# Hill climb and descent benchmark



## bwilson4web (Mar 4, 2019)

*Test Vehicle*

2019 Std Rng Plus Model 3, Odometer 49824 mi
Version 2021.4.18.2
4,000 lbs weighed in 2019 at truck stop scale
18" Bridgestone ECOPIA, light weight rims, 50 psi
*Test Protocol*

73 F, 4:30 AM, no wind, dry pavement, 63 mph, Autopilot steering and speed control
Flat segment:









1st pass: 1.5 mi, 229 Wh/mi
2nd pass: 1.4 mi, 226 Wh/mi

Hill climb and descent:









Climb: 1.4 mi, 776 Wh/mi ~= 1,086 Wh
Descent: 1.5 mi, -241 Wh/mi (charged) ~= -239 Wh
~2.9 mi, 847 Wh, ~292 Wh/mi
292 - 228 ~= ~64 Wh lost ascending and descending 525 ft hill
121.9 Wh / 1000 ft or ~0.53 miles / 1000 ft

Vehicle energy graph:









I do have the original photos. Questions?

Bob Wilson


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## Feathermerchant (Sep 17, 2018)

So round numbers you get back about 80% of what you put in thru regeneration?


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## Feathermerchant (Sep 17, 2018)

I had just guessed it would be 70%. 
If the drivetrain (inverter, motor, geartrain) were 90% each way you'd already be at 80% before considering the tires (both ways).


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## Nom (Oct 30, 2018)

Good stuff here! Thanks for doing this, I was curious. Not going to be lossless, I knew, but this end result is pretty impressive IMHO.


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## Feathermerchant (Sep 17, 2018)

Bob - Related. While descending out of Winterpark Co (several miles of regeneration) I did not have to use the brakes but once or twice. The car limited the regen though. Not immediately limited regen but after some time.
At first I thought it might be the batteries overheating but Supercharging can put much more kW into the batteries during a charging session. Then I though maybe the motor(s) or inverters. Anyone know the reason? 
The weather should have been warm enough for the batteries to take a full charge. Our charge state was around 70-75%. I don't have 'scan my Tesla' on the Y so I could not look at what was going on.


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## garsh (Apr 4, 2016)

Feathermerchant said:


> Anyone know the reason?


I would think that it has to be one of the usual reasons for limiting regen/charging speed.

battery too cold
battery too warm
battery state-of-charge is too high to accept that much power


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## Feathermerchant (Sep 17, 2018)

Looking at battery voltage vs state of charge, I think it is probably #3


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## bwilson4web (Mar 4, 2019)

Feathermerchant said:


> Looking at battery voltage vs state of charge, I think it is probably #3


If not going out of town, I normally charge to 67% SOC when leaving the house. There was plenty of head room to accept regeneration charge.

Bob Wilson


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## Feathermerchant (Sep 17, 2018)

Do you live on top of a hill? This was steep downhill with switch backs.


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## bwilson4web (Mar 4, 2019)

Feathermerchant said:


> Do you live on top of a hill? This was steep downhill with switch backs.


I live in Huntsville AL which is part of the Tennessee Valley. A river valley, there are hills about 2-3 miles to the East, about 8-10 miles across the river to the South, and fairly flat in all other directions:









Bob Wilson


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## PNWmisty (Aug 19, 2017)

Feathermerchant said:


> Bob - Related. While descending out of Winterpark Co (several miles of regeneration) I did not have to use the brakes but once or twice. The car limited the regen though. Not immediately limited regen but after some time.
> At first I thought it might be the batteries overheating but Supercharging can put much more kW into the batteries during a charging session. Then I though maybe the motor(s) or inverters. Anyone know the reason?
> The weather should have been warm enough for the batteries to take a full charge. Our charge state was around 70-75%. I don't have 'scan my Tesla' on the Y so I could not look at what was going on.


The amount of energy the battery can take is a moving dynamic involving several factors. If your battery temperature had been 100 degrees F, it probably wouldn't have limited regen. If your state of charge had been 30%, it probably wouldn't have limited regen. There's a third complicating factor. It's become apparent to me that a battery at any given state of charge and temperature can take more charge for a few minutes than it can after having been charged continuously for a few minutes and that this factor is independent of any changes in temperature or state of charge caused by the couple minutes of charging. This explains why maximum regen is often reduced after a few minutes of descent on a long grade and why a Supercharger only stays at the 250 kW maximum briefly. I don't think the initial reduction in charging speed is thermal in nature and I base this on how quickly it will reduce regen even if the pack temperature is starting out at freezing.

From a practical standpoint, this reduction in regen gets a lot more attention than it deserves. I've yet to have it reduce regen so much in the middle of a long descent that I needed to apply the friction brakes merely to maintain a slow enough descent. If the display didn't notify me that regen had been reduced, I probably would never have noticed it to any significant degree.

The only kinds of reduction in regen that has caused me to use significantly more friction brake are:

1) Cold soaked when parked outside in very cold temperatures. Mild temperatures will often result in a mild reduction in regen but not enough to cause me to need much friction brake. Mad Max drivers who use the throttle as an on/off switch will obviously have a different result. When I'm in traffic, I look ahead and drive with the flow of the traffic. And when I have the road to myself I anticipate stops by easing off the throttle well in advance. I did it like this when I drove ICE cars all the time as well.

2) Charging above ~80% (the exact amount will depend upon how cold it is).

Since I only charge above 80% when leaving on a longer trip it's really only those really cold mornings that I notice myself reaching for the friction brakes much at all. Or, if I'm tearing up a rural twisty road! :yum:


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## Feathermerchant (Sep 17, 2018)

It wasn't real cold and the car had been in the garage anyway. But the battery charge state was probably 75% or so and the limiting regen did not kick in right away. I wish I had been able to use 'scan my Tesla' like in my other car so I could see the batt voltage and temp. That would have helped.


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