Cybertruck Will be a Towing GOD - Part 1: Torque (Newest Video)

[ldjessee]

I think that will be a factor of how much heat this heat pump will be able to pull out of the motors and battery and dump it into the atmosphere.

I have seen detailed analysis of trying to get battery packs up to temp for peak performance, but have not seen as much about dumping excess heat while under load.

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[ajdelange]

No question but that heat management will be a major factor in the design of this truck. There are a couple of thing working in the favor of BEVs though. First, of course, is that of the energy required to tow a trailer up a grade an ICE vehicle must shed 4 - 5 times that much energy whereas a BEV perhaps only 5%. For example, to tow a 14,000 lb trailer up a 15% grade at 60 mph requires 350 kW. A diesel truck would have to dispose of 1.4 MW. The CT only 17.5. That's still a lot of heat, of course, but only a portion of that is dissipated in the battery's internal impedance. Let's say it's 1/3 of it or 6 kW, with the remainder being dissipated in the inverters and the motors (and bearings, tire patches...). A Class H motor can have a hot spot temperature of 180 °C and the new silicon carbide transistors which will doubtless be found in the inverters allowable temperatures are also quite high (but I don't know how high). IOW these components can operate at temperatures much higher than the battery can which means the heat pump won't be needed to cool them. The more usual radiators should be able to do the job. Thus the heat pump might, even in this rather dramatic scenario, only have to deal a ton or 2 of cooling. That doesn't seem too demanding. The evolution of the apparently very sophisticated system of valves, heat exchangers and pumps in the Octovalve suggests (but does not prove by any means) that such an approach may be taken in the CT.

Should going 60 mph up a 15% grade be too demanding the truck's computer will simply sound a chime, display a warning and slow down. Thus I think the CT will acquit itself well in this regard.

 

[TyPope]

Sweet god in heaven make it stop

A combination of Regenerative and friction braking will stop it.

 

[TyPope]

I'm sure the good Professor Singh would approve of the use of calculators provided that you retained enough understanding of the physics to appreciate that 121 kW consumption at 14.6% grade ( 8.3 °) is not consistent with 88 kW at 6% grade (3.4 °).


A truck traveling at 60 mph covers about 1600 m in one hour. On a 6% grade (3.4 °) it climbs 6% of that (0.06*1600) = 96m. If it weighs 20000 lbs its mass is (20000/2.2) = 9090.9 kg and (20000/2.2)*9.8*(1600*0.06) = 8.55273e+06 joules potential energy was gained (supplied by the motors in addition to all the other energy they supplied in covering this mile). 9.8 m/s/s is the nominal gravitational acceleration. That's a lot of joules equivalent to 2.375 kWh (a watt hour is 3600 joules) required to pull the rig up the hill over one mile to which must be added the other loads which are at least 700 wH/mi for a total consumption of about 3 kWh/mi which is 6 - 7 times the expected consumption of the unloaded truck so the 500 miles nominal range would be reduced to 70 - 85 miles or so. But note that this 3 kWh is consumed in a minute so that the power consumption is 60*3 or 180 kW - 142 of them just for the uphill load which would be, of course, the dominant one.

Now let's try to put that in perspective. A Model X has a nominal consumption of 280 Wh/mi and so the nominal power delivered at 60 mph is 14.8 kW. But the first mark on the power meter is 75 kW with full scale being 300 kW and it's not uncommon to see power levels get up to and above 75 kW in the course of normal driving in country that is not hilly. Thus even the X is designed to a couple hundred kW power levels if briefly. Nonetheless we do hear stories of current Tesla vehicles operating in the desert in the summertime having power restrictions imposed with reduction in cabin cooling to protect the battery. So this is a very good question.

Here's a chart showing the power used for going up hill as a function of vehicle weight and speed. Where towing 14,000 pounds up an 8% grade (and there are those that persist for a couple of miles in the US) on a hot day you are going to have to slow down.

Let's not get too carried away. 200 kW at 400V is several hundred for sure (500) but if I were driving along and saw my power meter nearing full scale and staying there I would certainly back off the pedal.

Hey, you've got the physics down. Put it simple... 500 mile unloaded range from a 200Kw battery pack will net _____ miles when loaded down with a 14,000 trailer.

Keeping it simple.

 

[ajdelange]

The whole point of the discussion is that while the physics are relatively simple there is no simple answer to the question other than "It depends." In particular, as the graph shows, it depends on speed, grade and trailer weight. But it also depends on wind, road surface, time type and pressure, temperature, trailer characteristics and driver habits.

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