resistance of brass strip

I want to make a battery tester. I am in the UK.
I'll use a fixed metal sheet which I will press the positive stud of a
cell on. (A meter probe will go to the other end.)
(1) I tried an aluminium sheet for the metal but it didn't make good contact possibly on account of repeated re-tarnishing.
(2) I'm considering a metal strip like the contacts on a 1289 (3LR12) battery:
http://www.smallbattery.company.org.uk/sbc_3LR12.jpg
However I think the strips are and when I look at the electrical conductivity of brass it seems quite poor compared to copper. If brass is really a poor conductor then why is it used on a battery?
(3) What alternative material could I use? Perhaps a plated metal sheet of some sort?
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Parl wrote:

Proably mechanical properties - it is nicer to machine than copper

Brass would be OK until it tarnishes, at which point you would need to clean it with sandpaper. Brass is a very poor conductor compared to copper, but for a few amps it is OK, e.g. the pins of 13 Amp plugs are brass. Nickel-plated brass or copper, or bare stainless steel (which is impractical to soft-solder under normal circumstances) may be more resistant to corrosion and tarnishing, or gold would be ideal - either as a plating or solid depending on budget.
Chris
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Alloys are going to have lower conductivity than pure metals. Electrons scatter from defects (crystal disorder). But usually alloys are good enough. Even a thick nichrome is likely to be good enough for your purpose. Tin/lead solder is a poor conductor, but because it melts at a low temperature, it is used to provide good connections in electronic equipment,
Bill
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Use might try brass with a blob (pad) of soft solder where you want to touch the battery - it will be soft enough to break any tarnish each time you use it. In your application the higher resistance of the brass compared to copper will be completely negligable. Cheers, Roger
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wrote:

Tin plated copper strip is also available out there in various gauges.
Tinning the attachment hole will kill any tarnish problems.
Silver Plated Copper wire works real good as a conductor too. ;-)
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Parl wrote:

Put a blob of high silver content silver solder on your brass or copper
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Parl wrote:

The amount of brass involved isn't going to make much difference from copper contacts. It is a very small part of the total circuit resistance. The advantage of brass is that it is harder and wont deform when you slot a battery between the contacts. In addition, it is going to allow a higher contact pressure and wiping of the surface each time you put the battery in place. This wiping is the important factor as it cleans the contact surface.
Where a brass contact is iffy is in the mv or lower range. As an example, consider a modern AC 120V 15A switch (which is rather poor in wiping compared to a DC rated switch). In an application for a gas fireplace using a millivolt source, it works well- for a while - then contact problems occur (this doesn't happen with a 12V automotive switch) which has good wiping action) - and, my personal experience is that a nickel plated 120V AC switch (a bit more expensive and also non-wiping) works well for a much longer time- how long- I don't know as after about 10 years, there have been no problems where 6 months with a brass non wiping contact gave problems. Note: nickel has roughly twice the resistivity of brass so the advantage is due to less of a surface film. So you don't want to simply press the battery contact to the brass plate but put it on with a rubbing action as in most chargers or battery holders.
Don Kelly snipped-for-privacy@shawcross.ca remove X to reply
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