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Discussion in 'Electric Motorcycles' started by RedRocket, Jan 19, 2019.
With regen you should never need brake pads.
When I got my EV inspected early in its life the shop said the brakes looked untouched. My car doesn't even have very sophisticated regen, but I rarely use my brakes above 20 mph. Since the energy dissipated goes up with the square of speed, that's very light use.
I'm wondering how this will evolve. AWD is much easier with electric power (even for motorcycles), and also allows all-wheel regen. Some EVs today let you regen very hard, all the way down to a complete stop. Might we someday have all braking done electrically (with inherent ABS), and have only vestigial hydraulic brakes sufficient for only one hard stop (in case of electronic failure)? Maybe no hydraulics at all if you can rig up properly redundant electronic systems?
EDIT: Just thought about this a little more. I can see it being very safe using electric-only braking if you set up the drivetrain so that redundancy requirements are met - sort of the equivalent of protections from failure that today's hydraulic systems have. Of course, the FMVSS would have to be updated to make it legal.
That only works if your EV has enough power to smoke all the tires. If you don't have the power output to break traction on dry, sticky pavement, you can't accept the power input from braking to the limit of adhesion under the same conditions.
So low-power runabouts will always have hydraulic brakes. Electric-only braking from regen only works on high-power vehicles.
There is also the issue of living on top of a long hill and descending with a full charge in an EV with regen-only braking. You can't regen into a full pack, so you'd have to shunt the braking power across some big honkin' resistors. An inelegant (and possibly smelly) solution at best, and even that would be marginal on a really long descent.
So I'm thinking all EVs will always have hydraulics.
Turning kinetic energy into heat is wasteful. Turning it back into electric energy you can store for later use is smart.
We are likely a long way from the complete elimination for hydraulic brakes on road vehicles due to safety regulations. But I can see the day that almost 100% of stopping power for most vehicles will come from regenerative braking.
I use very little hydraulic braking when I drive my Tesla. It even applies the rear brake lamps when deceleration occurs from regen.
I think it’s important that hydraulic braking is present as an safety back up and will likely remain for quite some time. I don’t expect to need brake pads replacements for 10+ years
I understand that the more energy we recover by breaking the best, but c'mon guys, does it really make a difference in running cost if You need to change 40$ of brake pads every 15.000 km? The argument around saving on maintenance for brake pads is really futile when You are carrying 10000 Euros worth of batteries. It may make a difference for taxi drivers driving stop and go 300-400km/day 2.5T of car, but for the rest of us, on 250 kg motorbike it's just marketing.
And by the way electric brakes has been (and still is) used for ages to slow down heavy vehicles (electric retarder), mostly to avoid fading.
I've never understood why the focus of discussions on maintenance is always regarding money only. That's important, but for me the biggest issue is logistics. Scheduling the service, finding a ride to drop it off, again to pick it up, or waste an hour in the waiting room if it's something small. Who needs it?
It's not the money so much (though that can be substantial) as the collateral damage to living your life. It's a big part of the reason I do so much of my own work. At least I get more flexibility that way. For me, brakes are a half-hour job at my convenience, so essentially a non-issue. For others, brakes are a logistics issue as well as a cost.
The last time I did a valve adjustment on my Ninja 250, it was a big help that I could spread it out over a week or so during the winter in my garage (including ordering shims). But it's still WAY better to never have to deal with that again. Electric power is a significant improvement in quality of life.
Sure, I see your point even though I keep reading about saving on maintenance, when on a motorbike that's 4-500 euros every 20000km (for the engine and transmission alone). I'm looking into a ducati now (never been cheap maintenance wise) and the service interval is 30000km for the valves and it cost 400 euros at the dealer. Still, pace of mind was one of the reason I looked into electric motorcycle, I was about to pull the trigger on a zero, but the price is still to steep for me, and it could not be my only bike. Most likely my next bike in 5 to 10 years will be electric.
I remember reading about the possibility of retaliatory tariffs on Zero motorcycles, but I'm not sure if they were actually applied. Hopefully that insanity wasn't implemented, or if it was, let's hope sanity prevails again soon. It's something to look into, because as I recall it was a 25% tariff - plenty to make or break a buying decision.
A Ducati eBike?, sounds interesting! Finally, a big player getting into eBikes should (and will) shake things up.
As for regen negating the use of disc brakes - umm, no. Even brake pad wear reduction, that's like gas mileage ~ it varies.
Screw those brake pads -- leave 'em for emergency and parking only. Having that on EV as primary brake is just clinging again to stone age and never letting it go, so much instilled by big daddies pumping out oil for centuries. Electricity can stop you as smooth and as powerful as you want, does not care if pads are dry or wet, ceramic, organic or sintered, how long does it take to warm 'em up, properly run in etc. Just so damn retarded are those ICEs.
I dont. The brakes on all vehicle tend to be way more powerful, i.e. several times more powerful than the engine. After all you need to be able to come to a stop from 60mph within a distance of a 100 feet or so. Imagine the beast of an engine required to bring to 60mph within the same diatnce, from a dead stop. In an EV that braking power just by regen would require power electronics that are also several times the size needed for normal acceleration, and the battery would have to be able to cope with a charging current thaat would be several times higher than what it puts out during acceleration. So, in short, pure regen braking isnt going to happen anytime soon. And I havent even mentioned lack of redundancy yet.
The simplistic way to look at this is that the ICE only allows power to flow one way. An electric powertrain can shuttle power both ways, but power capability is the same in both directions. The batteries, electronics and motor need to be up to the highest demand.
The fact that brakes are stronger than any ICE is easy to see by simple logic. In order for an ICE to be as strong, it would have to be able to break traction at any speed. It can't. Any decent hydraulic brakes can.
Grocery-getter acceleration is perfectly acceptable in a grocery-getter. But even grocery-getters demand full-gonzo limits-of-traction braking. Grocery-getter power won't provide that.
So for an EV to use regen only as brakes, the only way regen braking would be acceptable is if the vehicle can accelerate so hard it can break traction at any speed. On all wheels. That is a VERY POWERFUL EV. Mind you, it's not hard at all to make a 1000+ hp EV. (Which would be perfectly smooth and docile, no lumpy idle, no peakiness, no attitude, just well-behaved power at all times.) But they aren't exactly common. Anything less in the acceleration department would detract as well from regen braking. You can't take in more than you can put out. So regen-only braking is not gonna happen.
Braking at rates that exceed max acceleration, let alone break traction/activate antilock braking, is not something that happens all that frequently in everyday driving. At least it shouldn't.
As I already stated, friction braking will likely remain due to safety regulations. I just don't anticipate lots of brake pad a rotor replacement work on most EVs in the future since the regen brakes will be doing most of the day-to-day braking work.
I once lived at the top of a long hill and whenever I descended with a full charge in my i3 the car used the hydraulic brakes to simulate regen braking. It was so seamless that the only way to tell it was using hydraulics was that when you did depress the brake pedal it had no play and felt firm underfoot as if it was already braking , which it was.
It looks like the muffler shops that survived unleaded fuel and the brake shops are in for tough times once EVs become widespread .
Forgetting only that vehicles by themselves have tendency to stop, not accelerate
" the vehicle can accelerate so hard it can break traction at any speed"
Now we're taking
I was going to say yesterday this same thing. You can say you have all the regen braking power you want - on the back wheel - leaned over in a turn, a deer jumps in front of you, an idiot turns left in front of you....
That sounds like an emergency.