Mini-QC Rapid-Charger (RC) Project for LEAF QC Port

The general goal, that many have speculated about, is having a "small",
portable, not-too-heavy, 240v (standard split phase), not-too-expensive
DC charger for Rapid-charging our QC-equipped LEAF vehicles.

In Public places, 240v 50 amp service is not uncommon, like at
RV parks, and not difficult to have at home. With the higher-power
service available at some homes, 240v at 100 amps is obtainable,

Thus, 12 to 24 kW of input power is generally available, so we
hope to be able to dump 10 to 20 kW into a QC compatible port.

Thus, the Robomo Project took shape, and is making progress.

If you have experience that would help, want to participate or
just offer suggestions, we encourage you to let us know.
It is better to post any questions of general interest, so
that the posted answers can benefit all readers.

We intend to deliver our work into the public domain, and we
request that our collaborators endorse this same philosophy.

The Robomo Project breaks down into several sub-projects:

1. Understanding the QC interface, handshake signals, and CAN communication.
2. Construction of a plug that is sufficiently pin-compatible with the LEAF's QC socket.
3. Obtaining or building a suitable, controllable DC power supply.
4. Doing some very careful, well-controlled experiments.

Current Status of each area:

1. We think that we have a basic understanding sufficient for very
controlled laboratory experiments. An AVR-CAN board is being
programmed to control a DC power supply, and communicate
with the vehicle's QC port.

2. A plastic handle and pin-holder has been 3D printed, but
I am struggling with getting the pins made. Not difficult,
but I have been a bit dizzy recently.

Later, it would be nice to get the insert-ends silver plated.
Who knows a good way to do this?

3. We have a DC power supply that we expect to use for
some carefully designed feasibility experiments.

However, in designing our own experimental power
supply circuits, experience with toroidal transformer
design and winding would be useful.

4. The first experiments are broken into several types:

A. Controlling the Power Supply, both when un-loaded,
and when delivering power (just modest power to start).
AnAVR-CAN board is being programmed to interface
with the power supply, and regulate its output
voltage and current.

B. Communicating well with the Vehicle.
An isolated module to control the 4 handshake signals
and the CAN communication is being constructed
and programmed, at this point based on the AVR-CAN
development board that I use in the GID-Meter.

A Plug for the QC Port:

Goals:
1. Short term, get something to safely hold and align
the pins (2 big for power, 7 small for handshake) to
allow us to begin experiments involving the vehicle.

2. Long term, provide a method by which interested
folks can obtain a very inexpensive cable-end connector,
for their own experimental usage. No, not UL listed.

Progress:
First, reasonably accurate dimensions were needed,
and I think that we are doing well in that respect, at least
sufficiently well to make something that fits the LEAF's
QC port socket.

A 3D model was attempted on SketchUp, but it appears that
the free version is primarily suited for modeling shells,
or entirely solid objects. Maybe there is a way to model
internal voids within the solid, but I am not an expert in
using SketchUp, so I might be missing something.
However, a derived STL file could be used to drive
a 3D printer, I believe, with the appropriate settings
in the "slicer" for external walls and internal filler.

Another 3D model was made using Binder (?) and used to
print a 4-section 3D-Printed "plug" which will be sufficient
to hold the pins for our first experiments. No, it does not
yet have the latch and interlock, but that is being worked on.

Printed in PLA plastic, in a nearby country.

The handle is in two halves, connecting to a pin-retainer plate,
which attaches to the rear of the plug (pin holder part) that
mates with the QC socket.

The pins for the plug

A. The two 9mm diameter Power Pins

These are the easiest to make, using a small lathe, since
the material is sufficiently rigid to allow easy machining.

For our initial experiments, we are using stock 1/2 inch
diameter copper alloy rod, 2-3/4" long, with a hole drilled
about a half inch into one end to receive the power wire.

The pin is one piece, with a 3/8" diameter body, leaving
a 1/4" wide, 1/2" diameter retaining collar, and a just-shy
9mm mating-pin part, about 1-1/8" long, with about 1mm
of 45° taper at the tip. The "body" extends 3/4" from the
collar to the wire end, and 5/8" from the collar toward the
very smooth 9mm mating section of the pin.

B. The seven 1/16 inch diameter Signal Pins

Here, the mating part of the pin is about 5/8" long, and
only 1/16" diameter, so not strong enough in brass to
machine, at least by me. So, I plan to make the pin
in 3 sections, a body, a collar soldered onto the body,
and the mating part, soldered into a hole in the body.

So, I bought some 3/16" diameter stock brass rod for the
body of the pin, and 1/16" diameter brass rod for the
mating section. A 1/16" diameter hole drilled in one end
of the 2-1/8" long body will receive the 1/16" diameter rod
to form the 5/8" long mating part of the pin, resulting
again in a 2-3/4" long pin.

A hole drilled in the other end of the body, about 1/16"
diameter and 1/4" long, will provide for soldering in
the signal wire.

Then, some "thick" wall brass tubing, with
3/16" ID and 4/16" (1/4") OD can be cut into 1/4" long sections
to slide over the body and get soldered in place to form the collar,
again located 3/4" from the wire-attachment end of the body.

For me, cutting the tubing nicely and squaring up the
walls to form a nice collar is still problematic.

Communicating with the vehicle's QC port

There are 4 handshake signals, a Ground, and two CAN
bus lines, in addition to the two big power pins.

We have observed the 4 handshake signals, and they
seem to match what is described in open literature.

etc...

Controlling the Power Supply

Power Supply design

Experiments:

Future:

Planned:

Under Construction:

In Progress:

Done:

Miscellaneous FAQ:

1. Are you planning on selling this or will it be an Open Platform?

We intend to deliver our work into the public domain, and we
request that our collaborators endorse this same philosophy.

There are no specific plans to produce a UL listed product,
or even sell all the parts for a kit.

We are primarily interested in helping to provide the supporting
knowledge to everyone, and making one for our own (non-UL) use.

We are carefully staying away from reading, obtaining, or using
any proprietary documents. We are observing what is there.

So, OpenRobomo, perhaps?
Is that "Power to the People"?

2.

Miscellaneous #2

Nice! I'd like to participate. In my case, I have a 384-536V unregulated, 12kW *DC* source available (i.e. solar). What are you using to regulate? Can it take DC in if it is sufficiently above the "ask" voltage. I can do 12kW at 384V but the power tapers down above that so maybe I can only get to 80% without having the overhead of a high power DC-DC converter.

[Edit: Oops, sorry - didn't mean to steal the Misc. #3 slot)

Collaborators Projects

3D Printer aspects :

I hope to get a 3D Printer kit today, build it, add the missing
power supply, spool holder, build platform, etc.
Then, see if this delta-style printer can be calibrated
to print good parts. Kossel Mini legacy type printer.

Happy Summer Day!!

The CHAdeMO Association posted their protocol in English a few days ago, and I put it somewhere (search my posts). $160.

Will need to check out the material properties at high voltage. For some reason Shapeways feels compelled to strongly assert that their Nylon material "must not come in contact with electricity." I've been scratching my head on that.

I can't wait for this!

I will watch your progress expectantly.

TickTock said:

Will need to check out the material properties at high voltage. For some reason Shapeways feels compelled to strongly assert that their Nylon material "must not come in contact with electricity." I've been scratching my head on that.

Click to expand...

Probably porus after printing, so that water could penetrate,
so the solid nylon would be an insulator, but the printed body
might not be... solid?

TickTock said:

Nice! I'd like to participate. In my case, I have a 384-536V unregulated, 12kW *DC* source available (i.e. solar). What are you using to regulate? Can it take DC in if it is sufficiently above the "ask" voltage. I can do 12kW at 384V but the power tapers down above that so maybe I can only get to 80% without having the overhead of a high power DC-DC converter.

[Edit: Oops, sorry - didn't mean to steal the Misc. #3 slot)

Click to expand...

I just finished installing the solar panels. Using the solar panels to DC charge the car off the grid was next on my list.

About the connector: can we use an off the shelf two (or 3... 4) pin connector for the DC and another connector for the handshake? Do all connections have to be done in the same time, or we can connect the DC and then connect the handshake connector? Making my own connector is not something I would like to do.

Edit: Even an MC4 connector will do 20A (I believe I saw 30A too). It is not like I am ever going to unplug the connector under load. I see many plugs rated 600AC/250DC (30-200A), is this rating for unpluging under load? I could read about it, but I sure somebody here knows the answer. Since we are not going to unplug under load, does the 250DC only rating still apply. I do not see why a 600AC insulation rating will not be ok at 400 VDC.

TickTock said:

snip...
In my case, I have a 384-536V unregulated, 12kW DC source available (i.e. solar).
What are you using to regulate? Can it take DC in if it is sufficiently above
the "ask" voltage. I can do 12kW at 384V but the power tapers down above that
so maybe I can only get to 80% without having the overhead of a high power
DC-DC converter...

Click to expand...

Solar panel DC is a bit elusive to use dependably, for example if a cloud happens
to float by (you know, the sky covering in monsoon season).

Since the Chademo vehicle expects the input current (thus power) to follow
its requested current, and there "appears" to be no provision for providing
substantially less (or more) than requested by the car, or abort the charging
session.

True, there is a negotiation (kind of a mating ritual) at the beginning of the session,
before any charging actually starts, and part of that is the QC machine saying how
much voltage and current it can supply, and then the car wanting a demonstration
of the voltage "dance" from the QC machine. If the ritual is satisfactory (to both
sides), charging begins with a relatively fast, but controlled (by the car) ramp up
of the charging current, done at the present battery voltage, of course.

The car seems to allow for some lag in the current ramp, as the QC device
struggles to keep up. The current ramp is typically about 20 amps per second
(really plus 2 amps per 0.1 second).

Although this type of control is not difficult to do at low power, voltage, and
currents, where some wasted power is easy to handle, it most be done
quite efficiently when passing 50 kW, because even a 90% efficiency would
require 5,000 watts of cooling (think of the heat produced by 50 conventional
100 watt light bulbs).

Regulating a relatively dependable higher-voltage power source down to
a lower voltage, with a variable current (up to some maximum current or
temperature) is the job of a typical regulator. Another design allows a
relatively constant lower voltage source to be raised to a higher voltage.

Designing a regulator to do both jobs, at higher power, efficiently is more
what would be required to handle the Solar Power, even if it could provide
a dependable source of power.

The typical Solar Inverter has a slightly easier job, since it can produce
any amount of power at any time, and just "stuff" that power into
the grid. Producing more power requires drawing more current from the solar
panels, but the increased current flow causes a reduction in the DC output
voltage. The inverter typically "hunts" from the maximum power point,
since it is determining the amount of current to draw from the panels.

So, amateurs in power supply design rarely produce a single-stage, well
controlled, efficient design that will both decrease the voltage and increase
it.

Isolation and voltage raising usually require a transformer. Low frequency,
high power transformers are very heavy, and usually get quite hot, often
requiring a cooling system. Using a higher frequency, modern-material
torroidal transformer might work, but the losses in the transformer might
require too much cooling to be nicely portable.

So, we are doing some experiments.

However, someone really experienced and skilled in this design area might
be able to provide a good solution, but patents and proprietary information
might obscure the state of the art.

We don't get too many cloudy days in Arizona but when we do there is always the grid - my main motivation is to have an alternative charging method if/when the grid goes down and if it is down on a cloudy day, well, I'm no worse off than before. I will have to make the rate selectable depending on the time of day since I only get 12kW at noon.

I picked up on an earlier comment indicating the car requests a particular voltage but thought that was strange. I would have though the car would request a particular current (and just have a max voltage safety setting). A few years back, I designed and built a 5kW NiCd battery charger (during my BattleBot days - we only were guaranteed 45 minutes between bouts to bring the robot back to battle-ready condition) so am somewhat familiar with the nuances of semi-hi-power regulators. Still have it - it is about the size of a mini-fridge. I only intend to attempt ~10kW with this (leave some wiggle room on the solar capacity). Constant current supplies aren't really any more difficult than constant voltage - particularly for a linear regulator (non-switching) but of course I am limited by my feed voltage then and will have to dump some heat as you say. However, I don't think that will be much since the solar array itself will drop it's voltage in response to high current so I won't have to dissipate all that V*I in the regulator. So I think my solar will work well for a constant current regulator - at least up to ~80%. If I need to go to 100% (394V), I will have to reduce the current provided (perhaps abort and re-negotiate?) or just be satisfied with an 80% charge.

Is there a document you are reading that describes the start-up protocol or are you just sniffing and reverse-engineering it?

picked up on an earlier comment indicating the car requests a particular voltage but thought that was strange. I would have though the car would request a particular current (and just have a max voltage safety setting)

Click to expand...

I have just started looking at the DCQC, so If I'm off here , my apologies.
I have watched my meter system while the Car was QC'ing, and it seems to me that it "pivots" around the Max KW output of the charger.

As the Voltage of the charging pack increases, the current output decreases accordingly.
I take it that this is why it takes almost no time to get to 80%, but it has been noted that QC'ing beyond that is not time effective.

So I assume that the system is adjusting the output VOLTAGE to remain above the pack voltage, but not drastically so.