EV Attack project

[Jeff]

Jeff, can you post a new thread with info on your drivetrain and component selections? Are you using any kind of multispeed transmission or going with fixed gear ratio? I've been toying with the idea of an all wheel drive setup since it would be relatively easy given the ability to drive the front hubs.

Also, did you pony up for the cost of the cells or did you get A123 to sponsor you?
__________________
Alex Lear
attackforums.com administrator

The Drive Motor is the AC-150 gen2 system from AC Propulsion. Details on the Motor and Controller can be viewed from the link below:
http://www.acpropulsion.com/Products/AC_150.htm

This system also utilizes the motor windings/rotor for battery charging. The induced energy as an SMPS transformer requires the motor to be electrically isolated from the frame. ACP calls this "reductive" charging.
The motor is isolated from the reduction drive input shaft using splined couplers having a delrin block between them.

The fixed reduction drive was formerly an Si 5sp transmission. The transmission has a custom heavy duty 1st gear set (low noise), with all other gears removed to reduce static friction. It is locked into first year, with a ratio of 9.65 to 1.

Custom hollow tube halfshafts (1.75 inch diameter) couple the reduction drive to the hubs. The usual solid shafts added unnecessary weight, and could possibly fracture under the extraordinary torque available at zero RPM.


The batteries were purchased for this project. A123 does sponser the Killacycle, and possibly some others. I preferred going it privately and unconstrained. A large volume of cells had to be ordered, along with providing credentials and information on my specific application. A123 required assurance that I knew what I was doing, and posessed the skills to safely integrate their M1 LiFEP04 cells into this project EV.

My biggest challenge has been designing a package to contain 3600 cells operating in a harsh automotive type environment. Vibration and natural frequencies are some of the issues, along with thermal management.

I'm struggling to stay under 2100 lbs dry curb weight. I originally was optimistic at 2000 lbs, but I failed to factor in numerous structural reinforcements, and the extensive amount of copper needed to pass 150kw to the drive system without losing some it as waste heat.

I've provided links to a few PDF files at the bottom of this post showing how the cells are assembled into clusters. 0.062" Cu cathode and anode Cu collector plates are sandwiched to 0.062" FR4. The clusters interlock like legos. Each cluster is 3.6v, and a total of 120 clusters are arranged in series at 432vdc. Voltage and temperature sensor monitoring of each cluster is reported back to the host CPU using the Dallas 1 wire communications protocol (each cluster has an assigned software address).

Clusters are interlocked into groups, and these groups are distributed in front of, and behind the passenger compartment, along with the side sill areas. Excellent weight distribution.

Power steering was added by using the electric servo steering package removed from a new 2006 Accord Hybrid wreck. Aside from a small 3ph AC controller module, everything is contained in the rack. It uses the HV DC pack voltage to power it. Very clean, and no wasted energy.

This is a well funded project. Yes, I could have just left a deposit for a Tesla, but I'd much rather have assembled it all myself. And learn more along the way.

That's all the time I have for now.

PDF Files and jpeg:

One cluster ready to resistance weld cells together.
http://www.evbones.com/cluster.jpg

Solidworks design of planar battery containing 120 cells (4 clusters linked)
http://www.evbones.com/a123battery.pdf

Assembly drawing of two cell cluster designs.
http://www.evbones.com/assy_drawing.pdf

[Alex]

Looks good Jeff. I'm jealous of your ac-150 system. I couldn't afford it 3 years ago at $35,000 and I still can't afford it now at $25,000. The closest thing I'm using for another project is an Azure/Solectria AC-55/DMOC445 and it doesn't exactly scream performance but fits for the other application. I'm curious and have more questions...

How are you cooling the battery pack?

Where are you mounting the battery pack clusters?

Which pump are you using for the brake booster?

Did you put a limited slip differential in the transmission when you modified the gears?

What is your estimated performance 0-60, 60+, range, etc.?

Did you consider keeping more gears to optimize efficiency and determine it wasn't worth the weight in gears/clutch?

What is the main use for the finished car?

Are you building in a ceramic core heater? A/C? (not a problem where I'm at but maybe a necessity in AZ)

Thanks,
Alex

[Jeff]

Questions from Alex:

Q-How are you cooling the battery pack?

A-Notice the perforations through the Cu and FR4 collectors on the cluster assembly drawing; they are used for pass air between the individual cells.
The separate battery boxes are made of PTFE, and are ported on each end for powered ventilation.
The clusters are individually conformally coated using GE90 in a dip process. This thin silicone coating insulates the batteries and still delivers acceptable thermal conductivity. Though the ductwork is only sketches, the right side body intake distributes ambient air to a manifold containing a boost fan, and then is divided to deliver air to the side and rear battery modules. The front battery box is fed by an intake where the radiator used to be. The left side body intake feeds air to the Motor/PEU (Power Electronics Unit)

Q-Where are you mounting the battery pack clusters?

A-32 clusters are in the front, 40 clusters are behind the driver / passenger, and 20 in each of the two sill areas.

Q-Which pump are you using for the brake booster?

A-Brake vacuum is provided by a Pierburg 12VDC diaphragm pump. It's a small pump with an excellent reliability history, and is quiet. The vacuum is stored in a .7 cubic foot aluminum cylinder. The pump/cylinder/control switch are located immediately in front of the rack on the floor truss.

Q-Did you put a limited slip differential in the transmission when you modified the gears?

A-No, but I agree that would be very wise. I believe the Quaife LSD is the item I should opt for. Thanks for mentioning it. I've been too distracted by engineering minutia and software.

Q-What is your estimated performance 0-60, 60+, range, etc.?

A-Based on weight, I'm estimating 0-60 in under 3.4 seconds. Top speed is 82 MPH (fixed gear speed at 12k motor RPM). I don't expect anything better than 80 miles per charge -considering the way I will be driving. Normal range, driven like an average car would deliver around 120+ miles. The true available pack capacity is 27kwh, and cruise at freeway speed will consume energy at 15kw.

Q-Did you consider keeping more gears to optimize efficiency and determine it wasn't worth the weight in gears/clutch?

A-a clutch is unnecessary because it's AC, and unlike the Tesla -I didn't need more than 80mph.

Q-What is the main use for the finished car?

A-I've rationalized a bunch of excuses to use on my spouse why I'm doing this. It's not practical for utility needs, it's an open top roadster, and it'll probably ride like a go cart. It will be fun though.

Q-Are you building in a ceramic core heater? A/C? (not a problem where I'm at but maybe a necessity in AZ)

A- Though the car arrived to me with heating and A/C hardware hacked into it, I tossed it all out. An open top car is great here from Oct-June, and we hide out in our air conditioned homes during the other months.

Regards, Jeff

[Jeff]

I made some time today to order a Quaife LSD for the modified Si Transmission. If I had not described it before, the transmission has been "gutted", and functions only as a single gear reduction drive, and directly coupled (no clutch). It reduced the weight to 1/2 of original, and provides a little more space to accommodate the heavy duty gear set. Lubricant is Mobil1 0-40w.

Jeff

[Jeff]

I have a few images showing the motor and reduction drive disassembled.
I'm waiting for the Quaife LSD to arrive before final assembly.

Images:
The adapter plate between the motor and the reduction drive.

The isolation coupler between the motor and reduction drive.

The reduction drive with all unneeded gears removed, and heavy duty forged gears installed. (two images)

The motor coupled to the reduction drive.

Regards, Jeff

[Alex]

It's looking really nice Jeff. You're posts are always fun for me to read.

I have some questions about the isolation coupling, etc.

1) Does the isolation coupling just deal with minor misalignments in the motor-to-transmission shaft connections?

2) Does it reduce shock to the drivetrain from the instant torque of the motor?

3) Where did you get it?

4) Do those AC Propulsion motors need water cooling?

5) How's the pack and BMS coming along?

6) Any chance you'll have this on display at the Altcar Expo in Santa Monica on Oct. 19-20?

[Jeff]

Originally Posted by Alex

It's looking really nice Jeff. You're posts are always fun for me to read.

I have some questions about the isolation coupling, etc.

1) Does the isolation coupling just deal with minor misalignments in the motor-to-transmission shaft connections?

2) Does it reduce shock to the drivetrain from the instant torque of the motor?

3) Where did you get it?

4) Do those AC Propulsion motors need water cooling?

5) How's the pack and BMS coming along?

6) Any chance you'll have this on display at the Altcar Expo in Santa Monica on Oct. 19-20?

Alex, no sorry, I'm a long way from completion.
The isolation coupling is required solely for electrical isolation of the motor from the vehicle. The motor housing as well as the output shaft are electrically isolated from the frame and other components.
This isolation is necessary because of the battery charging system design.
ACP's patented "reductive" charging utilizes one of the three phase motor windings as a PWM controlled autotransformer to deliver energy to the batteries, with the induced currents through the rotor core being coupled to the other two stator windings. Because the rotor is now a "live" element in the charging system, it requires complete electrical isolation. Bearings supporting the rotor electrically couple the rotor to the motor housing, and so the motor housing must be isolated as well.

Though it may sound a bit hinky, this is an exceptionally sound and efficient use of the motor in a secondary application. Supporting up to 20kw charging energy, and operable from 120vac to 240vac 50-60hz.
This is one of the critical items licensed by ACP to Tesla Motors. The output Inverter design was basically a "freebie throw in" for Tesla.

Though ACP provided the complete design/assembly drawing for the coupler, I decided to buy these pre fabricated components from them (coupler, delrin ring, and spacers).

Alignment of the coupler is very critical, as any minor offset will translate into significant tangent force when high power thrust is applied.
The coupler is composed of two modified spline assemblies, possibly salvaged from modified clutch plates. These are bonded to a gauze embedded phenolic disk using resin impregnated glass thread looped through eight holes in the spline assemblies and phenolic disk, similar to how a button is attached on a shirt.
The coupler can withstand more than a thousand foot pounds of force if aligned correctly during assembly. A tenth mil resolution indicator is used to characterize the offset error between the motor and reduction drive using the adapter plate as the transfer measurement tool.

Motor Cooling:
The AP150 requires air cooling because of the inherent need for electrical isolation.
The pdf file shows a drawing of the motor with the outer Fiberglas clamshell installed for cooling purposes. The two concentric rings around the outside of the motor contain accordion folded copper sheet bonded to the housing, similar to a radiator in design. Forced air is directed through these heat sink rings, then it escapes through the staggered holes distributed around the clamshell.

Batteries/BMS:
On the battery pack, I'm held up until the drive unit is located and mounted to the frame. I pretty much know how the modules will be located, but I can't fabricate any structural framework until then.

I have hopefully short tracked the time to completion for the BMS software.
ACP held a meeting last week to discuss whether they would use their resources to engineer a new BSM system compatible with the new lower voltage iron-phosphate lithium chemistry cells.
Unfortunately, they have decided against it, and will continue on with engineering products compatible with the higher voltage/energy density cobalt based chemistry.

The functional cell voltage differences between these chemistries would have required ACP to design new cell-level monitoring hardware/software. Their existing hardware will not operate below 3v, and the A123 cells I am using require monitoring down to the 2.4v area.

Already knowing this may be their decision beforehand, I also asked to be provided with a single-use licensing agreement with ACP in granting access to the source code used in their VMS2001 series BMS package.
This particular BMS package is based on the Motorola HC12 processor family, is entirely written in assembly language, and fortunately an instruction set I have extensive experience in working with. Much of the embedded control work I perform in my day (paying) job involves this processor family.

This will eliminate my having to completely engineer the BMS host control hardware/software from scratch, and focus only on the critical BMS software changes, and the replacement individual cell monitoring hardware/software components.


Regards, Jeff

[Alex]

Ahhh, I see now its an electrical isolator. I was thining mechanical isolator when you were mentioning the motor and transmission coupling.

I like how ACP uses the motor for charging. Gets rid of an onboard charger (for the use of a charger/inverter) and reduces weight/space. I agree this is one of the more unique and rare aspects to their product.

One question about the ACP charging circuit. Will it auto-adjust between charging from a 240V circuit and "opportunity" charges from 120V?

20KW of charging capabilities is fantastic. Is there a drop in charging efficiency at that high a level? I read a while back that there was plans for Tesla to develop 16KW charging stations. See: http://www.californiagreensolutions.....h,content=668
Do you know if there are any recent plans to bump that up to 20KW?

I also have extensive experience with the HC12 (and every other mainstream processor and FPGA) and it confuses me why they have written the code in assembly. I'm a big fan of elegant and efficient code. However, in this application there isn't a need for that level of program execution efficiency. Also, the code will be inefficient to maintain and expand for applications like your cells or other changes in the future. Just my opinion. By the way, what is your day job with embedded system work?

Anyway, I enjoy your posts. Keep up the good work.

[sgraber]

Originally Posted by Jeff

Alex, on the isolation coupling:
I had hopes of appearing at the EVS23 (electric vehicle symposium 23) show in Los Angeles this Dec. I've resigned myself to the fact it will not be finished in time by doing it all myself. I've reset my schedule to completion for June '08.
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Jeff, I am located in Phoenix and would very much like to talk to you about your project and tell you a bit about mine.

I have sent you a U2U.

Steve Graber

[cbulen]

subscribing

[Jeff]

I received the two replacement CV shafts from Mark Williams on Monday.
These were the new shafts that replace the two I received the first week of Jan that were rejected for a spline error on their part (see earlier post).

To ensure there were no more mistakes; I shipped the CV joints and the Tripods back with the rejected shafts to use for test fitting at Mark Williams.
Long story shortened, on arrival to me, the Tripod spline was oversize on one shaft and required a 12 ton press to install the Tripod. I wondered how they tested them?


The saga goes on and on like my aunt Margie's ass.

So, I sent the one shaft back to Mark Williams on Tuesday for rework along with a few choice words to describe my disgust. It arrived back to me on Friday, and appeared they had broached the spline to allow for a slip fit on the Tripod. It wasn't the cleanest since they originally cut the splines with an indexing horizontal mill, and the broached reworking looked like crap, though it does fit. Thankfully it appears I have closure on this.

I'm now ready to complete the drivetrain installation work.
No compliments to the folks at Mark Williams Enterprises...

Regards, Jeff

[Jeff]

I've been busy with work and had little time for the Attack lately. The brakes were completed a few months ago, as was the new firewall.

The brake lines were assembled from 3/16 steel tubing and standard flare to tee's. I used aftermarket flexible steel lines between the flange mounts and the calipers. The flanges were fabricated and welded to the tube frame.

The original fiberglas firewall was full of holes, and a complete mess. I decided to fabricate a new firewall from sheet stock rather than trying to trying to salvage it. It's made of .040" sheet aluminum (two pieces), and coated with a plastic spray-in truck bedliner coating.

Jeff

[Jeff]

I welded a support bracket for the Bias Valve to the back side of the front shock support. It's close to the master cylinder, and easy to adjust if needed.

The brake system is vacuum assist by a compact electric diaphragm pump. A vacuum switch is attached to the storage cylinder. The storage cylinder delivers enough volume for two complete pedal cycles before the pump activates. The switch activates at 14" Hg, and stops at 21"Hg (7"Hg hysteresis).

Jeff

[Jeff]

I have some images to post showing the Attack before the body was installed.
I forgot how dirty the shop was from all of the fiberglas dust. Anyway, there are images showing the PEU (Power Electronics Unit) installed to the rear frame and view of the new outriggers that needed to be fabricated. The outriggers carry a battery payload on each side, and accessed from beneath for service. The zig-zag rows of rivnuts around the outriggers for the side pod battery packs dictated the 1.5" square stock material dimensions I used. I'll follow up with images of what the side pod packs appear like later.

Regards, Jeff

[Jeff]

One images shows the flexible brake lines coupled to the hard lines. And another image of the motor and controller.

The next images will be of the body installed, and my troubles with the door hinges explained.

Regards, jeff