Soapbox on regenerative braking

Post by **zeva** » Wed, 17 Feb 2010, 01:59

Matt: Yes, for me the most attractive aspect of regen braking is reducing brake use. 2nd most attractive is just the technical elegance of energy recovery. 3rd is additional range. I would love to have regen on my next EV, but I still don't see any compelling solutions on the market.

The "wear and tear" of a charge cycle is *roughly* proportional to the depth of discharge, i.e a regen event might recharge the battery by 1%, and you can do that 100x for the same effect it would have on your battery's cycle life as one full depth charge/discharge. (The math really isn't that simple, but you get the idea)

Low RR tires, you'd definitely notice the difference on a racetrack but unlikely to on public roads. Prius come standard with pretty good LRR tires if I remember correctly, have a drive in one of those and see if you notice any compromised handling. The coefficient of friction is maybe 10% lower so only an issue if you're pushing the limits of traction. (The Tesla Roadster as tested on Top Gear was wearing LRR tires and managed to equal a Porsche 911 GT3 around their race track - so they're clearly not too bad around corners!)

Post by **Tritium_James** » Wed, 17 Feb 2010, 02:33

Don't forget the fun factor! Especially if regen is set up on accelerator pedal lift-off, you get a wonderfully smooth and controllable transition from drive, to regen, and back to drive, as you push through a corner. It's great!

Post by **acmotor** » Wed, 17 Feb 2010, 06:22

Here here ! now you're talking.
Few people have experienced the no gears, real regen driving experience.
Even in the non handling of a Suzi, it is not hard to imagine the future of performance motoring.
I guess it will truely come together when hub motors when TCS,EBD,ESC etc are lines of code in the drive computer !!!

Post by **acmotor** » Wed, 17 Feb 2010, 06:57

zeva wrote:
The "wear and tear" of a charge cycle is *roughly* proportional to the depth of discharge, i.e a regen event might recharge the battery by 1%, and you can do that 100x for the same effect it would have on your battery's cycle life as one full depth charge/discharge. (The math really isn't that simple, but you get the idea)

I'm not certain that you could produce data to back that 'rough' thought.

e.g. most Li cells will provide maybe 1000 cycles at 100% DOD, 2000 at say 80% DOD, 3000 at say 70% DOD, 7000 cycles at say 50% DOD and if that is any indication then maybe 100,000 cycles or more at 1% DOD
So your reasoning doesn't seem to follow (your maths too simple ? the relationship is not linear)
Excessive charge rate (for the chemistry/construction) is the only wear and tear you are likely to experience.
Keep in mind the overall reduction in DOD by as little as even 1% by regen is actually far more likely to increase battery life if manufacturer's stats are to be followed.

Prius is a classic example of vast numbers of shallow cycles with regen, so much so that the battery packs now have 8 year warranty !

Post by **acmotor** » Wed, 17 Feb 2010, 07:18

Look, even a graph to back the reasoning !!!

from http://www.mpoweruk.com/life.htm

Post by **unheardofinstruments** » Sat, 02 Feb 2013, 08:22

To my mind AC or DC is less appealing than a big axial flux PMDC for the following reasons;
-mostly the weight savings
-overclockable to not need reduction in the drive train thus even more efficient and light
-much less back emf so high speed is good
-simpler
-smaller
-cheaper
-DIY capable, both controller and making the motor yourself
-REGEN (is that the thread we are on?) is easy and very efficient
-hub motor shaped
-air cored is advantageous re saturation etc.

Also I am building an 80% efficient hydraulic regen setup for my range extending trailer but it could easily be fitted to a DC series motor especially one with a shaft at the other end. Very simple and reliable, cheap, light and DIY capable. Leaves the controller side of things very simple and cheap. I will try and find the hydraulic drivetrain patent that inspired me, it made the car very efficient, works for heavy machinery very well and is much more efficient than direct diesel.

Post by **BigMouse** » Sun, 03 Feb 2013, 21:52

unheardofinstruments wrote: -cheaper

Can you show an example of a car-capable axial flux PMDC motor that's cheaper than a comparable AC or DC?

Post by **unheardofinstruments** » Mon, 04 Feb 2013, 04:26

It has been frustrating getting any answers to price inquiries but Agni at $3000 (800 freight) for two 95R motors which would be ok for a lightweight car are the best so far and they have prototyped and tested their soon to be released 300mm high torque version. Waiting to see.

http://www.gkn.com/driveline/our-soluti ... fault.aspx

and Yasa motors are teaming up with these guys
www.axcomotors.com/axial-flux_technology.html

they said;

Base YASA-750 Motor                                        £7900 ea.
Sevcon Gen4 Size 8 Controller                        £3500 ea.
Delivery is usually circa 6 to 8 weeks               Delivery price to be agreed in advance

YASA-400 motors will be available for general sale in February. The sale price will be circa £7000. CAD and dimensional data will be available in the next few weeks.
The YASA-250 will follow in mid 2013, this motor will be a 15kg 85kW peak, 250Nm peak motor, ideal for motorcycles or small city car traction units directly into a differential.

these are supposedly going to allow them to be made cheaper using unique magnetic materials and yokeless design, pretty cool but expensive at low production volume 3 years in.

www.enstroj.si/Electric-products/emrax-motors.html from slovenia are expensive 2490euro (in 2011) and made for gliders and HV but seem very good
These guys are in sydney, waiting for an answer;
www.evans-electric.com.au/

ultramotive.com make a great motor, expensive but very high torque density
apex motors, saminco, soloman tech, zytec, UQM, Williams (of F1 fame) and many others never answered.

Launchpoint technologies ones are probably the best I have seen but they only seem to supply the military.

A dude in San Fran called Carl said he will make me two that would power a car for $2500US each and has made a few just for himself.

PML Flightlink, Volvo, Aisin Aw Co Ltd., Sim-Drive, Tepsc, Protean Electric, e-Traction, TM4, Ziehl Abegg, mitsubishi and Siemens amongst many others are working on hub motors too using axial flux designs so I would suspect someone in china is also and when they get into mass production they should be cheaper as they are much simpler to make, small companies hand making them for the ones who can afford it makes them seem more expensive than they should be with 7.5kW solar challenge motors (using the best of current design, hallbach arrays, variable gap, composites...) charge $12000 and no I can't get one of the hallbach arrays they use or know where they come from....aaaargh.

I think I will have to make my own and Craig from Turquoise Energy in vancouver supplies a very reasonably priced kit but I plan something a bit different; direct drive/low speed but the right magnets are proving hard to find. I have Axel Borgs book on how but waiting to see how the Agni one goes first.
If you can get them to write back let me know, I would love to find out what the various systems cost.

Post by **Canberra32** » Mon, 04 Feb 2013, 13:29

Ok I'm just curious.

I looked at the Agni motors and after much comparing I settled on the mars me913

Is there something wrong with the mars?

Post by **Canberra32** » Mon, 04 Feb 2013, 13:44

Also regen round a corner? U mean braking round a corner?

No that's cool if your into that...

However as those who brake before the corner and power on will wave as they pass you

if you don't spin out.
On a race track that is

Coz for those of us like me n zeva with brute power and no regen we will be too busy lapping the AC tail runners

Perhaps they could pass a law that all AC must be put in combi vans with peace symbols and fight the man stickers

Sorry couldn't help myself

Post by **Johny** » Mon, 04 Feb 2013, 14:58

Then the AC powered guys with regen will wave as they overtake you while you'r in the pits changing brake pads.

Edit in, not ein

Post by **unheardofinstruments** » Mon, 04 Feb 2013, 16:08

The Agni R series are reinforced so rev out to 6000 rpm instead of 4000 and 30kW over 22kW peak and all of their motors have the upgraded design Cedric planned for the E-tek/Mars/LMC motors (before he got shafted) providing higher torque per amp and a speed per volt making the gear reduction ratio smaller. The Mars is cheaper though. From india I was quoted 3000 including the 800 shipping for two which would be good for a 750kg car without a gearbox.

Post by **BigMouse** » Mon, 04 Feb 2013, 17:23

Any PM motor is still so expensive, not to mention reliance on rare-earth materials with wildly fluctuating prices (controlled by China). A custom wound induction motor only has aluminium, copper, and steel in it. Mine cost $1800 brand new delivered, and wasn't made in China. With the right controller and batteries, it'll be easily capable of "overclocking" to 100+kW.

For me, induction beats any PM motor due to material availability and cost.

Post by **jonescg** » Mon, 04 Feb 2013, 20:12

If making an affordable yet punchy EV is the goal, induction is the way to go. If you want performance and don't mind paying for it, then PMAC is the only option. PMDC still has brush arcing and armature heating issues, but for the price of a decent one an induction motor is an attractive alternative.

Post by **Canberra32** » Mon, 04 Feb 2013, 20:53

That seems very high price for shipping on the mars unheardof...
My warp11s cost 600 a pice to ship from the states and they are 100kg.
Most of the mars motors I have found are all around the $700 mark per motor

Post by **Richo** » Mon, 04 Feb 2013, 20:53

You'll even get free regen when your PM ev is being towed.
Unlike induction which will free wheel.

Hub motors again

People are trying to reduce the hub weight not jam more into it.
Convientent maybe, practicle not really.

Post by **Canberra32** » Mon, 04 Feb 2013, 20:55

And on the regen issue... Considering the extra cost of AC why not put those dollars into a bigger battery pack and enjoy the power of DC

Post by **Johny** » Mon, 04 Feb 2013, 21:11

Canberra32 wrote: And on the regen issue... Considering the extra cost of AC why not put those dollars into a bigger battery pack and enjoy the power of DC

Because the car gets heavier and more difficult to get approved (and to stop).

Post by **Canberra32** » Mon, 04 Feb 2013, 21:33

Only if its a conversion

Currently the rolling chassis with batt pack sits at just over 700kg and gets pulled up by 350mm willwood brakes

There no pass issue here

The body shell will be no more than 100kg unless I lay it up like a tank lol.

Post by **Richo** » Tue, 05 Feb 2013, 21:08

Yep DC would be a good cost saving.
But the downside is, in my opnion, no DC motors meet NCOP.
Get the gaffa out and seal up those brush vents please...

Post by **Canberra32** » Wed, 06 Feb 2013, 00:56

Splitting hairs richo

You gotta see the up side of what I'm building

check my CNC body thread for the shell shape and drool bebeh

Post by **Richo** » Wed, 06 Feb 2013, 21:04

Yeah I know and I do.
I started drooling about the CNC before I saw any pics of the cars

Post by **Canberra32** » Wed, 06 Feb 2013, 23:27

Machining up new parts ATM so I can increase the Z axis travel and add a pivoting head but its all not happening fast enough lol

Post by **unheardofinstruments** » Fri, 08 Feb 2013, 05:40

I am now considering moving my hydraulic regen from the range extending trailer to the front shaft on the motor in the car as I have nothing on it at present having crippled the power steering and made it manual and I will probably like it when I am doing short trips too, lots of hills around here so it will definitely come in handy. I wish I had bookmarked the link to a 150 dollar addon regen unit for series DC motors from somewhere in eastern europe as I can no longer find it. Seems that was a niche with some promise, I think it was switchmode IGBT based current control and field excitation to make it happen. It would add some extra braking power and charge rather than save takeoff amp sucking. No reason not to skin the cat both ways. Anyone found such a thing? I remember someone from Australia asking about importing it.

Post by **unheardofinstruments** » Fri, 08 Feb 2013, 06:02

This is something that I had thought of ages ago, well explained. I wonder if it could be as simple as driving 3 coils in a four coil motor and using one to charge.

http://www.davidicke.com/forum/showthread.php?t=159243