Should pedaling charge the battery? Or going downhill?

[ebikemom]

Hi all,

When folks hear about my ebike, I fairly frequently get the question "does pedaling charge the battery, or does the battery charge when you ride downhill?"

It makes sense to me that pedaling wouldn't charge the battery, as we want that energy to propel the bike during the riding process. I saw the Mando Footloose EV where pedaling extends range by charging the battery. It seems to me, from reading the specs, that the amount of range extension is pretty negligible, so that there's no way that pedaling can really keep a battery charged. And, it makes sense to me that pedaling on conventional ebikes which don't charge the battery immediately applies the energy to the road surface, also extends range, perhaps more efficiently than pedaling-to-charge-the-battery would, since I think bicycles are pretty mechanically efficient to transfer rider energy output to the road.

But one thing I wonder is about going downhill. This is a common experience for me, since I live in a very hilly area. Sometimes I pedal downhill, if it is not very steep, to get more speed. Other hills, well, I end up BRAKING. That braking is wasted momentum, isn't it? Mighten there be some kind of software solution that takes excess energy and puts it back into the battery? I imagine that any such system, though, would produce drag. Hmmm...

I'm sure you can tell by reading this that I have no technical background. Just using my ordinary imagination ... Musing ...

 

[Ken M]

The only motor configuration that can take advantage of regen is a gearless hub motor (I've heard there may be some geared hub motors with the capability but never seen them for sale anywhere). The main benefit of regen is reducing brake wear and if progressive regeneration is implemented corrected it would be possible to control downhill speeds without braking and even stop the bike without using the brakes (this is possible in some of the current EV cars).

As for recapturing wasted energy, range could likely be increase in the 5-10% range so it's not going to extend the range that much but it's not something that should be ignored give the other merits mentioned.

 

[ebikemom]

Good points, @Ken M . Thanks for the reply! When I look at folks' maps of how much effort they expended versus how much energy was provide by the bike (like those posted by @Alaskan , I think??), the bike is definitely doing most of the work so it makes good sense that any generation wouldn't have a large impact.

 

[rich c]

There isn't must wasted energy with human and bicycle weight added together. Our son has a Chevy Volt. He can almost stop the car driving down a little hill in our neighborhood with regenerative braking. That's close to stopping a nearly 2 ton plug-in hybrid. That's the real place for regenerative braking! Otherwise, you are searching for a perpetual motion machine in a bicycle form to capture all the energy.

 

[Mr. Coffee]

... Otherwise, you are searching for a perpetual motion machine in a bicycle form to capture all the energy.

What most people don't understand is that charging a battery is not a one hundred percent efficient process. If you are very generous I'd guess that the typical charging efficiency for e-bike batteries is under fifty percent. So to fully charge that 700wh battery will require at least 1400wh from your outlet. And faster charging systems are generally even less efficient.

 

[MetroDuck]

I like the downhill speed of a coasting bike and wouldn't want to slow down in order to charge a battery. The amount captures would be rather small and would bring added mechanical complication. I am often asked the same thing about capturing energy followed quickly by "do you charge it when you get to work?" Almost everyone is surprised when I tell them no, I charge it once a week because I can easily make five 11 mile round trips to work without charging. I think most people must instinctively believe that they have about a 5-10 mile range at most.

 

[ebikemom]

I like the downhill speed of a coasting bike and wouldn't want to slow down in order to charge a battery

That's such a good point. I had a bike in Japan that had lights that were operated by electricity generated by riding the bike--the light had a little wheel that rolled against the front tire, producing the energy to power the light. This produced quite a bit of drag, so I only used the light when it was getting dark or at night.

 

[6zfshdb]

Another down side to pedal regeneration is the drag created when walking the bike or peddling without power assist. To further complicate the process, an electrical / mechanical device would have to be installed to disable regen for those situations.

 

[6zfshdb]

Per the Pedego website:

Charge By Pedaling

The battery is charged by plugging it into the wall, and the more you pedal the farther you can go. Your pedaling conserves the battery, but it doesn’t actually charge it.
The technology does exist that would allow you to charge your bike by pedaling, but it’s expensive and we’ve found that it just doesn’t make sense in the real world.
The main problem is that it makes it hard to pedal, and that’s not fun! Even under the most ideal conditions, like riding downhill, the amount of energy you would get back is negligible.

 

[pnop]

If I remember I'll check my car and see how much regenerative energy I've created. Mine is an Electric/Hybrid. (C-Max Energi). It tells me how many miles I've used gas/electric/Regenerative. I haven't checked it in awhile. It's not a lot.

When I was in the mountains the last time I went pretty far because of regenerative energy. I could use electric uphill and then it was creating a decent amount of energy downhill as they were pretty long stretches.

As noted, on a bicycle, it would add a good bit of cost and weight. Probably not worth the gain.

 

[AHicks]

"Regen" works much like engine braking in your car/truck. It does need to be turned on as it basically works by turning the DD motor into a powerfull generator using some electrical wizardry. You can't have both the motor and generator functions working at the same time. It needs to be one or the other. The amount of power actually going back into the battery is pretty much insignificant. Think of the regen as more of a brake than a generator.

The "regen" function (when enabled) is generally turned on with the same switch that turns the motor off when pulling on either brake handle. Though some systems have multiple levels of regen braking available in the setup, you have to be cautious as there can be some pretty serious amounts of electricity getting pushed into the battery. Your system may get a little more than it cares for if getting carried away here. For that reason, the actual braking power we feel when using regen going down a hill is nothing super, though it can be felt. Normally, it just helps hold the bike's speed to a reasonable level. Braking may still be required, in addition to the regen, especially on those hills that feature a stop sign at the bottom of them. Those that operate in coastal areas with rolling hills know exactly what I'm talking about here, I'm sure! Flatlanders will have very little use for the regen function. It's most effective on those long grades that can have you hitting speeds (30mph+) that can make most of us pretty uncomfortable.

Last, the regen (generator) function twists the axle in the opposite direction that the motor does. This is note worthy as the 2 forces work together doing their darndest to loosen your rear axle nuts. Twisting it one way under acceleration, then the opposite way under brakeing (regen). Left unchecked these forces loosen rear axle nuts on regen equipped bikes regularly, and can leave the user with an expensive repair. Point being, those nuts need to be checked/tightened regularly. It should be part of your normal (monthly?) maintenance! -Al

 

[ebikemom]

I’m learning a lot! Thanks!!

 

[Mikey-]

There are a few systems that had that capability, but the companies didn't fare too well (perhaps for other reasons). BionX, and GoSwiss are the first that come to mind.

 

[mrgold35]

I have a Radrover geared hub and the wife has the Radcity direct drive rear hub with re-gen braking. I think the re-gen feature only engages in PAS levels 1-5 (no regen in PAS 0). The issue with regen braking is you need to coast down declines to take advantage of this feature. You end up using more battery power on inclines and you only get back about 10% max on the same hill on the decline if you coast. The regen braking on my wife's Radcity slows her down when coasting on steep inclines and she needs to pedal more than me on my Radrover to maintain her speed (I end up braking more to match her speed). Even getting back 1% on her Radcity is better than 0% with my Radrover. Considering it takes almost 5 hours to recharge a battery, not sure how much regen will put back after coasting down a hill for 1-2 minutes?

 

[tomjasz]

1000W MXUS direct drive with regen controller, Lyen 6FET with CA3 link. Regen is negligible. Not enough downhill runs, and then a DD is a weak motor for uphill runs. From my view an interesting process that doesn't give much back in my use.

 

[AHicks]

I have a Radrover geared hub and the wife has the Radcity direct drive rear hub with re-gen braking. I think the re-gen feature only engages in PAS levels 1-5 (no regen in PAS 0). The issue with regen braking is you need to coast down declines to take advantage of this feature. You end up using more battery power on inclines and you only get back about 10% max on the same hill on the decline if you coast. The regen braking on my wife's Radcity slows her down when coasting on steep inclines and she needs to pedal more than me on my Radrover to maintain her speed (I end up braking more to match her speed). Even getting back 1% on her Radcity is better than 0% with my Radrover. Considering it takes almost 5 hours to recharge a battery, not sure how much regen will put back after coasting down a hill for 1-2 minutes?

Rad City regen (as well as many others supporting regen) is activated as soon as either of the brake levers are applied. It's the same circuit that would kill the motor in an emergency. Trick here is not to have them adjusted so tight the brakes engage right away. If you're able to pull the brake levers in about 3/8-1/2" or so prior to the pads actually hitting the disks, you can ride with brake lever(s) pulled just slightly w/regen activated, but the disc brakes are not. Flatlanders won't care....

 

[ebikemom]

Thanks, everyone! This helps me answer questions that people ask me!

 

[harryS]

Finally, say it takes about 1 kilowatt-hour to charge the bigger ebike battery. That costs about 10 cents here in the USA. If regen gets us back 10%, it saves a penny. Clearly, one is not looking at it to save money, although some riders feel they do save lots of money on brakes.

We picks our bikes for all kinds pf personal reasons. No single motor type meets all situations and needs. If you happen to choose a motor where regen is possible, might as well use it.

 

[ebikemom]

The natural braking aspect of regen is an interesting feature that could be a plus in very hilly areas (like where I live!)

 

[jazz]

My e motorcycle has regenerative brakes and I love it. I can almost completely stop my bike by laying off the throttle when coming to a stop.

I know the former Polaris ebikes had regen brakes that worked when you used them and also if you went above 20 miles per hour the regen would kick in.