Adapter to combine two 30A level2 into one 60A J1772 - faster charging

[hcsharp]

Unless I'm missing something, I don't think you can ever get it to work with 3 phase. Like Eberhard said in post #21, they are 120 deg apart. You'll discover this yourself when you wire the polarity lights so they are both off when it's OK to charge.

It would help if we could also see the "resistors" that were switched on to start the chargers (did you also have diodes?), and how you handled all three pilot signals, one of which you have to generate.

I assume the circuit had 3 phase power as it was showing 212V and if I charge the car it drops to 207 volts. To check between phases I have two 220V lights and a 30 amp DPDT switch I can use to change polarity. I assume if the lights are on then I have voltage between the phases. Both phases with voltage then I assume I am good and can turn on the curcuit breakers. I realize this may not always work on 3 phase power but I figure I have a 2 out of 3 chance of it working. On two phase power I thought it would always work

I left off the switches to turn on the J-1772 circuits. I do this with resistors going to ground from the signaling wire on the J1772 plugs.

I realize I may need signaling to tell the car I can charge at above 30 amps but I was taking this a step at a time.

Now that I look at the wiring diagram I should probably wire my signaling lights between the phases such that if they are both off, then the phases are the same flow.

[dhrivnak]

Yes on the switch i have a diode then i think a 2.7k resistor and the switch adds a 1.3k resistor to close the contactor. I have two switches one for each inlet adaptor. I will work on a better drawing. Here is a CRUDE first iteration of the combiner.

The two rocker switches tell the charger to turn on, the two light switches (30A 3 way) allow me to change phase of the one J-1772 and the two lights tell me if there is voltage between the phases of the two J-1772 feeds.

Not quite shown, as it is resting on it are two 30 amp breakers hoping I would trip a one of the 30 amp breakers before the 40 amp breaker of the charge station would trip.

I was planning to limit to 54 amps to keep from overloading.

[dhrivnak]

Three phase is definately a problem. I tried two different stations tonight and they both appeared to be different 3 phase legs. With most charging stations being on 3 phase power there may be very few places I can use this. I will keep testing but as of today things are not looking hopeful.

[hcsharp]

Three phase is definately a problem. I tried two different stations tonight and they both appeared to be different 3 phase legs. With most charging stations being on 3 phase power there may be very few places I can use this. I will keep testing but as of today things are not looking hopeful.

Sorry Dave. At least we were able to learn from your experiment.

I think maybe you can modify the equipment to use it with two NEMA 14-30 or 14-50 outlets. If so, then not a total waste.

[driver_EV]

Drivnak, If you encounter 240V at an EVSE that may indicate a single phase service, and might allow your box to work. I have started noting the Voltage provided on charging locations listed in PlugShare app.

I think this project still has great potential at RV parks where the typical 240V+ service probably indicates single phase service.
Setting up 80A charging for a Model S (or 70A for Roadster) is still an attractive backup for travel charging. Superstations will eventually provide good "S" coverage along Interstates, but that will take a while, and may not provide as much coverage as needed when traveling rural routes.

I am ordering a Model S HPC and plan to try building a parallel box to provide the HPC 80A service from two 50A RV 14-50 outlets.

[Ceilidh]

Any updates on this proposition?

driver_EV, why bother with buying an expensive HPWC to lug around to RV campsites when you could buy an output J1772 cord and connector from the box you build for much less with the same amperage?

I'm still mulling this over but it sounds like it has been done before for roadsters by at least one person who posted here so it should be doable for the Model S. I'm just trying to figure out how to build it safely and as cheaply as possible (with safety 1st, of course) in the smallest and lightest possible configuration for lugging around in the trunk.

After the Supercharger network is up an running this may become a moot point, but until 4 years or so from now (and even after that if you travelling away from major highways) this may be a way to make long trips much more practical. Cutting in half the charging time stuck at an RV park would really do a lot and may be well worth the cost of assembling such a box.

If anyone does this and has a schematic and parts list I would really appreciate it.

As far as connecting 2 J1772 charging stations, this sounds like a much more difficult proposition, and one less likely to be able to be utilized on a regular basis.

At the RV parks, I'm sure many would be happy to have you take up the 2 empty/idle spots for a couple of hours in the afternoon (when many RVs are checking out and the new overnight RVs have not yet checked in) to make some $ off of you. On the streets at EV charging network stations, as more and more people buy EVs, I'm thinking those spots are going to be full more and more often... especially since many are just 30 amps which means sitting at them a LONG time if you want a full charge in an EV with a battery the size of a Model S.

I don't plan on taking a ton of long distance trips, so if this is too expensive or difficult then it may not make sense in the end. But if we can figure out a way to make it reasonably compact (other than the extension cords to the 2 50 amp hookups, of course) and lightweight (I realize that lightweight is very relative with the components required) for a reasonable cost that won't catch fire or electrocute you then we may be on to something here...

Cheers

[driver_EV]

On the J1772, I understand that to require an EVSE circuit, and I have ordered the parts to provide 70A for the roadster. (Because the roadster is said to not be happy over 70A)

Since I want to get full 80Amp for the Model S, and to make the initial (80A) version easier to get operational, having the HPWC makes the whole project simpler/faster to get going. I imagine the parallel box would be modular, and can work with either the HPWC for the S, or later the 70A EVSE for the roadster.

I am now driving the S, and see the roadster version as not an urgent need, because traveling in the Model S is so nice.

[dhrivnak]

As I said I was unsuccessful in my attempt to combine two circuits. I think there are two issues I was not able to overcome. The first is the majority, the vast majority of public stations are a single phase of three phase. In the three stations I tried I was not able to find balanced legs to tap into. The second challenge is GFI protection. If the GFCI detects more than a 4 mili-amp difference in legs it will trip. So if the two circuits do not have the exact same wire length and connection impedance the GFCI trips. Then you and all others behind you are out of luck unless you are able to rest the breakers, a very unlikely occurrence. I think we need to push for faster public charging, that is a uphill fight as most cars do not need more than 30 amps.

I think this can be made to work if you isolate both circuits but that is beyond my capabilities.

[FlasherZ]

The second challenge is GFI protection. If the GFCI detects more than a 4 mili-amp difference in legs it will trip. So if the two circuits do not have the exact same wire length and connection impedance the GFCI trips.

I assume you mean GFCI breakers in the panels at the RV park? GFCI there wouldn't require the two different circuits to have precisely the same length, but it would require that the resistance of L1 and L2 conductors on C1 be equal, and L1 and L2 on C2 must be equal. Since they're usually pulled as parallel cables, it should be close enough, but I'll be honest that I haven't considered what tolerance they would have. It is possible to have two imbalanced circuits each with GFCI.

The GF detection in your EVSE shouldn't have a problem as it should sense the sum of the currents going through both circuits.

[dhrivnak]

Correct the car was not the problem. But when at a public garage and the breaker feeding the J-117 station trips you are out of luck with no easy way to reset.