Solarfun4jim
Solar seduced :-)
Just goes to show how many people are stripping these threads no matter how careful they try to be !
Avoiding Galvanic Corrosion
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The batteries that Iam building are going in my boat. Since this will be a marine environment I purchased zinc plated studs, I was thinking of purchasing yellow zinc nuts, maybe yellow zinc nylocks if I can find them and lock washers, and using noalox or ox guard, what do you guys think?
I have to agree with @Hedges.
In a marine environment, you need to stick with aluminum all the way through to the BMS, or go stainless. Either way, the connector lube is a vital preventative step
Solarfun4jim
Solar seduced :-)
For locking the studs permanently into the terminal, i have seen the following suggestions.... Red loctite, Blue loctite, Red thread locker, JB weld, Araldite. Do these all have very similar properties or is there a clear winner as regards permanance?
Hedges
I See Electromagnetic Fields!
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My suggestion of JB weld was as repair of stripped threads, an alternative to tapping oversize. If the materials are clean, it will never come out.
The others have various degree of locking strength. Purpose being to keep stud from turning when tightening nut, likely any is good enough once it cures.
The others have various degree of locking strength. Purpose being to keep stud from turning when tightening nut, likely any is good enough once it cures.
Solarfun4jim
Solar seduced :-)
Thanks Hedges.
I didnt read the whole thread so some of this might have been mentioned before.
Physical cleaning of aluminum terminals and connections is a bit of a risk and depending on how much current you are moving can increase the resistance in the connection. Hand held wire brush would be the safest. Sticking something on a rotary tool, whether its a wire wheel, scotch brite, sand paper or WHY is crazy. You need the faces of the connection as flat as possible to maintain as much surface contact as possible. Every single scratch you put on the surfaces reduces the surface area available to make contact with the mating surface. That said, you have to make due with what you have and if the connections are already beat then your not going to do anything worse to them so WTF, you might as well. If the connections are flat and smooth then I suggest (and will use) a chemical deoxidizer such as aluma brite. I use this on all the aluminum I weld and am going to use it on my batteries and aluminum busbar. Before anyone starts pointing out all the drawbacks and risks, no you cant be stupid and do a poor job of the clean up. You must be careful and sparing when using and have to make sure you wash away/clean it off. Its important and there is no getting around it. If your not detailed oriented and dont understand, then use a physical means of removing oxide and live with the downsides of that. If you are careful and understand what is going on, using a chemical method to remove oxides will maintain a smooth flat surface and increase surface contact.
Physical cleaning of aluminum terminals and connections is a bit of a risk and depending on how much current you are moving can increase the resistance in the connection. Hand held wire brush would be the safest. Sticking something on a rotary tool, whether its a wire wheel, scotch brite, sand paper or WHY is crazy. You need the faces of the connection as flat as possible to maintain as much surface contact as possible. Every single scratch you put on the surfaces reduces the surface area available to make contact with the mating surface. That said, you have to make due with what you have and if the connections are already beat then your not going to do anything worse to them so WTF, you might as well. If the connections are flat and smooth then I suggest (and will use) a chemical deoxidizer such as aluma brite. I use this on all the aluminum I weld and am going to use it on my batteries and aluminum busbar. Before anyone starts pointing out all the drawbacks and risks, no you cant be stupid and do a poor job of the clean up. You must be careful and sparing when using and have to make sure you wash away/clean it off. Its important and there is no getting around it. If your not detailed oriented and dont understand, then use a physical means of removing oxide and live with the downsides of that. If you are careful and understand what is going on, using a chemical method to remove oxides will maintain a smooth flat surface and increase surface contact.
Im going to epoxy studs in right from new. An epoxied threaded connection, especially into a soft material is far stronger than the threaded connection. 0 worries about damage at 8nm.
Edit: The 8nm spec quoted above is not the recommended torque spec for the terminal fastener. I had understood as others had that this was the torque spec and terminal threads are failing below that torque.
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Ampster
Renewable Energy Hobbyist
Alumabrite does look effective. It does contain hydroflouric and sulfuric acid so I should wear gloves and use it outside with plenty of ventilation. That way i could rinse them with plenty of water as recommended. My studs are already permatexed into to terminals so I hope that won't be a problem. I am already planning on using aluminum buss bars so I can easily just dip them in the Alumabrite also.
Ampster
Renewable Energy Hobbyist
Remember the 8 Nm is the anti torsion of the terminal top. I think epoxy is a good idea. I just think other readers still need to be careful that they don't twist the terminal top off the connection to the innards of the battery. Four to five Nm is the recommended torque of the nuts to get good connection of buss bars and lugs to terminal top.
Hedges
I See Electromagnetic Fields!
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And someone mistook 8nm for proper torque, stripped the thread out.
Is it stronger? I wouldn't count on that. But maybe true. Have an explanation?
But the math I did for 6mm stripped hole 6mm deep came up with 5000 psi JB weld having 800 pound ultimate load.
That exceeded 500 to 600 pound ultimate load of 6mm aluminum bolt.
4nm torque DRY gave 150 pounds clamping force, so all good.
4nm torque lubricated was in the range 500 to 600 pounds, likely to cause failure.
My attempt at math on stripping threads was off from users experience by an order of magnitude.
Get the torque value right and make sure threads being turned are dry.
When Im rinsing them I am planning to hold the cell upside down and use a squeeze bottle with a straw.
If you double nut the top of the stud or have an internal hex you can apply the counter force and have reduced risk of twisting the terminal.
Ampster
Renewable Energy Hobbyist
I can only offer a wild ass guess that the epoxy would increase the effective surface area in contact with the soft aluminum. I don't know how that compares with Permatex Red. Either one has to be better than nothing because the studs were loose when just inserted in the terminal tops.
Hedges
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That takes care of twisting.
But torque produces clamping force. What is the safe working limit of the female thread in aluminum terminal?
Unlike engine bolts, these have relatively short engagement.
Once you put something on top of stud to restrain it, can't use a socket extension with torque wrench.
Some of the applied torque is lost due to friction, which is increased by radial load. Less clamping force for same torque, but probably goes in the "error" bucket, isn't accounted for.
Ampster
Renewable Energy Hobbyist
Yes, both good strategies. So far no one has reported twisting off the terminal tops possibly because the threads strip first and torsion on the terminal tops is probably reduced by the leverage of a buss bar attached to an adjacent terminal.
Threads dont engage the entire land area of the opposing thread (the major diameter of the male thread is smaller than the major diameter of the female threads). filling the gaps in the threads and at the bottom of the blind hole/end of stud provides more surface area as well as preventing threads from deforming into space that is now occupied by epoxy.
