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Cold weather regen?

Soolim

Member
Jun 11, 2015
852
38
Vancouver, BC, Canada
Unless you receive or place a phone call (if you keep it on the right side) or have the navigator active with pop-up directions (if you keep it on the left side) in which case you don't know how much regen is available. And even when you do "know" since Tesla made the gauge much more difficult to read, it's much more of a guess than it used to be.
I don't use the phone while driving, hands-free or otherwise. I always have space for the power meter. For me, there is no need to know the kW regen capacity to the accuracy required by others. Regen kW is just a rough indicator and I adjust driving accordingly. Regen kW does not change quickly, so no need to keep watching the dial. That is just me driving conservatively, and I don't have the P. Maybe I am the minority?:wink:
 

Cyclone

Cyclonic Member ((.oO))
Jan 12, 2015
5,058
1,143
Charlotte, NC
Really I think they should also show the yellow dashed line extending all the way from zero. It's about a consistent UI.

"You must spread some Reputation around before giving it to green1 again."

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We have to remember the non-AP cars still have the full power meter, so his experience may be different.
Versioning pleasures!!!

I have to admit that is one nice thing about my Classic. Every day lately I'm waking up to regen limited around 20 kW and I can see and be ready for that as I'm driving around.
 

mguw

Member
Oct 9, 2015
14
3
FR
I agree, I actually think they should have an option where it mimics regen using the brakes (optional!) to keep a consistent experience, but failing that, I want to be notified so that I at least know what to expect!
Agreed also. Easy and efficientwy would be to direct the energy in a resistor that heats up the battery coolant
 

green1

Active Member
Mar 25, 2014
4,548
1,123
Calgary, Alberta, Canada
That is one good idea! Maybe they might do that in the next production batch because some new hardware (contactor) is needed.
They have the hardware now to mimic regen with brakes. If they didn't, autopilot wouldn't be possible. This could be implemented entirely in software (at least for ap vehicles, unsure for pre-ap cars)
I like the idea of dumping the regen in to a battery heater, but the full 60kw of regen is a LOT of power to try to dump.
 

AWDtsla

Active Member
Mar 3, 2013
4,266
3,960
NE
They have the hardware now to mimic regen with brakes. If they didn't, autopilot wouldn't be possible. This could be implemented entirely in software (at least for ap vehicles, unsure for pre-ap cars)
I like the idea of dumping the regen in to a battery heater, but the full 60kw of regen is a LOT of power to try to dump.

You don't need 60kW. Even 30kW would be plenty. Fortunately, water has a lot of thermal mass, with the addition of a coolant thermos, they could easily sink and store that 30kW of heat load. This would be hugely helpful even if this was implemented with the existing 5kW heater.
 

Lon12

Member
Oct 12, 2015
849
1,046
Calgary, AB, Canada
I totally agree. Why are we throwing out the regen heat when we need it the most to heat the car up? A consistent one pedal driving experience would be nice in all weather conditions. Either use the brakes or recover the regen somehow to decelerate.
 

thegruf

Active Member
Mar 24, 2015
2,286
1,978
indeterminate
Suggestion for Tesla would be that when you pre-warm the cabin from the App the car could recommence charging (assuming connected and not at 100% of course!) for this limited period of time to heat the battery.
 

green1

Active Member
Mar 25, 2014
4,548
1,123
Calgary, Alberta, Canada
You don't need 60kW. Even 30kW would be plenty. Fortunately, water has a lot of thermal mass, with the addition of a coolant thermos, they could easily sink and store that 30kW of heat load. This would be hugely helpful even if this was implemented with the existing 5kW heater.
Heaters can only draw about 12kW (pack and cabin combined) Beyond that, it's about consistent feel. When I lift off the accelerator the car should behave the same, always. I shouldn't have to guess.
 

David99

Active Member
Jan 31, 2014
4,850
7,026
Brea, Orange County
Of course it would be great if we had consistent regen power, no matter what. Unfortunately the nature of batteries doesn't allow it. Having a little bit of technical knowledge, I know that it would take quite some extra engineering to add an alternative system that gradually takes over to keep regen consistent. It's not as simple as having a large resistor in the battery that is heated up be taking the power. There is some serious power coming from regen at time. It would generate a very strong burst of heat. That element would get crazy hot is a matter of seconds. It would require separate wires and it's own power controller to adjust the amount it contributes. The heat would have to be moved into the battery quickly to prevent overheating. Probably not possible with the existing coolant pump and line diameters.
 

AWDtsla

Active Member
Mar 3, 2013
4,266
3,960
NE
Of course it would be great if we had consistent regen power, no matter what. Unfortunately the nature of batteries doesn't allow it. Having a little bit of technical knowledge, I know that it would take quite some extra engineering to add an alternative system that gradually takes over to keep regen consistent. It's not as simple as having a large resistor in the battery that is heated up be taking the power. There is some serious power coming from regen at time. It would generate a very strong burst of heat. That element would get crazy hot is a matter of seconds. It would require separate wires and it's own power controller to adjust the amount it contributes. The heat would have to be moved into the battery quickly to prevent overheating. Probably not possible with the existing coolant pump and line diameters.

It's not that much heat. You can take a hint from electric tankless hot water heaters to do some napkin estimates. Just look up one at random. Here's one, 36kW draw to heat up 40F water to 105F at 3.8 GPM.

Let's say you want to be able to sink a solid minute of regen at 0F, you would raise 1.9 gallons of coolant to 130F. This is not even considering the fact that you're pumping the coolant through the pack which has a large thermal mass. I'd put the heater element in a thermos and the coolant around 200F, that way leftover heat could be pumped through the pack at next startup.

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Cold climates are away games for Tesla. They've practiced for it but they're not as good as they could be.
 

green1

Active Member
Mar 25, 2014
4,548
1,123
Calgary, Alberta, Canada
Of course it would be great if we had consistent regen power, no matter what. Unfortunately the nature of batteries doesn't allow it. Having a little bit of technical knowledge, I know that it would take quite some extra engineering to add an alternative system that gradually takes over to keep regen consistent. It's not as simple as having a large resistor in the battery that is heated up be taking the power. There is some serious power coming from regen at time. It would generate a very strong burst of heat. That element would get crazy hot is a matter of seconds. It would require separate wires and it's own power controller to adjust the amount it contributes. The heat would have to be moved into the battery quickly to prevent overheating. Probably not possible with the existing coolant pump and line diameters.
I agree, that's why I think the option should be to allow the brakes to simulate the missing regen. Dump the ~12kW in to the existing heaters, simulate the rest with the brakes, keep the "feel" consistent.
 

Andyw2100

Well-Known Member
Oct 22, 2014
6,542
2,393
Ithaca, NY
I agree, that's why I think the option should be to allow the brakes to simulate the missing regen. Dump the ~12kW in to the existing heaters, simulate the rest with the brakes, keep the "feel" consistent.

I understand why you want to keep the feel the same. But the idea of braking, just to simulate the feeling of regenerative braking, flies in the face of what Tesla is doing from an efficiency standpoint. You're suggesting that instead of coasting, the car should brake, just to provide a consistent experience for when the driver takes his or her foot of the accelerator. While I agree there is something to be said for a consistent driving experience, it would seem in this case, the cost is just too high.

That's my opinion, anyway. Obviously others will have different ones.
 

green1

Active Member
Mar 25, 2014
4,548
1,123
Calgary, Alberta, Canada
I understand why you want to keep the feel the same. But the idea of braking, just to simulate the feeling of regenerative braking, flies in the face of what Tesla is doing from an efficiency standpoint. You're suggesting that instead of coasting, the car should brake, just to provide a consistent experience for when the driver takes his or her foot of the accelerator. While I agree there is something to be said for a consistent driving experience, it would seem in this case, the cost is just too high.

That's my opinion, anyway. Obviously others will have different ones.
You will note I said "optionally"
 

Andyw2100

Well-Known Member
Oct 22, 2014
6,542
2,393
Ithaca, NY
You will note I said "optionally"

I did note that.

I just don't think Tesla would even want to give owners the option to do something that would have such a negative impact on efficiency. I could be mistaken. They have provided the "Max Battery Power" option, which is also pretty inefficient, from the sound of it, so who knows.
 

David99

Active Member
Jan 31, 2014
4,850
7,026
Brea, Orange County
I think the reason Tesla didn't implement that heater element to capture regen energy is because it would be a lot of extra parts and complexity for a rare case and a small overall benefit. If you time your charge so it finishes before you leave, you will an OK amount of regen, even in very cold weather. From there the battery will heat up with the existing systems. The vast majority of cars would never need it, and even those in cold climates would only use it in a few cases.
 

AWDtsla

Active Member
Mar 3, 2013
4,266
3,960
NE
I think the reason Tesla didn't implement that heater element to capture regen energy is because it would be a lot of extra parts and complexity for a rare case and a small overall benefit. If you time your charge so it finishes before you leave, you will an OK amount of regen, even in very cold weather. From there the battery will heat up with the existing systems. The vast majority of cars would never need it, and even those in cold climates would only use it in a few cases.

California thinking. It is the nominal case here.
 

Lon12

Member
Oct 12, 2015
849
1,046
Calgary, AB, Canada
Of course it would be great if we had consistent regen power, no matter what. Unfortunately the nature of batteries doesn't allow it. Having a little bit of technical knowledge, I know that it would take quite some extra engineering to add an alternative system that gradually takes over to keep regen consistent. It's not as simple as having a large resistor in the battery that is heated up be taking the power. There is some serious power coming from regen at time. It would generate a very strong burst of heat. That element would get crazy hot is a matter of seconds. It would require separate wires and it's own power controller to adjust the amount it contributes. The heat would have to be moved into the battery quickly to prevent overheating. Probably not possible with the existing coolant pump and line diameters.

When my car is cold soaked at -25c I would welcome anything that was "crazy hot in a matter of seconds"! I'd be willing to pay for it in an "extreme winter package" if need be. Maybe we could throw the extra heat into the wheel wells and melt all that snow.
 

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