How to Make Homemade Springy Battery Clips?

[fuzzoli]

I need to make battery clips for a small #504 battery holder.  I have brass and stainless steel strips, but they aren't springy.  I've done a little reading about annealing the metal, but I'm not sure if that's the way to go.  I also understand that brass isn't the best for springiness.  The clips wouldn't have to hold the battery forever, but would have some stress / compression at times (this would be something inside a model rocket, and would experiences forces upon launch, etc.) 

Any thoughts?

Thanks!

-Frank

[bob91343]

I think creating a spring is not an easy task, especially for us amateurs.  Far better to find a spring and adapt it to the particular use.

[T3sl4co1l]

Annealing is the opposite of what you want; you need work hardened (full hard if available?) stock.  Preferably of phosphor bronze or beryllium copper, which are stronger and therefore springier than plain brass.

Bending to shape is a skill; you need to bend just far enough past the desired shape to set it, without bending so tight it fractures.  At full hard, there isn't much bending left before fracture.  Expect to make many whoopses, figure out the motions, and make a few good parts in the end.  Make jigs if you have to: even just a few rods or radiused corners can help, if not a full (finished shape) die.

But battery clips haven't exactly gone away.  Are you sure you can't find one?  Have you looked at say, fuse clips at DK, or rod/dowel clips/hangers at McMaster?

Tim

[profdc9]

If you have a 3D printer, you might be able to 3D print a tube with bayonet-lock type end caps on both ends and a metal contact inside the end caps.  Because a material like PLA is a bit stiff, you may have to have a deep hook cut in the tube to allow for enough springiness to not deform the plastic.  I use FreeCAD to design similar parts.

[Berni]

You need the correct alloy for it, they even have a fitting name, it's spring steel. This sort of steel is typically not used for anything that doesn't have to be springy due to being more annoying to form into shape, it always needs to be bent way past the shape you want so that it springs back into the shape you actually want.

Also when it comes to battery contacts you run into a problem that steel rusts and so might stop making a good connection. You also can't solder wires to steel so making a connection to it is also problematic. For this reason battery contacts are also electroplated with something like nickel or tin as this keeps it from rusting while being solderable.

So its just easier to buy the correct battery contact. You can find a large range of battery contacts at all the big distributors like DigiKey, Mouser, Farnell... etc especially for common battery types. While if you have a product that needs some weird special battery contact that is not available anywhere, then you can get a chinese company to metal stamp some for you custom for a pretty reasonable price as long as you are talking decent volumes.

But for DIY you can still use the brass and 3D print a battery holder with some compliance built in to act as a spring. PETG can make reasonably springy parts when designed correctly.

[jpanhalt]

There are copper alloys that are springy, such as beryllium copper.  Like the others have said, if don't advise making trying to make them.

Are you aware of Keystone: https://www.keyelco.com/index.cfm

It is a source for all sort of contacts.

[ttx450]

I need to make battery clips for a small #504 battery holder.  I have brass and stainless steel strips, but they aren't springy.  I've done a little reading about annealing the metal, but I'm not sure if that's the way to go.  I also understand that brass isn't the best for springiness.  The clips wouldn't have to hold the battery forever, but would have some stress / compression at times (this would be something inside a model rocket, and would experiences forces upon launch, etc.) 

Any thoughts?

Thanks!

-Frank

this is for rockets and/or others.  You could make the same thing inside.  everything is stainless, I just stretch out the SS springs. 

[NiHaoMike]

Perhaps spot weld or solder tabs to the battery, then have some way to connect it before launch? Maybe even solder it in just before launch using a portable soldering iron.

[mathsquid]

Tim Hunkin has a video on springs as part of his Secret Life of Components Series.

The section on making springs and the section on compression springs are probably the most relevant here, but the whole video (and the whole series) are well worth a watch.

[Siwastaja]

Spot weld or properly solder any reliable connector to it. Plug the connector before launch, instead of having the cell terminals act like a connector. Connectors are engineered for the task.

[pardo-bsso]

Buy a cheap toy and cut to size?

[ttx450]

spring clips

[coppercone2]

I get copper sheet that's moderately thick, put it over a ball bearing that's placed into a drilled out hole  to make a detent, put the copper sheet on that then use a peen hammer to deform a little mound over it and hit it for a while to harden it. Then I sand it down to say 600 grit or more and do a electronickel plate on it, glue it in with a flexible epoxy (perhaps mask the side thats unplated, it would be better adhesion), and coat with grease.

If you want to make springs, get beryllium copper spring wire, but you will need to experiment with the thickness (its hard to use).

Make sure it fits before plating because if you bend it after it will break, but it should be pretty tough.

Brass sheet might be an option also. Berylium copper sheet too if you figure out how to cut and bend it nice, but beware, you only can saw that with a jewelers saw and dust collector that you dispose of properly because the dust is toxic. I recommend the wire since you only need to cut it.

I do recommend keystone though, their battery holders are top notch, I only do this for custom stuff.

[fuzzoli]

I want to thank everyone for their wonderful ideas on how I solve my problem.  I see that I should have been more specific about what the clips were intended for. 

Over on my other thread I explain what I'm doing.  Basically the clips must be of a specific design. 

What I ended up with was cutting brass strips to size, and then tinning the side which will touch the battery.  The thought is the tinning will help strengthen the brass.  The battery won't be inserted and removed many times, so this should work in the long run.

Again, thanks all for your suggestions and ideas!

-Frank

[coppercone2]

I did not use solder because its supposedly bad for screw terminals but for a big spring like that I am wondering if its acceptable, I would like to hear other peoples opinion on this, I cannot say for sure, it seems that it should compensate for the creep so long the solder was applied well with a good flux that got rid of subsurface oxidation and cleaned well

[T3sl4co1l]

I've had terrible results with a small (wait... large?) "Joule Thief" style flashlight I made, a long time ago.  Instead of a AA cell holder, there's a blob of solder at one end of a cavity, and a copper spring at the other.  I think the combination of low holding force, and easily abraded solder, plus environmental contamination (skin oils from handling would suffice), tend to work up the solder pad into a rough, tarnished mess.  Like, the metal abrades into fine granules very easily, and then they end up stacked between oil films rather than forming a conductive path.  So the contact is very poor quality.

Tim

[coppercone2]

yeah a blob of solder I know is for sure bad because I see that on flashlights alot, but if you put solder on a spring contact I don't know, nickel is probobly better, but the coating is fragile

if I were to do it again I would just use berylium copper spring and keep it greased with deoxit, since I got the material in sheet and spring form I am very impressed by it, I am worried the nickel plating will flake off and short out the 'piles' I made actually, kind of wish I reduced simplicity, their just lab bias supplies, and I noticed the nickel plating job I did is pretty good and it cracks and does not really flake off unless you really beat it up, but still, it was fun to make a few but the price of real ones is really low and it does not have you wondering when something is gonna short out, the batteries are bad enough in terms of reliability themselves, making them equals to working for like 1$ an hour with hazardous sharp bullshit and fine jobs, you need to debur them, plate them, etc..

with flashlights etc I keep the batteries by my technician workbench now so I have alcohol and deoxit grease to wipe the cells and grease em, and service flashlight threads, during each battery change, there is less flicker

I am not sure about stainless contacts because I think my pace resistance soldering tweezers are made of stainless and they are easy to get to a state where they need scraping in order to heat connector barrels (from only touching clean fresh from the bag pins). if you compared copper with the same look to stainless the copper would conduct well but the stainless gets non conductive layers, aka more susceptible to fouling, because I saw variacs run brass covered with coal and function ok, but stainless is a weak in this regard

I suggest just buying berylium wire and doing away from the solder, I think Tesla is right, if you are hell bent or have a custom pile/battery, otherwise buy contacts from keystone

https://www.digikey.com/en/products/detail/keystone-electronics/5231/316380?utm_adgroup=Battery%20Holders%2C%20Clips%2C%20Contacts&utm_source=google&utm_medium=cpc&utm_campaign=Shopping_Product_Battery%20Products&utm_term=&utm_content=Battery%20Holders%2C%20Clips%2C%20Contacts&gclid=CjwKCAjw55-HBhAHEiwARMCszuy_aWc8vLyjVA1Z013L7g7eq0qu79DBj6jD2oz5TFuucFc07Q8nxBoCTTcQAvD_BwE

[Siwastaja]

Yeah, that will work for some time but will fail later. Doesn't sound like a solution I would use in a rocket. Why not properly spot weld or solder the wires into the cell terminals and plug it with an actual connector. Or even just buy off-the-shelf battery with such connector, JST connectors being very typical; not designed for rockets, but still orders of magnitude better than such soldered clips.