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Discussion Starter #1
Hello

Yesterday evening I was measuring voltage drop accros the standard battery connects that were are supplied with Headway batteries. (ordered only four 38120P(?) cells through a german webshop for evaluating the cells)

The voltage I measured diffference between the interconnects is massive. factor 5 difference!
47uOhm vs 235uOhm. (I know battery resistance is mili-ohms, just consistancy checks)

Testing with four cells, and a regular 55W H7 bulb. (4.2A amps or so)
Two interconencts showed 0.2mV, one does 1.0mV to 1.2mV. Thats a crazy difference.

Retorqued the screws, same results.



What would be the simplest conclusion?
 

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Discussion Starter #4
Actually it is the voltage across the interconnect itself.

Thus excluding the voltage jump from the battery to the interconnect


Ill look into an anti corrosive compound
 

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Whoa !!

If it is that high at room temperature & a light load.

What can you expect at several hundred amperes ?????

Time for 1 of my negative statements...............GARBAGE !!! Recycled junk from somewhere.

Do not buy from that company.

Thanks for the testing of just the jumper bar. Sanding should do absolutly nothing to reduce the resistance of the bar. The sharp points of your probes should easily pierce any surface oxidation. It is not electrical grade copper.

You are sticking the probes into ONLY the bar material ONLY ??? Not the bolt or screw heads.

Test your instruments on a piece of plumbing Copper or even a piece of electrical copper wire. A single strand of # 10 solid.
Beg a 1' piece from somewhere. Must be new & unused
That is still / should be 99.9 % pure. Post the readings. We would love to know what is going on.
 

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Hi Steven.

Did not want to join another forum.:) Was a requirement to see your video.
I have faith in your abilities to stick a piece of metal with 2 pointy probes.
Did you get similar readings ?

Rich
 

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Discussion Starter #8
Does not compile.

That link should be public viewable :S atleast it is here. Is Vimeo Blocking the link?
Name of the video "Boring Testing - Testing Battery Interconnects"

Puzzled now.



Not yet, having a lazy day. Bought an overall for working on the car. And took the to be converted roadster through a car wash :rolleyes: That sums about it what I have done today.

I have thin pure copper sheets I also used for constructing the IGBT busbars to fill in the FR4 isolator thickness. will try to run a current through
now ;-)

BBL
 

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Discussion Starter #9
Ok

Performed a measurement on a 180x20mm strip of copper. The copper strip is 0.3mm thick.

The measurement resulted a resistance of 633u Ohm. That is too high. (3A results in 1.9mV acros the strip)

But what am I proofing with this?
Relative difference of the cell inter connects remains. Even if theres low range gain error or a copper strip not being copper.... :rolleyes:

 

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Fantastic recycled QC.:mad:

Bigger question.
How high can the bars resistance be sold at ?
Are the bars being made with large high impurity spots in them. ETC
 

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Ill post a video of how I measured it.
edited: here is the video


http://vimeo.com/20136611
based on the video, it looks like you have one bad terminal connection, (upper left) I would try the sanding + noalox to see if the voltage drop from screw to bar went away. it's hard to tell, but it looks like you have small wires soldered to the bus bars to power the light??? if this is correct you will get all sorts of random stuff measuring randomly along the bar because of where/how current is flowing. The test in the photo looks more valid because you are measuring end to end resistance. Keep in mind that what appears to be solder joints at the ends of the bars probably make up the majority of the resistance you are measuring. Solder is actually a pretty poor conductor. I took one look at the supplied headway bars and put them back in the box. I used 1/8" aluminum, machined them and assembled the pack using deoxit all in a very short period of time. I'm also using steel bolts at the moment because that's all I had. It's not perfect, but it's consistent.
 

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Discussion Starter #12
Hi

Just inspected the interconnects, the one showing a high resistance is also corroding on the darkside, eh, I meant downside! Grabbed a magnet and it was showing to be strongly attracted to the magnet..
Unlike the other interconnects which are weakly attracted by the magnet.


All two (both) battery ends are quite strongly attracted to the magnet.. I guess that means it is not made of aluminum or aluminium.



PS: the thin wires on the tabs/interconnects where for the over voltage shunt
 
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