Ill throw out one possible explanation on how the HV estimated range can drop a few miles while driving in “EV”.
As an aside,
@insightman correctly reminds us, there is no pure “EV Mode” we can select. And to add to the confusion, Honda uses Drive Mode to describe Econ, Normal (which doesn’t even have a button and is just being in neither Econ nor Sport), and Sport which all can be used to modify the 3 propulsion or power sources of EV, HV and, HV Charge. And again, like the Normal Drive Mode, EV has no button and is actually achieved by being in neither HV nor HV Charge. I’m still a little confused by the way Honda chose to define and implement all this even after 2 years and
@insightman ’s tutelage. Fortunately it all works fine since the car’s programming doesn’t care about how Honda mangled the manual on all this.
I bring all that up to remind us that you can’t put the Clarity into a pure EV state that prevents the ICE from ever turning on even if you don’t go past the click/detent in Econ Drive Mode (or the pre-click/detent advanced point in Normal or Sport).
Even when driving in what most call “EV mode”, the ICE can come in for various reasons such as heavy use of climate control, temperature extremes, extremely low high voltage battery SOC, and System Checks. While it’s not mentioned in the manual, there is also a well documented “Regen limited by a full battery so ICE comes on to somehow protect from over charging” scenario. And then throw in the fact that once the ICE comes on, it’s programmed to stay in until it reaches operating temperature. Also, the System Check can even cause the ICE to stop and restart on occasion.
In your description, I would conjecture that a System Check may have occurred. I drive ~95% in EV, and have noticed that every month or two, my ICE will come on for for just a few minutes (2-4) for no apparent reason and when the battery is not fully charged so it can’t be the limited regen/ICE start scenario. I attribute these short and infrequent ICE runs to be System Checks which are keeping the ICE lubed and ready to instantly start whenever called upon. When this happens, I lose a couple of miles of HV range and since it’s only at idle or near idle rpms, it’s very easy to not even notice it until you see the HV range drop.
I have observed the following when this happens and you can be on there lookout for these indicators next time.
The EV indicator will not turn off even though the ICE is running. The small engine icon in the center screen Power Flow Monitor will indicate, but again it’s easy to miss since it’s small and just lights up a little more, and you have to have that display called up. The only real indicator I’ve found of a System Check is that the Power/Charge Gauge will turn completely white with no blue and stay that way until you restart the car even when the ICE has turned off and you’re back to driving solely on the battery.
On two occasions, I’ve noticed my HV range drop a few miles when I’ve sworn the ICE had not come on. However the hour meter I installed on the engine had incremented for one of these and since it only reads down to tenths of an hour, it may have missed the other. That’s not to say that the HV range can’t change without an ICE start, as in the fuel probe reads the gas level a little differently. It just seems that for my car any reduction in HV range is always accompanied by an ICE start or a fuel addition in the case of a gain.
Next time it happens, be on the lookout for the Power/Charge Gauge turning all white but you will have to notice it before you turn off the car. In any event it’s not something to worry about.
