Do cell terminals & cell links need corrosion protection?

[JmanC]

Everyone who shows how to build these LFP batteries doesn't talk at all about it. I would have thought a tiny amount of oxidation on the copper is unavoidable and will lead to a problem with resistance not being equal.

[nebster]

I use nickel-plated copper bus bars, and they really help minimize the problem.

I have found even a single newton-meter of torque differential on the lug nut can change the connection resistance meaningfully. So I am sure corrosion can also have an influence, yeah.

[Kiwi Dave]

Hi - I had my 400 Amp Hour LiFePO4 BMS start shutting off the charge bus contactor when both engine alternators kicked in. After my expert logged on remotely it was found that cell 3 was reading a higher internal resistance and thus refusing to accept more than 120 amps by turning off the Charging Bus Contactor.
After cleaning all connections (copper bus bars and wiring taps) problem was sorted with Delta Cell Resistance back from 0.38 to 0.01, . The bank was 4 1/2 yrs old. Now everything is fine again.

[aybabtme]

Personally, I sanded all my busbars and contactors before installing them, and applied dielectric grease to all the connection surfaces.

When I did testing at home, it was straight copper with no dielectric grease. My BMS measured about 0.25mΩ for all the cells. After installing it in the boat and using the dielectric grease, the measured resistance is ~0.35mΩ. So a slight increase in resistance because of the dielectric grease, but I'm sure it will age much better long term.

I didn't do anything to the rest of the surface of the busbar. I could cover them with liquid rubber or heat shrink, but I figured I'd just monitor them over time and see if it's needed. It'll also give me a reference point to compare "dielectric grease vs. bare copper" over time.

[JmanC]

Originally Posted by aybabtme

Personally, I sanded all my busbars and contactors before installing them, and applied dielectric grease to all the connection surfaces.

When I did testing at home, it was straight copper with no dielectric grease. My BMS measured about 0.25mΩ for all the cells. After installing it in the boat and using the dielectric grease, the measured resistance is ~0.35mΩ. So a slight increase in resistance because of the dielectric grease, but I'm sure it will age much better long term.

I didn't do anything to the rest of the surface of the busbar. I could cover them with liquid rubber or heat shrink, but I figured I'd just monitor them over time and see if it's needed. It'll also give me a reference point to compare "dielectric grease vs. bare copper" over time.

Thank you aybabtme, that is what I wanted to hear. Since we coat all our lugs, terminals etc it just made absolutley no sense to me having bare copper or even bare tinned lugs on a battery you expect to get near 10years of life in a marine enviroment.