Speak EV - Electric Car Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
Does anyone know if the motor in an EV would suffer any damage it was driven hard from a cold standing start? (this is not a question about the battery).

If you parked over-night at a motorway service station, got up on a cold morning (1 or 2ºC ) and drove immediately out on the slip road and accelerated as hard as you could up to 70mph, would the motor suffer any damage?

The manufacturers of fuel cars state that fuel engines (ICE) need to warm up and the oils need to be hot to lubricate the engine parts before hard revving begins. The temperature expansion on the metals inside the fuel engine is one thing, and the viscosity of the oil is another. A fuel engine needs to come to an equilibrium of temperatures throughout itself, and for the oil spread around the moving parts before very high revving is started. Is this the same for the motors when racing in a Tesla Roadster, Model S, Nissan Leaf or BMWi3 for example?

Thanks
 

·
Waiting for Model 3
Joined
·
138 Posts
I hope not because I do this almost every day. I live next to dual carriageway and it's been really cold recently (-2). I don't go as fast as 70 (speed limit) but I use all the power I have (heavy foot and always late).
I drive Zoe and haven't noticed any difference.
 

·
Moderator
Joined
·
9,719 Posts
got up on a cold morning (1 or 2ºC ) and drove immediately out on the slip road and accelerated as hard as you could up to 70mph, would the motor suffer any damage?
No because your battery condition wouldn't let you draw that much power, unless it was preconditioned.

When preconditioned it would let you run to its normal limits, the limit isn't really the motor in any EV its the battery. The i3 has some thermal protection for the motor but you have to drive with a real lead foot to trigger it, and your never really sure whether the power bars have been taken off you because of battery or motor temp.
 

·
Registered
Joined
·
429 Posts
No because your battery condition wouldn't let you draw that much power, unless it was preconditioned.

When preconditioned it would let you run to its normal limits, the limit isn't really the motor in any EV its the battery. The i3 has some thermal protection for the motor but you have to drive with a real lead foot to trigger it, and your never really sure whether the power bars have been taken off you because of battery or motor temp.
I believe for example you are only allowed to use the full 120kW of power for 13 seconds or something anyway, that is to prevent damage to the motor before the power output is throttled back.

I say don't worry about it as only hard acceleration (think full power for extended periods of time) should have any potentially damaging effects and the car protects against you doing that anyway.
 

·
I'm not crazy, the attack has begun.
Joined
·
23,656 Posts
The answer IS; No, because the motor will protect itself, but it will cause some degree of premature ageing.

Machines are designed to operate at some operating temperature. Whether it is an ICE or whether it is a can opener, there is always some optimum temperature, away from which wear and tear will be elevated during stressed use. The designed-for operating temperature is that which the equipment would typically reach under equilibrium conditions, i.e. where it would be once used in its expected duty cycle at the end of a long period of use.

The power limitations are usually due to the maximum discharge rates for different battery types. This is more true for small batteries with relatively high powered motors. So a car like Model S with a large battery and relatively low powered motor (continuous power) will tend to limit on the motor.

But these systems are designed to protect themselves against damage. Wear and tear, and overall ageing processes, however, are always accelerated when any machine is used to its limits.
 

·
Registered
Joined
·
1,560 Posts
No. The motor isnt an issue, the bearings used in the motors are actually slightly looser when cold, so that as they heat and expand they dont seize. So if you ever rebuild a motor get the right sort of bearing. In terms of the windings etc thats what cooling is for. More damage is caused by running a motor too hot than cold. The battery pack is going to be the limiting factor in terms of cold weather usage, but the BMS will im sure on the BMW deal with that and any appropriate cut backs.
Just enjoy it.
 

·
Registered
Joined
·
1,917 Posts
The I3 has restored my motoring sanity. No longer do I have keep telling my dear wife that driving a 4 cylinder diesel car to the local shops a mile away isn't good for the car. That said, my days of being a 'boy racer' are long gone.
 

·
I'm not crazy, the attack has begun.
Joined
·
23,656 Posts
No. The motor isnt an issue, the bearings used in the motors are actually slightly looser when cold
What point are you trying to make there? Bearings are not like pistons in a cylinder block. They wear quicker when they are loose, and can suffer an assortment of very unpleasant degradation mechanisms if not properly pre-loaded. They also wear quicker when they are hot too. They wear the least at their designed-for operating temperature.
 

·
Registered
Joined
·
1,560 Posts
Most wear in a motor is related to bearings and high temp seizures. Not low temp wear, as they heat up to operating temp quickly, and the motor temp tend to lag behind, as thats caused by the flow of current rather than friction .
 

·
I'm not crazy, the attack has begun.
Joined
·
23,656 Posts
I agree most wear is due to high temps, and the rest is due to low temps. There is almost no significant wear at all on a bearing at its operating temperature and with the specified pre-load and lubrication, practically zero.
 
1 - 12 of 12 Posts
Top