Hybrid scooter/moped

[Teh Stork]

Hello Recently found this forum while searching for info on regenerative braking, but found lots of interesting information. My "quest" is to build a fast, relatively cheap, fun and maintenance free hybrid scooter. I'll tell about the things I'm planning to implement, I hope you have criticism to come with

I'm using a Gilera Dna as the base of my project. Originally it has a variator - but I will be getting rid of that I think. The engine is tuned with a 70cc cylinder kit and comes in at around 5kW, most likely the power will be toned down - aiming for efficiency.

Supercapacitors. I will be using a bank of 25 boostcaps, each are rated at 2,5V 2600F with 0,7mOhm internal resistance. Total capacitance will be 104 Farads, total voltage will be 62,5 volts. Total energy stored (fully charged) will be just over 200 kJ. 13 kg all in all.

Charging/discharging. The boostcaps has a maximum rating of 600A, but I won't be getting near that i think. A long term, performance oriented goal, is 20kW (60V 333A). Internal losses in caps will be nearly 2kW at this power output. The boostcaps are not, like LiPo's, restricted when it comes to charging. Also, they can't be overcharged - so I can hook as many as i want (before the ESR gets nasty) in series. Charging the caps with regenerative braking is one of the reasons I will use boostcaps - these can handle the rather big braking loads).

Some more numbers. The "moped", including driver, will weigh in at around 180 kg. At 80 km/h, that's 43 kJ. (100 km/h: 70kJ)(125km/h: 110kJ). Capacitor bank at 50V: 130kJ. Capacitor bank at 60V: 200 kJ. Capacitor bank at 35V: 65kJ.

Internal combustion engine. I will be modifying the original engine with, mounting a injection system and a new ignition system controlled by a Arduino or similar. I want this to kick in if the Capacitor bank drops under 50V, charging it up to - say - 55V before it shuts off again. Will probably be user variable ofc. I'm planning on using a small ~3kW ish electic engine to generate electricity to the caps. 60V output, possibly a DC/DC converter between if voltages doesn't match.

Electic engine nr1. This one from hobbyking, 80-100 is my best bet atm. 7kW will give nice acceleration, even tho doubling that will be a second goal. The back of the variator already have a gear system capable of handling the torque produced - question is just what the ratios are. Will figure this out later on This engine will be mounted to the rear wheel. I will be afterinstalling Hall sensors.

Electric engine nr2. Mentioned under ICE engine, will be working as a generator.

Electric engine nr3. Will be mounted to the front wheel. Not the first priority, but this will be better for regenerative braking - especially in rainy weather (rear wheel slip while braking could be a prob). This engine will most likely be the same as nr1. It will need to be shielded from the environment and be mounted on the forks (they are inverted), shouldn't be a problem. Plexiglass could make for a nice view aswell.

Regenerative braking. I've been reading some about it in this instructable. As the revs comes down, the need to step up the voltage will come into play. A step up converter is the obvious salvation, but building this will be a new experience for me.

Who am I? I'm at my first year towards a bachelor degree in electronics/automation, the basics are there - but the experience is lacking.

Wanted; Input

 

[Hillhater]

.....I will be using a bank of 25 boostcaps, each are rated at 2,5V 2600F with 0,7mOhm internal resistance. Total capacitance will be 104 Farads, total voltage will be 62,5 volts. Total energy stored (fully charged) will be just over 200 kJ. 13 kg all in all.

Interesting ..but WHY ?
Unless i am missing something, those S'caps have a Specific energy Density of 4.3Whr per kg, ( ref the spec),
... that will give you about 56 Whrs total from your 13kg of caps !

For your target 7kW drive ( 120A @ 60V ) that will give you something less than 30 secs run time ??
Your ICE is going to be running most of the time !

 

[full-throttle]

Not only that - caps have an exponential discharge curve, so do require some kind of a SMPS to extract the energy

 

[Teh Stork]

Not only that - caps have an exponential discharge curve, so do require some kind of a SMPS to extract the energy

Ofc, but still: Between 50 and 62 volts, there is like 70 kJ - enough to get the moped up to speed w/o a large voltage drop. Between 35V and 62V, there is 130 kJ - see where I'm going?

.....I will be using a bank of 25 boostcaps, each are rated at 2,5V 2600F with 0,7mOhm internal resistance. Total capacitance will be 104 Farads, total voltage will be 62,5 volts. Total energy stored (fully charged) will be just over 200 kJ. 13 kg all in all.

Interesting ..but WHY ?
Unless i am missing something, those S'caps have a Specific energy Density of 4.3Whr per kg, ( ref the spec),
... that will give you about 56 Whrs total from your 13kg of caps !

For your target 7kW drive ( 120A @ 60V ) that will give you something less than 30 secs run time ??
Your ICE is going to be running most of the time !

Well, it will only need about ~6 (43 kJ) seconds to get up to speed (80 kmh), so the capacity will be of no problem.

Why? Because normal Li-Po's can't handle the huge charging loads while regen-braking.

Why? I'll drive this much around town, regenerating energy in towards a traffic light - and then releasing it when it turns green - is my vision. The ICE will probably be kicked in if I cruise at 90 km/h, but at 60 km/h around town, it will rarely engage.

Regenerative braking is a HUGE part of this project, and what differs this project from a normal E-Bike - making this will be a challenge..

Looking at controller design now, planning to build my own using logic chips (= time consuming)

 

[Hillhater]

Why? Because normal Li-Po's can't handle the huge charging loads while regen-braking.

Why? I'll drive this much around town, regenerating energy in towards a traffic light - and then releasing it when it turns green - is my vision. The ICE will probably be kicked in if I cruise at 90 km/h, but at 60 km/h around town, it will rarely engage.

What are these... "huge charging loads",..and where are they coming from ?
You are proposing using the HK 80-100 BLDC motors, so the charge current cannot be "huge" ( =- 100A ?)

I'll drive this much around town, regenerating energy in towards a traffic light - and then releasing it when it turns green - is my vision. The ICE will probably be kicked in if I cruise at 90 km/h, but at 60 km/h around town, it will rarely engage.

.. Hmm, ? .. so you are anticipating perpetual motion then ! :lol:

 

[Teh Stork]

Why? Because normal Li-Po's can't handle the huge charging loads while regen-braking.

Why? I'll drive this much around town, regenerating energy in towards a traffic light - and then releasing it when it turns green - is my vision. The ICE will probably be kicked in if I cruise at 90 km/h, but at 60 km/h around town, it will rarely engage.

What are these... "huge charging loads",..and where are they coming from ?
You are proposing using the HK 80-100 BLDC motors, so the charge current cannot be "huge" ( =- 100A ?)

I'll drive this much around town, regenerating energy in towards a traffic light - and then releasing it when it turns green - is my vision. The ICE will probably be kicked in if I cruise at 90 km/h, but at 60 km/h around town, it will rarely engage.

.. Hmm, ? .. so you are anticipating perpetual motion then ! :lol:

-100A will be just about max, but I plan to up the regen/total power later on (raising this figure up to 200A). Adding a motor to the front wheel will be the second step, having finished everything (up and running) for the rear wheel. In case you missed it, these "huge" charging loads are coming from regenerative braking. One fast charging 5C LiPo 5Ah would be able to charge at 25A, given the price of supercaps - they come out much cheaper than the needed battery package needed. They can also withstand more cycles, so I find it a fair tradeoff for some added weight. They are not prone to overcharging either, making them rather robust.

Well, I'm not planning on challenging any of the thermodynamic laws - but greatly reducing fuel consumption/increasing fun factor in town is defintely possible.

Please, It's not like I'm some expert here, but look over what I'm laying out here before you dismiss it.

 

[REdiculous]

that will give you about 56 Whrs total from your 13kg of caps !

It's not like I'm some expert here, but look over what I'm laying out here before you dismiss it.

If you only carry 56 Whrs then your electric range is gonna suck hard...really hard. A good ebike might make it 3 miles on that but a Dna weighs 3x as much (dry and unmodified) and you're talking about going at least twice as fast. :|

 

[Hillhater]

I am not intending to criticize your efforts,.. indeed i admire your ambition and respect your ideas .
Caps could be the ideal storage medium , but they do have their limitations..capacity, weight, voltage & balance management, etc.
fundamentally i just think you will need more storage capacity to make the project practical.

PS:- You know there are lipos that charge at 10C continuous ( and much higher charge rates in bursts !), ..so a 10ahr pack would handle that and give you 10 times the storage of those caps ( and at less than half the weight )

 

[Teh Stork]

I am not intending to criticize your efforts,.. indeed i admire your ambition and respect your ideas .
Caps could be the ideal storage medium , but they do have their limitations..capacity, weight, voltage & balance management, etc.
fundamentally i just think you will need more storage capacity to make the project practical.

PS:- You know there are lipos that charge at 10C continuous ( and much higher charge rates in bursts !), ..so a 10ahr pack would handle that and give you 10 times the storage of those caps ( and at less than half the weight )

Well, I've been thinking about combining lipos and supercaps - one as a high storage medium, and the other as a high power medium. Some of Hobbykings Nano-tech packs are at 15C continuous charge, so it would probably be suited for the first part of the project. Problem is second stage with bigger current regen.

Is really voltage & balance management a problem with supercaps? As I've understood it, if a cap is full - the resistance goes through the roof and no voltage can pass through? I'm really uncertain here, but won't the "non full" caps still suck up charge? A part of me says no - a different says yes xD

Capacity/weight is not the greatest - no, but having lipos + caps will mean even more electronics. If this really becomes a problem - upsizing the ICE part will be a no-brainer in comparison...

that will give you about 56 Whrs total from your 13kg of caps !

It's not like I'm some expert here, but look over what I'm laying out here before you dismiss it.

If you only carry 56 Whrs then your electric range is gonna suck hard...really hard. A good ebike might make it 3 miles on that but a Dna weighs 3x as much (dry and unmodified) and you're talking about going at least twice as fast. :|

Well, as said - over and over - electric range isn't a goal - It's a hybrid. Petrol energy density is something like 45000 Kj/kg, given 25% efficiency in generating electricity (totally reachable): I'll be looking at just over 11000kJ/kg. Last time I checked, batteries still have a long way to go to reach numbers like that.

 

[Mozart]

Hi, it's almost a year after your last post and since I'm currently converting my DNA, I was very happy to find another case with the same motorbike!
You had a great idea there with the supercapacitors and I've already seen a dragster car that runs like that,(only for some miles but still),SO... how did your project turned out?

 

[Teh Stork]

Hi, it's almost a year after your last post and since I'm currently converting my DNA, I was very happy to find another case with the same motorbike!
You had a great idea there with the supercapacitors and I've already seen a dragster car that runs like that,(only for some miles but still),SO... how did your project turned out?

Well, the project turned into a Ebike - a very fun one indeed. With more knowledge, I'll attempt something with my DNA scooter. Not sure what to do Nano techs, advanced controllers and powerful "non-hub" motors would probably be a fun project - something like lukes commuter bicycle - only beefier

The supercaps turned into a capacitive discharge spot-welder, be it with some problems tho (kills a supercap and some mosfets every once in a while)

 

[Mozart]

I see, well I'm a bit sad it didn't worked out
Thanks for your reply!