Hacker News Reader

Comment by NickM | Hacker News Reader

given a fixed budget we're probably better off buying 2 diesel buses rather than a single electric bus.

I think the situation is a little more complicated than that. Electricity is a much cheaper fuel than diesel, and maintenance costs are lower for electric vehicles too, so in the long term electric buses may end up saving more money than they cost.

Add to that the fact that interest rates are very low right now, and it may even turn out that financing the electric buses and charging systems could allow cities to save money from day one, though I haven't crunched any numbers so this is admittedly just speculation on my part.

View on HN

> maintenance costs are lower for electric vehicles

I think there is a <citation needed> here. Do ICE drivetrains really constitute a large fraction of the maintenance costs on cars and buses? In my experience, suspension and steering, and auxiliaries, are the things that break.

My anecdotal evidence of ~90k miles on our EV says yes. A coolant flush, tires and windshield wiper fluid are the only things I've done in that time.

Compare that with Brakes, Oil changes, Transmission service, DPF + DEF and the host of other things you get with a diesel engine + transmission.

We've got a diesel truck, diesel tractor and EV, it's pretty easy to see the maintenance differences between the three of them over the years(the tractor being the highest with the added complexity of a hydraulic system).

I don't know anything about cars. Why did you need work done on your brakes on a diesel but not on an electric?

Regenerative braking

Electric vehicles and hybrids use regenerative braking from the motor for a lot of their stopping power. They do still need brake work but significantly less often (100-200K mile interval vs ~50K though there is considerable variance depending on driving habits) because the friction brakes are engaged less often and so wear down more slowly.

The EV gets to just run everything backwards when you step on the brakes. This won't stop you, but it'll make a huge difference to the remaining force needed to stop you, so it massively reduces wear on brakes and (which is why they did it) increases the effective range of the vehicle. And since they aren't worn out, the brakes need maintenance far less often. Driven gently the brakes on a EV might last its useful lifetime.

You can't do this with ICE, if you put diesel fumes in a compression chamber and pump the cylinders up and down, it doesn't turn back into diesel fuel, combustion isn't symmetric, so you need to actually have brakes.

I doubt it's due to the EV's regenerative braking; if anything, that's a more complex system with more things that can go wrong.

The answer is probably easier: a Prius is 3300 lbs and a Dodge Ram is 6600 lbs and carries much, much more if working. Those truck brakes are going to be thrashed much harder.

Not really, the 85D weighs nearly the same as our Ram 1500 EcoDiesel(taken both to the dump scales at one point or another).

It really does come down to the fact that you brake in the 5-10mph range on the EV(or not at all in stop/go traffic).

The regenerative braking system is not complicated at all. In fact, it comes basically for free!

All that happens is you cut power to the motor but leave the wheels attached to the motor. This is the same as "engine braking" on a manual. The wheels turn the motor, which steals kinetic energy from the car and charges the battery.

There's no extra bits or anything. It's all in the drivetrain that's there already.

It's not complex at all and it's a consequence of electric motor operation. The engine goes into generator mode if you turn the supply into a load, which is very easily done and can also be easily done gradually. Regenerative braking uses this generated power to recharge the batteries, but you can essentialy do anything with it, the easiest thing being converting it into heat using a resistor.

Did you not pay attention in high school? When you step on the gas your car, you are converting electrical energy into kinetic energy. When you release your foot, the kinetic energy that is stored into the car moves tires, which moves the shaft of the electric motor. What happens if you manually rotate a conductor inside a magnetic field? Obviously induction happens, which converts the kinetic energy back into electricity and heat.

>more things that can go wrong. Eddy Current Brakes are a passive system with an extremely high safety track record. If you ignore the bearing that holds the wheel/motor in place there are no moving mechanical parts. I couldn't think of a safer way to stop moving objects.

Electric braking, useful 90% of the time to slow down. Hydraulic brakes only get used for a full stop. It's like engine braking on steroids and fully integrated into your brake pedal so that you don't need to know which brake system operates at a given time.

Certainly suspension, steering and auxiliaries are the things that break, but every year (or 15,000km, or whatever your manufacturer recommends) you need to replace the engine oil and filter. Less frequently you need transmission fluids, coolant, air intake filter, brake pads and other consumables. On diesels you also need to refill the emissions compensation tank (the one VW cheated with), replace particulate filters. Heavily used vehicles need these replaced more often.

Electric motors will need their bearings replacing eventually, but they have no transmission fluids, no circulating oil picking up combustion products, and regenerative braking removes a huge amount of wear on brake pads.

I have a plug-in hybrid (EV infrastructure isn't great where I live) and after 2500km the brakes still stick like new. They've barely been used.

Yes. Fluid changes, filter changes, brake pads, clutch maintenance, sparkplugs, injectors etc.

Reply on news.ycombinator.com