I have also noticed this on my CALB powered EV.
It was traced to just one cell by measuring the voltage between the chassis and
the cells.The leaking volts swung negative on one side and positive on the
other and when the reading was zero, I had found the faulty one. It was about
half way down the pack and vanished after I removed the cell, cleaned and
replaced it.
The cell was visually perfect and like Collin, I wondered if there was some
imperfection in the plastic to allow leakage. These are 100Ah cells and the
plastic seems to be very thick but just a tiny sliver of conductive material in
the case would be enough to cause the fault.
From: Collin Kidder via EV <ev@lists.evdl.org>
To: Rick Beebe <r...@evgrin.com>; Electric Vehicle Discussion List
<ev@lists.evdl.org>
Sent: Thursday, 2 June 2016, 14:25
Subject: Re: [EVDL] Ground Faults
Yes, I've had this same trouble with LiFePO4 cells (Thundersky). I
believe that the cases might be ever so slightly conductive. Also, the
car was in a somewhat salty environment by the ocean and sea mist and
dirt caused a build up of conductive material over the top of
everything. So, I cleaned the tops of all of the cells, especially
around the terminals. This helped quite a bit. I still ended up with a
small amount of ground leakage but much better than it was. I don't
know that it can be very easily fixed for good with Thundersky cells.
I'd probably have to insulate every single cell from each other and
the case.
On Wed, Jun 1, 2016 at 11:56 PM, Rick Beebe via EV <ev@lists.evdl.org> wrote:
> When I had a lead pack in my truck I had rampant leakage from the pack to
> the frame. I think the acid mist and dirt are conductive. I kept trying to
> find the culprit battery by segmenting the pack and the leak would literally
> just move around.
>
> And I had the same problem as you--it was tripping the GFCI outlet. I had to
> take out the GFCI outlet and install a regular one. (The truck had a 110v
> Russco charger in it).
>
> I don't think LiFePo4 cells are as susceptible although I have heard several
> stories of different makes having conductive cases. When I put lithium in
> the truck put all the cells in insulated boxes. If I have a ground fault now
> it will most likely be carbon buildup in the motor.
>
> --Rick
>
>
> On 6/1/2016 11:48 PM, John Lussmyer via EV wrote:
>>
>> I mean EVERYTYHING other than the charger.
>> There are contactors on both sides of the pack, so the controller and
>> motor are fully disconnected.
>> I also disconnected the volt/amp meter, and BMS (12v power) as well.
>> Also disconnected the "battery +" wire to the zilla hairball.
>> Unhooked the DC-DC.
>>
>> I'm wondering if I'm getting dirt/damp leakage from the pack to the frame.
>>
>> On Wed Jun 01 18:08:15 PDT 2016 ev@lists.evdl.org said:
>>>
>>> Could you be a little more detailed? You disconnected everything from
>>> what? Each other? The battery pack? Etc? If you have a series wound DC
>>> motor then carbon build up from the brushes can create a path.
>>>
>>> Sent from my Verizon, Samsung Galaxy smartphone
>>> -------- Original message --------From: John Lussmyer via EV
>>> <ev@lists.evdl.org> Date: 6/1/16 7:35 PM (GMT-06:00) To: Electric Vehicle
>>> Discussion List <ev@lists.evdl.org> Subject: [EVDL] Ground Faults
>>> Well, I've discovered that my truck has a ground fault of some kind in it
>>> somewhere.
>>> For a long time, I've been charging off the Welder outlet in my shop. I
>>> recently installed a nice big 240v 60A GFCI breaker for a charging outlet at
>>> the house.
>>> The GFCI trips every time I try to charge. It doesn't trip if I plug a
>>> welder into the outlet.
>>>
>>> Poking around the pack with a voltmeter, I get some solid voltage
>>> readings to the frame of the truck.
>>> So, I started disconnecting things. Disconnected everything except the
>>> charger (kinda need that!).
>>> Still trips the GFCI.
>>> Still getting weak voltage readings from various points in the pack.
>>> (Not always consistent, not always constant.)
>>>
>>> Running out of ideas...
>>>
>>> --
>>> Worlds only All Electric F-250 truck!
>>> http://john.casadelgato.com/Electric-Vehicles/1995-Ford-F-250
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>>
>> --
>>
>> Worlds only All Electric F-250 truck!
>> http://john.casadelgato.com/Electric-Vehicles/1995-Ford-F-250
>>
>> _______________________________________________
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>> Please discuss EV drag racing at NEDRA
>> (http://groups.yahoo.com/group/NEDRA)
>>
>
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>
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