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Battery Posts and Loctite: Will it Add Significant Additional Resistance?

digitalabacus

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May 3, 2022
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Hello all. While reading though the resources section, particularly "Rules of Thumb for Terminal Posts", I see that Red Loctite + primer is often recommended to secure stainless grub screws to the delicate aluminum sockets on many batteries. This seems like a sensible mechanical precaution to me, however, electrically speaking, I am dubious.
  1. Won't the Loctite and/or primer serve as a resistive layer between the threads, effectively increasing the ISR of the entire battery bank?
  2. Even if all threads aren't completely covered, won't this reduce the "usable" area of the stud; potentially increasing heat and charge imbalance (since each battery cell will effectively have an extra voltage drop from the semi-random resistance between it and its neighbor)?
  3. Or is the effect so negligible to the point of non-consideration?
I am not the most delicate of people so I would prefer to add Loctite once and never have to worry about ham-handing these again. That said, I am also acutely aware the dangers of the extra resistance from a poor crimp, let alone some proprietary metal-bonding compound of unknown chemical makeup.

Thoughts?
 
Hello all. While reading though the resources section, particularly "Rules of Thumb for Terminal Posts", I see that Red Loctite + primer is often recommended to secure stainless grub screws to the delicate aluminum sockets on many batteries. This seems like a sensible mechanical precaution to me, however, electrically speaking, I am dubious.
  1. Won't the Loctite and/or primer serve as a resistive layer between the threads, effectively increasing the ISR of the entire battery bank?
  2. Even if all threads aren't completely covered, won't this reduce the "usable" area of the stud; potentially increasing heat and charge imbalance (since each battery cell will effectively have an extra voltage drop from the semi-random resistance between it and its neighbor)?
  3. Or is the effect so negligible to the point of non-consideration?
I am not the most delicate of people so I would prefer to add Loctite once and never have to worry about ham-handing these again. That said, I am also acutely aware the dangers of the extra resistance from a poor crimp, let alone some proprietary metal-bonding compound of unknown chemical makeup.

Thoughts?
Exactly.
And that is a good thing.
The stud won't have the same resistance as the terminal, so the flow will be entirely through it to the lugs.
 
electrically speaking, I am dubious.
The curent flows from the Aluminum terminal top to the bottom of the bus bar or lug. The grub screw is for mechanical strength to make sure those surfaces are well mated. The resistance of the stainless is already higher than the aluminum to copper interface and a little additional resistance from the loctite is not going to affect the path of least resistance across the terminal top.
NOTE: @Supervstech beat me to the explanation.
 
The stud won't have the same resistance as the terminal, so the flow will be entirely through it to the lugs.
The curent flows from the Aluminum terminal top to the bottom of the bus bar or lug. The grub screw is for mechanical strength to make sure those surfaces are well mated.

I see, I hadn't thought of the grub screw as just a mechanical fastener. Explains why I saw another person in a different thread saying they were using JB Weld to fix stripped threads.

Thanks for the quick responses!
 
Only downside it will be if you are using bms leads for balancing on the screws and you didn't clean top side of the bus bar for good connections. Taking good care to the details are important.
 

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