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Discussion in 'Roadster: Technical' started by W.Petefish, Aug 30, 2011.
Yes, please open it (it's only two screws..).
Recapping also that the Swiss UMC seems to have different current settings from the USA version.
Swiss: 10A through 32A
USA: 12A through 40A
I bet the different UMCs use the same "keying" system to detect different plug types, but have different current levels depending on which version of UMC.
For instance, if you put in a Swiss end labeled "10A" into a USA UMC would it then tell the Roadster that 12A was available?
Edit: the 10A vs 12A may not be the best example as this is the "default" charge rate. Comparing how 24/32/40A plugs work is probably more relevant.
Don't think so. I believe that minimum current is what the Roadster draws when the pilot signal is connected to ground. Swiss Roadsters default to 10 Amps since that's what is set in their firmware.
Stop believing and start knowing
Tonight I pulled apart the 10A california twist lock (the one with no purple signal wires) and plugged in some lab cables to play with. I installed one on ground and one on the white rind (where the pilot wire comes in). The I tried various situations together with the UMC (see image).
So here are the results:
Wires open = 10A (this is the same way the stock 10A is wired)
Wires shorted = 32 A (this is the same way the 32A connector is wired)
Diode (Cathode on white ring) = 13A (INTERESTING!!!)
Diode (Cathode on ground) = 10A (Interesting too!!)
So what's the conclusion? Right, the Firmware of the UMC is modified to the needs of the local infrastructure (therefore the minimal current is 10A). I guess each setup (wires open, wires closed, diode one way or another) can be programmed into the UMC to generate the appropriate pilot signal.
To answer TEG's question: The roadster draws what the UMC tells him. The pilot signal is generated according to the charging standards - I don't think Tesla played with that. The UMC senses which setup is wired inside the twist lock connector and the generates the appropriate pilot signal to signal the Roadster how much current to draw. I think TM just adjusts the minimal current the Roadster draws when any pilot is absent. If a UMC is present a pilot is always generated.
Another view of the diode test:
OK, so if you brought a USA spec Roadster to Switzerland, and plugged it into a Swiss UMC w/ Swiss "10A" adapter (as labeled) it would still charge at 12A...(?)
I wonder if the gray market imports had their firmware changed to charge at the lower Swiss "default" rate?
How about at the other end - if you brought a Swiss UMC to the USA, and plugged it a US Roadster with US 40AMP plug could it still charge at 40amps?
Perhaps this is all just academic, but I do think (at least from a labeling standpoint at a minimum), that they intended all the parts (plug, UMC, Roadster) to be a "matched set" for a specific region.
Worth pondering since we have both US and European owners examining their UMCs to figure out how they work. If there are actual differences in the UMC between USA and Europe it would be good to know.
I think it's all in the firmware of the UMC. Send me an US UMC and we can proof it...
Love that quote! :love:
For some reason, I cannot view your images. They aren't showing up inline.
Yes, I thought/assumed it might be like that.
So if you brought a Swiss UMC to USA, it may cause a USA Roadster to pull different current through it even if you used the USA adapter plugs.
The labels on the plugs (showing ampacity) assume that the UMC (and possibly Roadster) are all from the same region.
I knew from the RFMC scheme that there were limited possible types of plugs it could sense.
Assuming that the UMC did something similar, I thought they may want to reuse the same signal types for different plugs and current levels in other regions.
10A is the lowest Swiss outlet, 13A is the UK setting. What do other EU Roadsters default to - in countries where normal outlets are 16A?
In Germany the Roadsters were set to pull 16A if no pilot was available. But TM Germany had a couple of issues with that (people blowing fuses of installations that weren't supposed to deliver 16A for 8+ hours etc.). So now the new Firmware Update sets German Roadsters to 13A (if I remeber correctly).
What I don't quite understand is why there is no 16A UMC Adapter available in Switzerland. Ok, the Firmware of the UMC has no option for 16A, but they could add the setup "cathode on ground" to the UMC's firmware to allow a 16A plug. But I think they designed the UMC for Regions, not for signle Countries.
Indeed, not available in home depot though, it's a specialist, non-standard part that has to been ordered from a bespoke supplier. And, I wasn't able to see a california one that had the metal plate inside the recess. I do believe that's just there for show or creating a firmer grip as the UMC female has a nice spring pressing against the metal plate.
I'm going to pick up the set; quick & simple need right now. I'll wager that the diode in the set will be a zener diode similar to the roadster end to crow-bar down the pilot to signal the EVSE that we're ready and/or need extra ventilation... though I don't know of anyone that implements that.
You have to special order them from home depot.
I have a strong suspicion that it is not just for show and not just mechanical. I imagine that it is made of a conductive material with a conductive contact for a reason.
The metal plate and side contact are the ground connection (marked with green). The three twist lock contacts are black, red and white for L1, L2 and neutral.
That makes sense. So, the metal plate is a safety ground, but I suppose it doesn't carry charging current. I assume the charging current flows between L1 and L2. Is Neutral separate from ground?
That may depend if you are using a 3 prong or 4 prong plug end... (?)
So far, the UMC adapters that I have inspected do not use the 4th prong (or is it technically the 3rd prong that they're not using?).
Since most all 14-50s you may encounter (except for some wacky cable contraptions you might find at an RV park) will have 220/240V across L1 and L2 then you don't need the Neutral.
If you had an appliance which plugs into 14-50 that wants 110/120V it could use Neutral plus one of the legs, but the Roadster charging doesn't need that lower voltage, so just using L1 & L2 is enough.
The ground, I assume, is for safety. So for the 4 prong plugs I gather they could just leave neutral disconnected. For 3 prong plugs, there isn't even a neutral to even think of hooking up... (?)
As a 240 volt electrical connector the green ground and neutral wires must be passed through separately per NEMA code. (They are bonded at the entrance electrical panel but isolated at subsequent panels and wiring) The green wire will not carry any current other then leakage up to any amount allowed by the GFI device but without it the car will be ungrounded and I would certainly expect a charge fault.
In the case of the Tesla as well as any other pure 240 volt device the white neutral is not needed. The RFMC and the UMC use this otherwise unneeded white contact to provide allowable current draw signals. It does this by not connecting the white California connector contact to the neutral electrical connector contact but rather tying it to the green ground connect using various options.
The RFMC adapters tie the white directly to the green to indicate a plug overheat condition by using a thermal fuse. They use a regular non-zener diode in one orientation for 24 amps and in the other orientation for 40 amps. If the white connection is unconnected it only allows 16 amps.
Since I don't have a UMC I am uncertain on their configuration but it would appear from other posts that they are not using the shorted position as a thermal condition but rather as another current level option.