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GE Watt Station Fries Leaf...possible on Model S?

Have you all seen this story?:

http://www.environmentalleader.com/2012/07/19/ge-admits-wattstation-coul...

Looks like there's been a few instances of GE Watt Station's bricking Nissan Leafs. Is this possible with Tesla's on board chargers? Is this a concern for future Model S owners who may be remote charging at one of these stations?

Thought I'd ask the tech gurus on this forum for their $0.02.

What do you all think?

Whatever caused the problem with the Leaf caused a diode (used by the J1772 protocol) to fail in the car. GE claims that the problem is not with their WattStations:

http://www.engadget.com/2012/07/19/ge-says-its-wattstations-arent-behind...

I would guess that it's not an issue with the Model S, but that's just a guess.

DON'T say bricked. Bricked has a very specific meaning. Bricking a tesla size battery is a 20k replacement. This was a power diode - a ten buck part. Its the difference between replacing an engine, and replacing an automotive fuse.

Bricking means its permanently rendered unusable. Refers to a computer dying and being used as a door stop. Like a brick. Permanantly inert.

To be honest, I would be VERY dubious of anything sold at your local hardware store with this much technology. My last two dishwashers were GE’s, and both of them were recalled because of fire issues.

A classic case of fear of the unknown. EVs are new, so people assume the worst before they have the facts.

This issue is a molehill puffed up by nervous Nissan dealers. They needed something to blame other than the car they are selling.

Jbunn is correct to point out that this Leaf problem is not bricking (i.e. the battery is not damaged in this case).

From the scant info available, here is my surmise:

Anything is possible, but from a circuit architecture point of view, it is highly unlikely that the GE charger caused the diode to blow out.

Here is the logic as to why: the Wattstation charger does not produce any unique voltages, it merely connects the available 220V AC lines to your car. (it's internal computer just figures out the favorable times of day to allow the connection, it doesn't make any new voltage or phase).

Therefore, the Wattstation can only apply voltages that the built-in Leaf charger is designed to see. Since the supply is alternating current (AC), the Wattstation can't get the polarity backwards either - it's already reversing on its own 60 times a second.

The charger inside the Leaf takes this 220V input voltage and outputs different voltages needed to charge the batteries (converting voltages is what "inverters" do).

In that inverter circuit, diodes are used to control the direction of current. If those diodes are defective, or if the circuit around them fails and overdrives them, they can blow.

Usually that means that they become an open circuit (like a fuse that blows), and they no longer conduct electric power.

If the diode blows, it has to be replaced before you can charge again. That is pretty cheap and simple for a repair technician to do.

To me, the overwhelming probability is that the Leaf's built-in inverter had a some defective diodes, or had a circuit flaw that made them vulnerable to this failure.

After Nissan completes their analysis, I think that's what they'll find. And Nissan will correct them it under warranty.

And that will be that.

Shazam! No explosions. No brain cancer. EVs are just machines like any other, that occasionally need fixing.

It looks like those GE stations can charge the Leaf battery in four to eight hours. The 11 vehicles that blew the diodes were probably trying to get a 4 hour quick charge and the diodes failed under that much current.

It's only reasonable to expect people to select the fastest charge time possible. I'm guessing GE didn't really test this (though right now it appears the problem is in the car not the ESVE)

Mark did a good write up. A diode works like a one way valve, and unlike a fuse does not have a failure limit at the rated current. Diodes have a healthy safety margin and are oversized for their intended use. I'm going with bad diode in the car or faulty circut design in the car.

@ Mark K: Great write up! Thanks for the explanation.

From the articles it looks like the diode involved is not touching the high voltage charge system but is part of the 1772 comunication link which runs up to 12 V, Unless the GE stayion is doing something to send that signal over 12V, it's very unlikly to be their fault. The part should be sub $1...


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