pmaupin
Posts: 23
Joined: Tue Apr 21, 2015 8:21 pm

Re: What yr did DC fast come standard? Was it an option pre2

Fri Aug 05, 2016 8:33 am

Don wrote:
pmaupin wrote:You cannot input DC into the onboard charger and you cannot modulate the cars use of whatever amount of DC energy the sun is giving you. The pilot signal limits the amount of AC current the charger will draw based on what the EVSE can supply


Do you have first-hand knowledge that the first thing that happens to the AC isn't rectification? Because if the first thing IS rectification, then it doesn't seem like there would be much to keep you from putting in an equivalent DC voltage, or building a DIY EVSE circuit that allows modulating the pilot duty cycle to change the current draw.

JoeS
Site Moderator
Posts: 3223
Joined: Thu Dec 15, 2011 5:47 am
Location: Los Altos Hills, California

Re: What yr did DC fast come standard? Was it an option pre2

Fri Aug 05, 2016 11:07 am

pmaupin, we've had this discussion before and IIRC the problem was that, although the i-MiEV charger itself might be ok with a dc input because, as you've pointed out, the first thing that happens is that the ac gets rectified, but the problem was using the Mitsu (Panasonic) EVSE on dc wouldn't work because the power supply within the EVSE needed an ac input. No one, to my knowledge, has bitten the bullet and made the mods and subjected their i-MiEV to a dc input on the J1772 port.

The discussion is somewhere on this forum, and hopefully not within a thread that drifted...

(Moving this thread from Batteries and Battery Management into EVSE.)
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

pmaupin
Posts: 23
Joined: Tue Apr 21, 2015 8:21 pm

Re: What yr did DC fast come standard? Was it an option pre2

Fri Aug 05, 2016 12:16 pm

Ah. I guess I wasn't clear. It wasn't about modifying a preexisting EVSE -- I do electronics for a living and I've studied the specs and the openevse implementation.

FWIW, the specs actually mandate that the car dynamically adjust max current input according to the state of the pilot signal (with, IIRC, a max of a 15 second lag), so if the iMiev faithfully follows the spec, you've already got half of an MPPT circuit already built in -- all you need is the control loop.

PV1
Site Moderator
Posts: 2864
Joined: Fri Apr 27, 2012 4:22 pm
Location: Pittsburgh, PA
Contact: Website

Re: What yr did DC fast come standard? Was it an option pre2

Fri Aug 05, 2016 3:01 pm

I believe someone tried here feeding 120 VDC to the car. It errored out and wouldn't charge.

While the charger can likely take DC power, and even if you can get an EVSE to shuttle DC power, the i-MiEV can't read incoming voltage when it's receiving DC power instead of AC power. The car may engage for a minute, but it will error and shut down because AC input voltage will be zero. AC and DC volts are measured differently.

Although I don't think anyone has tested varying the pilot signal with an i-MiEV, it has been tested on a Model S and works well.

A lot of this conversation has already been covered in other threads. I know the forum's search engine doesn't work very well, so go to http://google.com and use the query string below to search the forum:

site:myimiev.com (your search criteria)

Some keywords to try are:

Solar Power
Solar charging


Here is one of the more thorough threads that would likely be appropriate to continue this conversation:
viewtopic.php?f=23&t=2857
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
Solar-powered since 10/10/2013

"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015

2017 Bolt EV LT in Orange with QC - 7/31/2017

Driving electric since 2-21-2013.

pmaupin
Posts: 23
Joined: Tue Apr 21, 2015 8:21 pm

Re: What yr did DC fast come standard? Was it an option pre2

Fri Aug 05, 2016 4:44 pm

PV1 wrote:I believe someone tried here feeding 120 VDC to the car. It errored out and wouldn't charge.

While the charger can likely take DC power, and even if you can get an EVSE to shuttle DC power, the i-MiEV can't read incoming voltage when it's receiving DC power instead of AC power. The car may engage for a minute, but it will error and shut down because AC input voltage will be zero.


That makes sense. There are a lot of ICs out there designed for AC powerline metering applications, so it probably uses one of those in the design.

And as I mentioned earlier, DC GFCI breakers are difficult to come by and not cheap.

So you're probably stuck with the inverter, but to extract the maximum power from your panel, it's still probably worthwhile to build an EVSE that will control the pilot line according to the voltage it sees coming from the panels, to do MPPT tracking.

BTW, if anybody parting out one of these things would like to offer any of the PCBs for reverse engineering (if they aren't potted), I'd be happy to take a look at them.

Thanks,
Pat

Don
Site Moderator
Posts: 2464
Joined: Thu May 10, 2012 3:55 pm
Location: Biloxi MS

Re: What yr did DC fast come standard? Was it an option pre2

Fri Aug 05, 2016 5:10 pm

The pilot signal doesn't 'meter' the power coming into the car - It's an output signal from the EVSE to the car, not the other way around. The EVSE tells the charger how many AC amps it can supply and then the car uses that info to set the onboard charger to draw that amount of current, no more, no less. The pilot signal is to regulate the 3.3 Kw charger down to the power the wall outlet can supply

Yes, the first thing the charger does is rectify the incoming AC, but we don't know exactly how - It can take in any AC voltage between 100 to 270 volts and it rectifies that into a ~350 volts DC which is usable to charge the battery pack. The BMS controls the voltage and amperage supplied to the battery pack

How you would stick 100 volts DC into the charger and have that work in a circuit designed for an AC input is beyond me . . . . but then I never claimed to be the sharpest knife in the drawer :lol:

Don
2012 iMiEV SE Premium, White
2012 iMiEV SE, White
2014 Ford Transit Connect XLT SWB wagon, 14,000 miles
1994 Miata 60K miles - Soon to be sold
1979 Honda CBX six into six

PV1
Site Moderator
Posts: 2864
Joined: Fri Apr 27, 2012 4:22 pm
Location: Pittsburgh, PA
Contact: Website

Re: What yr did DC fast come standard? Was it an option pre2

Sun Aug 07, 2016 7:53 am

Yes, the pilot signal tells the car what it can draw, but a custom controller in an EVSE can look at solar generation and vary the pilot signal, which effectively throttles the on board charger. The car would be receiving AC power from an inverter, which gets power from a solar/battery power system.

It would be difficult to run directly from solar and use an inverter with the on board charger, one cloud burst before the car reduces power and it'll shut down. A capacitor at the least would be necessary to float the inverter until the car responds to the pilot signal change.
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
Solar-powered since 10/10/2013

"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015

2017 Bolt EV LT in Orange with QC - 7/31/2017

Driving electric since 2-21-2013.

Don
Site Moderator
Posts: 2464
Joined: Thu May 10, 2012 3:55 pm
Location: Biloxi MS

Re: What yr did DC fast come standard? Was it an option pre2

Sun Aug 07, 2016 10:33 am

The part I didn't understand is "Would you really need the inverter? If:

a) The first thing that the onboard charger does is rectify the incoming current . . . . "


Yes, I think you would if the onboard charger is looking to deal with an AC input

Don
2012 iMiEV SE Premium, White
2012 iMiEV SE, White
2014 Ford Transit Connect XLT SWB wagon, 14,000 miles
1994 Miata 60K miles - Soon to be sold
1979 Honda CBX six into six

Return to “EVSE (Charging Stations)”