Welded stainless steel m6 studs a good solution?

Lama

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Hello folks,

do you think the new solution by welding stainless studs to the alloy surfaces is a good idea? Im not shure.

1. galvanic corrosion of alloy and stainless steel.

2. Electrical conductivity of stainless steel is worse than from alloy.

3. I think the surface area is smaller than with the old alloy m6 thread holes.

Im hesitating to buy EVE 280 Ah welded cells, but the vendors of Alibaba seem to only cell welded cells at the moment.

Best regards
 

squowse

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1. Is going to be a problem (or not) anyway unless you use aluminium studs/bolts. And then you've got the bimetallic connection to copper.

I'm with you though. I don't fancy them either. The threaded holes in the aluminium weren't perfect but could be dealt with.
 

ken morgan

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I wasnt aware that you could weld SS to Aluminum.
you can coat the stainless with aluminum or vice versa and then weld the coated items together. so its not truly welding aluminum to stainless per se. eventually I think corrosion will be an issue I mean even chrome flakes off...
 

Lama

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The studs look like the outer ring is aluminium. I dont know, maybe its coated or pressed into each other.
 

ken morgan

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ok to clear the air hear. its not welded. to keep it simple, welding is a forging process that uses heat and pressure to mix the materials at the atomic level to form a single piece of the same material. Brazing, soldering, copper nickel "welding" are all adhesive processes. they use a softer lower temperature metal to fill the gaps and "adhere" to the other metal. For instance: the US navy in the past "welded" aluminum superstructures to the steel hulls of US Navy Vessels. they used bimetallic strips at the junction of the two materials to weld the two together. one side is aluminum the other steel. weld aluminum to aluminum...steel to steel but they are not welding aluminum to steel, contrary to some comments i have seen in other threads. its a bimetallic strip where the two dissimilar metals are bonded together in an adhesive fashion that is created when a metal that flows at a lower temperature is bonded to a dissimilar metal.

So at best they are brazing, soldering or "gluing" the posts onto the original terminals and FYI to really smash your gourd. the Lotus 111r's frame is all "glued" using a epoxy resin to bond aluminum to aluminum and its stronger and less prone to stress cracking then it would be if they welded the aluminum together so don't worry about the strength, worry about corrosion and expansion rates between two dissimilar metals... that's what screwed the navy more than anything.
 
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Bob B

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I thought they were doing some sort of laser welding technique ..... but I am far from a welding expert.
 

Luthj

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Its possible to forge an aluminum base over a stainless stud. Then laser weld the stud to the terminal. Not sure if that's the case here. Its also possible to friction/stir weld aluminum to stainless.
 

Zwy

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Hello folks,

do you think the new solution by welding stainless studs to the alloy surfaces is a good idea? Im not shure.

1. galvanic corrosion of alloy and stainless steel.

2. Electrical conductivity of stainless steel is worse than from alloy.

3. I think the surface area is smaller than with the old alloy m6 thread holes.

Im hesitating to buy EVE 280 Ah welded cells, but the vendors of Alibaba seem to only cell welded cells at the moment.

Best regards
I'm not worried, just ordered 40 cells this way. 8 go in my boat for trolling motor purposes.

I've done the stainless studs with loctite in the past. While it is ok, takes some time to clean all loctite off the terminals before final assembly. Best practice is install stud, install a busbar and nut and tighten down, then come back a week or so later and clean the excess off. I just used a plastic cap with a 1/4 hole in it with a piece of 1500 grit sandpaper sandwiched in between.
 

ken morgan

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Its possible to forge an aluminum base over a stainless stud. Then laser weld the stud to the terminal. Not sure if that's the case here. Its also possible to friction/stir weld aluminum to stainless.
which is the same in theory to what I explained the aluminum base might be welded to the battery cell but the aluminum base is not welded to the stud. it was cast around it or possibly die drop forged around it. in so far as the friction weld you have simply heated the aluminum up until it melts around the stainless. (adhesive process...not welding).
 

Hedges

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it appears these terminals have an aluminum ring over the head of stainless component, and is welded around the perimeter to cell terminal. The stainless has a head that is captured by the aluminum ring, rather than being threaded in like bolts/studs.

The stainless stud isn't the electrical path. Busbar or cable clamped to aluminum cap is.

Although contact area is smaller than when a bolt clamps busbar directly to cell terminal, I don't think that is any problem. It is OK for contact area to be much less than what would have ampacity for the current. Any heat generated in the (zero length) contact spreads to the terminals which are larger and is dissipated.

I think at the quite low 4 Nm torque specified for the threaded aluminum terminals, contact area is actually too large. It can't have enough pressure to make and keep good contact. More torque and more clamping force is more important than more area, compared to what that achieves. So the smaller area is probably an improvement. (For threaded cell terminals, maybe a 3-D busbar shape with smaller contact area or even specially textured surface to punch through oxide would be better.)

The actual contact area for bolted connections is quite low, many small contact points with the rest of the surface not quite touching. In the case of aluminum, points breaking through oxide. The weld bead is relatively narrow but provides more cross section. Unfortunately you still have clamped contact to aluminum (I think) with the welded-on studs. Would be better if the contact surface was plated, e.g. with tin.

Best solution would probably be welded busbars between cells, and welded terminals on the end cells, with larger/stronger threaded terminals to connect cables. Next to that, I would go for these welded on threaded terminals for every cell.

Make sure your cables don't experience force that causes them to rotate in the bolted connection.
 

Stepandwolf

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Have posted this elsewhere but will post again here for those who didn't see my other posts. As surmised, the SS bolt is molded into the aluminum. Then that is welded to the top of the battery. As mentioned, the bolt doesn't really play a role in the conductivity, it is basically to hold things together.
eve stud 2.jpg
eve stud.jpg
 

Brett V

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Have posted this elsewhere but will post again here for those who didn't see my other posts. As surmised, the SS bolt is molded into the aluminum. Then that is welded to the top of the battery. As mentioned, the bolt doesn't really play a role in the conductivity, it is basically to hold things together.
View attachment 60144
View attachment 60145

Are these a 1.00 pitch coarse thread? I think that's what they are. Not overly impressed with the hardware that was supplied, wanting to use flange nuts.
 

Stepandwolf

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In metric, if only the diameter is mentioned, i.e. M6, it is defined as coarse. If the thread isn't coarse, the definition says to put the pitch behind the size, i.e. M6 .75 would be fine. M8 is 1.25, if you get M8 1 or .75 would be fine.
 

Zwy

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Are these a 1.00 pitch coarse thread? I think that's what they are. Not overly impressed with the hardware that was supplied, wanting to use flange nuts.
M6 x 1.00 I just checked on the welded studs here
 

APhoton

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In metric, if only the diameter is mentioned, i.e. M6, it is defined as coarse. If the thread isn't coarse, the definition says to put the pitch behind the size, i.e. M6 .75 would be fine. M8 is 1.25, if you get M8 1 or .75 would be fine.
Are these the thread studs that are on the new EVE 200ah cells? If so is 4Nm the correct torque?
 

Bob B

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Are these the thread studs that are on the new EVE 200ah cells? If so is 4Nm the correct torque?
I think the 4 nm ... 35 in/lbs .... is for the cells that have threads tapped in them. I think it is 8 nm for the laser welded studs .... but I'm going from memory and that may not be accurate.
I'll see if I can find where I saw that.
 

APhoton

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I think the 4 nm ... 35 in/lbs .... is for the cells that have threads tapped in them. I think it is 8 nm for the laser welded studs .... but I'm going from memory and that may not be accurate.
I'll see if I can find where I saw that.
Thanks, love this forum but it is a nightmare finding things
 
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