280ah Lifepo4 Leisure Battery - Build Thread

Haugen · Aug 3, 2020

Both 6061 and 6063 are structural with nearly identical strength coefficients.
6063 has better corrosion resistance.
Corrosion resistance is the primary reason to use them. I live in Florida and my cells will be in the camper in the heat and humidity constantly. A 10+ year life cycle means that there is plenty of time for corrosion to set in.
When, noy if, galvanic corrosion starts, I want it to be somewhere I can see it and not removing the threads from my cells, which is exactly what will happen first with a steel bolt.

6061 Aluminum vs. 6063 Aluminum - Differences in Properties, Strength and Uses

This article presents a brief comparison of the properties, strength, and applications between 6061 and 6063 aluminum.

www.thomasnet.com

BiduleOhm · Aug 3, 2020

This graph shows 6063 is almost half the strength of 6061: https://www.researchgate.net/figure...ium-alloys-6061-T6-and-6063-T5_fig1_301273529

Ok, I see.

Well, based on the graph above I'd say the max torque for 6063 is a bit more than half the one for 6061 so 2.6-2.7 lb*ft would be the max

Edit: also this page https://www.industrialmetalsupply.com/aluminum-6061-vs-aluminum-6063 and this one https://www.clintonaluminum.com/6061-aluminum-vs-6063-in-extrusion-applications/ confirm 6063 is significantly weaker than 6061.

Haugen · Aug 3, 2020

BiduleOhm said:
This graph shows 6063 is almost half the strength of 6061: https://www.researchgate.net/figure...ium-alloys-6061-T6-and-6063-T5_fig1_301273529

Ok, I see.

Well, based on the graph above I'd say the max torque for 6063 is a bit more than half the one for 6061 so 2.6-2.7 lb*ft would be the max

Both alloys can be tempered to T6, so I don't know why the comparison was between 6063-T5 and 6061-T6 except to bias the result. There are comments that claim to contradict the results in further studies.
From the ThomasNet link I provided:

Material properties		Type 6061 Aluminum alloy		Type 6063 Aluminum alloy
Units	Metric	English	Metric	English
Yield Strength	276 MPa	40000 psi	214 MPa	31000 psi
Ultimate Strength	310 MPa	45000 psi	241 MPa	35000 psi
Fatigue Strength	96.5 MPa	14000 psi	68.9 MPa	10000 psi
Bearing Yield strength	386 MPa	56000 psi	276 MPa	40000 psi
Hardness (Brinell)	95		73
Machinability	Good		Fair

I see nothing that indicates 2X.
Anyway, there are very few aluminum bolts available out there. I only found M6 bolts in 6063. If you know where to find then in 6061, please share.

BiduleOhm · Aug 3, 2020

Ok, less difference than on the graph but still a significant difference.

First seller I found: https://www.ebay.com/itm/M5-M6-M8-M...x-Socket-Cap-Head-Screws-DIN912-/184106786596 but would I trust a chinese seller to sell the right metal grade? not sure...

Even on McMaster there isn't much choice: https://www.mcmaster.com/screws/sys.../thread-pitch~1millimeters/material~aluminum/ The extra large head ones are 40 kpsi so they are probably 6061, the standard hex ones are only 30 kpsi tho.

But personally I would just use stainless (with a high chromium content like 304 or 316) which is a lot easier to find and should not corrodes aluminium (well, maybe in 100 years...), especially if you add loctite. And if you know me you know I tend to be a belt and suspenders kind of guy.

Luthj · Aug 3, 2020

Stainless is much more cathodic than aluminum. Better off with zinc plated steel if you are worried about galvanic corrosion. Honestly if you use plenty of loctite thread sealant, you won't have moisture or oxygen present at the interface. In aerospace applications where moisture is present, stainless fasteners are not used in contact with aluminum. Especially 7 series. Physical isolation with a neutral material or sealant, or use of cadmium or zinc plated fasteners is used.

A good quality silicone grease (heavy body) on the contact areas will do wonders.

If you expect condensing temperature swings/humidity, additional precautions may be called for. Including greasing all connections, and conformal coating PCBs (assuming they aren't already so).

The typical battery box located in a dry area (even high humidity, but non condensing), is unlikely to see significant corrosion. Especially if a terminal grease is used.

Haugen · Aug 3, 2020

Luthj said:
Stainless is much more cathodic than aluminum. Better off with zinc plated steel if you are worried about galvanic corrosion. Honestly if you use plenty of loctite thread sealant, you won't have moisture or oxygen present at the interface. In aerospace applications where moisture is present, stainless fasteners are not used in contact with aluminum. Especially 7 series. Physical isolation with a neutral material or sealant, or use of cadmium or zinc plated fasteners is used.

A good quality silicone grease (heavy body) on the contact areas will do wonders.

Sounds like the sermon I've been preaching here the past month or two.
I spent much of my career in avionics where corrosion is an ever present danger. Navy corrosion control school always stuck with me.
I'm going with all aluminum until the lugs and wires. F-16 fighters crashed due to gold sockets being mated to tin plated pins inside "sealed" connectors. I'm keeping the opportunity for corrosion where I can inspect for it.

Mrdanielmh · Aug 7, 2020

sduser said:
Yeah that's not much. I can't use a torque wrench as I am using an hex key to keep the stud from turning while tightening the nut. I am using a nylock nut which would probably mess up the torque reading anyway. The cells will be in a wooden box preventing movement in any direction, and under compression from the end of the pack.

Sorry for posting in this thread, but I feel it is relevant to @Mrdanielmh installation if his cells have M4 terminals, especially in vehicle usage.

Hey there, sorry its taken so long to reply! Im looking at this now and im not sure if the threads are m4! Have you confirmed this?

sduser · Aug 8, 2020

Mrdanielmh said:
Hey there, sorry its taken so long to reply! Im looking at this now and im not sure if the threads are m4! Have you confirmed this?

I have the 105Ah cells and they are M4. The 280Ah cells may be M6 not sure.

Mrdanielmh · Aug 8, 2020

sduser said:
I have the 105Ah cells and they are M4. The 280Ah cells may be M6 not sure.

Ill have to take a screw out and measure! Im planning to change for threads nuts and lock washer

BenCos18 · Aug 8, 2020

I think the bolts would be m4 tbh

Mrdanielmh · Aug 8, 2020

They look pretty wimpy ?

Haugen · Aug 9, 2020

Please see the bottom of page 4 of the attachment. This is the datasheet for the EVE 280Ah cells.
Definitely M6

BenCos18 · Aug 9, 2020

Haugen said:
Please see the bottom of page 4 of the attachment. This is the datasheet for the EVE 280Ah cells.
Definitely M6

Thanks for that info
I think I got the screw types mixed up as even my cells have the same screw type

Haugen · Aug 9, 2020

BenCos18 said:
Thanks for that info
I think I got the screw types mixed up as even my cells have the same screw type

I also took one of my bolts to the hardware store and confirmed the threads.
The nice thing is, they even give you a torque spec. I'm not sure I believe that I can put 30inlbs on my 6063 bolt, but I'll see what happens at lower torque and work my way up.

tim0shel · Aug 10, 2020

I can confirm that the 280ah cells are M6 I had bolt stainless setscrews for them.

Mrdanielmh · Aug 14, 2020

Upgraded the battery yesterday to all aluminium busbars, nuts and bolts!

tim0shel · Aug 14, 2020

Mrdanielmh said:
Upgraded the battery yesterday to all aluminium busbars, nuts and bolts!

View attachment 19849

Nice, I see where as the torque specs for the M6 that there are no reasons that you could not go this way. For what you are using it for its plenty of connection. I still have the mix beans with mine of Copper, Aluminum and Stainless Steel.

David Pocock · Aug 14, 2020

Mrdanielmh said:
Upgraded the battery yesterday to all aluminium busbars, nuts and bolts!

View attachment 19849

I'm sorry to be that guy, but you have used heat-shrink terminals but not heated the shrink to seal it to the cables.

JoeHam · Aug 14, 2020

David Pocock said:
I'm sorry to be that guy, but you have used heat-shrink terminals but not heated the shrink to seal it to the cables.

Looks like electrical tape to me.

tim0shel · Aug 14, 2020

JoeHam said:
Looks like electrical tape to me.

No hes talking about the ring terminals. You can buy them that have heat shrink on the ends and just need to apply heat.

280ah Lifepo4 Leisure Battery - Build Thread

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