[EVDL List]

It is an imbalance of current between the neutral and the line or on a 240
volt charger it is an imbalance between line 1 and line 2, hence the term
leakage. Some current is not returning. I have a special clamp on meter that
I use to measure leakage on marine shore cords, it is a big deal around a
boat. Unfortunately it is an incredibly expensive clamp meter at something
over $300.00. I don't know how. The only thing I can think of would be to
take an old large toroid out of a dead battery charger and wrap some magnet
wire around it and connect it to a dmm. But there is no real reference and
not precise but you could at least use it to understand and you could
calibrate it for your own use by creating leakage with resistors on the line
to ground. Not for everyone but I have done it. Now that I am thinking about
it I have a few coils I wrapped a couple of years ago And a bunch of toroids
that could be wound.

I will look tomorrow to see what I have, could send them for the cost of
postage if anyone wants.

Mark Grasser

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Roger Daisley
Sent: Friday, October 15, 2010 12:39 PM
To: [email protected]
Subject: [EVDL] Measuring Ground Fault Current

As many EV'er know, popping a GFCI when charging their EV is fairly common.
It is especially embarrassing when it happens at a location other than home.

I am hoping that someone can describe a simple way to measure and monitor
this leakage current so preventive action can be taken before it gets to the
"popping" stage. I'm thinking that perhaps a GFCI could be tapped in some
way to measure the current it is seeing.

Roger Daisley

ElectricVW.blogspot.com

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[EVDL List]

Hello Roger,

In explosive proof areas, operating rooms, fuel stations we install a Ground
Detection system which detects a conductance path to ground. For this to
work, the installation has to completely isolated, meaning no direct
electrical grounds connected to any metal housings, conduit and electrical
panels. All this installation and electrical is isolated by using a large
isolation transformer and sometimes a capacitor bank.

The only thing you can detect on a EV is the DC leakage from the battery
pack to the frame of the EV. You first unplug the AC input plug which may
have a self grounding pin in the plug.

Next take a volt meter set in the lowest scale and place one lead on the
most positive and to the frame of the EV. If you should indicate a voltage,
then some where in the pack, a battery is conducting a current to the frame.

Lets say it reads 10 volts from the most positive to frame, then move the
test lead from the most positive to the next battery, you will see that this
voltage will drop until you get to the battery or batteries that are leaking
current the most.

Keep the meter connected and start cleaning the batteries until the voltage
indication drops as low as it can go.

Now, increase the voltmeter scale higher then the charging voltage of the
charger and turn on the battery charger. If the voltage indication on the
meter is the same voltage as the output voltage of the charger, this is
normal for a non-isolated charger. The meter it self is shunting this
current at this time.

You can do a permanent installation, by installing a panel volt meter
connected to switch to a 1 amp fuse which is then connected to the most
positive post of the pack. The other lead of the volt meter than is
connected to the vehicle frame.

If you use a low voltage meter, then you first must turn off this test meter
switch, as so not peg the volt meter if you forgot to turn off this switch.
You could also use a 2 pole double throw switch where in one position to
test out the ground fault while the other position of the switch it keeps
off the AC input power by use of a AC magnetic contactor. Turning the switch
in the other position, turns off the test meter and turns on the AC
contactor.

These ground detection units can be purchase from GE, Westinghouse, Square
D, etc. In any case when they detect a current leakage above a set
perimeter, it then is use to turn off a AC magnetic contactor.

Roland




----- Original Message -----
From: "Roger Daisley" <[email protected]>
To: <[email protected]>
Sent: Friday, October 15, 2010 9:38 AM
Subject: [EVDL] Measuring Ground Fault Current


> As many EV'er know, popping a GFCI when charging their EV is fairly
> common.
> It is especially embarrassing when it happens at a location other than
> home.
>
> I am hoping that someone can describe a simple way to measure and monitor
> this leakage current so preventive action can be taken before it gets to
> the
> "popping" stage. I'm thinking that perhaps a GFCI could be tapped in some
> way to measure the current it is seeing.
>
> Roger Daisley
>
> ElectricVW.blogspot.com
>
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>

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[EVDL List]

Roger Daisley wrote:
> I am hoping that someone can describe a simple way to measure and monitor
> this leakage current so preventive action can be taken before it gets to the
> "popping" stage.

You can add a meter that will show the ground fault leakage current.
Here comes one of my bad old ASCII schematics. View it with a fixed
width font like Courier:

pack+_______up _ ____
\_________/ \______|~ +|________________
___ com I1 \_/ | | | _|_+
ground__| down 120v 4watt | | C1 +_|_ / \ M1 meter
| light bulb | | 2200uF ___ | | 50ma DC
|___up | | 6.3vdc | \___/ full-scale
\__________________|~ -|_________|______| -
pack-_______ com |____|
down D1 bridge
S1 DPDT

Parts list:
S1 - DPDT center-off, momentary-off-momentary toggle switch
(www.mpja.com 16090SW $1.49)
C1 - 2200uF 6.3vdc electrolytic capacitor (Jameco 609342 $0.39)
M1 - analog panel meter, 0-50ma DC (Jameco 316523 $9.95)
D1 - bridge rectifier, 50v 1amp (Jameco 178001 $0.29)
I1 - 120v 4watt light bulb (child's night light, Xmas tree lamp)

The switch sits in the center-off position when not in use. This avoids
any connection between the pack and ground.

To use it, push the switch up, then down. The meter reads the ground
fault current (if any). The lamp limits the current to about 30ma even
if there is a direct short between some point in the pack and ground. If
your pack voltage is much above 120v, use two lamps in series.

You will feel an unpleasant tingle with a ground fault current of about
1ma, and a GFCI will trip if the current exceeds about 5ma. This circuit
can measure ground faults as high as 30ma (or whatever the lamp allows).

It can also test a GFCI. If you plug into a GFCI protected outlet, and
your charger is not isolated, then the GFCI should trip when you move
the toggle switch up or down.
--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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[EVDL List]

Wow - 5mA trips the GFCI?
No wonder there are so many nuisance trips!
The breakers with GFCI that I am used to
from The Netherlands to protect rooms without
carpet such as bathrooms, will typically trigger
at 30mA that is why the test resistor is 7 kOhm
(230V / 7kOhm = 33mA)

Regards,

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Lee Hart
Sent: Sunday, October 17, 2010 8:28 AM
To: [email protected]; Electric Vehicle Discussion List
Subject: Re: [EVDL] Measuring Ground Fault Current

Roger Daisley wrote:
> I am hoping that someone can describe a simple way to measure and
> monitor this leakage current so preventive action can be taken before
> it gets to the "popping" stage.

You can add a meter that will show the ground fault leakage current.
Here comes one of my bad old ASCII schematics. View it with a fixed
width font like Courier:

pack+_______up _ ____
\_________/ \______|~ +|________________
___ com I1 \_/ | | | _|_+
ground__| down 120v 4watt | | C1 +_|_ / \ M1 meter
| light bulb | | 2200uF ___ | | 50ma DC
|___up | | 6.3vdc | \___/ full-scale
\__________________|~ -|_________|______| -
pack-_______ com |____|
down D1 bridge
S1 DPDT

Parts list:
S1 - DPDT center-off, momentary-off-momentary toggle switch
(www.mpja.com 16090SW $1.49)
C1 - 2200uF 6.3vdc electrolytic capacitor (Jameco 609342 $0.39)
M1 - analog panel meter, 0-50ma DC (Jameco 316523 $9.95)
D1 - bridge rectifier, 50v 1amp (Jameco 178001 $0.29)
I1 - 120v 4watt light bulb (child's night light, Xmas tree lamp)

The switch sits in the center-off position when not in use. This avoids
any connection between the pack and ground.

To use it, push the switch up, then down. The meter reads the ground
fault current (if any). The lamp limits the current to about 30ma even
if there is a direct short between some point in the pack and ground. If
your pack voltage is much above 120v, use two lamps in series.

You will feel an unpleasant tingle with a ground fault current of about
1ma, and a GFCI will trip if the current exceeds about 5ma. This circuit
can measure ground faults as high as 30ma (or whatever the lamp allows).

It can also test a GFCI. If you plug into a GFCI protected outlet, and
your charger is not isolated, then the GFCI should trip when you move
the toggle switch up or down.
--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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[EVDL List]

"As many EV'er know, popping a GFCI when charging their EV is fairly common."

>From what I've seen, this is mainly a problem due to a somewhat conductive
buildup on FLA batteries. I have LiFePO4 cells and charge from a 240VAC/50A
GFCI breaker and it never trips. I expect the same is true for sealed lead
acid batteries. The GFCI does work - once while hooking up a cell log8 I
had some leads connected to cells and dropped one. It touched the side of
the painted steel battery box and immediately kicked off the breaker.
--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Measuring-Ground-Fault-Current-tp2997757p2999076.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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[EVDL List]

Cor van de Water wrote:
> Wow - 5mA trips the GFCI?

Yes. There is no magic current above which it is fatal, and below which
it is safe. Instead, as the current gradually goes up, the effects get
progressively worse. There are considerable difference between
individuals as well.

5ma was established as the level that will not hurt a healthy human
being, and who will still have sufficient control of their muscles to
let go.

0.5ma was established as the maximum level for infants, the elderly, and
people who are otherwise incapable of getting away from the source of
the current. Long term exposure to this current causes damage, but isn't
fatal unless it adds to existing conditions. Hospital equipment is
designed for this level, for example.

The auto companies established their own standards at 20ma, because it
is cheaper and easier to meet. At 20ma, you typically can't "let go",
and so you are depending on some external device to break the current.

> The breakers with GFCI that I am used to
> from The Netherlands to protect rooms without
> carpet such as bathrooms, will typically trigger
> at 30mA that is why the test resistor is 7 kOhm
> (230V / 7kOhm = 33mA)

30ma! That is well up into the region where it could kill a significant
fraction of people! Are you sure it's this high?

--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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[EVDL List]

tomw wrote:
> "As many EV'er know, popping a GFCI when charging their EV is fairly
> common." From what I've seen, this is mainly a problem due to a
> somewhat conductive buildup on FLA batteries. I have LiFePO4 cells
> and charge from a 240VAC/50A GFCI breaker and it never trips.

It's worse with flooded batteries, but will happen with *all* types of
packs.

Flooded batteries of any kind (lead-acid, nicad, or nimh) naturally
"gas" during charging. The gas that comes out the vents also carries out
tiny amounts of the electrolyte (dilute sulfuric acid or potassium
hydroxide". They tend to deposit on surfaces on and around the battery.
They are conductive, and the main cause of ground fault leakage currents.

Sealed batteries of all kinds don't normally vent, so problems from this
source are much less likely. But, they *will* vent or leak in some
cases, due to overcharging, failed seals from mechanical stress on the
terminals or case, and swelling due to age or abuse. It may not happen
today, but when you look at an old battery pack at end of life, it is
very common to find evidence that some cells vented or leaked.

Besides electrolyte leakage, there are other sources of ground faults.
High humidity and falling temperatures will condense water on every
surface, including the tops of your batteries. When there's dew on the
grass, there's also water on top of your batteries!

Pure water isn't very conductive, but here you can have hundreds of
volts to drive that current. Over time, things also get dirty. The tops
of the batteries can collect dust, dead bugs, mouse droppings, salt
spray in coastal areas or places that salt winter roads, and other
debris that greatly increases the conductivity.

The only cure is to completely seal up the batteries, and mount them in
a nonconductive box so there is no over-the-surface path from batteries
to ground.
--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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[EVDL List]

The marine industry considers the current level of 2ma to be deadly.

American Boat and Yacht Council (ABYC) has made recommendation to use 30ma
Equipment Leakage Circuit Interrupter (ELCI) devices in all boat main
breaker circuits. The reasoning is that a fault to ground even in fresh
water will trip the 30ma breaker before the person even enters the water.

In the EV charging situation salt water being a very good conductor will
trip the 30ma ELCI whereas the fresh water, such as rain water and early
morning dew won't probably trip the 30ma GFCI until your body resistance
shows up. My studies have shown that fresh water is far more deadly than
salt water.

Mark Grasser

Saltwater is conductive and if there is lea

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Lee Hart
Sent: Sunday, October 17, 2010 12:08 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Measuring Ground Fault Current

tomw wrote:
> "As many EV'er know, popping a GFCI when charging their EV is fairly
> common." From what I've seen, this is mainly a problem due to a
> somewhat conductive buildup on FLA batteries. I have LiFePO4 cells
> and charge from a 240VAC/50A GFCI breaker and it never trips.

It's worse with flooded batteries, but will happen with *all* types of
packs.

Flooded batteries of any kind (lead-acid, nicad, or nimh) naturally
"gas" during charging. The gas that comes out the vents also carries out
tiny amounts of the electrolyte (dilute sulfuric acid or potassium
hydroxide". They tend to deposit on surfaces on and around the battery.
They are conductive, and the main cause of ground fault leakage currents.

Sealed batteries of all kinds don't normally vent, so problems from this
source are much less likely. But, they *will* vent or leak in some
cases, due to overcharging, failed seals from mechanical stress on the
terminals or case, and swelling due to age or abuse. It may not happen
today, but when you look at an old battery pack at end of life, it is
very common to find evidence that some cells vented or leaked.

Besides electrolyte leakage, there are other sources of ground faults.
High humidity and falling temperatures will condense water on every
surface, including the tops of your batteries. When there's dew on the
grass, there's also water on top of your batteries!

Pure water isn't very conductive, but here you can have hundreds of
volts to drive that current. Over time, things also get dirty. The tops
of the batteries can collect dust, dead bugs, mouse droppings, salt
spray in coastal areas or places that salt winter roads, and other
debris that greatly increases the conductivity.

The only cure is to completely seal up the batteries, and mount them in
a nonconductive box so there is no over-the-surface path from batteries
to ground.
--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

_______________________________________________
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
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| OTHER HELP: http://evdl.org/help/
| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev

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[EVDL List]

A few things I didn't see on the GFI and about getting shocked . Just
because you measure say 2 ma with your meter between say the chassie
and ground don't mean 2 ma will be flowing throw you it you touch the
two . Your body has a high resistance and this will cut the current
way back ,, you may still feel it but its not the same current as what
is going through a meter with one probe hooked to the ground . Also
an easy way to find where the leaking is , is to set your volt meter
to volts and put one probe on the chassie and the other on the
traction pack cables ,or battery post , start at the most + if you
like or any where that easy to get to and if you see voltage move the
probe to the next battery . Head in the direction that makes the
voltage go down . When you get to the point where the voltage is 0
that's where your leakage is . Don't stop at the first one either as
there can be a few spots . funny but I always enjoy doing this , as
it shows right where the problem is .
Steve Clunn

--
Tomorrows Ride TODAY !
Visit our shop web page at: www.Greenshedconversions.com

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