Cold Weather Range

D

David Towle

Well-Known Member
The drop in range was especially stunning for me this Fall. I drive 100% on gas and bring the battery to the max allowed 60% charge with HV Charge before each fillup. We had a drop in average temperature of about 30F from 70 to 40, at 70 I got 49 mpg gas and on the next tank at 40 it dropped to 38, a drop of 22%. No snow tire change, and I did pump up the tires to make up for the cold weather pressure loss. Never used heat until the engine was fully warm. Do owners who drive electric see similar cold weather losses? (Or maybe bigger due to electric heat usage?) The car is stored outside for now so it doesn't have the benefit of a warm garage.

With my old ICE car I would have expected to see a loss of 5% max in these conditions. All data based on measured miles and gas, ignoring the car's calculations. Last winter I got as low as 31 mpg in the depth of winter with the Clarity.

Any explanations why these cars plunge in efficiency so bad in the cold? Are they just so optimized for warm conditions and colder weather ignored? Its also quite noticeable in HV charge required time, it takes about twice as long to recover a given charge in this weather.
 
Even when driving on gas with a warm engine, I think the Clarity uses the electric heater: This causes the huge loss in mpg.

I drive 200 miles per week on electric, and 300-500 miles per week on gas: I see similar mileage losses on both.
(My miles on electric decrease in winter because I get less miles per charge - 45 summer, 28 winter).

Mileage reduction is less when I limit the heater.

I read somewhere that it uses ICE for heat when temperature drops to 15F - Doesn't make sense, but Honda software has not impressed me.

(I am in the food industry, and Covid has not affected my travel.)
 
Watching. I'll admit I've never tracked gas mpg since I always drive blended and no matter what its better than the truck ;)

Side bar, why would you drive 100% gas and not even start the day with full SOC on home 120v circuit overnight?
 
ClarityBill said:
I read somewhere that it uses ICE for heat when temperature drops to 15F - Doesn't make sense, but Honda software has not impressed me.
Click to expand...
After thought - It would make sense with a heat pump system, so maybe it is a carryover from the BEV version... Or maybe it is not true for the PHEV, but my anecdotal evidence would prove it is in the PHEV.
 
ClarityBill said:
After thought - It would make sense with a heat pump system, so maybe it is a carryover from the BEV version... Or maybe it is not true for the PHEV, but my anecdotal evidence would prove it is in the PHEV.
Click to expand...
The PHEV doesn't get the BEV's heat pump system. Also, based on Honda's priorities for the most energy-efficient operation, I'm certain the electric heat shuts off when the engine is producing more than enough heat to warm the cabin.
Here's a heat-pump thread and a heating the car thread and here is the diagram from the PDF document that @AnthonyW provided us:
heating_system.jpg
 
Last edited:
How much does your SOC drop, from 60% assuming you never charge with house power, while you burn through 6 or so gallons of gas and travel ~200-250 miles?


The BMS will limit charging rates in cold temperatures, so it makes sense that it takes more time and fuel to bring the batteries to 60%.

Operating in HV, the vehicle attempts to maintain SOC. The ICE reportedly fires up, to restore the level, when a 4% decline is detected. Depending on where, in that ~4% range, the batteries are, it is possible to “lose” up to 4% SOC every time the vehicle is powered down. It will also take more time and fuel to “maintain” the SOC in cold temperatures. I believe you are seeing a perfect storm of reduced fuel economy in cold temperatures and an increased inefficiency of HV Charge in cold weather.

As reported, a 40% decline in EV range is not unusual in cold temperatures.
 
I realize the PHEV does not have a heat pump like the BEV, but they do share some software. I was implying that the Honda engineers did not bother to remove this 'feature' from the software that crossed over.

I have been disappointed by Honda's lack of priority for energy-efficient operation:
2018 uses brakes to control speed in cruise control (2020 has 'corrected' this - poorly)
Brake pads are activated with light touch of pedal.
HV charge mode does not allow the drive to go into 'gear mode'.
Engine rpm goes from zero to full-throttle on gentle hills. (HV mode only uses less than 10% of the battery before going to full-throttle.) It uses the same mapping whether the battery is zero, or full. It should use the available battery charge to maintain an efficient RPM.
HV mode with a high battery SOC tries to maintain full battery, but does not effectively use regen. (Owners have the shared the workaround to let the SOC drop a little before going to HV mode.)

These obvious energy-efficiency blunders make it possible to believe they also use the electric heater when it is not necessary. Maybe this will be corrected on the 2021: But it is harder for owners to recognize, so less incentive to change.

The hardware on the Clarity is really impressive... I am not as impressed with the software.

It is nice to hope and believe they are amazing engineers (programmers), but that does not make it true.
 
You left out that the Clarity PHEV activates the engine and burns gas if you use regen braking when the battery is fully charged.

When I activate the cruise control on my 2018 Clarity PHEV, I can see the POWER/CHARGE gauge indicate that regen braking is slowing the car going downhill.

I believe the Clarity activates the brake calipers lightly when you first touch the brake pedal but mostly uses regen braking at that point, then, as you press the pedal harder and/or as the speed drops, the proportion of caliper to regen braking increases. That makes for much smoother operation than the two-step braking with my first-gen Honda Insights.

You're right that Honda's programming for the Clarity PHEV abandons max efficiency when HV CHARGE is active. Based on how narrow the Engine Drive zone is in HV, it's not surprising that Honda didn't think the engine could charge the battery and power the car directly at the same time.

When the engine is revving on gentle hills, the car is responding to the load and the accelerator. It's not as if the car turns into a runaway train when the engine is revving--it's a 2-ton car with a little bitty Atkinson-cycle engine.

Wouldn't it be great if Honda offered a software developers kit we could use to tweak the way the car works? Of course, there would be a waiver of warranty we would have to sign.

I ordered one of those Autel OBDII scanners. I wonder if it can tell when the electric heater is active?
 
David Towle said:
The drop in range was especially stunning for me this Fall. I drive 100% on gas and bring the battery to the max allowed 60% charge with HV Charge before each fillup. We had a drop in average temperature of about 30F from 70 to 40, at 70 I got 49 mpg gas and on the next tank at 40 it dropped to 38, a drop of 22%. No snow tire change, and I did pump up the tires to make up for the cold weather pressure loss. Never used heat until the engine was fully warm. Do owners who drive electric see similar cold weather losses? (Or maybe bigger due to electric heat usage?) The car is stored outside for now so it doesn't have the benefit of a warm garage.

With my old ICE car I would have expected to see a loss of 5% max in these conditions. All data based on measured miles and gas, ignoring the car's calculations. Last winter I got as low as 31 mpg in the depth of winter with the Clarity.

Any explanations why these cars plunge in efficiency so bad in the cold? Are they just so optimized for warm conditions and colder weather ignored? Its also quite noticeable in HV charge required time, it takes about twice as long to recover a given charge in this weather.
Click to expand...
You have to remember that, with only narrow exceptions, even when in HV mode the Clarity is essentially an electric vehicle. Colder temperatures will reduce battery efficiency, which in turn puts more load on the ICE generator to provide power to the traction motor. It's not really such a surprise that MPG in colder temps while in HV mode would drop more than would be the case with a conventional ICE car.
 
Dislin said:
Wow, really?? Which country is that?
Click to expand...

In some parts of the US electricity is more than $.20/kWh and gas is less than $2/gal. A full charge, at 14kW could cost $3. That full charge may yield 30 miles in freezing temperatures, or, $.10/mile. The gallon of gas might yield 40 miles when driving the Clarity in HV mode. The OP reported 38mpg. Forty miles for 2 bucks works out to $.05/mile.

That example represents a situation where running on electricity costs twice as much as running on gas.

In which country do you reside?
 
Landshark said:
In some parts of the US electricity is more than $.20/kWh and gas is less than $2/gal. A full charge, at 14kW could cost $3. That full charge may yield 30 miles in freezing temperatures, or, $.10/mile. The gallon of gas might yield 40 miles when driving the Clarity in HV mode. The OP reported 38mpg. Forty miles for 2 bucks works out to $.05/mile.

That example represents a situation where running on electricity costs twice as much as running on gas.

In which country do you reside?
Click to expand...

Ah, that is true as well. It looks like it could be possible in parts of New England.
 
Dislin said:
Ah, that is true as well. It looks like it could be possible in parts of New England.
Click to expand...

It’s more than possible. There are several owners on this forum who drive primarily or exclusively on gas because it is the lower cost option for day to day operation.

There have been charts and graphs posted that illustrate the prices at which each fuel is less costly to use.
 
I think everyone can agree that the range drop in winter is disappointing. Lower than we would have thought reasonable.


Sent from my iPhone using Inside EVs
 
I've been driving hybrid cars since 2000 and though disappointing, I consider the Clarity PHEV's cold-weather range-reduction to be consistent with my more than 20 years' experience and not unreasonable. Battery technology has improved greatly since my first Honda Insight and it will continue to improve with time.
 
Same thing occurs in Los Angeles. Now that nighttime temps are lower, we typically get a 39 mile EV range, whereas in warmer weather, it's close to 50.

On a separate note, prior to the pandemic, I had a really long commute to work. So, my Clarity lease was for 20K miles per year for 3 years. Now, I work remotely from home and the car mostly sits there. It's great not to have to drive all those miles, but in hindsight, should have opted for fewer miles.
 
Landshark said:
In some parts of the US electricity is more than $.20/kWh and gas is less than $2/gal. A full charge, at 14kW could cost $3. That full charge may yield 30 miles in freezing temperatures, or, $.10/mile. The gallon of gas might yield 40 miles when driving the Clarity in HV mode. The OP reported 38mpg. Forty miles for 2 bucks works out to $.05/mile.

That example represents a situation where running on electricity costs twice as much as running on gas.

In which country do you reside?
Click to expand...

I live in Hawaii and pay almost 30 cents per KW. Gas is about $2.30. I don't charge up at home any more. I don't enjoy driving in HV because of how loud it is going from electric to the engine coming on all the time so I do the same where I run HV charge for a while and the drive electric the rest of the time (and then of course charge at free places like Target). I thought the MPG range would drop a lot due to inefficiency in converting gas to electric but I have been doing this for the last couple months and from my calculations I am still getting about 45-50mpg (not counting the free electric I may be able to get once in a while).
 
You must log in or register to reply here.
Back
Top