cost of driving style

[gwatpe]

There is a lot of chatter RE: cost of driving.

If I had to buy my Electricity @ $0.35/kWh, the typical power cost I would pay for grid supplied power then a typical drive I do, would return a cost like this.

As a comparison I have also done the same drive using SAVE mode, with a full battery, and resetting the SAVE when the ICE first starts. The present petrol cost is close to $1.20c per litre.

The returned total cost is very similar.

If the electricity cost was much lower, then some savings for a short trip would be gained.

The costs are still in the 5c/km range, so the PHEV is still certainly economic.

The closer the cost of the Electricity is towards free, then the PHEV is in a world of its own.

PS edit: The white trace is elevation, the pink trace is instant total cost, and the dark blue is the Battery %SOC.

 

[gwatpe]

In the drive above in the first pic, the battery started at 90%SOC and ended at 27%SOC.

the 90% equates to close to 0.90x320Vx36.9Ah=10.6kWh
the 27% equates to close to 0.27x301Vx36.9Ah=3.00kWh

this is 7.6kWh difference, yet the PHEV only used 6.88kWh measured by PHEV from the battery. The battery required 10.5kWh to recharge, measured from the power cord metering.

10% of the energy was lost just being drawn from the battery. The losses in the motor controller and motors is close to a total of 10% as well. This is why use of high B settings results in reduced EV range, as only about 80% of the energy is restored. This is compounded if the original energy was from the battery.

The losses are proportional to the square of the currents, and thus higher power demands equate to bigger proportional losses.The same losses are present during REGEN and battery corded recharging.

Higher battery currents mean more losses both ways. Lower recharging currents, and driving currents offer higher efficiency of the battery alone. A good reason to not use high energy recharging, and explains why the energy from a fast charger does not seem to go as far as from an overnight home recharge.

Many PHEV owners are reporting widely varying achieved EV ranges. Driving style may be contributing more than the average driver thinks and combine this with other variables like temperature that also affects the battery and it becomes clearer as to why EV range obtained can be so varied between drivers.

The PHEV computer is an optimist and seems to overstate the estimated EV range, maybe as an MMC feelgood gesture. :? or just simplified calculations.

 

[Regulo]

Thanks for this info, gwatpe. It certainly goes a long way to explaining the way the losses mount up during the conversion from electricity stored and mechanical power used, and vice versa. I've definitely noticed a difference in the "feel" of the car when using B0 to when using B5, Anko suggests the throttle is re-mapped in different B settings. Whatever, the car just feels "looser", even at a steady throttle opening. I'm going to try driving with B0 set as standard, and braking as much as possible using the paddles. That's probably the best use on longer trips, but I don't think there'll be much, if any, advantage in heavy city traffic.

 

[anko]

the 27% equates to close to 0.27x301Vx36.9Ah=3.00kWh.

We have to be careful, as we do not know what the 27% means. It could mean this, but it could also mean:
27% * current capacity (which would be in your case 27% * 320 v * 36.9 Ah = 3.19 kWh) or
27% * original 'claimed' capacity (which would be 27% * 12 kWh = 3.24 kWh) or
...

this is 7.6kWh difference, yet the PHEV only used 6.88kWh measured by PHEV from the battery.

Could it be that the PHEV reports what is needed for driving, where your measurements include everything else?

This is why use of high B settings results in reduced EV range,

High B settings do not result in reduced EV range. It is high speeds and / or variations in speed that do. If you can prevent abrupt variations in speed, than it does not matter what B-level you select, as there will not be regenning anyway (in theory, but yet). If you cannot prevent abrupt variations in speed (which is quite common in dense Northern Europe), than selection of higher B-levels will help you to reduce the use of friction brakes and thereby improve system efficiency.

The PHEV computer is an optimist and seems to overstate the estimated EV range, maybe as an MMC feelgood gesture. :? or just simplified calculations.

My daily commute is very constant. Same road every day. Same driving style every day. Same low traffic density. Only changes in wind conditions (and temperature). Taken into account wind conditions, I find the estimate not that bad. On many days, I have a moderate tail wind in the morning and a moderate head wind in the afternoon. Under these circumstances, in the morning, it predicts 38 - 39 km and I manage to get 40.5 out of it (that is how far the office is). On the way back, it will predict 40 or 41 and I end up 2 km short.

 

[gwatpe]

My battery in my PHEV is still showing a high state of health, according to the Car computer. Down about 3% from the factory calculated number. I have only ever seen 100% for a fully charged reading. I believe that the PHEV is using the calculated present maximum Ah number for the PID I am using. If it used the plate reading of 40Ah, then it would always report a number <100% for full as the real capacity now decreased. There are 2 %SOC numbers and it is likely that as the battery ages that I will see the values reported differ. The fact that "Anko" has reported elsewhere of 104%SOC for full, suggests that the PID he used, is not using a 40Ah plate number for battery capacity. I only see a value in reported day to day capacity that is based on the present capacity and not on a value the battery manufacturer gave when new.

I don't have the same day to day regular work commute, and certainly don't recharge twice per day. I am at a disadvantage with collection of the same data, day after day, week after week etc. I have to make do with a mixture of different drives and the data collected from them.

I am interested in the prediction of the cost of typical drives I make in the future, with estimates of petrol cost and electricity. If we are able to get a rapid calculation of the differences between two ways to the same destination and compare, we can make more informed decisions as to which route we should drive. Comparing with different usage of the battery and ICE where possible also becomes an option.

I now have a tool that will allow me to wade through GB of data per day with clicks of the mouse. If there was a traffic hold up, or a re-route around a smash, or a slight change to a departure time, the $ differences can be seen and any benefits used in the future. I would still have to dissect a trip into portions and rebuild for the comparison. It is a relatively simple process with some notes and adding up for some totals for comparison of $, or petrol used, or Battery used, or distance traveled. Having tools to make informed decisions is going to be useful, to hopefully improve driving economy.

 

[anko]

My battery in my PHEV is still showing a high state of health, according to the Car computer. Down about 3% from the factory calculated number. I have only ever seen 100% for a fully charged reading. I believe that the PHEV is using the calculated present maximum Ah number for the PID I am using. If it used the plate reading of 40Ah, then it would always report a number <100% for full as the real capacity now decreased. There are 2 %SOC numbers and it is likely that as the battery ages that I will see the values reported differ. The fact that "Anko" has reported elsewhere of 104%SOC for full, suggests that the PID he used, is not using a 40Ah plate number for battery capacity. I only see a value in reported day to day capacity that is based on the present capacity and not on a value the battery manufacturer gave when new.

I don't think it is likely based on the 40Ah figure either. I only wanted to point out that we have to be careful with making assumptions on what the SOC% means.

On the other hand .... we do have the numbers. I have plenty of logs, where I have Battery Total Volt, Remaining Ah and SOC% side by side from the beginning of the trip to the end. I have looked at one of my logs, where SOC dropped from 96.5% at the start of the trip to 27.5% as the end of the trip.

When I compare Ah * volt, both at the end of trip with Ah * volt, both at the beginning of trip, I end up with an SOC of 26.75%
When I compare Ah * volt both at the end of trip with max Ah (based on current health) * volt at the beginning of trip, I end up with an SOC of 25.87%

Both are lower than the reported 27.5% SOC.

When I simply compare Ah at the end of trip with max Ah (based on current health), I get an SOC of 27.46, so extremely close to the reported number. As a matter of fact, when I compare Ah at any point in the trip with max Ah (based on current health) and I compare the number with reported SOC at that point of the trip, the difference is never more than +/- 0,38%, which can easily be explained by rounding effects.

For the time being my bet is on:

%SOC = remaining Ah (how much Ah is in there now) / current Ah (how much Ah can be in there according to health report) * 100

Knowing that voltage drops when SOC gets lower (difference can be close to 10%), this would mean that there is more kWh (or KMs or miles) between 90 and 100% SOC than there is between 30 and 40% SOC.

 

[gwatpe]

I have yet to find a flat straight section of road to test the linearity of the metering. Maybe next time I drive on the NullarBor plain 90mile straight.

The battery gauge is based on Ah, and the energy per bar on the gauge will be bigger when the gauge is showing a level towards the full than towards the empty.. The battery will certainly provide more energy per Ah when fully charged than when empty, and this a normal battery fact.

I am not concerned about the 1%'s. The 10%'s draw a red flag and deserve investigations.