Battery contact ideas

kuksul08

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What have you guys used as battery contacts for an AA size battery? I'm trying to minimize the contact resistance in a design similar to a mini-maglite. I don't really like the conical springs commonly used, but I can't think of anything better.
 

AnAppleSnail

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Use the conical spring, but get a thin metal ribbon (or braided grounding strap) and connect the top of the spring to the bottom.
 

kuksul08

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I've seen that done, and I'm sure it works great, but it doesn't look good IMO. Having machined and polished everything so far, I want it to look professional.
 

AnAppleSnail

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I've seen that done, and I'm sure it works great, but it doesn't look good IMO. Having machined and polished everything so far, I want it to look professional.

If you have the measures down just right, you could use a metal nub behind the spring. You might dent the battery tops and bottoms though.
 

kuksul08

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This is what I came up with. Plain old spring behind a copper plug. It almost bottoms out when the tail cap is tightened down. Low contact resistance I hope.

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Cavi Mike

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Did you solder a wire from the plug to the base of the spring? Because otherwise I don't see how that is going to change anything considering the copper still has to transmit power to the spring. If anything, you've just added something to build resistance; copper corrodes so that plug is going to end up being the weakest link. That's why bare connections like butt-splices, ring terminals, spades, etc. are either silver or gold plated. If anything I'd look into getting a silver or gold plated spring, ditch the bare copper plug.
 

fyrstormer

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Did you solder a wire from the plug to the base of the spring? Because otherwise I don't see how that is going to change anything considering the copper still has to transmit power to the spring. If anything, you've just added something to build resistance; copper corrodes so that plug is going to end up being the weakest link. That's why bare connections like butt-splices, ring terminals, spades, etc. are either silver or gold plated. If anything I'd look into getting a silver or gold plated spring, ditch the bare copper plug.
This.
 

yazovyet

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I would expect the copper plug to hit the metal (steel?) sides that it is housed in. If better was needed, rather than worry about a fancy spring I would go with a copper braid (solder wick) soldered to the bottom of the plug that goes through the spring and is held under the spring so it is in contact with the bottom of the hole.
 

kuksul08

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No, I didn't do anything special beneath the copper plug. I have the tolerances just right so that when the cap is fully tightened, it just bottoms out the spring and touches the aluminum sides of the cap.

Galvanic corrosion did cross my mind, but I didn't really think about good old normal corrosion. You're talking about the green/brown-ish coating that copper gets, right? I was hoping that it would still be far better than a tiny spring since it contacts a larger area.

Thanks for the input :) I do appreciate it.
 

LDGator

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No, I didn't do anything special beneath the cGalvanic corrosion did cross my mind, but I didn't really think about good old normal corrosion. You're talking about the green/brown-ish coating that copper gets, right? I was hoping that it would still be far better than a tiny spring since it contacts a larger area.
Oxidation of contact points such as bare copper will negatively effect resistance. I prefer bare copper and treat with Caig Gold (or Deoxit if already tarnished). Treated properly per Caig's directions once a year is quite sufficient and visual inspection on battery change should verify.I often use a copper rivet inserted into battery contact end of copper spring for improved contact surface area.But for form and function yours is sweeeet!
 

kuksul08

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Good info.

I was also considering putting a layer of solder on top and smoothing it out to protect the copper, but solder oxidizes too doesn't it?
 

hellokitty[hk]

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Beryllium copper will not oxidize and retains high electrical conductivity; it also makes for good springs.
 
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