EV West's web site can be a really convenient source of quick specifications, and you might even choose to purchase from them some day, but in most cases (including this one) more detailed and authoritative information is available from the company which actually makes the products. In the case of this motor and inverter is Cascadia Motion.
Posts by brian_
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That's supposed to be "ARMS", meaning "A" for amps (the measure of current) and a subscript "RMS" for "root mean squared", meaning the type of average value used for sine waves. It's the way you need to consider current if you are using that current value to calculate power - the same applies to voltage. Often specs will just say "A" for amps and assume that you know it means the RMS version when it is an AC current.
1.6 kWh is the amount of energy stored by the module. In electricity, power is current multiplied by voltage, and energy is charge (product of current and time) multiplied by voltage. So this module can produce 63 Ah (amp-hours) of charge output, which could be 63 amps for one hour, 126 amps for half an hour, 21 amps for three hours, etc.
They don't really need to provide both of these specifications if they are also providing the nominal voltage. If you have any two of nominal voltage, amp-hour charge capacity, and energy capacity, you can calculate the other one. For instance, they say that this module has a nominal voltage of 25.55 V, so
- energy capacity = 25.55 V * 63 Ah = 1600 Wh or 1.6 kWh
- nominal voltage = 1.6 kWh or 1600 Wh / 63 Ah = 25.55 V
- charge capacity = 1.6 kWh or 1600 Wh / 25.55 V = 63 Ah
Yes.
You would need that many modules ("packs" usually means something a little different), but how they're connected doesn't change the energy capacity.
It doesn't change the required energy; the motor needed to operate the motor properly determines how the battery needs to be configured, not how much total battery is needed.
What's the factor of 1.32 for - are you converting 360 VRMS of motor current to DC battery current?
Yes, if your battery is to have 28 kWh of energy capacity and 360 V nominal voltage, it would have 78 Ah of charge capacity.
A motor doesn't draw voltage. It gets whatever voltage the controller gives it. The voltage specified for a motor is usually the voltage that it need to deliver the stated power output at the stated speed. At low speed the controller will give it much lower voltage; the controller can put out less voltage (and proportionately more current) than it gets from the battery, as required to operate the motor as desired.
The stated motor current will be a maximum - more than that and it gets too hot. That same amount of current will be required to produce the maximum rated torque - torque is basically proportional to motor current.
If you want to get the full rated performance over the expected speed range, then yes you need that voltage. Yes, you connect modules in series to reach that voltage, since the controller can only reduce voltage from the battery, not increase it.
Power is something that you haven't addressed at all before this. With a large enough battery to get the desired range, it's usually large enough to handle the power demand, although an unusually high-power motor and a battery capacity chosen for short range can combine to result in a battery that can't handle the power requirement.
In this example, the motor is apparently capable of 210 hp peak output, which is 157 kW. Due to motor and controller inefficiency you might need 170 kW. If you had 17 of the linked modules providing 500 amps (which is what the EV West spec claims they can do), that would be 17 times 25.55 volts times 500 amps which is 217 kW... more than enough.
The other way to look at power requirement is to compare it to energy capacity: a 28 kWh pack could deliver 170 kW for 1/6th of an hour before running out... if it could handle that rate of discharge. That's called "6C" (six times the battery capacity per hour), which is substantial but probably manageable (briefly) for typical EV modules.
Right - lower battery voltage will only affect performance at higher motor speed, where more voltage is required (for the same current and torque) to overcome back-EMF.
Correct... except that if you make the battery small enough in energy capacity it may also have insufficient power capability for peak power demands.
There's not much peukert effect with lithium-ion, but allowing for a reserve makes perfect sense. In published specs for EVs you'll often see "nominal" and a substantially smaller "usable" battery capacity for this reason.
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