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9kW "stator heater" ON when supercharging. Hypocritical waste?
- Thread starter googlepeakoil
- Start date
That was the mid cell temp, I expect it is a fluid temp. But they likely have the thermal masses and resistances well modeled as to what the cells are doing.
DirtyT3sla
Member
The stator didn't used to use this much energy. I don't remember what it was, but it used to use less kW and it would warm much slower. Over time, Tesla figured out it was safe to bump the temp (I assume), so they did that via OTA. imo Tesla does not screw around with batteries. If it looks like a medium-high % of batteries will go bad for any reason, it would be really terrible for business.
Agreed. It would be. That is why it is somewhat ominous the very small uptick of owners reporting battery failures after the "improved battery diagnostic" update that happened over Christmas. Very few reports right now (only about 10 on the forum), but they all happened shortly after the update, which is interesting. Time will tell if that trend grows or not.
Do you have any scientific knowledge to provide that heating the packs up to 50C isn't useful? Because just it's "well known" that cold batteries have trouble charging and discharging, it's also relatively well known that hot batteries can be charged more quickly without damaging them. Tesla surely did not go through the effort of all the heating/cooling stuff just to waste extra power.
I think more than anything Tesla just wants your car out of the stall ASAP. It’s better for the company, EV’s, and the customer if they have consistent and high power charging options available. Giving the customer the option to heat the battery a bit less to potentially save energy likely isn’t terribly appealing. People complain about slow charge rates as is, adding an option that makes it even slower isn’t that exciting. I don’t see this being an issue. Tesla appears to be much more concerned about the sustainability of transport, rather than the environmental impact of it.
What if heating the battery to ~50C dramatically extended its useful life? Then you’d have to take into account the environmental impact of potentially manufacturing a new battery over the thermal losses. Realistically, this is unlikely to happen, most likely people would end up buying a new car early and selling the one with a degraded battery cheap enough nobody would pay to replace the pack. The impact is more or less the same though.
What if heating the battery to ~50C dramatically extended its useful life? Then you’d have to take into account the environmental impact of potentially manufacturing a new battery over the thermal losses. Realistically, this is unlikely to happen, most likely people would end up buying a new car early and selling the one with a degraded battery cheap enough nobody would pay to replace the pack. The impact is more or less the same though.
To all the people that found my post funny. Well maybe part of it was because you weren't being charged for that "extra" energy that was used to heat the pack to speed up your supercharging!
Ironically - Tesla have just announced they're going to charge you for that energy you use while plugged in - and surely that will include the energy used to heat the pack - which will then be thrown away after.
https://electrek.co/2020/01/13/tesla-updates-supercharger-billing/
Now it's hitting you in the pocket are you sure you don't want an option to turn off the pack heating ?
This is going to confuse a lot of "less well educated" Tesla people who'll be saying. Well - I added 40kWh - why am I being charged for 50kWh.
"Well sir, there's some overheads, you had your heater on didn't you, also, we decided that we wanted you to charge faster, so we spent 7kWh to heat your pack, you're welcome, dialtone".
Ironically - Tesla have just announced they're going to charge you for that energy you use while plugged in - and surely that will include the energy used to heat the pack - which will then be thrown away after.
https://electrek.co/2020/01/13/tesla-updates-supercharger-billing/
Now it's hitting you in the pocket are you sure you don't want an option to turn off the pack heating ?
This is going to confuse a lot of "less well educated" Tesla people who'll be saying. Well - I added 40kWh - why am I being charged for 50kWh.
"Well sir, there's some overheads, you had your heater on didn't you, also, we decided that we wanted you to charge faster, so we spent 7kWh to heat your pack, you're welcome, dialtone".
I would only be happy with an option to turn off, if there was a penally charge like idle fee when the charger is busy. It's fine that you want to save a $/€/£ or so, but it isn't if a line of people are waiting for the charger.
Agreed. Would only be a good idea to have an option for slower charging (and less charged $) if there was no queue / less than 50% occupancy.
If the charger wasn't busy, and I was doing an errand, having a sit-down meal that's going to take an hour, then I think having the option to turn off pack-heating and charge 20% slower would be fine for me and most people. "Charge to the max (incur slightly higher charging costs) / take it easy" button.
You're getting kWh and kW confused. Unless you're at the charger for an hour and the battery heater is actually on the entire time, you won't be using 7kWh. Most supercharging sessions are closer to 30 minutes (or maybe even less), so that's 3.5kWh, or 3.5kWh out of 50kWh. Not nearly as much.
And, I'd be GLAD to pay that extra fee to have my car charge 3-4x faster. You're paying for the convenience, of course it's more expensive. If the battery is ice cold, you won't get any charge until it heats up... which could be forever if it's cold enough outside unless you heat the battery up.
If you give the option to offer a 'slow, cheaper' charge and a 'fast charge, more cost' charge option, then you're going to annoy a lot of people. It creates congestion at Superchargers (already a huge problem in Cali), and provides a bad experience to the majority of the 'less educated' people.
Are you really complaining about 7kW of power being used over 30 minutes? That's a dollar at 30 cents per kWh. I really take issue with your claim that they're "throwing away" power to accomplish faster charging. You're at a fast charger. What are you expecting? Slow charging? The entire service is built around how FAST they can charge your car.
Charging a cold battery is pretty much the worst thing you could do to a lithium battery short of... well shorting it physically. If Tesla didn't aggressively heat the battery for charging we would be sitting here complaining about their negligence in battery conditioning. At the end of the day the battery HAS to be conditioned if you want to charge at these rates. Whether you want that kind of speed is ultimately your decision anyway.
If you want slow charging, Level 2 is the answer. If you want an in-between then sorry- The market has decided that you're in the minority. If you feel super strongly about charging slowly without any "wasted" power then I would highly recommend you buy a Nissan LEAF or Chevy Bolt. The LEAF even has this amazing feature where it does literally nothing if it's overheating or freezing.
Charging a cold battery is pretty much the worst thing you could do to a lithium battery short of... well shorting it physically. If Tesla didn't aggressively heat the battery for charging we would be sitting here complaining about their negligence in battery conditioning. At the end of the day the battery HAS to be conditioned if you want to charge at these rates. Whether you want that kind of speed is ultimately your decision anyway.
If you want slow charging, Level 2 is the answer. If you want an in-between then sorry- The market has decided that you're in the minority. If you feel super strongly about charging slowly without any "wasted" power then I would highly recommend you buy a Nissan LEAF or Chevy Bolt. The LEAF even has this amazing feature where it does literally nothing if it's overheating or freezing.
In Bjorn's latest video "Supercharging a Model 3 SR" it hits an impressive 170kWh (an amazing 3.4C on a 50kWh pack) but the battery is also heated to around 54-55C - not the 43 mentioned above. Oddly when it's at 170kWh the pack is only around 35C, as it's only between 12 and 18% SOC. The pack is still being actively heated at 50,60,70,80% state of charge, and the charge rate is down to around 50kWh. So it seems the really high temps are "only" needed as the battery gets closer to 90%.
Anyway - to prevent heating the pack to 55C it seems if you unplug / get back on the road at 60% charge the pack won't be heated to such extremes. In terms of best speed for your journey frequent short-sharp charges between 10-60% is what Bjorn recommends anyway - see his "1000km challenge". I personally think using nearly 20% of your power (9kWh of energy to supply 50kWh) of charge is quite wasteful. Remember Elon (and quite rightly) doesn't want to do inductive charging because it's "only" 92% efficient - not circa 99% (cable).
If you don't think 55C is harmful to lithium batteries just google "lithium battery degradation temperature":
eg. Effect of Temperature on the Aging rate of Li Ion Battery Operating above Room Temperature
"The increasing degradation rate of Qm during cycling with increasing temperature is because the degradation mechanisms of irreversible capacity loss are accelerated by elevated temperature, as reported in many studies"
Tesla does only keep the battery at this temp for about half an hour as it's quickly cooled down after leaving the charger.
Of course Tesla could have some magical lithium properties where 55C is not at all harmful. But that might also be why they started lowering model S/X peak supercharger kW after a 100 or so supercharging cycles. Not heard of this issue in 3's yet - but maybe I haven't been on here enough.
In the UK I believe the cost is £0.25 per kW. But electricity is also a "high level" energy compared to gasoline. So it's additionally wasteful.
Also the peak charging speed of 170kW on a SR+ and 250kW on a Long range/AWD is hit when the temperature is much lower, 30-35C aprox - so actually fast charging does not require 55C.
It seems that the high temperatures are only required when cramming the battery at higher states of charge. It hits 45C at 60%, 50C at 75%, 55C at around 85-90%.
Heating a battery from cold is good - but heating it to 55C is unnecessarily stressful for the battery imho. I would personally recommend only supercharging between 10 and 70%, or 30-90%. It seems the 50-55C is only reached when doing a long 30-40minute charge.
Can you please get your units right? You talking about 170 kW charging rate?
What do you mean by "charge rate is down to around 50kWh"?
Charging rate is measured in kW, a unit of power. Energy is measured in kWh.
What does this mean? I didn't watch his video but you talked about 9 kW in your OP and kW is a measure of power. 50 kWh is a measure of energy.
You mean per kWh?
I've elaborated more about kW vs. kWh at Near Turtle to cells balanced: 20.8 kW with 2015 Leaf with 24 kW battery: Low kW? As expected? Battery losing capacity? - My Nissan Leaf Forum.
Additional factor: heating the pack to counter the cooling that will occur as soon as it is back on the road, in winter. Taking the pack over the nominal target means the the vehicle's heater doesn't need to run for some amount of time thus increasing your range by that amount. Also, a warmer battery can provide more energy (and power, but that isn't important here) than a cold one.
If you are going to sell EVs only to ecologically minded buyers you are setting yourself up for failure.
An EV truck is going to need 'sizzle' to compete with the professional truck makers. It's a highly competitive market.
The Tesla truck has sizzle. It's certainly greener than Ford Raptor by a wide margin (EPA 16 mpg combined, and they can't build enough of them, they even export them to China).
I've never bought a car, EV or otherwise, based primarily on ecological reasons. Why? I know full well I could use a bicycle for many of my trips. If I wanted to be green I would not own a car at all. "Green" cars/trucks/motorcycles is just icing on the cake for me. Given the choice of two vehicles with identical features, I'll pick the greener one. Think about it. You can buy a used Fiat 500 EV for lunch money then use your savings to buy solar panels if you wanted to be green.
And use your bicycle more.
Stop getting kWh and kW confused. Your figure about 20% is flat out WRONG.
If the battery heater is 9kW for the ENTIRE supercharging session, and you supercharge for 30 minutes, then 9kW used for a 50kWh charge is 3.5kWh for adding 50kWh to the battery. That means you're only 'losing' 6.5% efficiency in order to vastly increase charging speed.
Elon rightly thinks inductive is stupid because you have 92% efficiency with essentially no added benefit. The added benefit to heating the battery is to actually be able to charge it quickly at a supercharger.
As per your article, try reading it more carefully. That article discusses cycling a battery while at elevated temperatures, which includes the discharge cycle. Someone else in this thread linked to another Nature article about how heating batteries is great for charging them quickly.
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