Does brake regeneration make any difference?

[Morrison]

I noticed the bosch bikes don't have this, is it something of a gimmick?

 

[amigafan2003]

It only works on direct drive motors.

As the Bosch uses a centre mount freewheeling motor it can't do regen. The Bafang/Cute motors are freewheeling as well so they can't do regen either.

Regen only adds a few % to battery range but it can help with braking - the motor provides alot of resistance when in regen mode meaning you have to use the brakes less.

 

[Ian Spencer]

I think the simple answer to the question is how much do you brake on a typical ride. If you ride in hilly areas there may be a benefit, if you live in less hilly areas then typically you don't brake much so there isn't much opportunity to gain regeneration. For example, around Warwickshire you have miles of fairly flat riding, so regeneration is not going to give you much. Over in Wales, you will get more out of it.

The comparison with hybrid cars is that they are useless on motorways - no opportunity to regenerate, just dragging heavy batteries around, vs. stop start driving in town.

 

[flecc]

Regen has been tried on e-bikes a few times but most makers have abandoned it. Only BionX have retained the facility long term, and that's an optional system with user switched levels of energy recovery. Most BionX users either don't use the facility or only use it very rarely.

Panasonic have more recently been making determined attempts to introduce it on various hub motor designs. There's a front hub motor with the electronic brake being the only front brake, with it's regeneration as a bonus, and a somewhat similar rear hub motor arrangement now. It's too early to say if they will succeed, but the signs were not good for the front motor version which after a two year large scale trial in Japan failed to appear in the large EU market.

Widely held technical opinion is that bikes and riders have insufficient mass and speed for regen to be worthwhile. The results from KERS regen on circa 600 kilo formula 1 cars very hard braking from 200 mph aren't especially spectacular, so 100 kilos of bike and rider modestly braking from speeds like 20 mph isn't going to do much.

The best cyclists avoid braking as much as possible, since it loses hard won gain from effort, so they stand to get hardly anything from regen.
.

 

[Sacko]

My ebike hits 45mph frequently, the braking force regen offers is excellent. If it wasn't for regen, I would be going through disk pads like no tomorrow.

The % put back into the battery is minimal, even travelling at 30mph+, on a 250w bike it wouldn't be of much use imo.

 

[peerjay56]

...Panasonic have more recently been making determined attempts to introduce it on various hub motor designs. There's a front hub motor with the electronic brake being the only front brake, with it's regeneration as a bonus, and a somewhat similar rear hub motor arrangement now. It's too early to say if they will succeed, but the signs were not good for the front motor version which after a two year large scale trial in Japan failed to appear in the large EU market.
.

I'm fairly sure that to be introduced into the UK, you would still need to fit a front friction brake, to meet current specs which require front and rear brakes. The lack of friction brakes (regenerative braking only) on Segways has been a major stumbling block in getting them accepted for road use in the UK. The rest of the world gets it, but not the DfT. As far as they are concerned, no friction brakes means 'no brakes, period'.

 

[Footloose]

Real world experience.....
My KTM eRace P with Panasonic motor uses regen braking. It tells you the % battery charge which is very interesting. On a long hill which may have sapped 3% of charge going up, it will probably put back in about 1% going back down. The 'constant' regeneration mode with 3 levels appears to be most efficient at about 10mph. I think it does less over about 15mph, perhaps because it generates too much power for the controller/battery to cope with. I like the regen with braking for off road riding where you go between power and braking frequently. The system switches over instantly. I am cautious though that I could loose traction on some surfaces if the rear wheel starts to brake more forcefully than I would like.

 

[flecc]

I'm fairly sure that to be introduced into the UK, you would still need to fit a front friction brake, to meet current specs which require front and rear brakes.

Good point, but oddly enough our regulations don't require front and rear brakes they only require two brakes. Some trikes for example just have two front brakes to satisfy the regulations, hub and rim, since it's not easy to fit rim brakes on trike rear wheels.

An e-bike with that electrical front brake could have those two friction brakes on the rear wheel, rim and back-pedal for example, or rim and hub with a balanced single lever operation.

 

[peerjay56]

Good point, but oddly enough our regulations don't require front and rear brakes they only require two brakes.

Thanks. I knew they need two, I assumed that would be front and back