Battery Corrosion in Terminal Posthole

[Veratas]

Hi all -

Looking for a little bit of advice. Still fairly new to dealing with batteries.

I order four Varicore 90AH LFP cells about 4 months ago off of AliExpress, but just finally got around to using them. Long story short, the negative post hole on one of the cells looks to have some corrosion in it. It took a bit of force to get the screw in place, and once it was, I would get <1v across the cell measuring screw to screw. Testing from the actual pads on the cell, though, gives a normal voltage, so the cell itself seems to be fine.

So, I'm wondering if anyone's run into this, and if they have suggestions for cleaning it out. Or are there possible issues with the cell that would warrant a return? Am I likely

On a side note, I'm curious if anyone else has bought similar Varicore/Liitokala (sounds like they're the same thing) and what kind of experience they've had with them. I didn't find much information on them when I bought them, which was a bit of a red flag. I still bought them, even though the price seemed too good to be true.

Appreciate any advice/info anyone might have.

 

[gnubie]

It's possible the cell has been breached when the terminal was drilled out at the factory but regardless it's clearly defective so I'd be asking for replacement. Running a matching tap in and out might clean up the thread but if the damage has been caused by an electrolyte leak it's probably chewed up the metal to the point where that won't be much help.

Any chance of a high-res picture? Post to an external image hosting site as the forum will probably resize the image if you post it direct.

 

[Veratas]

Not the greatest, but here's what I was able to get.

 

[carlos1w]

So, in the end did things work? I am amazed how inexpensive these Varicore cells are. Would love to buy a set of 4 but if someone has a review already we can all use some info! Thanks!

 

[Veratas]

Well, unfortunately, I'm still very much a novice. I don't really have equipment to properly test them. And, while trying to drain them for bottom-balancing, one of the cells dropped down to around 1.5v. Charged it back up (AFAIK, it was only that low overnight), but I don't know if that might have done any damage to the cell. I'd consider any testing I would do to be suspect.

It might be worth starting a separate thread to ask about them. I have to think someone on this forum has taken a flyer on them already, or can at least tell us why we shouldn't beyond the "too good to be true" argument.

As far as the corrosion goes, though, I screwed/unscrewed the post a few times, and that seemed to help. I also found there was something on the post itself that was causing issues. Took a wire brush to it, though, and that did seem to help.

While that did help with getting things connected, I'd really like to know, though, if anyone knows of a safe way to clean the corrosion from the holes, though.

 

[Steve_S]

I would normally use a Tap & Die to clean the thread but using the screw will sorta do it too.
Next, take a Q-Tip, dunk it in Pure Rubbing Alcohol and clean out the gunk from the hole, may have to repeat a couple of times.
IF the bottom of the hole is NOT clean shiny aluminium the cell may have broken through, so make sure what you are looking at.
Next, wipe down the surface with rubbing alcohol, including the bolt threads (no point in putting a dirty thread back in a clean hole eh).

Note that using dissimilar metals will usually result in corrosion over time, especially if the area is humid and worse if it's salty (coastal waters), therefore it is generally suggested to use a very "wee dab" Noalox or Ox-Guard on the contact surfaces. a very thin wiped on layer is all that is needed and do not apply it to the threads !!! Acts like grease and can cause you to over-torque and strip the threads in the cells (which are medium aluminium).