My incessant, often asked question is so esoteric that it's probably not appropriate for your review.
When descending a grade in a non-hybrid car, smart drivers use engine braking to prevent having to ride the brakes all the way down.
However, Honda's i-MMD hybrid system doesn't have a way to perform engine braking. When an i-MMD hybrid decelerates, the traction motor switches to become a generator, which slows the car as it generates power to recharge the battery.
The big question come up when the battery is fully charged. Honda's engineers had to come up with another way to provide a form of pseudo engine braking that did not involve charging the battery.
A paper Honda engineers wrote about the operation of the Honda's Accord Hybrid's i=MMD system explains that when the battery is fully charged the power from the traction motor (still acting as a generator to slow the car) is directed to the starter motor/generator instead of the battery. The starter motor/generator then spins the engine operating in a resistance mode, where the engine's valves are kept closed and no fuel is supplied.
However, Clarity PHEV drivers decelerating when the battery is fully charged have noted that the car starts its engine! How can the running engine use up electrical power generated by the traction motor as it slows the car? The starter motor/generator is still the only plausible destination for the excess energy the battery cannot accept.
The only theory I can come up with is that the heavier Clarity needs to burn off more energy than the lighter Accord when descending so, at the expense of burning fuel, the Clarity PHEV reverses the action of the starter motor/generator so it burns up more energy than the Accord Hybrid's dead-engine scheme by opposing the torque of the operating engine.
A few drivers on this forum have said they purposely do not fully recharge their batteries simply to provide headroom for the battery to accept regenerated power when decelerating without having the car unceremoniously start its engine. Somehow that doesn't seem right. However, it also doesn't seem right to reduce the Clarity's efficiency by burning fuel to use up excess regenerated power.
Too esoteric a question? OK, why does the rear-seat fold-down armrest in US Claritys have a cover over the cup holders, but the Canadian Claritys have no cover? Does Honda expect those Canadian rear cup holders will always be in use, making the cover superfluous?
