The SOC KM equation

Is this the Holy Grail of Hybrid?

It's one of the most recurring questions: how many km can you drive with a single battery bar?

No one knows this equation, but if theory is too hard, we can try to solve it by trial and error.

Let's pick all the EV sequences out of a trip.
For each sequence, calculate the difference between ending SOC and starting SOC.
Dividing that difference by the distance in the same sequence, we'll find how many km have been done with each percentage point of SOC.
Iterate for all sequences and get the average value.
This values seems to be related to road and driving style.
Different car models should have different values too.

Here are some results on my common trips:

highway: 3.249163337
hill road: 2.466879256
urban: 8.811943764

Please note that the numbers above represents how many SOC % points are needed to drive 1 km in EV in the specified road types.
Some explainations:
in a urban environment, you need 8% SOC to drive 1 km, while driving up and down hill a little more than 2 will suffice.
One of the reasons is that city driving is usually full of starts, stops and changes of pace, while country roads lead to higher and constant speed.

There's a thread about this on the Hybrid Synergy Forum here: http://www.hybrid-synergy.eu/showthread.php?tid=47601

V47

• corrected error in rpm load chart
• corrected error in rpm heretical chart
• added menu item "Analyze all" for those who have sidebar issues
• corrected error in EV range estimate
• error in map size fixed by google
• added SOC/Km evaluation
• rewritten load chart with highlight of different states (thanks to alesf76 of the Hybrid Synergy Forum)

V46

News:

• Explorer mode on charts (mouse wheel to zoom, drag to pan)
• RPM / Engine Load chart

Comparison of Engine Load on Hybrid and Diesel engines

According to this definition, Engine Load somewhat indicates engine efficiency at a given RPM.

Here are two chart of the same trip, first with a Yaris Hybrid, and then with a CMax Diesel

The Hybrid engine has a steady higher efficiency.

V45

News:

• Fuel flow / Engine Load

Yaris Sweet Spot

This seems to be a sweet spot:

Environmental conditions:
straight extraurban road
indicated speed around 70 km/h
HSI indicator on the exact half of the ECO zone

After an acceleration phase, with RPM over 1500, revs settle down a little over 1000.
SOC is slightly growing, speed is constant in the ending.
The road is slightly downhill, but only 5 meters over 1 km.

Let's substitute elevation with accelerator pedal position:

After the initial pressure, pedal was settled down on a steady position.

Maybe it's the electric motor that is helping the petrol engine keeping its revs down?
Let's see the electric aid chart:

Current is flowing only in the initial acceleration phase, not during the following run.

Here's the engine load:

It doesn't change significantly over the sweet spot.
We can also see that the sweet spot happens during the heretical car state.

Let's add fuel flow to the chart:

The flow has values comparable to the S1 phase.

Starting up

Fast and furious or slow and steady?

Scenario: urban road, no one ahead or behind. Starting from standing still and accelerating to the maximum admitted speed of 50 km/h.

Method n.1: start using the electric engine up to 20 km/h and then forcing ICE with HSI just above the upper half of the ECO area.

Method n.2: immediate ICE usage, by pushing HSI over ECO.

Test n.1:

You can clearly see the electric peak at 5 sec, where ICE turns on.

Test n.2:

Here, electric contribution is nearly absent, given the immediate ICE usage.

Observations:

- Time:
To achieve the same speed, the electric start needs 20 seconds versus 14 of the engine start.
Note that in both cases, we're talking about a relaxed start, not a sporting one.
Both starts are anyway enough to dab a preceding car starting at the same time at our same traffic light.

- Fuel:
1: 0.01909781 litres
2: 0.01972395 litres
immediate ignition burns more fuel

- SOC:
1: SOC goes down about 1%, but by the time we reach target speed, SOC value has recovered what we lost
2: Even in this test, SOC maintains its starting value.

While interesting, values involved in this test are of little magnitude, so nothing conclusive can be inferred.