Hello I am another newbie here with some questions; but I’ll start with a little background. Back in June I bought a new Chevy Bolt, which is my first foray into the EV world. Then this month I took the Bolt to a National Drive Electric Week event where I came across a 1976 AMC Pacer Conversion; this got my brain juices flowing. I began researching a DIY conversion which brought me to this forum and I’m hoping that you all can clear up some mysteries of the magic that happens under the hood of an EV.
How is pack voltage related to motor voltage? My though experiment involves a pickup truck, from what I have read it would be wise to go with a 144 VAC motor because of the weight and poor aerodynamics if I want to attain and maintain highway speeds. For now, let’s assume LiFePO4 cells, which are a nominal 3.2v. 45 in series would create a 144V pack. Then depending on the Ah capacity of the individual cells this would determine the capacity: 100 Ah cells would be 14.4 kWh, 200Ah->28.8kWh etc. So far so good?
Now if I double string to 90 cells in series I get a 288V pack (with 100Ah -> 28.8 Kwh). Does the motor controller then regulate that Voltage down to the 144V that the motor is rated for, or does the motor run at 288V? If it runs at 288V does it use less amperage to maintain a given rpm, effectively drawing at .5C? Does it decrease the life span of the motor?
Or is it wiser to take that same 90 cells and pair them in parallel then in a series of 45 pairs of 100Ah cells to maintain the 144v at 200Ah for the same capacity of 28.8 kWh?
Thanks,
Dad
How is pack voltage related to motor voltage? My though experiment involves a pickup truck, from what I have read it would be wise to go with a 144 VAC motor because of the weight and poor aerodynamics if I want to attain and maintain highway speeds. For now, let’s assume LiFePO4 cells, which are a nominal 3.2v. 45 in series would create a 144V pack. Then depending on the Ah capacity of the individual cells this would determine the capacity: 100 Ah cells would be 14.4 kWh, 200Ah->28.8kWh etc. So far so good?
Now if I double string to 90 cells in series I get a 288V pack (with 100Ah -> 28.8 Kwh). Does the motor controller then regulate that Voltage down to the 144V that the motor is rated for, or does the motor run at 288V? If it runs at 288V does it use less amperage to maintain a given rpm, effectively drawing at .5C? Does it decrease the life span of the motor?
Or is it wiser to take that same 90 cells and pair them in parallel then in a series of 45 pairs of 100Ah cells to maintain the 144v at 200Ah for the same capacity of 28.8 kWh?
Thanks,
Dad