Enter the vacuum pump. It is exactly what it sounds like.
Most vacuum pump systems on EV parts websites are over $300. I found a vacuum pump on eBay for $65. However, when I got it in the mail, it turned out to be much smaller than I thought it was. It is actually meant for supplying vacuum to HVAC systems on diesel pickup trucks.
I decided to test it out anyway. I powered it with a toggle switch and hooked it up to the brake booster. Whenever I braked I turned it on and left it on for 10 seconds after I braked. It worked okay for a single brake application, but two brake applications completely depleted the vacuum booster of vacuum. Not good enough.
A while back I made a discovery. It turns out that many Volvo cars use vacuum pumps for their braking systems. So the other day I bought a used one on eBay:
It should arrive this week. Soon I will install it and start to test it out.
I also bought a whole bunch of things on Cloud Electric's website:
-Throttle potbox - hooks up to the "gas" pedal and tells the motor controller how much throttle is being applied; contains a potentiometer (hence the name) and a microswitch for idle-validation/safety purposes.
-Two 400A fuses - circuit protection between the batteries and motor controller.
-Vacuum switch - turns the brake vacuum pump on and off to maintain a preset vacuum level.
-Pre-charge resistor (1000 ohm) - allows a trickle of current into the motor controller to slowly charge the giant capacitors inside it before the main current contactor is closed; without the resistor, a giant inrush of current would possibly damage the contactor when it is powered on.
That pretty much does it for parts that I need. I might need some more battery cables (which I can probably get for free at a truck salvage yard) and a small 115V space heater, but more on that later.