32A OpenEVSE is sold

[jpadc]

Hmmm, does this mean the Leaf is violating the J1772 protocol? I thought the car was expected to adjust to a changing pilot signal in real time. For example if using the "Hydra" or other dual-headed EVSE one might start charging at 30 amps but then have that cut in half to 15 amps without interrupting the charge if a second car plugs in, and similarly, if the second car unplugs the car should ramp back up. This isn't a safety concern for the second case of course, but it's very troubling that the Leaf would apparently keep charging at 28 amps even when the pilot drops to 12 amps.

Well, an EVSE can't "know" what other things are on the same electrical circuit that it is on so it can't possibly adjust allowable amperage draws based on other things on the same circuit (including other EVSEs).
It can detect a voltage change (i.e. one power leg being dropped), but the amperage setting are programmed into the software of the EVSE (or are adjustable like on the Juicebox). An EVSE only reports and delivers the amperage the car has requested up to its programmed max setting. I don't know about Open EVSE, but the Juicebox has a separate adjusters for the max amp draw allowed for 120 verses 240 volt input. The EVSE encodes that max setting in the pilot duty cycle (ie, signal frequency) and that is how it conveys maximum allowed amperage information to the car. The pilot signal does not encode the voltage level (i.e., 120 versus 240) as that is directly known to the vehicle depending on the presence of current on the AC Line 1 and AC Line 2 pins of the J1772 plug.

So if the car is told via the pilot signal, when it is first plugged in that the EVSE is programmed to deliver up 30 amps, the car may ask for up to that. I don't think there is anything in the specification of the protocol that requires the car's charger to keep monitoring the pilot signal's duty continuously, only its voltage swings (to know when to start and stop charging). It is required to check the duty cycle when it when its first plugged in. Even a drop in power (i.e., a power failure) does not require a reread of the pilot signal's frequency as it should come back up the same as it was before the power failure. It is required to set the voltage back to -9/+12 volts so the car will delay the restarting of charging for a short while after power is restored. Read here if you care about details of the protocol: https://code.google.com/p/open-evse/wiki/J1772Basics.

Long and short, if you want to be safe, pull the J1772 plug out of the vehicle (which will be detected and registered on the proximity signal by the car) before ever changing any voltages to the EVSE. That way the car will be sure to get the proper information when plugged back in and not try to draw more ams than it should.

P.S. I think the "two headed" Hydra actually limits charging by programming to 15 amps to each head so it can be ready for a second car. I don't think it adjusts amps available based on one or two cars being plugged in. - But you have me curious.

 

[fooljoe]

• If both cars are charging and one stops, the other pilot is immediately raised to 100%. The car that stopped continues to get 50% in accordance with the above rules.

• If only one car is charging, and the other enters state C, it will be given a delay. During that delay, the other car's pilot is reduced to 50% and it will be given a brief interval to respond and reduce its draw. After the delay, the second car's power will be turned on.

https://code.google.com/p/open-evse/wiki/Hydra

 

[jpadc]

https://code.google.com/p/open-evse/wiki/Hydra

That is a good read... I had not had much interest in the device, given I just have one EV, but I'm glad your thoughts gave me the opportunity to read it. I found this line that you did not include in your quote interesting and makes me want to reread the SAE J1772 protocol again regarding which device (EVSE or the EV charger) is responsible for staying within the programmed amperage limits.

If any car exceeds its current allowance for for too long, it is errored out.

But we are way off topic about the sale of this devise.

 

[kipduff]

Glenn:
Just go a 2015 Leaf- amazing! I need to get an L2 charger. I'm a bit confused by these posts: I think these questions pertain to a special, non-standard charging situations. Just so I understand, doesn't a normal Open EVSE like your's automatically sense the source voltage and go to the user selected present amp rate for L1 or L2? And isn't the amp rate setting for L1 and L2 independent? (in other words, when plugged into 120V with adapter, charges at preset amp rate for L1, 14A for example; and when another charging session is initiated at a different outlet at 240V, atomically goes to the preset amp rate for 240V, 26A for example)

I'm in Costa Mesa. If you prefer to communicate by phone, that's OK- I'll PM my number.

Thanks, Kip......

 

[kipduff]

Glenn:
PS: my charging will be done mostly at my apartment, hanging from a 14-50 outlet (not installed yet) on an outside weather exposed wall. I think I want a more portable type for possible 120V/240V charging use at other locations.

 

[GlennD]

Glenn:
PS: my charging will be done mostly at my apartment, hanging from a 14-50 outlet (not installed yet) on an outside weather exposed wall. I think I want a more portable type for possible 120V/240V charging use at other locations.

I think you will be better served with Ingineer's conversion of the stock Nissan EVSE. It is weather resistant and it retains its weatherproof after its conversion. I think it is around 20A at 240V

You could also go with this kit from the OpenEVSE store.

http://store.openevse.com/products/30a-charging-station-combo-with-j1772-and-input-coard?variant=1070075716" onclick="window.open(this.href);return false;

A 30A unit can charge at 24A and that is very close to the 27.5A of a Leaf.

I do not usually make up weather resistant units. If you are not into construction, I will be happy to assemble your OpenEVSE kit at no charge.

The OpenEVSE will work on both 120V and 240V. It detects the voltage and sets the pilot appropriately. Starting at one voltage and finishing at another is a very unusual situation. I do not recommend it. Stay with one voltage for the entire session.

 

[cwstnsko]

GlennD, you should see Paypal payment from me shortly.

Thanks

 

[GlennD]

GlennD, you should see Paypal payment from me shortly.

Thanks

This EVSE is sold and I will ship it out today.