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Hello, just created my account today.

my SO is anti-ICE cars generally, and especially hates my Thing (exhaust smell, mediocre fuel efficiency). So for the planet and marital harmony, I either have to sell it, or do an EV conversion.

Using the extra time provided by the lockdown to start doing my research. I have some super-basic questions. Like why do I even need the gearbox anymore, given that electric motors provide full torque at 0 RPM? Also, why do I need mechanical brakes, if my EV system has regenerative braking? Probably there are specific threads around these topics where these questions would be better posted (I just haven't poked around this Wiki enough to find them yet) so I'm not necessarily expecting an answer here.
 

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I have some super-basic questions. Like why do I even need the gearbox anymore, given that electric motors provide full torque at 0 RPM? Also, why do I need mechanical brakes, if my EV system has regenerative braking?
"Full torque at 0 RPM" is why a clutch is not needed, not why a transmission is not needed. A transmission provides a lower-speed and higher-torque output, rather than using the engine or motor's output directly; a motor with enough torque output to drive the vehicle's wheels directly with sufficient performance is too heavy and bulky. Multi-speed transmissions exist to allow the motor to run at a speed which it needs to produce enough power, despite a wide range of road speeds.

Modern high-voltage EV motors can produce the required power over such a broad range of speed that they can (and almost all do) use a single-speed transmission. Until people started using salvaged EV motors and batteries, most DIY conversions didn't have enough power over a wide enough speed range, so more than one transmission ratio is typically used.

So with the right motor and battery, you can use a transaxle (transmission and differential) with a single-speed transmission instead of the original transaxle.

Also, why do I need mechanical brakes, if my EV system has regenerative braking?
You need brakes on all four wheels, so you still need mechanical brakes on at least the front wheels. Many DIY conversions use motors which are not capable of effective regenerative braking. Even with regenerative braking, it will not be adequate at very high or very low speeds, and the drive system is generally not considered reliable or redundant enough to depend on for braking, so a complete and effective braking system still has mechanical brakes on all wheels.
 
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