Corroding Battery Terminals

[Xplode]

One of my off grid installs is starting to show corrosion at the battery terminals, although only 2 of the 12. Install is 6 months old, and I applied anti oxidant compound (burndy penetrox) to the lugs and mating surfaces on the battery studs.

The crimps are Panduit and sized correctly for the cable. Crimps were applied using the proper T&B manual crimper with the correctly sized die and handle spread adjustments made.

Aside from wire brushing and cleaning up the terminals, any insight or advice?

[Mike90250]

That's caused by acid. Either mist from battery caps, or wicking up thru the terminal post in the case.

Baking soda will neutralize it today, but as more acid accumulates, it will corrode again. Wire brushing only removes damaged metal and the protective tin plate.

Auto parts stores used to sell felt washers (red & green) impregnated with a Base to reduce corrosion from acid wicking up the post.

[Paul Land]

6 months after install mine too started to show corrosion. Cleaned and sprayed that red stuff.and I respray every 30 days ( H2o replenish)and it keeps corrosion at bay.

[littleharbor]

Looks like excessive acid all over the tops of the batteries. Are you possibly charging at a higher voltage than necessary?

[Xplode]

That's caused by acid. Either mist from battery caps, or wicking up thru the terminal post in the case.
Baking soda will neutralize it today, but as more acid accumulates, it will corrode again. Wire brushing only removes damaged metal and the protective tin plate.
Auto parts stores used to sell felt washers (red & green) impregnated with a Base to reduce corrosion from acid wicking up the post.

I've seen those felt pads on batteries before. But I've only ever seen them used on automotive style battery posts. Is there a similar product you know of for the marine style (threaded) posts?

ooks like excessive acid all over the tops of the batteries. Are you possibly charging at a higher voltage than necessary?

I don't think so... Charging is at ~29.3V (+/- for temperature) and is the value suggested by Crown when I contacted them... My controller charges at this rate for 180mins and then lowers to a Float voltage of ~27.6V... I'll go back and double check what Crown sent me just in case, but It's pretty much the same my 235Ah Crown batteries are running at and none of them are showing signs of corrosion like this... I was a little surprised to see the batteries this dirty, this quick. So maybe I should lower the time or the voltage? what would you guys suggest?

[Mike90250]

Look at the tops of the batteries, do you see tiny speckles that could be caused by acid mist from the vent caps ? How often do you have to add water ?

There are only 2 ways acid can get to battery terminals, mist from the vent caps, or wicking up thru the terminal post.

[Xplode]

Looking at the photos again, it does look like speckling. And I do suspect its mist from the batteries, I'm just surprised to see it.
I just added water for the first time, which is when I found the corrosion starting. The levels were not very low, but I had a half jug of distilled water left from topping up my other batteries and figured I would add a couple liters (spread across all 12 cells). The electrolyte levels are still at least 1/4-3/8" from the bottom of the vent tube.

checked on the batteries a couple months ago and they were not corroding, and didn't seem dirty like this.

The caps on these batteries just snap down (its a single 3-cell cap), and do not have a twist-to-lock type system. Perhaps there are better caps I should look into?

[Mike90250]

I've used the water miser battery caps before and liked them. They are plain plastic caps, with some little beads to trap the acid mist and return it to the battery, instead of venting it outside.

They are not catalytic caps that recombine gases and reduce water usage (those will fail quickly with acid mist)