Analysis of regen on an ebike

[serious_sam]

Thanks.

Can you link to the chevybolt.org thread please?

 

[Warren]

Can you link to the chevybolt.org thread please?

It is not a single thread. This comes up all the time, but here are two fairly long ones.

https://www.chevybolt.org/threads/hypermiling-driving-habits.30055/

https://www.chevybolt.org/threads/range-hypermiling-modifications.13466/

 

[Jil]

My 2 cents :
I have ridden my GMAC in the Pyrénées mountains a few days ago.
Battery output limited to 300 watts, loop of 26 km & 1040 m D+, many parts above 10% inclination.
I have consumed 6.65 Ah (360 Wh) to go up, and going down I got back 2.35 Ah with regen, i.e. 35% of the energy spent to climb.

 

[Jil]

Question : from your experience, considering only geared motors, does it worth it to have regen when travelling on an ebike, or a motor with inner freewheel is preferable ?
I'm talking about GMAC vs Shengyi SX2 (or equivalent).

On hilly areas, my recent experience tends to confirm that yes, regen is a big plus to save your brake pads and optimize your range.
And the electronic freewheel on my GMAC consumes around 20 watts only, which means that in case I run out of battery when travelling (let's say when I have only 50-100 Wh left), I can just turn of the assistance and use only the electronic freewheel for the next 50 km or so to avoid all inconveniences due to the drag.

 

[E-HP]

My 2 cents :
I have ridden my GMAC in the Pyrénées mountains a few days ago.
Battery output limited to 300 watts, loop of 26 km & 1040 m D+, many parts above 10% inclination.
I have consumed 6.65 Ah (360 Wh) to go up, and going down I got back 2.35 Ah with regen, i.e. 35% of the energy spent to climb.

It seems like if you could climb the hills without the motor, then you could get to infinite percent regen?

 

[Jil]

It seems like if you could climb the hills without the motor, then you could get to infinite percent regen?

Yes, and then you don't need a battery anymore
If it's what your comment is about, 300 watts uphill was enough, for me and my girldfriend also (even though she is not an experienced biker). What's important is to have a correct gear ratio to keep sufficient pedaling rpm at any time (on my bike the smallest gear is 30x46). Of course you have to climb slowly, but it remains much more agreable than without motor. The GMAC is very good at this exercise.
By the way, for such long and steep hills, more than 300 watts continuous can quickly lead to overheating even with a GMAC (I have reached 95 °C).

 

[E-HP]

Question : from your experience, considering only geared motors, does it worth it to have regen when travelling on an ebike, or a motor with inner freewheel is preferable ?
I'm talking about GMAC vs Shengyi SX2 (or equivalent).

On hilly areas, my recent experience tends to confirm that yes, regen is a big plus to save your brake pads and optimize your range.
And the electronic freewheel on my GMAC consumes around 20 watts only, which means that in case I run out of battery when travelling (let's say when I have only 50-100 Wh left), I can just turn of the assistance and use only the electronic freewheel for the next 50 km or so to avoid all inconveniences due to the drag.

Your situation, and mine, are exactly why regen works better for some folks (for energy recovery) than others. For me, 270 watts or so of regen is the optimum level for energy recovery, given my bike, motor, controller, weight and terrain. Any more than that, and the bike won't maintain the speed necessary to recover energy. Pedaling uphill is the key.

When I go for a longer ride, I expend most of my own energy up front, climbing about 800 feet to the top of the ridge, with a decent amount of pedaling. Works out, since I'm still fresh. I can ride along the ridgeline with gentle grades without using much battery, and then take a long route to descend, ending up 4 cities away, but basically at sea level, which again is flat riding, following the bay, with a short climb to my house at the end. 40-50 miles, still lots of battery left. I don't think the route would work as well in reverse, since I'd be doing that pedaling at the halfway point when I'm more spent (and too old). The descent at the end would be short, so less recovery too.

I have a poor man's freewheeling/coasting button I use, that I have set to 50-60 watts, which will coast forever on flat ground. I use it mainly when navigating around foot traffic, but it would work in a pinch for pedaling home.

So, if you don't pedal much, crank up the amps, and just use regen for braking. Pun intended...your mileage may vary. :lol:

 

[Jil]

For me, 270 watts or so of regen is the optimum level for energy recovery, given my bike, motor, controller, weight and terrain. Any more than that, and the bike won't maintain the speed necessary to recover energy. Pedaling uphill is the key.

In my case, I found that 10-12A (i.e 5-600 watts) of regen were an minimum to slow down enough the bike. On very steep descent, 15A would even be better (but I'm limited by my battery).

When I go for a longer ride, I expend most of my own energy up front, climbing about 800 feet to the top of the ridge, with a decent amount of pedaling. Works out, since I'm still fresh.

Pedaling is the key indeed to optimize the range. During this 26 km/1040 m D+ trip, as per the CA, I have used the same amount of human energy (350 Wh) than electrical (360 Wh).

 

[E-HP]

For me, 270 watts or so of regen is the optimum level for energy recovery, given my bike, motor, controller, weight and terrain. Any more than that, and the bike won't maintain the speed necessary to recover energy. Pedaling uphill is the key.

In my case, I found that 10-12A of regen were an minimum (i.e 5-600 watts) to slow down enough the bike. On very steep descent, 15A could even be better (but I'm limited by my battery).

I have a lot of flexibility on choosing my descent, and usually look for a long steady route to recapture energy. But, I may do some experimenting since maybe a steady slope isn't optimal; I watched this video last night that made me think about finding a route that varies between steep and flat. Not sure if it will make a difference, but fun to test it out:
https://www.youtube.com/watch?v=MBSRPuUibxk

 

[Jil]

Here is a simulation to feed the discussion :wink:

Geared motor with regen vs mid-drive (GMAC vs BBS02)
28" wheels, fully loaded bike for travel (i.e. 130 kg bike+rider+luggages)

To simulate hilly trips, let's assume a 10 km/7% hill, climbed at 12 kph with 100 watts pedaling, followed by the same descent where regen is used with the GMAC at 30 kph limit (and no pedaling).
https://ebikes.ca/tools/trip-simulator.html?m=GMAC10T&v=mountain&ms=130&h=100&w=28&sp=12&wv=0&b=B36LiGox10&c=BRL10&rg=false&t=21&ct=21&st=21&i=man&p=16A0BJ32&mo=&md=&x=&y=&lx=&rx=&rw=
https://ebikes.ca/tools/trip-simulator.html?m=GMAC10T&v=mountain&ms=130&h=0&w=28&sp=30&wv=0&b=B36LiGox10&c=BRL10&rg=true&t=21&ct=21&st=21&i=man&p=1636BG9T&mo=&md=&x=&y=&lx=&rx=&rw=
GMAC : +268 Wh for climbing, -127 Wh with regen --> net consumption 141 Wh (i.e. 7 Wh/km)
BBS02 : +235 Wh used for climbing, 0 Wh with regen --> net consumption 235 Wh ((i.e. 11.7 Wh/km)

Simulating flat trips is not possible on the Trip Simulator for the BBS02 (speed limit at around 13 kph, probably because of gear ratio), but from the Motor Simulator, at 30 kph on flat road both motor efficiencies are the same, around 81-82%, with consumptions of 8 Wh/km.
https://ebikes.ca/tools/simulator.html?mid=true&motor=MBBS02&gear=1&tr=14&batt=B36LiGox10&cont=BRL10&wheel=28i&mass=130&grade=0&autothrot=true&throt=10.540157419807164&autothrot_b=true&cont_b=BRL10&motor_b=GMAC10T&batt_b=B36LiGox10&wheel_b=28i&mass_b=130&throt_b=10.902972275276522&grade_b=0&bopen=true

Overall, the GMAC is more efficient than the mid-drive motor.

 

[ZeroEm]

Don't buy an indoor exercise machine. I can block up my trike and engage regeneration and pedal until tired.

 

[Toorbough ULL-Zeveigh]

Justin Grin wayvin his middle fingers @chalo
[youtube]gYCj4asp9pE[/youtube]

 

[calab]

What is the issue?
Must be the previous page, which I checked and dont see.

Interestng video, looks like March 2021 should be a good listen.

Justin Grin wayvin his middle fingers @chalo
[youtube]

 

[E-HP]

I just realized that I'm coming up on 4k miles on the original pads that came with the BB7 brakes. I barely even touch my brake levers since I use my throttle with slide regen, which takes me down to around 6 mph, and going down a 15% hill, I can keep the bike at a comfortable 20mph or so, instead of coasting down at 35+mph. I have my regen set up for energy recovery, but still helps a lot with the braking. :thumb:

 

[calab]

What controller you using?

I just realized that I'm coming up on 4k miles on the original pads that came with the BB7 brakes. I barely even touch my brake levers since I use my throttle with slide regen, which takes me down to around 6 mph, and going down a 15% hill, I can keep the bike at a comfortable 20mph or so, instead of coasting down at 35+mph. I have my regen set up for energy recovery, but still helps a lot with the braking. :thumb:

 

[E-HP]

What controller you using?

Power Velocity 18 FET, but a lot of controller support variable regen.

 

[xmtx]

Power Velocity 18 FET, but a lot of controller support variable regen.

Well I'm a little bit at loss finding out those type of controllers.

I'm looking for a low power (I intend to use it around 300W), regen capable controller.
As it's for a not tech savy person, the phaserunner are a complete overkill (in price and in functionnality) for this task.
Do you know anything cheaper than that?

 

[Chalo]

I'm looking for a low power (I intend to use it around 300W), regen capable controller.
As it's for a not tech savy person, the phaserunner are a complete overkill (in price and in functionnality) for this task.
Do you know anything cheaper than that?

KT controllers support regenerative braking (settable to different levels, but not proportional) if you use a compatible display. You can also turn down their maximum current in steps to cut their rated power by up to 50 percent.

I can't attest to how their regenerative braking performs, because I haven't used that feature yet.

A low powered KT controller plus an LCD4 display will cost you maybe $70 combined if you shop around on eBay.

 

[calab]

PSW Power sells those display kt controllers.
https://www.pswpower.com/
I never seen any powerful kt's, I went looking one time for 2-3kw of power, nothing but crickets.
The problem is with those kt display units controllers is when you get an error code, try to fix it and cant. So come to a place like this, but I often wonder about all the kt problems error codes that have been posted, how many rolled their ebike deep into the back of shed, with perhaps even 0v, who knows, maybe they went on to a Jetson by Costco, or went entry level with a Bafanged Townie or they went all out with a $4k+ Trek that they lock up with a cable lock.

 

[Chalo]

I honestly could not tally all the KT controllers I've used in conversions, but none has ever thrown an error code when everything was plugged in.

I buy them mostly from Chinese sellers on ebay. They've been a big win for me. Very cost effective and very reliable, when those things are not at all a given.

 

[xmtx]

KT controllers support regenerative braking (settable to different levels, but not proportional) if you use a compatible display. You can also turn down their maximum current in steps to cut their rated power by up to 50 percent.

I can't attest to how their regenerative braking performs, because I haven't used that feature yet.

A low powered KT controller plus an LCD4 display will cost you maybe $70 combined if you shop around on eBay.

PSW Power sells those display kt controllers.
https://www.pswpower.com/
I never seen any powerful kt's, I went looking one time for 2-3kw of power, nothing but crickets.
The problem is with those kt display units controllers is when you get an error code, try to fix it and cant. So come to a place like this, but I often wonder about all the kt problems error codes that have been posted, how many rolled their ebike deep into the back of shed, with perhaps even 0v, who knows, maybe they went on to a Jetson by Costco, or went entry level with a Bafanged Townie or they went all out with a $4k+ Trek that they lock up with a cable lock.

Thanks to both of you. I'll look into that!