AndyH
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Re: Q: 120V emergency cord

Fri Jun 25, 2010 9:35 am

Part of your answer is in the post immediately above yours.

The internal processes of the EVSE appear to be based on the 12VDC supply in the EVSE. That suggests that there are no resistors to swap based on input voltage. As an EE - would it make sense to you that a device designed to operate from 208-240VAC would require resistor tweaks when the voltage changes? ;)

I've posted the info on what J1772 does with the pilot signal in another thread. If I can find it, I'll duplicate it here.

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garygid
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Re: Q: 120V emergency cord

Fri Jun 25, 2010 9:56 am

No, no resistor change from 208 to 260v, but perhaps a change between 120 and 240?
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AndyH
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Re: Q: 120V emergency cord

Fri Jun 25, 2010 10:24 am

No resistor changes because of voltage changes.

No signaling from the EVSE to the car about EVSE-input voltage. The EV charger is directly connected to AC thru the EVSE. The AC wiring - for both L1 and L2 - runs directly from the AC source (120V outlet or 208-240VAC hard-line) thru the J1772 connector to the car's charger.

According to the SAE J1772 document, the EVSE for both L1 and L2 has internal control electronics that uses 12VDC. The signaling resistors and pilot signal 'buss' are fed from the 12VDC-operated control electronics 'module'.

Sorry Gary - I don't want to come across snarky, but there are only so many ways to say it...

Andy

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evnow
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Re: Q: 120V emergency cord

Fri Jun 25, 2010 11:01 am

AndyH wrote:The AC wiring - for both L1 and L2 - runs directly from the AC source (120V outlet or 208-240VAC hard-line) thru the J1772 connector to the car's charger.


So how does max current setting work ?
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garygid
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Re: Q: 120V emergency cord

Fri Jun 25, 2010 11:01 am

OK, I did not expect to standard to be so "limited".

However, it might make it easier to "convert" the "included" 120v EVSE to 240v operation, at least at its default max current (possibly 12 amps). Of course, use of the modified EVSE would not be completely legal, I suspect.

Apparently all J1772-complient vehicles either need to accept 100 volts to 260 volts AC as input, or do their own voltage-checking before "connecting" internally to the car's internal charger.

Since a "120v-only" charger in a car (or a "240v-only" charger) cannot determine the supply voltage until after it "turns ON" the AC power through the EVSE, the car would need to isolate the input from the one-voltage charger, turn ON the AC power, check for an acceptable voltage, and then either connect the charger and begin charging, or refuse to charge (and probably shut OFF the EVSE).

What are the resistor values specified for the EVSE, the "nozzle", and the car?
Thanks.
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EVDRIVER
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Re: Q: 120V emergency cord

Fri Jun 25, 2010 11:03 am

AndyH wrote:No resistor changes because of voltage changes.

No signaling from the EVSE to the car about EVSE-input voltage. The EV charger is directly connected to AC thru the EVSE. The AC wiring - for both L1 and L2 - runs directly from the AC source (120V outlet or 208-240VAC hard-line) thru the J1772 connector to the car's charger.

According to the SAE J1772 document, the EVSE for both L1 and L2 has internal control electronics that uses 12VDC. The signaling resistors and pilot signal 'buss' are fed from the 12VDC-operated control electronics 'module'.

Sorry Gary - I don't want to come across snarky, but there are only so many ways to say it...

Andy



This makes complete sense and is similar to the AVCON chargers, I used a resistor and cap to tell the unit to engage and start charging.

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Re: Q: 120V emergency cord

Fri Jun 25, 2010 11:06 am

The "maximum available" current is indicated by the EVSE to the car using the duty-cycle of a square-wave signal on the Control Pilot line.

It is up to the car to regulate how much current it actually draws.
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Re: Q: 120V emergency cord

Fri Jun 25, 2010 11:09 am

Have we confirmed yet (my suspicion) that L1 (120V/12A) does not require a pilot signal ?
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AndyH
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Re: Q: 120V emergency cord

Fri Jun 25, 2010 1:20 pm

evnow wrote:
AndyH wrote:The AC wiring - for both L1 and L2 - runs directly from the AC source (120V outlet or 208-240VAC hard-line) thru the J1772 connector to the car's charger.


So how does max current setting work ?


The j1772 spec gives the 'overview' but doesn't define how any of the companies implement anything.

My guess is that the installer will configure the EVSE during installation - and set the max available current based on wiring/breakers/etc. Once the car's connected, the EVSE will modulate the pilot signal to tell the car what's available. The car's charger might want a 6.6kW charge rate, but will have to reduce its draw once it knows it's only got 13A to work with.

We'll see...

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Re: Q: 120V emergency cord

Wed Jul 07, 2010 12:21 pm

Rat wrote:If I'm following all this (probably not) it has drifted from the thread title of the Level 1 emergency cord to mostly Level 2 charging specs and issues. My concern for the 120 cord is that I have seen statements on this forum that even the Level 1 charging may require its own dedicated circuit or socket. If that's true, then what good is it? The whole point of having it is for an emergency - i.e. you are NOT AT YOUR HOME when you need to charge. You roll into some motel or restaurant parking lot with virtually no juice but can pull up to the 120 socket near the sprinkler box or something. Can you safely charge there or not? If not, then why have the nominal capability? Why carry that extra 10 lb. cord, for that matter? We need some clear guidance on this.


This is the only US L1 cable for which I've seen hard specs: http://www.clippercreek.net/images/ClipperCreek%20PCS-15%20Brochure.pdf This device is designed for a 120V 15A connection.

These cables - because they're primarily intended for emergency or opportunity charging - should be as universal as possible. I expect that L1 will stay with the 'lowest common denominator' 12/13A draw from a 15A circuit.

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