Electric Car Build
We chose to use a Mazda RX-7
Light and strong chassis
Rear wheel drive
Strong manual transmission
Storage space in areas ideal considering moment of inertia (low and centrally located)
Electric Mazda 1985 RX-7
12 12v 60ah sealed lead acid batteries
Wired in series for 144v nominal
Enough capacity for 40 miles of driving per charge (small city)
AGM allows for faster charging times and higher discharge rates
1000 amp 120v motor controller
Allows car to reach highway speed
Allows for future water cooling
Limited to below batteries max current drain rate
Electric car build
We chose a series wound DC electric motor
1/10 cost of AC motor for small weight and efficiency penalty
More powerful than AC motor to deal with increased weight from batteries
Easily mounted to transmission using available tools/methods
Control Systems
We developed several circuits to trigger warning lights and relays:
Battery balance manager: If voltage sagged more deeply in some batteries than others, warning light and battery number shown
Battery charge balancer: Dissipates extra energy when one battery reached full capacity before others.
Total shut down relay: Set to trigger if current draw exceeded set level, if battery pack level dropped below preset level while not under load, and if any of several thermal sensors registered above preset levels (on battery, motor, motor controller)