Rules of Thumb for Driving Hybrid Cars

that is very helpful, thank you! again, well done.

 

Question: When going down hill, is it better to do some braking to increase the battery level as the video suggests, or is it better to coast and build up as much speed and momentum as possible if there is an uphill segment coming soon?

 

it's best to brake if necessary to stay at speed limit. if not reaching speed limit, don't brake.

 

That depends on the length and steepness of the hill. On short downhills, your latter option (with not even regenerative braking), assuming speed doesn't reach an unsafe level. On medium-sized hills, you might as well store some energy part-way down, then coast the bottom part to build speed for the next uphill. On still larger hills, the battery may run out of capacity, so you'll have to resort to "B" mode or friction braking.

 

Just a couple of comments:

1. Charging the traction battery causes it to heat up. When I'm descending tall hills, ~500 ft / 110 m, I prefer to use "B", especially on steeper grades. The battery will still get an acceptable charge but it won't be 'heat pumped.' It also lets me keep feet on the floor when descending a 8% grade hill.
2. Pulse-and-glide in traffic is less efficient than just finding some slow traffic to follow. Speed and excessive accelerations are the enemy. So when following slow vehicles, traffic coming from behind will see the Prius stuck behind the truck or trailer and smoothly pass. Meanwhile, you're driving is a very 'low stress' mode. I typically just control my speed with the cruise control, patting up or down makes a 1 mph change, up to three can be stacked. But if your driving needs to be more stressful, 'pulse-and-glide' will keep that heart rate up . . . especially if there is a woman in the car. <grins>

BTW, I especially endorse #6 and #7. When you borrow energy from the traction battery, it has to be replaced by charging. One of the characteristics of NiMH batteries is this is an exothermic reaction, more than just ohmic heating. Let the engine do the work and keep the traction battery cool. Just remember, a badly done 'pulse' can draw on traction battery energy so I'm lazy and prefer to let cruise control handle the speed.

Bob Wilson

 

B mode is intended as a preemptive measure, to forestall the battery becoming fully charged on long downhill runs. Coming down a ski hill for example.

That's the only time I use ours. Did just that xmas eve. Don't much like dragging the car up there, suspect it's tough on it. Who knows.

Here we are in the parking lot, kinda socked in:

 

Yes, best to you too. Hope for peace!

 

great work mate
useful video. thank you very much