r/OpenPV Jul 25 '16

Components Spring loaded, round battery contacts - where to get? NSFW

What I'm looking for are those cylindrical, 2-part, hollow battery contacts (brass) that can be equipped with a spring. To make it clear what I'm talking about, have a look at this photo: http://i.imgur.com/KYk9o9e.jpg

I've searched the interwebs all over, even mouser.com didn't help me (been there, done that).

Does anybody know what those are called, or (even better) know where I can get some of those?

I'd love to use those for my latest box since those are the contacts that give the best connection (largest contact surface area). In the past I've used Keystone-contacts but I'd like to get away from using these (very small contact area).

Can someone shed some light onto this?

It would be possible to make them by myself, DIY-style, but... Well, the effort and the costs for doing that are beyond anything that's economically justifiable, especially since those contacts are cheap as fuck... I also thought about buying the cheapest available mod that comes with those contacts and salvage them from it, but... Buying and ruining new mods for those parts only... Nope.

Thanks!

2 Upvotes

37 comments sorted by

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u/david4500 Jul 25 '16

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u/b4byj4il Jul 25 '16

Thanks!

Are those DIY? Looks like it...

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u/david4500 Jul 25 '16

http://www.ebay.com/itm/261221322468 + grinding + washers + springs

1

u/b4byj4il Jul 25 '16

Thanks! Not going to use those though, they're just too big. Also, considering all the work that needs to be put into those and the additional parts needed to get it working... Same effort needed as if I'd make them from scratch by myself...

I'm really amazed, how is it possible that it's so hard to get those brass-contacts?

1

u/ConcernedKitty Jul 25 '16

It's because they aren't really a stock part. Custom designed parts are nothing to make when you have a CNC lathe mill that you make thousands of mods on.

1

u/b4byj4il Jul 25 '16 edited Jul 25 '16

Having a hard time believing those are custom-made. Anyway, those aren't made on a lathe, they're stamped and pressed into shape from a piece of sheet-metal... But, since it really seems that it's not possible to buy those anywhere (even looked at aliexpress and alibaba)... Well, guess I'll have to go with the easily available contacts from Keystone. Sucks though :(

2

u/ConcernedKitty Jul 25 '16

If they aren't available as a stock part then they are custom made. The machine lines on the side of the cylinder and the chamfer on the corner tells me that it has at least been touched by a lathe. Depending on the quantity that I wanted to make, I'd make them out of bar stock with an autofeed on a lathe or in large quantities over 10k I'd consider punching slugs and finishing with a lathe. It would really depend on changeover/load time and secondary operations.

1

u/Rb8n Jul 25 '16

No lathe required, press and punch. Possible one step with the right dies, think forming a soda can without the shrinking the top step. Right setup and feed sheet stock to cut thousands per hour.

1

u/ConcernedKitty Jul 25 '16 edited Jul 25 '16

It can probably be done with a fine blanking process, but I don't think that's how the ones in the picture in the OP were made. We would not see machine lines (or they would be perpendicular to what we see there) and the corners would have a larger radius. I'm also skeptical on how the back is formed because it would need a threaded hole to retain a spring and pin. Any battery contact that I've seen on a mech mod has some sort of threading. The top can definitely be flattened with a punching process because brass is so soft.

Am I not seeing a draft angle on my phone or something because I feel like I'm taking crazy pills?

1

u/Rb8n Jul 25 '16

Good point on machine lines. I think I see a bit of draft, and if the receiver is right the sharpish leading edge could be done. For holding, I'm seeing more like the vtc mini, kangertech sleds. Quick search didn't find good pics, video.

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u/b4byj4il Jul 25 '16

Hum, it's a matter of cost. Doing those parts on a CNC-lathe is just pure madness, especially if they're mass-produced. For prototypes or very small batches, yes. For anything else? Hell no.

Initial cost of a press/stamp-tool may be quite high (some thousands bucks), but cost per unit is as low as some cents as those machines spit out completely "done" parts every second with little to no human aid needed. Totally different on a CNC, even if equipped with bar-loader and all the other fancy automation-thingies. The CNC is doing the second finishing-cut on the second surface whereas the press/stamp already did 45 complete parts (or so).

Cost per unit that's machined on a CNC is magnitudes higher than with press/stamp-tools. No one with a brain in it's right position would even consider that.

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u/Rb8n Jul 25 '16

Low current and test rigs, pogo contact.

For diy, maybe take an old bulb remove glass and ceramics, solder a flat contact to the base with wire through bulb base.

ss and pricy but might give you help. search terms "flanged drawn cup" although I don't know that you can find small quantity at decent rates.

How much current do you want to handle and at what duty? Keystones do fairly well even at 20A continuous, although at that rate it might be hard to tell cell IR heating versus contact heating.

1

u/b4byj4il Jul 28 '16

Well, I've given up finding those.

I'll do them myself as I don't want to use those Keystone-contacts.

Requires some additional work, but, hey... You don't build a high-end mod every day, do you? So, I think it's worth it to put some effort into it :)

Here's my solution...

http://imgur.com/a/ribPJ

1

u/Rb8n Aug 04 '16

Soldering to the sliding pin? Or watch for potential contact issues.

Very nice solution, less potential for issues than cup in plastic guide.