”Don’t Fear The Zero!”

Fast Eddie B

Fast Eddie B

Well-Known Member
One great thing about the Clarity is the way you can “fine tune” battery use as desired, by deciding when to go to HV to maintain battery reserve beyond the built-in reserve Honda engineered into their design - usually seen as “two bars”.


We often drive right around 100 miles between our two homes, one in N GA and one in E TN. And on occasion, even local drives can slightly exceed our EV range. We settled into a pattern of switching to HV mode when we had 10 miles of EV range remaining, then switching back to EV mode about 10 miles from home trying to time it to hit zero as we pulled into our driveway.


But recently we’ve tried just letting EV run down to zero in situations like that. For instance today’s trip back to E TN let us go 54 miles on EV before hitting zero, and allowing the car to do the hybrid thing on its own after that. And it works just fine, even with the rolling terrain here in the Southern Appalachians. Neither one of us can sense anything untoward going on doing it that way. As I posted to Facebook earlier, the car does not suddenly morph into an angry bee pumpkin when you hit zero EV miles.


The only caveats...

1) I would not do this if I had mountains to climb enroute - I would then choose to hold onto at least 10 miles of EV range - maybe more with really serious mountains in the plan.

2) On long road trips where charging isn’t likely, I tend to just run in HV, keeping maximum EV range until close to a charging stop.


Anyway, my point is there’s no practical reason to studiously avoid zero EV miles - Honda’s done a darn good job of engineering a system where it’s pretty hard to do anything “wrong”.
 
I’ve been wondering for a while - what’s the best way to handle mountains? HV mode on the way up (with a healthy amount of battery, say 50%)? I wonder because in theory HV mode should try to maintain a certain battery % which might cause the engine to work very hard on the way up.
 
I have hills that engine rpm goes over 4000, especially when using the heater.

I do an HV reset, and the car goes back into gear drive mode.

Uses the available battery, with full use of the gas engine, but never have to experience the noise of high rpm.
 
This car behaves very differently from summer to winter. I have never experienced high revs in the summer, but driving in colder temps with the heat on is a different story.
 
If I know I will exceed the EV range on a trip, I will continue to hit HV for the highway portion, and save EV for the non-highway portion. The main reason for this is that if I have EV range left and am in HV on the highway, 97% of the time I don't really notice the gas engine running. Versus on local stop and go driving, I do hear the engine running and revving higher than it seems to need to be. Not angry bees at all, just noticeable and out of step with power needs. I MUCH prefer EV running for stop and go, versus on the highway it doesn't make much difference to me.

Another temporary issue is that currently with the very low gas prices, and high electricity rates in the Northeast, it's actually cheaper to run in HV on the highway.
 
When I went to zero I noticed that I was a lot more comfortable with two sources of propulsion - EV and HV - than I was with just one. So if I am driving distance I'll drive HV on the off chance that the gas station I was planning on was closed. I would still have EV to fall back on. When I get to within EV range of my destination I'll switch to EV - especially if I know there is free charging at the destination.
 
insightman said:
No second guessing about when turn HV off for the final leg home, hoping to get there just as the battery charge is exhausted.
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That almost seems like a question without a question mark.

Even on familiar routes conditions can change that impact actual EV range. Ten miles of travel that is faster or slower than anticipated, for example. I’ve covered 10 miles in slow traffic and used almost zero EV range. Other times those 10 miles may use 12-15 miles of range.

Stopping and starting at 4-5 traffic signals will have a more detrimental effect on EV range than stopping at 1 or 2.

If you meant to ask a question, then yes, it is always a guess when determining the correct time to switch to EV mode.
 
Mark W said:
The main reason for this is that if I have EV range left and am in HV on the highway, 97% of the time I don't really notice the gas engine running. Versus on local stop and go driving, I do hear the engine running and revving higher than it seems to need to be.
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On the highway there is more road noise, wind and tires, than in urban traffic. Also, at 65-75mph, it only requires 35-40hp for a 4,000lb vehicle to overcome aerodynamic and rolling resistance on a flat road and maintain a set speed. The engine has it quite easy in this situation.

Requests for greater power output can get the ICE, revved up. Even in EV mode the ICE will come on with a sufficiently heavy right foot. At speeds below 45mph, the source of motive power is electricity. Either from stored energy in the batteries, electricity from the ICE powered generator, or a combination of the two. The only thing that propels the car is an electric motor.

Using HV mode below 45mph places 2 burdens on the ICE. Generate electricity to propel the car via the electric/traction motor and generate electricity to maintain the SOC of the lithium batteries. Some accelerations may require energy from both the generator and the batteries. What may be viewed as the engine revving higher than necessary, is the engine restoring energy to the batteries that was used while accelerating.

This can be moderately annoying and is why EV mode is preferred by many for stop and go driving.
 
insightman said:
If you follow the "let the charge go to zero" plan, there will be
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Not necessarily.

EV range can be depleted to 0 at any point on a drive that exceeds EV range and the drive can be completed in HV mode.

Arriving at a destination with less that 1 mile of EV range remaining is one way to maximize battery capacity. Using it all before arriving assures the driver that all capacity was used.

I’m still not sure if you had a question, or a point, but that’s my answer.
 
I have a ScanGauge II. I have a State-Of-Charge (STC) gauge programmed in it.

In my experience, my Clarity charges to 100%; however, when running on EV, it will turn the engine on, with the EV showing "0" around 10.6% STC. If I feather it the right way, after the engine running, and then it kicking off, I can get the STC as low as 7.4%.

I was going over a small mountain recently, with 0 EV showing. Going up the hill, I got the STC as low as 4.6% -- which is the lowest that I have seen it.
 
The few times that I've done longer trips, I would leave on EV until I hit the highway, then switch to HV until I get off. Usually I end up with about 50% EV range, hoping where I will park there is an available charger. But there never is. So I repeat the process on the way back and end up using all EV when I get home.
 
Mark W said:
Another temporary issue is that currently with the very low gas prices, and high electricity rates in the Northeast, it's actually cheaper to run in HV on the highway.
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And its also cheaper to drive around town alternating using HV Charge on higher speed sections and EV on stop and go sections. Saves all those stop and go cycles on the engine. But not good if you need heat in the winter then stick to HV.
 
insightman said:
The Clarity provides heat with HV off, HV on, and HV CHARGE, doesn't it? Or am I missing the way to calculate the cost of each of these three options?
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EV mode requires electrons for heat so its a waste (relatively). In HV or HV charge there's plenty enough engine waste heat (at least in my climate) to last even when the engine cycles off in HV. I hope this make sense.
 
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