At zero temperatures the starting ability of a battery is reduced to one-half its normal capacity, and its internal resistance proportionately increased. In other words, a battery that will crank the engine for five minutes at normal temperatures, will only crank it 2 1/2 minutes at zero temperatures, and only about half as fast. In addition, the amount of daylight driving is considerably reduced. Also due to congealed oil, the engine is stiff and requires considerably more power to turn it over. These conditions often result in a battery becoming partially or fully discharged.
When trouble of this kind is experienced, the remedy is to increase the generator charging rate by 3 to 5 amperes.
Do not use the ammeter on the instrument panel to adjust the generator charging rate. A master ammeter must be used for this purpose. (K. R. Wilson of Buffalo, N. Y., furnishes a device of this kind.)