Regenerative Braking Behavior Poll

[jgs]

Ah, sorry. "ISTR" is "I seem to recall". The 60% number is, as you now see, just my recollection. If I can put my finger on a reference later, I will. Similarly, where did the 85% number come from? Seems very optimistic.

Oh, and what is this "Tesla Chip"? Googling it just gives a lot of articles about Tesla's in-house ASIC development.

 

[aerodyne]

Ah, sorry. "ISTR" is "I seem to recall". The 60% number is, as you now see, just my recollection. If I can put my finger on a reference later, I will. Similarly, where did the 85% number come from? Seems very optimistic.

Oh, and what is this "Tesla Chip"? Googling it just gives a lot of articles about Tesla's in-house ASIC development.

Both came some where on this forum, but the 85% number I think is also mentioned on various forums and seems reasonable for motor gen efficiency.

Try Tesla Chip range extender. It is an Aftermarket product.

 

[Shadnic]

Try Tesla Chip range extender. It is an Aftermarket product.

I had never heard of Tesla Chip until this thread, which is surprising considering how much gets discussed on this forum. Reading about it now and it's really interesting. Is this something people commonly use?

 

[jgs]

The 60% number is, as you now see, just my recollection. If I can put my finger on a reference later, I will.

A Tesla blog on the Roadster (v1) regenerative braking cites "a net efficiency of at most 80% * 80% = 64%". That assumes battery-to-wheels efficiency of 80%, and vice-versa, and is probably the source of the "60% or so" number, I would guess. Possibly the Model S drivetrain is a little more efficient than the Roadster, but there's no way it achieves the 92%+ efficiency you'd need to get a RT efficiency of 85%. The 60% or less number feels about right, too, based on four+ years of driving one.

Remember we're talking about the whole drivetrain starting from the battery, not just motor efficiency. The Model S induction motor is said to be 93% efficient. LiIon batteries are said to have 80-90% charge and discharge efficiency. So best case -- assuming no other drivetrain losses, not realistic -- is 93% * 90% = 84%. So once you factor in that there are inevitably some other drivetrain losses, you end up with Model S looking not very different from the Roadster's 80%, and that overall 64% RT number.

 

[aerodyne]

I had never heard of Tesla Chip until this thread, which is surprising considering how much gets discussed on this forum. Reading about it now and it's really interesting. Is this something people commonly use?

I only recently ran across it. No idea if it is recommended or not.

 

[jgs]

For anyone curious about the so-called "Tesla Chip", here's a link to the site. Looks like it's an accelerator curve remapper, you interpose it between the accelerator pedal and the car, so it has an opportunity to lie to the car about how hard you're pressing the accelerator. There aren't any actual test results to back up the claims of greater efficiency and battery life, and without that I find them more than a little dubious, though of course I don't have evidence contra either. I for one wouldn't install one of these in my car if you gave it to me free, but I'd be interested in hearing from anyone who has!

 

[aerodyne]

I think I will pass on the chip, here is why....

Whether you coast more, by setting regen low, modulating the go pedal more, use the chip, or actually shift into neutral, you have to balance that with the increased probability of using the Bad (Brake) pedal, in which case ALL that excess kinetic energy is wasted.

In stop and go traffic, I find that TACC regens a lot more than I would, but it rarely brakes. With regen low, or coasting, I think brake useage would increse. By turning TACC off, and intensive modulation of the go pedal, I feel I am more efficient, but also more annoying to those following me.

So, on a deserted highway with lots of hills, I can see a possible range improvement, like the chip dyno vid implies, otherwise, not so much.

 

[jgs]

I agree. I did plenty of trying to hypermile (just for fun) with my old manual-transmission car. Coasting to a stop isn't really a thing, unless you're coasting uphill.