Regenerative braking is integral to hybrid and electric vehicles - but it just isn't a big part of the service story
With the advent of gas-electric hybrid and fully electric vehicles, and their increasing on-road presence, the associated energy management and capture systems have become a major element in automotive servicing. One element of hybrid technology, the slightly misnamed “regenerative braking,” enables the energy normally dissipated during braking in the form of heat to be recaptured as electrical energy that can be used to recharge a hybrid’s or EV’s storage and 12-volt battery systems.
The design of regenerative braking systems takes advantage of the fact that electric motors and generators share design elements. Regenerative braking converts the vehicle’s electric motor into a generator. When the brake pedal is applied, the vehicle’s regenerative circuit triggers the motor to operate in reverse, opposing the motion of the wheels and slowing the vehicle down. (Interestingly, an article written in the 1920s described regenerative braking — then used on railways and streetcar systems — as “electronic speed control.”) The electricity generated during this process is used to recharge the vehicle’s storage battery and is also stepped down to charge the vehicle’s 12-volt system.
Regenerative braking reduces energy waste. It also significantly cuts down the amount of wear and tear on the components of the vehicle’s hydraulic braking system, which is still very much required, not only because the braking effect of a regenerative system drops off at lower speeds, but also because regenerative braking can only be applied to powered wheels. So traditional friction braking, with all its added weight, complication and waste of energy, is still required to ensure all wheels — powered or not — have braking ability, to provide braking at all speeds, and to serve as a backup to the regenerative system.
From a servicing perspective, regenerative braking systems are definitely low-profile, says Hayato Mori, manager of Product Planning for Honda Canada. “There’s nothing to really touch in a regenerative system,” he says. “The term ‘regenerative braking’ is almost a misnomer because it makes it sound like there are special brakes involved — and of course there aren’t. From a servicing perspective, the generator may require servicing depending on how it’s being used and how long it’s been on the road, but there’s no additional braking mechanism in the wheel or suspension that requires special servicing.”
While regenerative braking systems require less servicing than traditional braking systems, the fact that they are relatively “hands off” — added to the fact that they reduce wear and tear on braking components — can lead vehicle owners, as well as service technicians, to underestimate the need for regular service. This at least has been the experience of Ed Jagt, owner of Pro-Tech Tire & Auto in Barrie, Ontario.
“Most of my customers who are Prius owners, I’m lucky to get them in for every other service stop that’s recommended in the manual,” Jagt says. “They’re putting too much faith in the hybrid system, and not putting enough into the old-school mechanical part of it.” The servicing still needs to be done, Jagt says, whether or not the components are being worn as fast.
“It’s not unusual to get anywhere from 150,000 to 250,000 kilometres from a set of friction materials” on a vehicle that has regenerative braking, says Al Playter, who teaches in the Automotive and Motorcycle Programs at Centennial College in Toronto. “However, because there’s less usage of the brakes, the technicians have to take extra care to make sure all the moving parts are serviced properly. So service becomes essentially doing a normal brake job but with the difference that you’re not putting parts in.”
Playter says that quality garages will disassemble the brake parts at the prescribed service intervals — regardless of their state of optimism about the virtues of regenerative braking, and of course assuming that the vehicle owner bothers to show up — and make sure that the front brake calipers are clean, properly lubricated and moving properly. “You’re doing what’s normally done in a brake job where the rotors or drums in some cases are replaced or machined. The tech now needs to do that but without assuming that replacement will be part of it. They’ll be putting the parts back together a lot more often.”
But Playter is quick to note the flip side of that equation. “Shops shouldn’t assume that the regenerative braking is taking such a burden off the friction materials that they don’t have to worry. The hydraulic brakes absolutely do need to function.”
As for problems within the regenerative system itself, Playter says these generally have to do with the stator in the generator, as the rotor component consists of a simple magnet, which is only susceptible to direct physical damage, which is unlikely, and not much else. The stator, on the other hand, consists of wiring and connections that can become loose.
But in most cases it’s just not practical to fix the problems that can plague regenerative systems, Playter says. “It’s just more practical to replace the system. But as for the actual motor/generator, if that had to be repaired — which isn’t a usual service item — you’d have it repaired at a shop that does heavy-duty electrical repairs like elevator motors, large industrial motors. That’s way out of the realm of the average technician.”
Jagt recalls the early days of regenerative systems, when shops like his were able to get inside the works of regenerative systems such as those on the early Honda Insight. Those days are gone, he says, and now everything is sealed up. But he takes pride in being a one-stop shop, and has been proactive about getting his techs up to speed on hybrid technology, ensuring for example that they have attended the Automotive Career Development Center (ACDC).
When it comes to work on regenerative braking units, however, so far Jagt and his technicians have only been called on to fix loose connections. Beyond that, the solution is replacement, and Jagt says rebuilt systems are so hard to find in Canada that he usually has to order from south of the border. Also, industry experience with the technology is still pretty thin in this country. Jagt has found only two other Canadian shops — one in Red Deer, Alberta and one in Surrey, B.C. — that he can share information and experience with.
Al Playter sees regenerative braking systems as occupying a niche similar to alternators and starters, and says that this will limit the ability of most shops to add them to their repertoire.
“In our business now there are very few people who overhaul alternators or starters,” he says. “Sure, we show students how to take them apart, but when you overhaul a starter or alternator in the shop, you pick up the phone and ask someone to send you one. Doing the actual work isn’t economical from anybody’s point of view.”
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