2011 Chevrolet Volt Owner's Manual - Page 385

Vehicle Care 10-19 Cooling System (High Voltage Battery) During vehicle operation and also during charging, the high voltage battery cells in the vehicle are kept within a normal operating temperature range. If the temperature rises above this temperature, the battery cooling system turns on the air conditioning compressor and cools the coolant until the correct temperature is reached. If the temperature falls below this temperature, a high voltage heater, located in the battery, heats the coolant until the correct temperature is reached. What to Use The high voltage battery coolant reservoir in the vehicle is filled with a 50/50 mixture of DEX-COOL engine coolant and deionized water. If using this mixture, nothing else needs to be added. Checking Coolant The vehicle must be on a level surface when checking the coolant level. The high voltage battery coolant reservoir is located on the passenger side of the engine compartment. See Engine Compartment Overview on page 10‑10 for more information on location. Check to see if coolant is visible in the high voltage battery coolant reservoir. If coolant is visible but the coolant level is below the cold fill line, there could be a leak in the cooling system. The high voltage battery coolant should only be serviced by a qualified technician.