It’s a lot easier to engineer an EV truck to handle steep gradients without overloading. We see from real examples that EV trucks are by default much more capable of driving fast uphill.
One part of this is the batteries. When you have the amount of batteries needed to drive a truck for a reasonable distance, you automatically get a high amount of power output as well. The power is distributed over many cells, so no overload there.
EV motors are significantly smaller than their ICE counterparts, they’re relatively cheap, don’t require significant maintenance and they generate much less waste heat for a given power output. Adding more motors+inverters to handle the required power is not over engineering in the case of an EV truck, it’s just good engineering. I suppose it’s even necessary to some degree, to deal with the lack of a multi speed gear box
As mentioned in the other comment, the problem is often overheating in brakes. This is also less of an issue with EVs. You can distribute the energy dissipation to the motors/batteries and the brake pads, so the heat load is less concentrated. Energy sent to the batteries is absorbed as energy stored, with very little waste heat.
I'm specifically talking about the windings in the motors themselves. There's only so much current they had take before they start heating up, and that's when they can start to fail - just as melting or burning the insulation, creating a short across some of the winding, making them even less effective and even more prone to short circuiting which can cause even higher currents.
In normal use, only one phase is active an a time, so the duty cycle is 1/3. When the motor slows almost to a stop, the duty cycle on that winding is 100% meaning that the effect of that current on heating the wire is much worse than normal.
The catastrophic failure is when the MOSFET fails in a way that it doesn't protect the winding or battery from a short circuit which could lead to runaway heating in the battery as well as the motor. But even before then, unless the controller is actively limiting current to safe levels, the motor will get destroyed.
The only happy day scenario is if the motor control is actively limiting the current to safe levels well below the expected failure point, and then the EV will just fail to move at all under that load, other than rolling backwards.
As I said, the limit for this will be based on what the manufacturer expects the maximum load will be, but people have a knack for trying to carry more weight than their vehicle was designed for, or taking it places that are unsuitable. That's just humans being humans.
It's possible to design an EV that could withstand significantly steep hills with heavy loads, e.g. by putting many more sets of individually wired windings in parallel, but it'd be expensive and unnecessary for the typical situations that they'd be used in, and so unlikely to be commercially viable.
One part of this is the batteries. When you have the amount of batteries needed to drive a truck for a reasonable distance, you automatically get a high amount of power output as well. The power is distributed over many cells, so no overload there.
EV motors are significantly smaller than their ICE counterparts, they’re relatively cheap, don’t require significant maintenance and they generate much less waste heat for a given power output. Adding more motors+inverters to handle the required power is not over engineering in the case of an EV truck, it’s just good engineering. I suppose it’s even necessary to some degree, to deal with the lack of a multi speed gear box
As mentioned in the other comment, the problem is often overheating in brakes. This is also less of an issue with EVs. You can distribute the energy dissipation to the motors/batteries and the brake pads, so the heat load is less concentrated. Energy sent to the batteries is absorbed as energy stored, with very little waste heat.