settings that are too high result in overcharge and reduced battery life. Settings that are too low result in undercharging, reduced performance and eventually a discharged battery.The voltage regulator should be checked every 10,000 miles, or 2,000 hours, or every time the oil is changed. The battery should be checked immediately if the battery is hot to the touch, or if the electrolyte is bubbling or spewing from the battery vents. This is evidence of the battery being overcharged.Caterpillar Battery Charging Parameters
Maximum charging volts for a 12-volt battery vs. temperature for lead acid batteries, utilizing an alternator.
Table 2
Temp °C     Temp °F     Maintenence Free     Low Anti-Mony     Hydrid     AGM     GEL    
Max. Voltage Max. Voltage     Max. Voltage     Max. Voltage     Max. Voltage    
>52     >126     12.94     12.64     12.64     12.64     12.64    
41-52     105-126     13.32     13.02     13.02     12.90     12.80    
26-40     78-104     13.80     13.50     13.50     13.02     13.02    
20-25     68-77     14.10     14.10     14.10