New PB! 80mpg(US) 2014 Toyota Aqua (Prius C)

[BlueCoast]

I just pumped 26.85L to full. Travelled 913.2km. 34km/L=80 mpg(US). The dashboard still estimated another 98km of range leftover; a conservative estimate since I travel further than the rate it ticks down. The dashboard estimated 933km range after pumping; another conservative estimate.

Other than the usual pulse-and-gliding and anticipating traffic flow, I started a couple of new driving habits which I found greatly increased the Toyota hybrid system's fuel efficiency:

• Maintain the hybrid battery state of charge 60% or above as much as possible.
• Ensure (to the best of my ability) all glides do not use any battery power.

[Ecky]

I have a newer Rav4 Hybrid for work - I wonder if you might give some tips, if it's even applicable. The Rav goes in and out of EV mode even at 100kph (on slight declines) and uses battery to propel itself. It appears to try very hard to maintain the battery directly in the middle of the gauge (whatever percent that equates to).

When driving around town, I can very easily keep it below the throttle position where it will stay fully in EV mode, until the battery is depleted. At 80kph on level ground, it's right at the edge of wanting to stay in EV, and could probably be convinced to stay in one or the other.

Any thoughts about managing when the engine runs? Better to let it drive as much as possible in EV mode, then let the engine run for long periods and bring the battery back up? Or, better to keep the battery bar right around the middle, with more frequent dips in and out of EV?

[BlueCoast]

Originally Posted by Ecky

I have a newer Rav4 Hybrid for work - I wonder if you might give some tips, if it's even applicable.

Absolutely! I am happy to provide tips that may help with operating Toyota's Hybrid Synergy Drive, assuming it operates same/similarly between different vehicle models.

Originally Posted by Ecky

It appears to try very hard to maintain the battery directly in the middle of the gauge (whatever percent that equates to)

I had a Google on a "newer" Rav4 Hybrid's battery display. I am assuming the display has space for 8 bars, i.e. the middle of the gauge is 4 bars. Relevant to any of my advice going ahead, we need to first establish that Toyota Hybrid Synergy Drive operates the battery's state of charge (SoC) between 40% and 80%. This is to maximise the battery's lifespan. On your battery display:

• 2/8 bars is ~40%,
• 4/8 bars is ~50%,
• 6/8 bars is ~60%, and
• 8/8 bars is 80%.

60% (i.e. 6/8 battery bars) is the middle of the SoC range. Correspondingly, the Toyota Hybrid Synergy Drive operates towards keeping the SoC at 60%. Every time the engine runs whilst your SoC is below 60%, a portion of the power generated by it is fed into the battery. If SoC is at 60%, all power generated by the engine drives the wheels. When SoC is above 60%, the electric motor draws from the battery to assist the engine with acceleration. The result is the engine using much less fuel whilst simultaneously slowly consuming SoC down toward 60%.

The exception to the above behaviour is if your demanded power pushes into the PWR range on your Hybrid System Indicator (HSI). In this range, the electric motor will assist the engine regardless of your SoC level. If your battery is close to depleted, the engine will instead work harder to compensate. This is because there is little/no battery power left to draw from.

Originally Posted by Ecky

Any thoughts about managing when the engine runs? Better to let it drive as much as possible in EV mode, then let the engine run for long periods and bring the battery back up? Or, better to keep the battery bar right around the middle, with more frequent dips in and out of EV?

I would recommend your last point, with the amendment your battery bar is kept as high as possible, and the caveat that your dips into EV mode avoid using any battery power.

Based on the Hybrid Synergy Drive's operating behaviour we established above, you'd make the most out of your vehicle when it is driven either with:

• the engine solely driving the wheels (at 60% SoC), or
• both engine and electric motor driving the wheels (above 60% SoC)

Below 60 km/h, pulse-and-glide is the most effective method of maintaining SoC at or above 60%. Limit use of the accelerator pedal to "pulsing", i.e. accelerating with the engine (plus electric motor assist if above 60% SoC). "Glides" in EV mode must not use any battery power. This requires a very light foot on the accelerator pedal to avoid the passive regenerative braking from lifting off the pedal completely, whilst also not pressed down on the pedal so far as to use battery power to propel the vehicle.

Any time you use the brake pedal, do so gently to maximise regenerative braking. If done correctly, this would increase your SoC to several percent above 60%. This recovered electrical power can then be used to assist with subsequent accelerations and pulses to reduce fuel consumption.

When above 60 km/h, driving purely in EV mode drains the battery SoC very quickly. The electric motor on hybrids is generally not efficient at maintaining high speeds. It is advisable to instead run the engine whilst above 60 km/h with a very light foot on the accelerator pedal to ensure the engine does not consume any more fuel than it needs to maintain speed.

If you find yourself below 60% SoC (i.e. 6 bars on the battery display), pulse-and-gliding in the manner I had specified above will eventually work your SoC back up to 60%. If you are travelling above 60 km/h with the engine running, the portion of power generated by the engine as electricity to the battery will eventually get you back up to 60%. Either way, once SoC reaches 60%, the engine will reduce its power output (and fuel consumption) to that which is only required to drive the wheels.

I hope the above is helpful and applicable to your driving.

[JRMichler]

Originally Posted by BlueCoast

[*]Ensure (to the best of my ability) all glides do not use any battery power.

This is my primary technique for averaging 50 MPG in the summer in a vehicle that is taller, wider, longer, heavier, and has higher drag coefficient than yours. The Maverick has a power meter. The IC engine turns on at over 10% power regardless of battery charge. If the battery has sufficient charge AND the engine is warm, the engine shuts off at 0% to about 3% power.

This truck is powerful - 10% power will accelerate slowly to 60 MPH, 20% power will accelerate to 55 MPH uphill, and 40% power will accelerate to 65 MPH up a short uphill onramp.

It helps that my shortest trips are over five miles, and the nearest speed limit over 55 MPH is 50 miles away.