# [EVDL] EValert: GE WattStation Damages Leaf?



## EVDL List (Jul 27, 2007)

Hi Roger,
This might be very well true.
In fact, I would suspect that it is not the diode
in series with the 880 Ohm resistor in the Leaf
charger that gets damaged, because that would be
very pitiful, but there may be damage to the sensing
input (processor pin) that reads the voltage on the
Pilot wire that goes to the diode/resistor combination.
If an ESD discharge or a surge from contactor closing
happens to ride on that Pilot wire and runs straight
into the sensing pin (if it does not have enough filtering)
then that may be the reason it turns the Leaf "blind" to
the Pilot signal and no more charging is possible until
the charger (or that sensing circuit) is repaired.

This would indeed indicate a weakness in the Leaf 
(J1772 charger interface) design, not so much an issue
caused by the WattStation, so there would be nothing
that GE can do except adding some protection on the
Pilot *output* to avoid they can pass a surge into
the Leaf - but then other charge stations may expose the
same weakness (at a lower rate) anyway.

Hmmm, maybe there is a market for Leaf surge protection
cords, to be inserted between any charging station and Leaf
(essentially a J1772 male/female plug on a short extension
cord with surge protection in line)

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Roger Stockton
Sent: Friday, July 20, 2012 9:49 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] EValert: GE WattStation Damages Leaf EVs = can
nolonger charge from any EVSE



> Cor van de Water wrote:
> 
> > Since GE confirmed that they did something wrong,
> 
> ...


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## EVDL List (Jul 27, 2007)

> Cor van de Water wrote:
> 
> > In fact, I would suspect that it is not the diode
> > in series with the 880 Ohm resistor in the Leaf
> ...


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## EVDL List (Jul 27, 2007)

If they say it's the diode used to load the pilot signal, that makes me
think of a SOT-23 Zener diode that pulls the signal down to 6V (relying on
the resistance of the signal to limit current) and can't handle the heat.

Or the resistor and diode are both SMT and share a single copper pour for
cooling, and the resistor is overheating and transferring its heat to the
diode.

Maybe the GE WattStation has a slightly higher voltage or lower resistance
than other charge stations, or maybe it's just coincidence that it's been
noticed more on the GE unit.

Just some more possibilities.

-Morgan LaMoore



> Roger Stockton <[email protected]>wrote:
> 
> > Cor van de Water wrote:
> >
> ...


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## EVDL List (Jul 27, 2007)

It can't be the steady state heat as the charging 
station is required by standard to supply the 12V 
through a 1kOhm resistor and the vehicle adds a 
880 Ohm resistor, so we are talking about approx 
6mA which may lead to a meager 5mW dissipation
in the diode and about 30mW in the 880 Ohm resistor,
not a power level that will kill even an SMD part.
I think it is the spike caused by contact closure
that sends a capacitive coupled 100+ Volts surge to
the pilot that can cause a breakdown.
Though I still expect that it damages the sensing
of the pilot instead of blowing the diode, although
a good surge that goes well over the breakdown voltage
of say 100V can create an instantaneous power spike in
the order of 10W or so. Most parts will survive a short
spike like that but it is possible that the diode in
the Leaf is more sensitive than usual and breaks down
permanently, which automatically disables charging
on compliant charge stations.

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Morgan LaMoore
Sent: Monday, July 23, 2012 8:03 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] EValert: GE WattStation Damages Leaf?

If they say it's the diode used to load the pilot signal, that makes me
think of a SOT-23 Zener diode that pulls the signal down to 6V (relying
on the resistance of the signal to limit current) and can't handle the
heat.

Or the resistor and diode are both SMT and share a single copper pour
for cooling, and the resistor is overheating and transferring its heat
to the diode.

Maybe the GE WattStation has a slightly higher voltage or lower
resistance than other charge stations, or maybe it's just coincidence
that it's been noticed more on the GE unit.

Just some more possibilities.

-Morgan LaMoore

On Fri, Jul 20, 2012 at 6:18 PM, Roger Stockton


> <[email protected]>wrote:
> 
> > Cor van de Water wrote:
> >
> ...


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## EVDL List (Jul 27, 2007)

> Cor van de Water <[email protected]>wrote:
> 
> > Hi Roger,
> > This might be very well true.
> ...


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