by Anura Guruge
on July 29, 2021
This, from what I understand, applies to many of the Volvo 2022 SUVs, at least to the XC60 & XC90. There are also electric & hybrid versions of the XC40. All the petrol (i.e., gas) engines, at a minimum, will have these SMALL, dual-role electric engines called ISGs. See caption on top.
As anyone who knows electricity will tell you, an electric motor can act as a generator & vice versa, i.e., a generator can act as an electric motor. Different modalities, i.e., it has to be one or the other at any given time, but the roles are interchangable. Depends whether you are giving it power from a battery in which case it acts as a motor, or whether you are spinning it with external power, in which case it generates electric power. Volvo is cleverly exploiting this — albeit with some very fancy & intricate electronics.
ISG acts as the cars starter & generator when it has to using the main 12V battery.
There is another 48V battery that gets charged each time you hit the brakes. This electrical energy stored in this battery is used to drive the ISG when the SUV needs extra power — e.g., when starting up or accelerating. So, the ISG only acts as a motor for very short bursts of time, seconds at that (if not shorter). Rest of the time it is the car’s alternator. The 48V battery sits there getting charged when you hit the brakes. In this type of system the ENGINES is first used to slow down the SUV (while charging the battery) before the brake pads are engaged. Very clever, BUT loads more of things that can go wrong! The electronics are so intricate ….
The ISG is NOT strong enough, by itself, to drive either the front or back wheels. So, this is NOT like a proper hybrid. With Volvo’s Mild-Hybrid the internal combustion engine drives ALL the wheels that need to be driven, depending on whether it is FWD or AWD. When I first ran into Mild-Hybrid, I was spooked that I would have to rely on the ISG for my AWD. Not so. Huge relief.
