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

[driver_EV]

I often see multiple EVSE units both unused and offering only 30 Amps or so.
What if someone created an adapter box with a little extra amount of smarts built-in that could safely combine (parallel) the two 30/32A EVSEs into one 60/64A EVSE connection for faster charging of Roadster?

In principle, the two side-by-side EVSEs will almost certainly be from the same transformer feed (this can be detected by the adapter circuit) and if the power at the two J1772's are out of phase, (one is 180 degrees out), then the adapter can simply utilize a DPDT relay circuit to flip the phase on one supply, to put the two in parallel, and verify they are safe to combine.

Presto change-o!
DIY ~70A Level2 !

 

[dhrivnak]

Dual J-1772 possible?

I wanted to float an idea about the possibility of making an adapter that could combine two 30 amp J-1772 plugs into a 60 amp option for the Roadster. While I have found MANY J1772 options they all have been limited to 30 amp. I know in theory one should be able to combine the legs assuming they are on the same phase. I think this would be typical for 240 installations but not sure one could count on this with 3 phase power (208V) that I find at many businesses. I know one would need to test the legs first to ensure they are the same phase but does anyone see other problems with this concept? Would I likely be able to build an adapter box?

With the slow rate of 30 amps while on a road trip and me normally being the only car to be charging such a combiner box would be most helpful.

Thank you

 

[TEG]

I suggested a while back that perhaps EVs should start coming with dual sockets so you could plug both in at once.
It would make sense for Model S which already has a logical charge flap location symmetrically on the other side of the car.
Plus they have a dual charger option. So why not make it so model S can accept two J1772 plugs at once (one to each side of the car) ?
Each socket could go to a different charger box that run in parallel...

If someone parks next to you and needs to charge they could remove one cable and still leave you charging at 6.6kW.

 

[rolosrevenge]

Parallel charging of batteries is tricky because even though the equipment may be "identical" variations in production tolerances will cause circulating currents and strange voltages and whatnot. I'd advise against trying things like that.

 

[VolkerP]

TEG suggests a setup similar to the Tesla supercharger which consists of 9 single-phase 10kW charging units similar to the Model S on board ones. The supercharger feeds on 3 phase AC so different AC phases are used. But the output is one DC circuit.
So it might be tricky but Tesla is about to do it.

 

[TEG]

Even the 20kW option in Model S consists of two 10kW chargers. It is just that the standard way would take one 60amp+ input instead of two (individual) 30amp inputs...

 

[smorgasbord]

I suggested a while back that perhaps EVs should start coming with dual sockets so you could plug both in at once.

Kind of like the old Jaguar XJ's that had two gas filler caps. Great for cannonball runs! (or, so I've read).

 

[TEG]

Kind of like the old Jaguar XJ's that had two gas filler caps.

Been there, done that:
What charge port connector?

 

[Eberhard]

and for the european version, there will be a third 10kW charger, each been connected to e different phase from the 3-phase socked - why not to connect to two different sources - simple double the charging power?

 

[jerry33]

Kind of like the old Jaguar XJ's that had two gas filler caps. Great for cannonball runs! (or, so I've read).

My Land-Rover Series III had two gas caps, two gas tanks, and two padlocks (to keep other Land-Rover owners from borrowing the gas caps).

 

[driver_EV]

Another possibility would be to build a DIY 70A EVSE that has this simple paralleling method that would source power by plugging into two NEMA 50A plugs in RV campgrounds.
One of the NEMA 50A plugs would need to be on a long lead to reach the second camping spot. Not a very elegant solution though.

 

[jackbowers]

I've actually built a front-end to a Tesla HPC that mobilizes it in this way, allowing 70A 240V charging. It's a crude approach that checks hot wire polarity (which is often reversed for every other RV slot to balance air conditioning loads), then engages a contactor to connect both 14-50 connector hot wires in parallel. I've got two 100A ammeters to monitor the current split, which usually splits pretty evenly (I'm using 30 feet of cable for each hookup to keep the wire resistance similar). I start at 40A, then step it up to 70A if things look okay. Strangely enough, the RV park operators don't seem to mind if they have open slots - I just tell them it cuts the charge time in half and reduces the odds of popping a breaker.

For a commercial version, someone could take two of those open source 10kw chargers and combine the power at the DC level. From there you could have "adaptors" that deliver up to 20kW one of three ways: 70-80A J1772 (inverter needed for this option), Tesla Supercharger (if it allows 20KW rate), and Chademo (20 kW for Leafs).

Jack Bowers

 

[dhrivnak]

Jack are you willing to share any detailed pictures? I would love to see how you are checking the phase and the reversing contactor. Then I would be happy to share what I come up with.

 

[bonnie]

I've actually built a front-end to a Tesla HPC that mobilizes it in this way, allowing 70A 240V charging. It's a crude approach that checks hot wire polarity (which is often reversed for every other RV slot to balance air conditioning loads), then engages a contactor to connect both 14-50 connector hot wires in parallel. I've got two 100A ammeters to monitor the current split, which usually splits pretty evenly (I'm using 30 feet of cable for each hookup to keep the wire resistance similar). I start at 40A, then step it up to 70A if things look okay. Strangely enough, the RV park operators don't seem to mind if they have open slots - I just tell them it cuts the charge time in half and reduces the odds of popping a breaker.

For a commercial version, someone could take two of those open source 10kw chargers and combine the power at the DC level. From there you could have "adaptors" that deliver up to 20kW one of three ways: 70-80A J1772 (inverter needed for this option), Tesla Supercharger (if it allows 20KW rate), and Chademo (20 kW for Leafs).

Jack Bowers

Welcome to the forum, neighbor!

 

[driver_EV]

I've actually built a front-end to a Tesla HPC that mobilizes it in this way, allowing 70A 240V charging. It's a crude approach that checks hot wire polarity (which is often reversed for every other RV slot to balance air conditioning loads), then engages a contactor to connect both 14-50 connector hot wires in parallel. I've got two 100A ammeters to monitor the current split, which usually splits pretty evenly (I'm using 30 feet of cable for each hookup to keep the wire resistance similar). I start at 40A, then step it up to 70A if things look okay. Strangely enough, the RV park operators don't seem to mind if they have open slots - I just tell them it cuts the charge time in half and reduces the odds of popping a breaker.

For a commercial version, someone could take two of those open source 10kw chargers and combine the power at the DC level. From there you could have "adaptors" that deliver up to 20kW one of three ways: 70-80A J1772 (inverter needed for this option), Tesla Supercharger (if it allows 20KW rate), and Chademo (20 kW for Leafs).

Jack Bowers

Yes, Jack you are off to a terrific start!

Any chance of a parts list and schematic, pictures etc?
This may be the simplest way to DIY a traveling 70A Roadster charge.

-widespread 70A level2 does not seem to be happening any time soon.

 

[jackbowers]

I need to find a new contactor source, as the one I'm using has been discontinued, but after can post plans. It's a very simple sense circuit: 2 120V transformers connected beteween neutral and opposite hot wires on each of the 14-50 plugs. The secondaries are wired in series so that you get 24V if the polarity is in phase (0V if not). That feeds a 24V coil on a 50A 4-pole contactor, which ties all the hot wires together. The HPC does the rest. Caution: A single wiring mistake could blow a fuse and take down a large section of the RV Park. Also, the transformer sense circuit leaves live voltage on the 14-50 pins due to primary loop current. It's not lethal, but at 90V it stings a bit if you forget to turn off both 14-50 breakers before pulling the first 14-50 plug out.

Jack

 

[TonyWilliams]

I need to find a new contactor source....
Jack

Looking forward to your drawing. Here's one with no safety devices (DANGER, DANGER) that we penciled together over at the Nissan LEAF forum:

 

[driver_EV]

I need to find a new contactor source, as the one I'm using has been discontinued, but after can post plans. It's a very simple sense circuit: 2 120V transformers connected beteween neutral and opposite hot wires on each of the 14-50 plugs. The secondaries are wired in series so that you get 24V if the polarity is in phase (0V if not). That feeds a 24V coil on a 50A 4-pole contactor, which ties all the hot wires together. The HPC does the rest. Caution: A single wiring mistake could blow a fuse and take down a large section of the RV Park. Also, the transformer sense circuit leaves live voltage on the 14-50 pins due to primary loop current. It's not lethal, but at 90V it stings a bit if you forget to turn off both 14-50 breakers before pulling the first 14-50 plug out.

Jack

RV parks I have visited do have breakers instead of fuses for each connection, so in that case, no risk likely to RV park.
I am imagining an enable/disable switch to separate the sense circuit to make 14-50 safe to touch.

 

[driver_EV]

I would like to build a 70Amp capable OpenEVSE with this as a front end option to supply power.
-Could save some money vs. buying a HPC, since I do not already have one.

 

[hcsharp]

... I've got two 100A ammeters to monitor the current split, which usually splits pretty evenly (I'm using 30 feet of cable for each hookup to keep the wire resistance similar). I start at 40A, then step it up to 70A if things look okay.

I've never tried this because I assumed the current would not split evenly. In fact I'm a little surprised it works! A warmer cable will conduct more current. No? So why would it be self-correcting? I would have thought one cable would keep getting warmer taking progressively more current than the cooler one.

For a commercial version, someone could take two of those open source 10kw chargers and combine the power at the DC level. From there you could have "adaptors" that deliver up to 20kW one of three ways: 70-80A J1772 (inverter needed for this option), Tesla Supercharger (if it allows 20KW rate), and Chademo (20 kW for Leafs).

Jack Bowers

If that would work then the European Roadster owners would have stopped complaining about lack of 3 phase charging a long time ago. The problem is a 10kw inverter with a pure sine wave output is too heavy and bulky to fit in the Roadster trunk.