Could regen be actively modified? For windmill use, or other

[Kin]

Hey, I am floating an idea that is perhaps simply a lame idea based on a lack of substantial knowledge. Ok, I admit that's not a good start around here, and it tends to get me worried when I sense/read such starts.

However,
I'm envisioning that in some conditions it could be useful to operate a small windmill off of modular ebike components (I'm thinking RC, but using a hubmotor would also be possible).

As I see it, one problem is that wind speeds are variable, and so you can't simply attach the windmill components to a controller with fixed regen current settings. I think you would probably need some way to start at very very low regen, and ramp it up at some response rate based on feedback from something testing that the turbines are still spinning and not stalled from the regen level.

I simply have no clue if there's any way to actively modify how much strongly the controller uses regen. I know some controllers are programmable, but I don't think that would be a very active process. If this isn't that interesting of a thought experiment or idea then I'll probably wrap up the thread in the morning or delete it. I was just thinking about this for a little while and quite curious if anyone has thought about it before. I really only have a rudimentary idea of how most controllers work, though.

The thought came around while imagining doing some lightweight camping with an E-trike, and perhaps propping up a very lightweight small turbine overnight to recharge some of the batteries. I retrospectively realize that the small turbine would probably not work well enough in these conditions to be worth it, but that there are still different conditions in which you might want to be able to convert your ebike to a tiny scale windmill.

[John in CR]

I'd give the chain drive from the turbine variable gearing to suit wind conditions.

[Drunkskunk]

Don't bother with the controller. Its not the most efficent way to convert power.
Even in high wind, a portable windmill will likely only be able to make 50 watts, and on a normal day, 10 watts may be all you can expect from something portable. A controller burns a few watts just to power up, so eliminating that power drain will improve your output.

You're better off building a rectifier like this, then a DC to DC converter to charge the batteries

[Xanda2260]

I'd give the chain drive from the turbine variable gearing to suit wind conditions.

This is what I'd do. Maybe a CVT so you dont need to shift yourself?

[whatever]

there was some brief mention on using infineon/xie cheng controller in regen mode for windgen purposes,
it was just a brief mention by knuckles and it was along time ago when he was working out how to use the xiecheng controllers, at that time with infineon chip, I cant remember anyone posting anything about trying it, if knuckles is still around he might be able to comment on it.

[John in CR]

Things have advanced quite a bit in Knuckle's absence.

[Kin]

Hey everyone, I'll keep the thread around if anyone is interested similarly and searches the forums.

I think I'd probably go the route of Drunkskunk's suggestion, if I get around to trying this. It will probably be something of interest for a cargo-trike camping build. It would be a lot of effort, though, for minimal effort. Still, the vision of it is nice in my head.

One trick I realize now that matters more than I thought it might- is that in either case you really want to avoid overcharging the batteries if by chance you do have the windmill up for a while and the batteries are near full. Important extra steps would need to be taken for that.

[John in CR]

One trick I realize now that matters more than I thought it might- is that in either case you really want to avoid overcharging the batteries if by chance you do have the windmill up for a while and the batteries are near full. Important extra steps would need to be taken for that.

Ideally your ebike controller should be properly tuned to cut off regen to match your bike's battery charge cutoff. I don't live at the top of a hill, so I haven't worried about setting the regen cutoff so exact, but it's not all that difficult. The hardest part of the whole plan is the turbine, since you need it portable and stable to fly with good linkage to the ebike's chainline.

[Dauntless]

Your windmill will cost you more electricity than it will generate, unless it's highly productive while the bike is sitting still. Two identical bikes, one windmilled and one without, will see the windmill bike go dead first. The windmill will create more drag than it will be able to cover. That is without considering that the turbine will make the bike heavier.

[iamsofunny]

Instead of bringing a windmill on your camping adventures I propose a better idea.

Bring a large box of small nocturnal animals.

put like a hamster wheel on the side of your tire. The animals will run inside at night. Presumably you will ride during the day and sleep during the night.

Then, as days pass, you will eat the animals one by one for nutrients. Or they will eat you if you chose a large animal such as a bear, anaconda or lion.

It is also possible to bring strong fish such as salmon. The hamster wheel can be positioned in a river such that the salmon will spin the wheel. Alternatively, the salmon can swim in a turbine to assist during riding. You could also capture many seagulls and put on ropes too.

[whatever]

did a bit of digging and found this from knuckles ( i've just cut and past it from my hd I assume the page still exists)
( to john in CR: you said things have advanced quite a bit but how does that relate to this thread?)

Re: Infineon has REGEN BRAKING (and more)

Postby Knuckles on Thu Jan 29, 2009 10:46 pm

solarbbq2003 wrote:thats brilliant on the regen lvc knuckles, I had same problem with v2 controller over 48v, you've solved it! will be extremely useful


Toa Chie for the praise. I just wish China would cater to the products we want (these mods do drive me crazy).
But hacking is fun and very productive.

It is so essential to use both the Software Interface AND a wee bit of hardware mod to get it just the way we want it.

Very cool result about the Infineon regen. I am very pleased. Highly efficient in both directions (I think).
The controller actually becomes an awesome "switching" regulator to provide DC power from a AC BLDC motor.
Heck ... Use a Chinese hub motor as the core of a wind turbine and generate any voltage you want!
(Ha Ha ... hit the throttle and generate a wind storm!)

Or ... Use your ebike as a free-standing exercise-generator that charges batteries (at any V) and/or powers your home appliances! F’n’A

In essence ... Regen is a way to create higher voltages at lower rotor rpm (a BEMF hack). This is very very cool.

Example:
(This is how I hacked the upper regen voltage limit)

1) Bike is upside down. No bats at all. LVC is software set to lowest possible LVC value (20.1V). eBrake circuit is closed.
2) Thin red and thick red wires connected together and connected to (+) voltmeter.
3) Thick black ground wire connected to (-) voltmeter.
4) I start spinning the hub motor by hand (like using the wheel spokes as harp strings ... I give it a good fast initial spin).
5) Voltmeter reads BEMF as I spin the wheel (no resistance at all).
6) Once BEMF exceeds LVC value the controller goes into regen mode.
7) Voltmeter value shoots up and I get resistance from wheel (only drawing 60ma to power MCU/pcb "ignition" so resistance is minimal).
'8) I add a little more “plucking” power to the wheel spokes and it starts to slip.
9) I observe that the voltage at the slip point is about 60 V (I am turning the wheel very slowly too).
10) So I figure … “trick” the MCU! F’n’A
11) Did the R12 mod and I can slowly “pluck” spin the hub and generate 85V (+).
12) Bada Bing!

Gosh ... I guess a vid is needed.

[John in CR]

There's no "tricking" the MCU and LVC isn't part of the equation. During regen the controller outputs whatever voltage the battery needs. The wheel rpm simply needs to be above the regen cutoff rpm. On my bikes that's about 100rpm, though that minimum rpm for regen may vary with pack voltage. Regen current gets higher with increased rpm up to the controller's regen current limit.

What you want to accomplish is really quite simple. You set regen up with a switch to activate it, even a rubber band depressing your ebrake handle will do the trick. Connect the turbine to your motor. Then as long as it turns your motor above the minimum rpm you will get efficient charging of your battery. 2 key aspects are:
1. Tuning the max voltage cutoff of the controller to match your pack is critical so you don't overcharge your battery.
2. You'll need to experiment with gearing in different wind conditions to find what works best. That tuning would also include experimenting with the different regen braking force settings in the controller which put a cap on the regen current.

Note that you won't want some little 3-4' diameter turbine only capable of low power, because it would probably have to be geared so low to turn the motor under regen load that it's likely to oscillate between sufficient motor rpm to generate charge, and slower rpm where it would just spin more freely using battery in the meantime. That's why I said the hardest part is coming up with a light but strong portable tower to fly your turbine.

To give you and idea of charging power potential of what you propose, one of my bikes runs peak regen current of over 70A, and another over 40A. That's at 74V nominal and with regen force set to low. That's 5000W and 3000W respectively. They would require some serious turbines to bring them up to max potential. Personally, I'd shoot for one capable of capturing 1000-1500W in typical wind, so it would still be able to produce in the low hundreds of watts in lighter winds. That might prove reasonably manageable, and wouldn't stress any of the system including the batteries. I've already got the blades for an 8ft turbine, so I might just give it a go for our July trip to the beach, though the support tower is a big ????

John

[Kin]

John! I'll be watching for your posts, if you get around to trying that. I assume your rebuttal to drunksquirrels' complaint about efficiency is that "if the turbine is in a couple hundred watts at minimum, the drain is relatively insubstantial."

In my own thoughts about the project, I've been thinking about the tricky parts of the support tower. My only thought right now is that perhaps I could figure out some way to use the battery cage on this hypothetical trike as part of the stand (perhaps if the batteries are hosted in a "cage" structure with fabric as opposed to a typical plate-style box, then I could make something that could be a bunch of pipes that could reassemble into a small support structure. But my initial are that it would be stupid and insufficient, or an absurdly overbuilt battery box [if you used enough pipe to make a decent small support structure]. Maybe I can think through some better ideas in the long run for a portable support stand.

If I go through with this project, I will be looking for something smaller that can generate 100-200 watts, to perhaps offer a 60% charge over 10 hours, while still being*potentially* portable. I'd definetively explore composite turbine props, or at least Al 5057. I've been wanting to try out some composites beyond fiberglass patching

Thing is, this is very backburner right now, since I've gotten caught up in a number of projects for my summer job. The downside is that I've put my own aside, but the upside is they're paying me for parts and labor to do a few things that relate very much to what I've learned on e-bike projects .

[whatever]

seems there are two grey areas on using the xie cheng controllers for regen with windmill:
1. point 6 of knuckles old post where he found low voltage cut off effects when controller initially goes into regen mode
( disputed by john in cr suggesting its rpm dependent not linked to lvc)
2. how the controller is adjusting output voltage to suit battery voltage being used
( I"ll have a stab in the dark on this one: maybe its not varying the output voltage at all, perhaps its set very high and the battery voltage brings it down, not likely I know but thats one for the gurus who understand how the switching is producing regen,
hope someone out there can chime in on that)