batteries for boats (hence "marine") and lawn garden tractors which are less likely to be operated in conditions where ice can form. Hot cranking amperes (HCA) is the amount of current a battery can provide at . The rating is defined as the current a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery). Reserve capacity minutes (RCM or RC) A battery's ability to sustain a minimum stated electrical load; it is defined as the time (in minutes) that a lead-acid battery at will continuously deliver 25 amperes before its voltage drops below 10.5 volts. Group size Battery Council International (BCI) group size specifies a battery's physical dimensions, such as length, width, and height. These groups are determined by the organization. Date codes In the United States there are codes on batteries to help consumers buy a recently produced one. When batteries are stored, they start losing their charge; this is due to non-current-producing chemical reactions of the electrodes with the battery acid. A battery made in October 2015 will have a numeric code of 10-5 or an alphanumeric code of K-5. "A" is for January, "B" is for February, and so on (the letter "I" is skipped). In South Africa the code on a battery to indicate production date is part of the casing and cast into the bottom left of the cover. The code is year and week number (YYWW), e.g. 1336 is for week 36 in the year 2013. Use and maintenance Excess heat is a main cause of battery failures, as when the electrolyte evaporates due to high temperatures, decreasing the effective surface area of the plates exposed to the electrolyte, and leading to sulfation. Grid corrosion rates increase with temperature. Also low temperatures can lead to battery failure. If the battery is discharged to the point where it can't start the engine, the engine can be jump started via an external source of power. Once running, the engine can recharge the battery, if the alternator and charging system are undamaged. Corrosion at the battery terminals can prevent a car from starting due to electrical resistance, which can be prevented by the proper application of dielectric grease. Sulfation is when the electrodes become coated with a hard layer of lead sulfate, which weakens the battery. Sulfation can happen when battery is