How will repeated heavy towing affect overall battery life?

[bfdog]

I see where people take about a 10% hit on battery capacity after driving about 100K miles overall on their Tesla Sedans. But I wonder the probable impact on battery life of heavy towing often. And the overall cost of towing. The worst case is someone that tows heavy 100 miles 5 days a week and charges from 10% to 100% (or 10%-80%) every night. Surely that would zap the batteries and they would need to be replaced in 2-3 years. Thoughts?

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[ajdelange]

I don't know about the numbers but the concept is definitely right. The harder you treat the battery the more rapidly its capacity will be lost. The kind of numbers you are talking about imply a nightly charge of 140-150 kWh meaning 13-15 hours charging. That may not be practical. The alternative is, of course, Super Chargers undesirable both from the POV that these are harder on the battery and the electricity will cost more. I note with great interest that the owners manual for my new X says to use super chargers only when necessary. I think this goes with limiting the charging rate to about 10.5 kW and also makes me think even more that perhaps a second charger/port may be offered as an option. Of course if you are really cynical you might surmise that the admonition to avoid SC's found in the X manual is related somehow to the fact that supercharging is free to X owners.

 

[bfdog]

I'm worried about the cost of degradation to the batteries. If new replacement batteries for a CT are 20K and the batteries are wiped out after 80K miles of abuse (i.e., towing), that's .25 a mile in cost for battery degradation. Even adjusting those numbers up and down, it's a real cost. I'm tempted to switch to single-motor and keep a diesel for heavy towing--maybe.

 

[ajdelange]

You are right to have some concerns as Tesla will have had much less experience in building trucks than they have had with cars at the time you take delivery of your CT but I don't think you need to worry much. Tesla will be using the same motors they use in their current products (plus whatever improvements 2 years evolution grants) and while I expect some new batteries they will have been thoroughly tested. Nevertheless neither the batteries or motors have been run for millions of miles in the heavy trailering regime and so something unanticipated may come up as it has done in all their other new vehicles (e.g. the half shaft problem in the X). As they know how your are thinking they will offer a warranty which should allay your fears. If the battery has to be replaced at 80K miles it won't be you who pays for it. Current warranty for Tesla vehicles is 4 years or 50K miles but the battery and drive train are warranted for 8 years and 100 - 150K miles depending on the model. I'm sure that there are warranty escape hatches for Tesla if you do abuse the vehicle but operating it within its specified envelope (towing up to 14,000 lbs) can hardly be considered abusing it.

 

[bfdog]

You are right to have some concerns as Tesla will have had much less experience in building trucks than they have had with cars at the time you take delivery of your CT but I don't think you need to worry much. Tesla will be using the same motors they use in their current products (plus whatever improvements 2 years evolution grants) and while I expect some new batteries they will have been thoroughly tested. Nevertheless neither the batteries or motors have been run for millions of miles in the heavy trailering regime and so something unanticipated may come up as it has done in all their other new vehicles (e.g. the half shaft problem in the X). As they know how your are thinking they will offer a warranty which should allay your fears. If the battery has to be replaced at 80K miles it won't be you who pays for it. Current warranty for Tesla vehicles is 4 years or 50K miles but the battery and drive train are warranted for 8 years and 100 - 150K miles depending on the model. I'm sure that there are warranty escape hatches for Tesla if you do abuse the vehicle but operating it within its specified envelope (towing up to 14,000 lbs) can hardly be considered abusing it.

Agreed. I think the warranty situation should cover my uses to allay fears. And I can add cost-per-loaded mile to any job I do with equipment.

Without evidence I suspect people from Texas and South African/Canadian U.S. immigrants have different ideas on what a "truck" is. People in Texas don't call an SUV a truck unless they are pussies. But Elon's space ships and cars work really well. And autonomous barges and ships. I'll hang on to my reservation and I'll reserve judgment on this alleged heavy-tow capable truck with 500+ mile range.

 

[ajdelange]

When I used to visit Texas frequently a vehicle like this was known as a "pee cup". But I don't know that they will sell that many down there as I don't see where the rifle rack will mount.

 

[bfdog]

Pickup trucks are a thing but haven't seen a rifle rack in a while. Maybe back seats and thieves solved the desire for window rifle racks. I keep mine flat in the case in the back seat if I travel with it. I wouldn't trust the scope otherwise. Or thieves.

 

[ajdelange]

You've forced me to think about it. That was 40 years ago!

 

[happy intruder]

I see where people take about a 10% hit on battery capacity after driving about 100K miles overall on their Tesla Sedans. But I wonder the probable impact on battery life of heavy towing often. And the overall cost of towing. The worst case is someone that tows heavy 100 miles 5 days a week and charges from 10% to 100% (or 10%-80%) every night. Surely that would zap the batteries and they would need to be replaced in 2-3 years. Thoughts?

don’t forgot to add in the effect of the new battery (Model 3)....

 

[bfdog]

don’t forgot to add in the effect of the new battery (Model 3)....

And what is the effect of the new battery (Model 3)....?

 

[Jhodgesatmb]

Couldn’t the rifle mount on the side in the back seat? Apparently lots of room, easier access, and wouldn’t mess with the window view. Someone asking about a clean cabin suggested a storage area under the dash that might be wide enough for a rifle but I think that would be harder to access. Or maybe a Texans (and others) just liked the idea of having their rifles be visible to everyone and it was only partly a functional decision putting them there.

 

[dmacmurphy]

Wait 'till battery day... I expect things will change 4 the better...

 

[happy intruder]

And what is the effect of the new battery (Model 3)....?

dont know........I dont tow with the model 3.......but the current model 3 battery is different than the current model s and model x......and the new truck will have a new battery that is probably larger than the current 100kWh.......and will have different chemistry make-up

 

[Kenzy]

If you haven't already, have a look at Cybertruck guy's video on torque. I don't know alot about towing physics, but this guy seems to, and from what he explained, the efficiency of the torque of the electric truck, and the fact that energy demand while towing after achieving a moving state is quite low, seems like the job of towing is not going to abuse the batteries. And as others have said the new battery announcement will put things in a different/better perspective, especially in light of the fact the new batteries will likely first come out in the semi and cybertruck...

 

[ajdelange]

The job of towing definitely will stress the batteries (and the drive train). A battery used in towing service is going to degrade faster than one that isn't. But the battery/drivetrain warranty is most probably going to be better than 70% capacity out to 100,000 - 150,000 miles and 7 or 8 years so it isn't something you need to overly concern yourself about.

Now why is towing going to degrade your battery faster? I got a new iPhone yesterday because my old one was losing charge fast (at least that's what I told my wife - the real reason is that my new X has a wireless charger in it and my old phone didn't have the wireless charging feature). In Apple's articles on batteries they use the term "chemical age" which isn't one I had heard before but I like it. The greater the chemical age of your battery the less charge it will hold. The chemical age depends on the clock, of course, but it also depends on how the battery is used. Charging and discharging a battery adds to its chemical age. Also how you charge and discharge it has an effect. It's probably obvious that if you charge it and discharge between nearly empty and nearly full and do this frequently its chemical age will be greater at the end of a given time period than if you cycle it infrequently between 30 and 70% using a Level II charger set at 5 kW. I've noted before that Tesla's new charging notes now advise using Super Charging only when necessary.

I think a good way to look at this is to consider how much energy goes through the battery, The average American evidently drive about 12,000 miles per year, The CT will use something like 0.4 - 0.5 kWh per mile so that means perhaps 0.5*12000 = 6,000 kWh of juice flow from the grid to the motors and they all flow through the battery. Charging at a very modest 5 kW rate means that 1200 hours would be required to take on this much energy in a year but that is only 3.3 hours per night. 5 kW for 3.3 hrs is 16.5 kWh which is only 8% of the capacity of a 200 kWh battery so all these charges are 1) shallow and 2) at a slow rate. The major factor is chemical age will be chronological age.

It is well known to people that pull trailers that their mileage goes way down falling to half or less than what they get when not towing. If towing a large load the CT's range might go from 500 to only 100 miles implying consumption of 2.5 kWh/mi i.e. 5 times the unloaded vehicle's demand. The yearly requirement goes up by factor of 5 to 30,000 kWh, Time to charge at 5 kW is 16.5 hr and the depth of a cycle is now 40% of the battery capacity, Charging for 16.5 hr per night may not be practical so the operator might well go to the maximum the vehicle can take (assuming they do not install a second port in the TriMotor) of 10 kW to get down to 8.25 hr. So now he is running more juice through the battery, putting it in faster and taking it out faster. All of these add to the rate of chemical aging.

So far we have said nothing about the various loads. The inertial load is definitely the largest and it is huge. When towing a heavy trailer the inertial load could easily go up to 300 - 400 kW and higher but I expect the vehicle computer will limit it to something in that range. 400 kW from a 400 volt battery is 1,000 Amperes. That's discharging a 200 kWh battery at 5C. That's not good for the battery's chemical aging rate.

Towing will definitely stress the battery and cause it to age appreciably faster but not so fast that you will be at 65% of capacity at the end of a year, Should that happen (and it will but it will be rare) the battery was defective and will be replaced under warranty.