Is REGEN, really worth it ?

General Discussion about electric bicycles.
rumme   100 kW

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Is REGEN, really worth it ?

Post by rumme » Aug 31 2017 9:56pm

Lets say you have a 20 mile commute using regen in the best conditions for it to be used, what is the max voltage input 1 can expect back into the battery ?

5% - 10% max ?

Are there any negative aspects to using regen , as far as wear and tear on the motor, magnets, controller, battery ?

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Re: Is REGEN, really worth it ?

Post by wesnewell » Aug 31 2017 11:21pm

Just consider anything you get back a bonus as compared to the braking safety and pad wear you gain from regen braking.
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Re: Is REGEN, really worth it ?

Post by cwah » Aug 31 2017 11:41pm

Yes.
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Re: Is REGEN, really worth it ?

Post by LockH » Sep 01 2017 1:17am

^^ Watt these folks mention re brake pad wear. Question? Much "stop-and-go" over your "20 mile commute"? Back in the daze of riding w/SLA, used to "pay" me NOT to need/use any brakes, but to see/anticipate stops coming and to just coast up to any stops. So using ANY braking was a waste of stored kinetic energy.

Regen would have been... super useful. :wink:
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Re: Is REGEN, really worth it ?

Post by spiros » Sep 01 2017 1:25am

I live in a place with steep hills I do a lot of steep road and if I had a regen brake I will not have to change pads on both my four piston caliper every 500km

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Re: Is REGEN, really worth it ?

Post by MadRhino » Sep 01 2017 2:34am

It is different for various riders, systems and conditions.

Performance doesn't live well with regen braking. It does produce heat, a handicap to a system that is running close to heat limit already. Good brakes in the hands of a good rider, are making a much shorter braking distance than regen in most riding conditions. Saving brake pads on the rear, is irrelevant unless the rider has no clue of performance braking technique. When you ride hard, you need to brake short, or break bones that have a greater value than brake pads IMO. Variable regen is good to have for it can be used advantageously in some situations, yet the rear brake is for a very little part of braking performance. Some pro motorcycle riders are doing a whole race sometimes, without touching the rear brake lever at all. The higher the speed, the less a rear brake is useful.

Now for lower power/speed systems, regen can be an interesting advantage. I use regen braking in the winter when the conditions are slow and slippery. Regen can improve efficiency, giving a longer range, and even shorten the braking distance of a bike that has brakes too small for its weight. In some extreme conditions, it is good to have regen braking option to help keeping the tail behind you.
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Re: Is REGEN, really worth it ?

Post by amberwolf » Sep 01 2017 3:23am


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Re: Is REGEN, really worth it ?

Post by dogman dan » Sep 01 2017 6:31am

If the stop and go is extreme, then the wasted power on the starts, plus brake wear, could make regen very attractive.

The main drawback of regen, is you need superb torque arms, nice and tight, or the back and forth motion of the axle, even very small, can loosen your axle nuts.

I ran regen for a while, but my less than superb torque arms kept me checking the nuts, and I wasn't using it enough to make it really worth it.

If you do regen, I really liked having it separate from my brake handles. a push button got me regen only, and handles got me regular brakes. I liked that setup a lot.

But like I said, not enough stops on my routes, so I never saw much over 2% back. On a huge hill, regen slowed me to 5 mph, which I did not like that much. I could not adjust the regen, so I was either braking hard, or not.

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Re: Is REGEN, really worth it ?

Post by Alan B » Sep 01 2017 7:01am

Safety. With a long 15% descent on the commute I found the brakes to get very hot, and there was little braking capacity left that was not used up, the brakes were close to fade just from the descent. If something required emergency braking during that descent the brakes would fade and stopping distances were not very satisfactory.

With variable electric braking (regen plus powered electric braking in the Sabvoton and a big DD motor) I found adequate electric only braking for the descent, and the friction brakes were fully available if needed for emergencies and the last MPH of stopping. I built a brake handle with a linear voltage output and a switch to actuate the Sabvoton, so it is pretty natural to invoke and control the regen.

I also appreciated the zero maintenance aspect for this commuting machine. No brake pad wearout to worry about. Charge and ride. Occasionally replace a worn out tire or fix a flat.

The extra range was not the motivation.

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Re: Is REGEN, really worth it ?

Post by pwd » Sep 01 2017 8:05am

I've been sporadically commuting to work over the last 5 years or so and it is worth it. My bike (2WD) stops much better with regen since it is quite heavy. My commute is short but frequent. I average around 14km per day when I ebike to work and see 3-5% regen power back. I love the feeling of regen braking and I don't feel as comfortable riding without it. I have my rear motor set for strong regen and my front has light regen so it doesn't shift the weight too much. I use regen to slow down from max speed and then apply the mechanical brakes to come to a complete stop.
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Re: Is REGEN, really worth it ?

Post by neptronix » Sep 01 2017 8:51am

I like it so much that i removed my rear mechanical brake so that it would no longer engage and rob me of power coming in. On my bike, regen happens at the same wattage as peak efficiency on my motor, so the added heat accumulation is so small that i don't notice it.
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Re: Is REGEN, really worth it ?

Post by Toorbough ULL-Zeveigh » Sep 01 2017 9:27pm

dogman dan wrote:I never saw much over 2% back.
you walk into the luna store or ebikekit or wherever you were working (kant member zaktly) to buy a battery.
they have a 1000 Wh battery that is the same size, weight & price as their 1020 Wh battery.

which one do you buy?
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MadRhino   100 GW

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Re: Is REGEN, really worth it ?

Post by MadRhino » Sep 01 2017 11:47pm

Toorbough ULL-Zeveigh wrote:
dogman dan wrote:I never saw much over 2% back.
you walk into the luna store or ebikekit or wherever you were working (kant member zaktly) to buy a battery.
they have a 1000 Wh battery that is the same size, weight & price as their 1020 Wh battery.

which one do you buy?
None. That is suspicious, and I prefer buying where specs are realistic.

Yet, I don't see what it has to do with regen.
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Re: Is REGEN, really worth it ?

Post by amberwolf » Sep 02 2017 1:48am

He's just saying if you can get 2% extra Wh for free, without any extra stuff being done or added to the system, why not go for it? ;)

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Re: Is REGEN, really worth it ?

Post by Chalo » Sep 02 2017 3:28am

On-demand regenerative braking is fine if you've already resigned yourself to a direct drive motor without freewheeling. On a crazy steep route, or one with lots of sprints and stops, it can increase your range.

But on any route that would seem appealing on a normal pedal bicycle, using a direct drive motor that's capable of regenerative braking is a huge drag, literally and figuratively.

If brake wear figures into your calculus, you're either a coward about routine maintenance, or you have the wrong brakes for the job. Good brakes require little attention, and they're easy to maintain. On the other hand, I once burned a set of disc brake pads down to their backings in less than 20 miles of city riding. So it's relatively easy to pick the wrong brakes for the job, especially if you buy into overhyped notions.

As for me, I'd rather be able to coast freely than have regenerative braking. All my habits as a pedal cyclist are attuned to taking advantage of coasting.
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dogman dan   100 GW

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Re: Is REGEN, really worth it ?

Post by dogman dan » Sep 02 2017 6:55am

Apples and oranges,, you won't have to constantly check your axle nuts for buying a different battery.

In my case, my torque arms were too loose to make running regen all the time worth it. And 2% back on a trip to Walmart that used 5 ah was not saving me much, when the bike carried 33 ah.

So it was not worth it,,, FOR ME, with the exact setup I had. If there was a 15% grade hill to go down on the way to Walmart, then I would have demanded regen, and improved my torque arms to have it. Because of the slower rpm motor I had on the bike, cogging alone slowed me to where I never overheated my brakes, on any grade under 8%.

2% back on a tour that used all of that 33 ah, would be priceless of course, but I really seldom used more than 25 ah on any given ride. 5% back even better. AS ALWAYS, the question of is anything worth it, depends on your needs.

In my case, not much chance to use regen, on a road that is over 50 miles long without a stop sign the whole way. Around town, I never came remotely close to needing that 2% more. And my disc brakes lasted fine, since I rarely was stopping from all that fast a speed anyway. When I'd go to the mountains, the dd motor would limit my speed to about 30 mph, and I would not be riding those brakes at all. A faster wind dd motor would have had me riding the brakes. But on the mountain, descending at 5 mph was not my style either, so even when I had regen, I rarely used it on a mountain, till the first stop sign.

Regen that limited me to 20 mph down a mountain would have been used, but I did not have that. I had 5 mph, or nothing.

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Re: Is REGEN, really worth it ?

Post by MadRhino » Sep 02 2017 7:32am

amberwolf wrote:He's just saying if you can get 2% extra Wh for free, without any extra stuff being done or added to the system, why not go for it? ;)
Ah! Thnx.
I had missed the image in translation.

Still, that is 20% capacity recovery. I have seen 20% regen on my first bike, just before my controller burst in flames. Now, my system is running very close to heat limits, and it does need the moments of cooling that regen would steal. That is the main reason why I avoid using regen in the summer. Building for reliable use of regen, would have a cost in performance and weight.
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Re: Is REGEN, really worth it ?

Post by miro13car » Apr 13 2018 7:59am

I cannot imagine my ebikes without regen.
Virtue of any electric vehicle is regen.
on my ebikes I use regular disc brakes only for emergency.
brake pads last forever, like thousends of kilometers.
On steep 20% downhills beauty of regen breaking is obvious when I dont grind anything.
Of course everyting depends on your DD hub system, how regen is implemented.

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Re: Is REGEN, really worth it ?

Post by John and Cecil » Apr 13 2018 9:03am

With all the hills I wish we could have regen braking, but we have a mid drive motor. I am guessing regen braking requires a hub. Perhaps if they come up with one that does not weigh too much I would not mind adding a small hum motor with regen to our front wheel if it was geared for a max speed of 6-8mph or so. It would be great to kick in when climbing steep hills for all wheel drive, and then on the way down it would add to our battery reserves and keep our brakes fresh and ready for action.

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Alan B   100 GW

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Re: Is REGEN, really worth it ?

Post by Alan B » Apr 13 2018 9:24am

It all boils down to how you want to use your ebike, and what you are used to. If your normal ride was a shaft drive water cooled motorcycle, or a modern car you don't have to get greasy every few weekends keeping on the road, migrating to an ebike that needs periodic tweaking is like stepping back in time to when you could not afford a good machine. If you want something extremely reliable, that gets you to work on time every day, and doesn't require fiddling with, then DD with regen and moped tires that laugh at glass and last 3-10K miles for the win. Chains don't wear out. No gears or clutches in the hubmotor to periodically need replacing. Brake pads last - nearly forever. And descending down that 15% gradient with variable regen instead of heating the brakes to near smoking temperatures increases your safety margins if you suddenly need to stop.

Justin measured DD motor drag, and it is not much energy. More an annoyance than an actually important loss. To avoid DD drag you must use a geared hubmotor or a mid drive (or a DD motor with a teeny tiny bit of power applied). Either of these has significantly more maintenance than a DD hubmotored regen equipped machine. Brake pads, gears, oil, grease, chains, sprockets, frequent fiddling. Some (who may make their living wrenching) don't mind or even enjoy the work, others of us associate frequent maintenance with inconvenience and inadequate suitability for the purpose.

To be sure I've built ebikes of each type, and enjoy every one. But the BEST machine for the daily commute is the DD motored variable regen equipped moped tired machine. The rest of the fleet is more toy than tool.

When riding for fun, with no deadline, climbing the single track, enjoying the weather - that's when the toys come out. Who cares if it breaks down, there's no time clock to punch, no repercussions from being late. Then the geared hub or mid drive shines. Lighter bike, less drag, more bike-like feel. If you want to pedal and coast, the DD drag is annoying.

But when you need to get somewhere, on time, no excuses, no flat tires, no melted gears or broken chains or smoked brake pads. Then the Regenned DD wins. It is a commuting machine, not a weekend warrior-toy.

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Re: Is REGEN, really worth it ?

Post by spinningmagnets » Apr 13 2018 9:47am

Well said, Alan. I agree...

When I was young and stupid (I am no longer young), I was riding a bicycle and came to a long downhill (Signal Hill in Los Angeles). I knew I had to "take it easy" on the downhill, but figured that I would simply bring it to a stop if the brakes were struggling, and then walk down.

Of course the brakes were worn and out of adjustment (it had bald tires for the trifecta), so they failed spectacularly, with me picking up speed rapidly. Halfway down the hill was a stoplight that I hoped would cycle enough to turn green before I shot through it. It turned red just before I got there, and one car crossed in front of me just before I shot through behind it. For a brief moment, I pondered the possibility that I should "bail out" and do a stuntman roll onto the asphalt, but by the time I made that calculation?...I was going even faster, and froze.

After I reached a section where the steepness was easing off, I was able to slow down enough to add Flintstone brakes (the soles of my tennis shoes). At least I was wearing a ballcap to protect me from head injuries...(my severe head injuries are from a completely separate incident)

Regen is nice to have, and...if your controller has it, you still don't have to use it, so...I'm thinking you are wondering if it is worth shopping for a DD hub and a controller that has that feature. Like Alan said, it depends on what you are going to do with it.

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Re: Is REGEN, really worth it ?

Post by John and Cecil » Apr 13 2018 10:08am

Do they make lighter hubs for just regen braking without the motor function? i think it might be a good safety feature to have as well as the energy it creates. We ride where there are a lot of steep hills.

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Re: Is REGEN, really worth it ?

Post by Chalo » Apr 13 2018 3:10pm

miro13car wrote:
Apr 13 2018 7:59am
I cannot imagine my ebikes without regen.
Virtue of any electric vehicle is regen.
Nope. Just the heavy inefficient kind.

If you have an electric bicycle, you might want it to ride like a bicycle-- which means having the ability to coast freely. That's something you can only have instead of regenerative braking, not alongside it.
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Re: Is REGEN, really worth it ?

Post by John and Cecil » Apr 13 2018 3:52pm

I do not understand how you cant have a bike that has regen braking without effecting it's coasting characteristics. If it had it's own hub (like an alternator I imagine) and a clutch type device that worked in reverse so it is always freewheeling but as you engage the handle it engages the alternator to generate electricity. It seems (at least theoretically) that it could be done, at least in a hub dedicated for only generating power. And as a dedicated generator it could probably be made more powerful to generate more power.

Now maybe the added weight of everything might make it not worth it due to more energy being expended to move the extra weight around, but it would seem possible to do it. At the very least you could lower one of those light generators onto your tire and that would generate power while slowing you down, then disengage from the tire and it does not effect freewheel.

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Re: Is REGEN, really worth it ?

Post by Alan B » Apr 13 2018 4:29pm

Rather than creating some complex mechanical system it might make more sense to use a regular DD hubmotor and set the controller up to apply the tiny bit of power to just cancel the drag. Then you can coast without drag. You could even add a tiny bit more power and have even better coasting. Plus you still have regen. One way to do this would be to use a torque based controller (like the PhaseRunner), and add a potentiometer set up to vary the minimum setting of the throttle. Then it could easily be tuned to just cancel out the motor's drag. Might be fun to try.

Some DD hubs have less drag than others. Searching out the lowest drag DD motor might be worthwhile if that is an issue.

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