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garygid
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Re: Mini-DC charger Project for QC Port

Fri Jun 21, 2013 7:31 am

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garygid
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Re: Mini-DC charger Project for QC Port

Fri Jun 21, 2013 8:03 am

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.
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TonyWilliams
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Re: Mini-DC charger Project for QC Port

Fri Jun 21, 2013 8:07 am

Happy Summer Day!!

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

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TickTock
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Re: Mini-DC charger Project for QC Port

Fri Jun 21, 2013 9:14 am

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.

KillaWhat
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Re: Mini-DC charger Project for QC Port

Fri Jun 21, 2013 10:12 am

I can't wait for this!

I will watch your progress expectantly.
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garygid
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Re: Mini-DC charger Project for QC Port

Fri Jun 21, 2013 10:28 am

TickTock wrote: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.
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?
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Re: Mini-DC charger Project for QC Port

Fri Jun 21, 2013 10:46 am

TickTock wrote: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)
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.
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Re: Mini-DC charger Project for QC Port

Sat Jun 22, 2013 8:16 am

TickTock wrote: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...
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). :o

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.
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TickTock
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Re: Mini-DC charger Project for QC Port

Sat Jun 22, 2013 8:53 am

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?

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Re: Mini-DC charger Project for QC Port

Sat Jun 22, 2013 9:25 am

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)
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.
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