# [EVDL] High resistance contact LiFeP cells



## EVDL List (Jul 27, 2007)

Hello David,

Every time you charge and discharge through this copper-aluminum connection, 
you will see a different color change at the point of contact, thus cause by 
the electro plating of these surfaces.

In our overhead line electrical work, we use a bi-metal connection between 
aluminum and copper which is a tin plated divider washer between these 
elements.

In some compression fittings we will use a contact paste, but this only 
works if the fitting is install under very high compression. I tested this 
contact paste on a tin plate battery connected to lead at a torque of 75 
inch pounds, it felt my EV was dragging something.

Even a tin-plated battery connector will de-plate it self between the 
elements of lead and tin. So, I am using a gold plated battery clamp that 
has even after 10 years of usage, looks as bright and new as the day I 
install it. I would tried a tin plated copper or gold plate copper washer 
between the aluminum and copper.

Roland


----- Original Message ----- 
From: "David Sharpe" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Monday, September 21, 2009 3:08 AM
Subject: [EVDL] High resistance contact LiFeP cells


> On a recent round trip of some 600ks done entirely on electricity except 
> for
> about one litre of hydrocarbon fuel, I became aware that I was getting
> voltage drops between the tinned copper straps & the positive cell 
> terminal
> which is aluminium. I realise I have dissimilar metals here (about 1.4V
> difference) and seek advice how others have solved this problem. I 
> remember
> there was a paste that was applied when making electrical joints between
> aluminium surfaces and suggest this might be the solution. However it 
> might
> also add a non conducting surface too. My bolts were tight enough I 
> thought.
> David S
>
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## EVDL List (Jul 27, 2007)

Roland,

Are you implying that if NoAlOx is used between the copper and aluminum that
the resistance will be higher? I'm going to be installing some LiFePOs in my
Gizmo and want to make the best connections I can. One post is aluminum with
an aluminum nut holding the post and the other one is a copper post with an
aluminum nut. Both are drilled and tapped. I was planning on using brass
bolts since brass has a lower resistance than stainless steel. I don't want
the same issue that David is having with his rig.

Thanks,

David



> Roland Wiench <[email protected]> wrote:
> 
> > Hello David,
> >
> ...


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## EVDL List (Jul 27, 2007)

Hello David,

Back about 30 years ago, I had one battery terminal that the tin plating had 
some copper showing, so I replace the fitting and tried some contact paste 
which was made by Burndy call Penetrox A which we only use in very high 
pressure crimp type fittings.

Coated the copper wire with this stuff and crimp on the terminal with a 
hydraulic crimper at 20 tons. I then tried some on the matting surfaces of 
the battery clamp to the lead battery post.

The batteries where already charge up to 100% SOC, but when I tried to move, 
it felt like less than 50% SOC. I then clean off the this contact paste and 
the drive was back to normal.

I just look up bi-metal connections, and one method that is use is inserting 
a brass fitting between a copper and a zinc plated fitting. While the 
copper will react with zinc and aluminum, the brass will not react with the 
copper and zinc. A person would have to test this out to see if brass would 
react to aluminum.

Brass fittings will tarnish after a while. I would also tried tin plated 
copper washers to see what happens.

To install battery clamps, I still use the standard lead post with a embed 
stud. I first torque the battery clamp around the post at 100 inch pounds 
and than using a stainless steel washer, lock washer and nut on the stud 
which I also torque to 100 inch pounds. This method put internal pressure 
on the stud head against the battery clamp.

This method prevents mushrooming of the battery terminal which also prevents 
the reduction of surface contact between the post lead which is normally 
call shrink back. I normally will torque the connections a second time about 
a week later and then I never touch them for the last 8 years.

Roland




----- Original Message ----- 
From: "David Nelson" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Wednesday, September 23, 2009 9:11 PM
Subject: Re: [EVDL] High resistance contact LiFeP cells


> Roland,
>
> Are you implying that if NoAlOx is used between the copper and aluminum 
> that
> the resistance will be higher? I'm going to be installing some LiFePOs in 
> my
> Gizmo and want to make the best connections I can. One post is aluminum 
> with
> an aluminum nut holding the post and the other one is a copper post with 
> an
> aluminum nut. Both are drilled and tapped. I was planning on using brass
> bolts since brass has a lower resistance than stainless steel. I don't 
> want
> the same issue that David is having with his rig.
>
> Thanks,
>
> David
>
>


> Roland Wiench <[email protected]> wrote:
> >
> > > Hello David,
> > >
> ...


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## EVDL List (Jul 27, 2007)

> David Nelson wrote:
> 
> > I'm going to be installing some LiFePOs in my Gizmo and want
> > to make the best connections I can. One post is aluminum with
> ...


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## EVDL List (Jul 27, 2007)

Thank you, everyone for the ideas. Take a look at the TS cell picture
here: http://picasaweb.google.com/GizmoEV/Gizmo?authkey=3DGv1sRgCNH1xsTbzbe=
fPQ#5385184643867229938
or http://tinyurl.com/y8v8925. This will give everyone an idea of what
I'm talking about.

Each battery post is mounted to the plastic case with an aluminum nut.
One post is made of aluminum and the other is made of copper. The
picture doesn't show this very well. A bolt is then used to hold the
cable lug or what ever to the post of the battery. This is what I
meant by the post being drilled and tapped.

I figured that since we aren't dealing with high frequency AC that
conduction would be throughout the material, not just on the surface.
A stainless steel bolt would tend to push more current through the
copper and aluminum into/out of the battery which could increase the
temperature. If I used a brass bolt maybe more would go through the
bolt and lower the resistance some. Note that with my current setup of
lead I'm pulling over 400A battery current. The more pathways I can
get to the battery the better.

The straps which TS sends are copper so at one post I'll have
aluminum-copper-brass or aluminum-copper-stainless steel and at the
other it will be copper-copper-brass or copper-copper-stainless steel
with a little aluminum around the battery post. It sounds like David S
has had some corosion/electroplating with his connections and I'm
trying to avoid this. As far as I can tell there is no lead involved
with these TS-LFP100AHA batteries. I don't believe aluminum will cold
flow as easily as lead but I know how quickly it can oxidize.

Hopefully this makes more sense.

Thank you,

David N


On Thu, Sep 24, 2009 at 12:51 PM, Roger Stockton <[email protected]> wr=
ote:
>


> > David Nelson wrote:
> >
> > > I'm going to be installing some LiFePOs in my Gizmo and want
> > > to make the best connections I can. One post is aluminum with
> ...


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## EVDL List (Jul 27, 2007)

> David Nelson wrote:
> 
> > I figured that since we aren't dealing with high frequency AC
> > that conduction would be throughout the material, not just on
> ...


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## EVDL List (Jul 27, 2007)

Eva and I recently installed TS 90 amp cells in the Wabbit (85 
Cabriolet). We discovered a few things I thought I would pass along.

Just before you put on the strap and connection, shine up the tops of 
the cell terminals with sand paper or the like. Then immediately 
apply a thin layer the black conductive goo (NOALOX) that 
electrician's use for aluminium wiring connections.
http://www.idealindustries.com/products/wire_installation/accessories/noalox.jsp

If you don't do this, you will not get a good electrical contact 
between the copper strap and the aluminum cell terminal top. The 
connection will get hot when you pull a hill.

How I know this is I didn't clean and NOALOX the terminals the first 
time around. When I took the car for a test drive, I noticed that 
"hot electrical parts" smell. I checked the terminals and some of the 
SS bolts looked like they got a little bit warmer than they should. 
Those straps were warmer than the others. Eva and I took loose the 
bolts and did the sandpaper and NOALOX thing and after that they are 
all working perfectly.

This afternoon, Eva and I pulled 3 minutes at 75 MPH up about a 2% 
grade (~4 miles) at 300 amps and nothing got more than luke-warm. Big 
difference. All fixed.

If you don't use the NOALOX, each time the connection gets warm, more 
aluminum oxide forms and the resistance gets even higher.

The Wabbit runs great with the Li-Ion pack in it. These cells don't 
sag much at all and they stay pretty stiff even when the SOC is not 
100%. The car certainly is happier with 300 lbs of batteries in it 
instead of the 700+ lbs of NiCads (previously Optima AGMs.) They hold 
about the same energy as the 700+ lb NiCad pack.

Bill Dube'


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## EVDL List (Jul 27, 2007)

> Bill Dube <xxx[email protected]> wrote:
> 
> > Eva and I recently installed TS 90 amp cells in the Wabbit (85
> > Cabriolet). We discovered a few things I thought I would pass along.
> ...


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## EVDL List (Jul 27, 2007)

> Bill Dube wrote:
> > Eva and I recently installed TS 90 amp cells in the Wabbit...
> > Just before you put on the strap and connection, shine up the tops of
> > the cell terminals with sand paper or the like. Then immediately
> ...


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## EVDL List (Jul 27, 2007)

> ----- Original Message -----
> From: "Lee Hart" <[email protected]>
> To: "Electric Vehicle Discussion List" <[email protected]>
> Subject: Re: [EVDL] High resistance contact LiFeP cells
> Date: Sat, 26 Sep 2009 21:49:34 -0500
> 
> 


> > Bill Dube wrote:
> > > Eva and I recently installed TS 90 amp cells in the Wabbit...
> > > Just before you put on the strap and connection, shine up the
> > > tops of the cell terminals with sand paper or the like. Then
> ...


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## EVDL List (Jul 27, 2007)

I find it best to use a bi-metal connection. We use them all the time in 
connecting copper to aluminum. A aluminum spade lug will have Al-Cu stamp 
on it. It is a mirror finish plating over the aluminum.

Then there are copper-brass ones that also have a mirror bi-metal coating on 
them. There is also tin plated washers or spacers that go between a copper 
and aluminum wire.

Also there are bi-metal connections where the spade end is copper and the 
barrel end is for a aluminum wire.

Just type in electrical bi-metal connections in your search engine and may 
sites will come up on this subject.

Roland


----- Original Message ----- 
From: "Dennis Miles" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Saturday, September 26, 2009 10:48 PM
Subject: Re: [EVDL] High resistance contact LiFeP cells


>
> > ----- Original Message -----
> > From: "Lee Hart" <[email protected]>
> > To: "Electric Vehicle Discussion List" <[email protected]>
> > Subject: Re: [EVDL] High resistance contact LiFeP cells
> > Date: Sat, 26 Sep 2009 21:49:34 -0500
> >
> >


> > > Bill Dube wrote:
> > > > Eva and I recently installed TS 90 amp cells in the Wabbit...
> > > > Just before you put on the strap and connection, shine up the
> > > > tops of the cell terminals with sand paper or the like. Then
> ...


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## EVDL List (Jul 27, 2007)

Does it have to be bolted or welded?

In the house I used to own, there were fuses
and fuse holders for 60A; I am sure a removable
clamp could be designed for higher amperages.
Building on the technology of ZIF sockets on computers.
Think, cable with a vise grip on the end.
(Vise Grip makes all kinds of locking pliers).

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