Figure 5: 2008 Toyota Prius High Voltage battery cooling system. The Hybrids and EVs that come into our bays for service all use some thermal management for their batteries. Most use " active " systems that can adapt, some use a passive (read: non-existent) system. The cooling system in mass-produced vehicles must also be able to function in any environment near to or far away from the equator. In hot climates, thermal management systems mostly operate in cooling mode. Of course, the occasional cool night will reduce the battery temperature to the point where they need to warm up, but the battery temperature rises to operational level very quickly and then require cooling for the rest of the trip. As I write this paragraph at 7am in late January, the temperature outside (50/80 miles/km North of April 2022 4 Toronto) is -32°C / -26°F. Not extremely cold but consider what happens when I jump into my son's '07 Escape Hybrid and fire it up. First, the engine starts and begins to warm up. Some Hybrids, like our Infiniti QX60 will display a message not to pull away as the " Do Not Drive...Hybrid System is warming up " at very cold temperatures. *One of the very " cool " things about Hybrids is the HV battery and one of the Motor/Generators is usually what cranks the engine to start, even when moderately cold. Hybrid motor/generators are much more powerful than a 12-volt starter and typically crank the ICE somewhere around 1000 RPM. For this reason, Hybrids usually start much easier in the cold. Cranking at that speed reduces the possibility of fuel dropping out of the air and flooding the engine. This also reduces HC emissions when the ICE fires up and begins to run on its own. MACS Service Reports Mike Bailey