Ambient temperature refers to the temperature of the air in the room or enclosure where the charge controller— and, usually, the inverter and other equipment—is located. Heat from a working charge controller is dissipated with cooling fins convectively, or is pushed out with a fan, adding heat to the space.
Systems with sizable arrays or with the equipment housed in small rooms require that the room be well ventilated, perhaps even actively with an exhaust fan. Too much heat can affect efficiency or damage the controller.
Equalization is a controlled overcharge of a battery bank. Battery cells are not precisely equal and will come to have different states of charge. The only way to bring them all back to an equal state is to periodically give the whole bank an overcharge.
Generally, flooded lead-acid batteries require this treatment every five to seven deep discharges (50% or more of capacity), or every two months, whichever comes first. The beginning of winter is a good time to do an equalization, as it will prepare a battery for the deeper cycles normally found at this time of year. Equalization also helps mix the electrolyte after watering the batteries, and helps remove old sulfate crystals from the plates. Some types of batteries (sealed) can be permanently harmed if they receive higher-voltage equalization.
Among the featured controllers, the C series products from Xantrex and all the controllers from Apollo, OutBack, and Morningstar offer both manual and automatic equalization. The other controllers offer only manual equalization.
Effective battery equalization requires a larger array than most systems have, so owners often equalize from an external charge source like a generator or the grid.