Going Down a Steep Hill?

[Senior_Cruiser]

Haven't got my first e-bike yet but have a question about going downhill.

Is your speed going down a steep hill restricted by the motor in the same way Cruise Control in a car slows you down?

How are you supposed to go downhill?

Thanks

 

[addertooth]

On both my E-Bikes, downhill speed seems "unrestricted". Funny thing is the digital display will show me going at 21.1 MPH in PAS 3 mode while peddling, but when I stop peddling, it show my higher true speed.

 

[Smaug]

None of my eBikes will do that. They just coast faster.

You should pay attention to the detail when you're buying your eBike too. Most of the Class 3 eBikes (which you want) will pedal assist up to 28 mph, but throttle only helps up to 20 mph, unless your eBike has some kind of Off Road mode, where throttle is legal above 20 mph.

---

Gas mopeds used to do that. The engine couldn't spin faster, so it was essentially engine braking.

When I was a kid, my grandpa bought a moped so he could go bike riding with my brother and I. I was on a folding single speed bike with 20" wheels, my brother was on this little chopper-style bicycle with 12 or 14" wheels, and my grandpa following on the moped. We were going down this steep hill in Lake Geneva, WI and my brother was in front; he and I were going at least 30 mph. That little chopper bike had not much weight over the front wheel, and it went into a death wobble and he eventually lost control and went flying through the air. Landed right on his face. Miraculously, he didn't break his jaw, but got road rash on his face and broke a tooth.

The reason I mention this here is because my grandpa was out behind us on the moped shouting: "Slow down Macker! Too fast!" But he couldn't catch up, as he was limited to 25 mph by the engine braking of the Jawa moped.

On gas scooters (with CVT transmissions) you also have to be careful as they can get coasting pretty fast down a hill, and when you engage the throttle again, it sets a gear ratio that may be a lot lower than what you were coasting at and there is some pretty immediate braking; rear wheel only. At really high speeds, that is usually not an issue, as wind resistance slows the descent significantly. But if you have a 49cc scooter that usually tops out at 35 and you're going down a steep hill and coast to 45, then hit the throttle, it can be ugly when the rear wheel skids.

 

[m@Robertson]

You go downhill just like on any bike: Use the brakes to keep your speed under control.

 

[HumanPerson]

Coast and use the brakes and caution

or just pedal like h e double hockey sticks lol

 

[HumanPerson]

one is not supposed to wide open throttle these electric bikes while going down a hill though

 

[pagheca]

Is your speed going down a steep hill restricted by the motor in the same way Cruise Control in a car slows you down?

I am not quite sure how the different classes of American e-bikes work, but if they work like the European ones, whose speed is limited to 25 km/h, I was able to reach up to 60 km/h downhill with mine.

The drop in power is not sudden. Sometimes it remains above zero at speeds above 30 km/h. But it gradually decreases and then disappears.

 

[JerryB]

Motor doesn't help braking when going down hill......I use my brakes to slow me down.....if that doesn't work.....up here in the Pacific Northwest.....in an emergency.....we have trees that will slow you down.....quickly!

 

[m@Robertson]

Motor doesn't help braking when going down hill....

Well, it DOES if you have a direct-drive hub motor and that motor has battery regeneration set up. Regen is effectively engine braking, and it can be set up to be quite strong so as to return a decent amount of energy back to the battery coasting down a long slope. But usually its only a mild recovery and a mild effect.

The vast majority of commercial ebikes do not have neither a DD hub motor or regeneration. Regen is typically something a builder sets up themselves.

 

[pagheca]

Well, it DOES if you have a direct-drive hub motor and that motor has battery regeneration set up. Regen is effectively engine braking, and it can be set up to be quite strong so as to return a decent amount of energy back to the battery coasting down a long slope. But usually its only a mild recovery and a mild effect.

The vast majority of commercial ebikes do not have neither a DD hub motor or regeneration. Regen is typically something a builder sets up themselves.

how much weight adds a regen typically?

 

[m@Robertson]

how much weight adds a regen typically?

No such thing, really. Regen is a function that can be found within a direct drive hub motor, and enabled via the hub motor controller. In real terms though, a direct drive hub motor that is of a decent amount of power is quite a bit heavier than a geared hub motor like you find on a commercial ebike. Plus a DD hub has much less torque due to its nature. Lets say you have a Bafang fat bike hub that is king of the geared hub hill at about 85 Nm of output. Even a bigger DD hub is going to be 45 Nm. You make up for this by using a much bigger DD hub which makes up for low torque with a buttload of watts that let you accelerate to very high speeds. Just more slowly (unless you compensate further by making the hub motor even bigger). This is how you see people ending up with 3000w to 6000w hub motors.

Here is a popular one. And it weighs over 27 lbs, and thats before you get to the battery or controller.

3000W Bicycle Motor is the perfect solution for bike, bicycle and motorcycle

3000W Bicycle Motor can speed up your Bike, Bicycle or Motorcycle to reach 100km/h in speed. This bicycle motor is applied to 17 to 26 inch rim.

www.qsmotor.com

 

[pagheca]

thanks. I was wondering if there is a way to install a regen (with an efficient AC/DC) on a hub motor ebike. I read there are some product like that but the real issue is the ratio additional weight / efficiency. In a situation like mine - as I told several time very hilly landscape everywhere - it could be convenient, but only if the regen efficiency is quite high, that I do not think.

p.s. our staff use battery electric vehicles to drive up to 2200m from sea level every day on a very windy road (aka slow speed, no traffic). For some technical reasons we have to recharge at the top. Typically, BEVs reach the top of the mountain with a 50% charge to 80%, and when they get back to sea level they are close to 100%. My next goal is to try it by bike even though I am not sure I will reach the summit with a residual charge. If I had a regen on the bike I could do the same thing without having to carry a charger to recharge before returning.

 

[HumanPerson]

thanks. I was wondering if there is a way to install a regen (with an efficient AC/DC) on a hub motor ebike. I read there are some product like that but the real issue is the ratio additional weight / efficiency. In a situation like mine - as I told several time very hilly landscape everywhere - it could be convenient, but only if the regen efficiency is quite high, that I do not think.

p.s. our staff use battery electric vehicles to drive up to 2200m from sea level every day on a very windy road (aka slow speed, no traffic). For some technical reasons we have to recharge at the top. Typically, BEVs reach the top of the mountain with a 50% charge to 80%, and when they get back to sea level they are close to 100%. My next goal is to try it by bike even though I am not sure I will reach the summit with a residual charge. If I had a regen on the bike I could do the same thing without having to carry a charger to recharge before returning.

Mate, regen is way over hyped on the ebikes...seriously.

You'll only ever get around 7% back on a good day.

If people arte good with that, and some are good with that small amount and some people are not good with that so they turn regen off
on some brands of ebike motors...make sense?

You're better off just using a second battery or getting a huge single battery. . . .

That's not just my opinion...there are alot of builders/ebikers that will say the same then there are others that will just shoot air out
of their blow holes lol

Do what's best for you

 

[pagheca]

Sure, I agree @HumanPerson.

The problem is that the ratio of motor mass, including the AC/DC and the additional control electronics, cables etc., to the total vehicle mass for a BEV is much lower than for an ebike. Therefore, what you gain in energy going downhill is easily offset by what you lose going uphill, also considering that the energy accumulated during braking is proportional to the vehicle mass.

 

[HumanPerson]

Sure, I agree @HumanPerson.

The problem is that the ratio of motor mass, including the AC/DC and the additional control electronics, cables etc., to the total vehicle mass for a BEV is much lower than for an ebike. Therefore, what you gain in energy going downhill is easily offset by what you lose going uphill, also considering that the energy accumulated during braking is proportional to the vehicle mass.

I wish you all the luck on that and hope you'll keep us posted on how it's going

Have a Safe & Happy Holiday mate

 

[HumanPerson]

Sure, I agree @HumanPerson.

The problem is that the ratio of motor mass, including the AC/DC and the additional control electronics, cables etc., to the total vehicle mass for a BEV is much lower than for an ebike. Therefore, what you gain in energy going downhill is easily offset by what you lose going uphill, also considering that the energy accumulated during braking is proportional to the vehicle mass.

It is fun to tinker with these ebikes isn't it

 

[pagheca]

I wish you all the luck on that and hope you'll keep us posted on how it's going

Have a Safe & Happy Holiday mate

Probably you quoted the wrong message but I guess you refer to the idea of going up to the mountain in ebike, and thank you for that!! I will be traveling for a while, but in December I will give it a try.

It is fun to tinker with these ebikes isn't it

One thing that is always on the back of my (poor) mind is to develop an app to foresee the range on a certain path, perhaps using also the record of previous ride by the same person.

 

[Smaug]

Normally, I would agree with Human Person; that it’s not worth it. But remember in this case that the OP lives on a very hilly island. Half of his riding is going downhill. That energy just goes into friction brakes > heat. Instead of burning up brakes going downhill, he could harvest that energy. Maybe more than 7% in that case.

HOWEVER…

He already has a mid drive bike, which makes the climbing so much easier. If I were him, I wouldn’t give up the mid drive climbing torque to get regen on downhills. (And by the way, give up a LOT of torque for climbing, because regenerating setups are always direct drive instead of geared)

Lastly, the OP strongly believes in just having one of everything, so he “can’t” just get another eBike.

 

[JerryB]

Well, it DOES if you have a direct-drive hub motor and that motor has battery regeneration set up. Regen is effectively engine braking, and it can be set up to be quite strong so as to return a decent amount of energy back to the battery coasting down a long slope. But usually its only a mild recovery and a mild effect.

The vast majority of commercial ebikes do not have neither a DD hub motor or regeneration. Regen is typically something a builder sets up themselves.

I hear ya......my Lectric isn't set up like that......so it's brakes for me.....haven't needed the trees yet!

 

[Pinhead]

Normally, I would agree with Human Person; that it’s not worth it. But remember in this case that the OP lives on a very hilly island. Half of his riding is going downhill. That energy just goes into friction brakes > heat. Instead of burning up brakes going downhill, he could harvest that energy. Maybe more than 7% in that case.

HOWEVER…

He already has a mid drive bike, which makes the climbing so much easier. If I were him, I wouldn’t give up the mid drive climbing torque to get regen on downhills. (And by the way, give up a LOT of torque for climbing, because regenerating setups are always direct drive instead of geared)

Lastly, the OP strongly believes in just having one of everything, so he “can’t” just get another eBike.

Would you not technically lose any benefits on the uphill that you would gain on the down ?

This is where mid drives win out every time