Regenerative breaking testing

[Kristian]

Regenerative breaking is discussed a lot. I guess one could have 3 different hypothesis for what gives the longest EV range:

1) B5 for most regeneration
2) B0 for long gildes
3) Some middle value like B2 which is the same a D and the PHEVS default value.

Has anybody tested this more systematically? There can be many theoretical arguments.

Pro1: Breaking is avoided, and perhaps a lot of breaking involves not only regen but also classical breaking where energy is dissipated as heat
Pro2: Requires the least energy conversion, and some is lost on all conversions (eg you add power and getsless back by regenerative breaking
Pro3: Perhaps there is a maximum between the two extremes? It seems most EV has this a default. It could be to make it more familiar to drive, but perhaps the factories has data it is the best setting

I guess there is a 4th possibility, that it is not really very important, then it is all a gimmick with paddles and the B shift and whatnot.

So anybody tested this seriously and systematically?

 

[Stvtech]

For me, it is a simple case of physics.

Physics fact 1) No form of energy conversion is 100% efficient, so you are never going to put back in what you take out.
Physics fact 2) It takes a lot more energy to increase speed than to maintain it.

So, (on flat ground) anything above B0 will reduce the speed of the vehicle when you lift the throttle, requiring more energy than the slowing will have regenerated, to get back to the same speed.

I suspect that the B2 default best simulates the behaviour of a regular internal combustion engined vehicle, and is set that way for 'driveability' rather than maximizing EV range.

 

[Regulo]

To get a definitive answer, you'd need access to a closed test track, some highly expensive test equipment, and a lot of time. That's because you'd have to be sure you started each test with exactly the same state of charge, and carried out the test under the exact same conditions each time. In normal everyday use, I really don't think you would notice much difference in using any of the B settings (unless you drive mostly on motorways or fast A roads, when B0 probably gives a tiny increase in EV range, IMO).

 

[maby]

I think it depends very much on road conditions. I would expect that B0 is more efficient than any other setting provided road conditions permit it, but it is difficult to look far enough ahead to use it effectively in anything like normal urban traffic conditions. The benefits of B0 assume that you coast long distances and this is likely to annoy other drivers behind you.

 

[Neverfuel]

I tend to adopt different driving styles according to conditions. On a motorway I use ACC nearly all of the time, the car uses regen braking when the traffic in front is moving below the set speed. Around town I use the paddles incrementally to slow down approaching stopped traffic, then my brakes to stop (sooner to show brake lights if cars are behind me). On a slight incline I use B0 to Coast at the speed limit with the speed limiter set (this uses regen braking even in B0 and won't let you have a heavy right foot). On larger hills I use the appropriate regen setting to maintain speed. On open country routes on my own, I coast using B0 then blip the accelerator after 5mph has been scrubbed off the speed. I seem to be able to get at least the indicated EV range from the start of the trip - sometimes more. But it does take concentrated effort.

 

[Hypermiler]

B0 is my default for the laws of physics reasons above. But also because it is the setting which should maximise my battery and motor life (although my paddles are another matter!). There is something very satisfying about gliding - some of my routes allow me to do it for more than a mile at a time. I do have the luxury of doing almost all of my daily driving on rural roads so it works well for me.
H

 

[Titan]

Yep, laws of physics wins it for me too. B0 most of the time, increasing the B-factor of there is a downward incline to help regenerate. I have noticed that I have become much more aware of conditions in the distance, and dare I say it, a better driver, as a result of wanting to retain as much energy as possible. I've even taken to waving to muppets, who burn past me on certain roads, when I catch them up later, having maintained a lower but constant speed.

 

[kentphev]

Hypermiling in normal cars involves a lot of naughty coasting. For that reason, and personal experience, B0 will allow you to maximise whatever forward momentum you have.

So any time you don't plan or need to slow down you should be in B0.

Once you've decided you need to trim speed, eg steep downhill, roundabout, traffic etc then B5 will both save brake wear and allow for the max possible regen.

To get the most out of slowing down I click up through B1-5 on approach to a junction then brake to finish off. With B5+brake you can often hit 30kW of regen power. With B0+brake I don't think you'd go over 10-15kw .

I do think that like F1 cars, EVs that are slowing during regen should indicate this, although perhap not with flashing brake lights. Otherwise the poor guy behind you might be in for a nasty surprise.