Melbourne to Mt Buller in a M3P with snowboards on roof racks

[Majkey]

I've had the Tesla since 2019 but I’ve never taken her to Buller so I had some range anxiety.

The tldr; version: range is not an issue on a 2020 Model 3 performance with roof racks and snowboards,

I had 12% left on the Yea->Buller->Yea roundtrip. Was I worried? No, but if I change my rims with lower efficiency I may be closer to 0%…
Drove at the speed limit. Very high average usage of 275Wh/km going to Buller with the roof racks.
I’ll do the trip again after lockdown without the roof racks to gauge the difference in efficiency.

I didn’t know how to warm up the battery so I didn’t have regen most of the way down the mountain.

Anyone with a Performance done the same trip? What was your average usage?

For those of you that like more data:

2020 Model 3 performance with 20” sport wheels, lowered with UP moderate springs
Roof rack + 2 snowboards
4 passengers
Tyre pressure: 42psi

Outside temp: 10°
Cabin temp: 20°
Mt Bulle tempr: 1°

Average usage:
SE suburbia to Yea: 96% -> 50% charge, 265Wh/km
Yea to Mt Buller: 97% -> 46% charge, 284Wh/km

Phantom loss after 8 hours at Mt Buller: 4.14km (sentry mode off)

Mt Buller to Yea: 46% -> 12% charge, 182Wh/km
Yea to SE suburbia: 67% - 32% charge, 202Wh/km

 

[cafz]

Could be worth merging this with the "Mt Buller from Melbourne" thread of a couple of days ago. Mt Buller from Melbourne

 

[Hairyman]

Apart from telling the car to navigate to a supercharger or just driving, is there any other way to warm the battery?

Did you have any regen at all, or just very little?

 

[Onshore]

What snow chain solution are you carrying?

Not too many options for the 20” rims and even less so if the car is lowered.

 

[cafz]

Apart from telling the car to navigate to a supercharger or just driving, is there any other way to warm the battery?

Yes, turning on the climate control through the app will warm the battery if it's significantly below optimal driving temperature.

 

[Majkey]

Apart from telling the car to navigate to a supercharger or just driving, is there any other way to warm the battery?

Did you have any regen at all, or just very little?

From what I’ve found out in the meantime you can switch on climate some time before heading back to the car to heat up the battery. Initially I had no regen but then about halfway down the mountain regen started working as per normal (similar to the other Mt Buller thread)

 

[Shock-On-T]

Another way to warm the battery (if you have time) is to time the charging to finish just before you depart.
So leave it at 80% and then start charging before you go to bed at an amperage that gives the right hours charge time before departure.

 

[Flatbat]

Another way to warm the battery (if you have time) is to time the charging to finish just before you depart.
So leave it at 80% and then start charging before you go to bed at an amperage that gives the right hours charge time before departure.

Scheduled Departure is a more eloquent way to achieve that. Both require a charger though, so not much use when in a carpark at Mt Buller.

 

[Shock-On-T]

Scheduled Departure is a more eloquent way to achieve that. Both require a charger though, so not much use when in a carpark at Mt Buller.

UMC charger would work if the cord could reach.
Other than that, you're probably better off not trying to warm the battery at all, and just accept reduced regen. Whatever gains you make in improved regen probably wouldn't offset the power lost in warming the battery.

 

[cafz]

Whatever gains you make in improved regen probably wouldn't offset the power lost in warming the battery.

There's a 1000m drop in the first 30km, I'm not sure that's true!

 

[Flatbat]

..Other than that, you're probably better off not trying to warm the battery at all, and just accept reduced regen. Whatever gains you make in improved regen probably wouldn't offset the power lost in warming the battery.

That sounds about right. Although I am not sure if you lose power warming the battery when coasting downhill.
As you head off downhill with a cold soaked battery you have no regen. Instead, the motor control strategy changes to waste heat mode to produce excess powertrain losses to heat the coolant. This in turn heats the battery. Once the battery is up to temp the motor control strategy returns to normal and you get regen back, presumably before the bottom of the hill. So while initially your are losing regen you are probably getting "free" heating of the coolant as you coast down when no torque is commanded, instead of wasting battery to preheat pre departure. Short of measuring it somehow which would be difficult we will never know.

 

[Shock-On-T]

There's a 1000m drop in the first 30km, I'm not sure that's true!

Maybe.
2000kg dropping 1000m has an ideal max potential energy of about 5.4kWh, I suppose about 8% of the average battery.
With charging losses you might get 4% back. With a cold battery you might only get 2% back.
So if it costs more than 2% you're better off not warming the battery.
Kind of complicated, because the regen itself will be gradually warming the battery.

 

[Shock-On-T]

That sounds about right. Although I am not sure if you lose power warming the battery when coasting downhill.
As you head off downhill with a cold soaked battery you have no regen. Instead, the motor control strategy changes to waste heat mode to produce excess powertrain losses to heat the coolant. This in turn heats the battery. Once the battery is up to temp the motor control strategy returns to normal and you get regen back, presumably before the bottom of the hill. So while initially your are losing regen you are probably getting "free" heating of the coolant as you coast down when no torque is commanded, instead of wasting battery to preheat pre departure. Short of measuring it somehow which would be difficult we will never know.

Yeah, I think very complicated, probably not much in it either way.

 

[cafz]

I believe the charging efficiency is much greater than 50%, at least 80%, probably more.

 

[Shock-On-T]

I believe the charging efficiency is much greater than 50%, at least 80%, probably more.

Charging efficiency is how much power goes into the battery compared to how much power is supplied.
Regen braking is a generator, so its inefficiencies are added to any charging inefficiencies.
I remember reading about a guy that measured power used going up a long slope then measured power reclaimed coming down. He was able to recover 32%.
The other factor is that even without regen, you're basically covering distance for free as you roll down hill, so that extends range too.

 

[Leeroy]

Drove at the speed limit. Very high average usage of 275Wh/km going to Buller with the roof racks.

Wow that is surprising. I posted the other thread in the sr+ and got antsy when the consumption peaked at 202, but no roof racks. I did not think that it would add almost 30% more consumption.
It’s funny, if I’m readying correctly we had very similar numbers. Yea 97% —> 44% top of Bulla —> 11% Yea.
Did your range reduce and then recover at all?

 

[cafz]

Charging efficiency is how much power goes into the battery compared to how much power is supplied.
Regen braking is a generator, so its inefficiencies are added to any charging inefficiencies.
I remember reading about a guy that measured power used going up a long slope then measured power reclaimed coming down. He was able to recover 32%.
The other factor is that even without regen, you're basically covering distance for free as you roll down hill, so that extends range too.

The 32% is a full round trip from battery->kinetic->potential->kinetic->battery. Starting with the potential energy as we did above you cut half of that out, so if you assume the driving side is as efficient as the regeneration side, we'd expect to see sqrt(0.32) or 57% of the potential energy recovered into the battery on the regen side.

Remember too that that battery ends up heated anyway. The energy to do that is from one of our two energy sources - the potential energy released as the car's mass descends in altitude, and the battery's energy. This is the case whether or not we pre-heat it - the only additional losses from pre-heating is whatever extra heat is lost by the warmer battery between pre-heating and driving.

So the question ends up - do we lose more energy from having a warmer battery earlier, or from having to use the brakes more on the way down?

 

[Leeroy]

So the question ends up - do we lose more energy from having a warmer battery earlier, or from having to use the brakes more on the way down?

And a tough one to answer as it would probably change every occasion depending on outside temp vs battery temp and how far a downhill run you have.

 

[paulp]

And a tough one to answer as it would probably change every occasion depending on outside temp vs battery temp and how far a downhill run you have.

Using brakes down hill could result in a major problem if you overheat them. You dont have gears, so you need to allow capacity to not ride the brakes.

 

[Majkey]

Wow that is surprising. I posted the other thread in the sr+ and got antsy when the consumption peaked at 202, but no roof racks. I did not think that it would add almost 30% more consumption.
It’s funny, if I’m readying correctly we had very similar numbers. Yea 97% —> 44% top of Bulla —> 11% Yea.
Did your range reduce and then recover at all?

I think by default the M3P+ has a higher consumption than your SR+, maybe that's why the consumption is almost 30%?

My battery pack is ~80kWh so consuming 86% (97%-11%) would mean that 69kWh were used VS your pack of ~55kWh consuming 84% (95%-11%) meaning 46Kwh were used.

So if my calculations and logic are correct (sometimes quite doubtful that would mean that a M3P+ with roof racks used 23kWh more energy for the same trip. That's 50% more energy!

I had the same problem as you did with cold batteries/regen on the way down. I started getting Regen about half way down the mountain.

I'll try the same trip without the roof racks for comparison if/when lockdown finishes.