mph vs range(duration)?

[bwilson4web]

The REX will shutdown at 6MPH/10KPH. It shouldn't replenish the battery, but would be interesting to see if extending driving at 15-20MPH will cause the REX to stop.

I did a hill descent, 8% grade at 45 mph, and saw the REx stop before reaching the bottom. The SOC was at least 1% over the set value.

Bob Wilson

 

[jadnashuanh]

The implementation of the REx is to try to maintain the battery level at nominally 6% if you haven't modified it in the USA...it does not stay on to build charge higher than that, but will stay on under some situations when required to maintain it. Descending a hill, the load is minimal, and regen is often capable of maintaining, and maybe even increasing the SOC, so the REx may not be needed, so it does shut off.

The implementation of the new 7-series plug-in hybrids just announced, allow you to charge the traction batteries from the engine to any value, up to 100%, so you have that full when, say, you get to the city for running around there only on electrical power. In that implementation, the electric motor can drive the car exclusively, but it is often a hybrid, where the engine is fully capable of driving the car at speed while also recharging the battery pack - lots more sophisticated and costly.

 

[gt1]

Using gas to charge the battery beyond the minimal buffer makes no sense under most scenarios.

 

[bwilson4web]

Hi,

I'm suggesting the charge can be sustained with with a significant reduction in fuel consumption by:

• no or minimum load warm-up
• after reaching operating temperature, always run it at peak BSFC
• cycle OFF-ON to maintain a +/- n% around the target SOC

This is a Prius trick because the engine mechanical overhead as a ratio of shaft output is not even close to 1-to-1 linear. It is cheaper to turn off the engine and run on the banked, excess power, than to throttle back the engine to match closely the target SOC. This is especially true if the engine is run at a constant speed and the power output controlled by the throttle plate and fuel injectors.

There are other Prius engine tricks and I plan to investigate one of them.

Bob Wilson