Hi all,
As most of you know I asked a bunch of questions to McLaren higher-ups and techs because I felt there was confusion about the drive train tech used in the P1.
To start this thread, I think it is best for me to get a few basic physics explanations out there so words or things I use in the actual post will not be misunderstood or maybe understood better than before by some.
Very low level... hope thats ok, not saying you guys are all physic-idiots, just better to establish a level playing field
Watt is a "unit of power". Short form: W
kW = kilo Watts, ie 1 kW = 1000 Watts
One Watt is the rate at which work is done when an OBJECT is kept at the velocity of 1 meter per second against the opposing force of 1 Newton.
Maybe a bit better example (which removes weird physics things like Newton that maybe not everyone understands): A person weighing 100kg, climbing a 3 meter high ladder in 5 seconds time does 600 Watts of work. {(kg * m^2) / s^3 - if anyone cares...}
1 HP is the old "unit of power" which was originally defined as the amount of work one horse could do pulling the wheel in a mill.
1 HP = 0.746 kW or 1 kW = 1.34 HP.
HP in a motor is calculated from its Torque and RPM. HP = Torque * RPM / 5252. So if an engine delivers 200 Nm of Torque and 2000 RPM, it delivers 76 HP at that RPM.
1 Watt is also 1 VA. Volt Ampere when looking at electrical units. So an electric motor converts VA into power and thus torque at a certain RPM of that motor. It can also be used as a generator by applying power to the shaft from outside which generates VA or Watt.
A BATTERY stores power. The power stored is measured in Wh. Meaning how many Watts it can produce over one hour period. So if you want to know how long it can deliver a certain amount of Watts, you divide the Wh by the Watts asked for. A battery has a certain max power output based on the Volts and Ampere it can deliver.
An electric motor converting electric power into kinetic power will always have a loss of conversion. So even if a battery can deliver 100kW and the motor can take it without issues (structural/heat issues in the end only) the power on the shaft will not be 100kW but a little less than that. How much depends on how well the circuits can convert the energy. How much heat is produced in the wiring and so on...
In my post below, note that when I talk about the ENGINE I will be talking about the PETROL ENGINE. When I talk about a MOTOR I will be talking about the ELECTRIC MOTOR.