Corrosion on Negative Battery Post

Stopped by boat over the weekend to take care of a few maintenance items. On the list was checking water levels in batteries (2 house, 1 starting) took off the lids and the house batteries were a little low, but not much. Opened up the starting battery box and was surprised to see significant corrosion on the negative terminal. I had last checked them maybe 6 mos. ago and I don't remember seeing any significant corrosion then. I didn't have time to investigate further and admit to being slightly 12 volt electrically challenged, but am trying to do a little research on why this has changed.
I will say that this particular battery is around 10 years old and probably on borrowed time.
So, a couple questions. Would the age contribute to this? Since it is the negative post only (positive looks fine) mean anything? There are 4 cables landing on this post (1 to each engine, one to battery switch, not sure where 4th one goes) contribute? It has bugged me that there are 4 cables landing here, but as far as I can tell has never been an issue. Should I change this to one cable running to a bus bar type set up?

Thanks!

I am not able to answer the questions, alas, but sure am looking forward to seeing what the experts have to say on the subject (I have the same type of problem).

There are products that you can apply (after cleaning this up) that will inhibit future corrosion issues. Buy one and use it.


Take everything apart and clean the post and all the terminals first.

From past experiance, when an unusually large amount of the white stuff shows up on either posts the battery has been in service for a long time. I've found that the post has deteriorated and the case which in turn has caused "off gassing" or leaking at the terminal. Use to spend gobs of time trying to clean them, only to reappear quickly.
After installing a new battery it goes away. Just my 2 cents worth, no federal granted study to substantiate.

Age can certainly be a factor (10 years is old), but usually it is a poor connection and no use of something like CorrosionX or dielectric grease (heck, even Vaseline) after the connection has been tightened down

Like John, I`m interested in the views of our resident electrical guys.It`s not a question of cleaning up, it`s finding/fixing the cause it indicates.
My amateur thoughts include a leak at the terminal, as suggested above. Also chronic undercharging. Corrosion under the clamp connector worsens that, I think it insulates.
An aged undercharged batt which can`t hold a charge is my best guess.

Don't forget too the way you stack on that terminal. The largest goes at the bottom, closest to the battery. Small leads above.

At least that is what I was taught. Perhaps it's changed o'er the years so I'll sit back and watch for the experts to chime in...

CLean it up. If it reappears in a relatively short time [month or two] then that post has lost its seal to the acid below and an ever so slight acid leak is occurring. You can live with it or replace it. There is no fix that I know of.

For the cleaning use some baking soda mixed in water to neutralize the acid. Just be carefull and use the minimum possible untill the foaming quits.

If you can use only one heavy lead to the battery post and terminate the other wires at a buss bar that would be best. However, often that seal can be damaged by clamp removal if the clamp is difficult and a puller is not used or on flag terminals if carefull wrenching is not done.
Usually I get away with not using a puller but if the clamp shows the least bit of fight then I use the puller.

Crusty Chief said:

...or leaking at the terminal....

Click to expand...

Yup! This is what I've experienced with significant corrosion where there was none a few months before.

Ten years is a good run for the money. You must be doing something right, like good depletion and charging practices and good maintenance. If you clean it and it returns or the bank shows signs of deterioration, maybe it's time to enjoy a new set at the house.

Max Simmons said:

Since it is the negative post only (positive looks fine) mean anything?
There are 4 cables landing on this post (1 to each engine, one to battery switch, not sure where 4th one goes) contribute? It has bugged me that there are 4 cables landing here, but as far as I can tell has never been an issue. Should I change this to one cable running to a bus bar type set up?
Thanks!

Click to expand...

Max
Could the 4th be the shore batt'y charger? if so one option might be to move that to the batt'y post of the sel sw... that's how mine is wired

I read this re: batt'y corrosion - interesting but I'm not an expert and haven't heard this before...

"Corrosion on the terminals is due to hydrogen gas being released from the acid in the battery. It mixes with other things in the atmosphere under the hood and produces the corrosion you see on the terminals. Generally, if the corrosion is occurring on the negative terminal, your system is probably undercharging. If on the positive side, it is probably overcharging. Most often it will be seen on the negative side because the battery is usually in an undercharged situation. This is just the nature of the beast, I'm afraid."

Newly armed with all the knowledge imparted on this thread, I went down today to check my batteries (finally got a break in the weather). Well, corrosion on BOTH terminals! Kind of a silver-colored corrosion on the negative terminal, and kind of a gold-colored corrosion on the positive terminal.

Didn't clean them up, though, because I couldn't locate the puller. So will do that next time (I just ordered a new puller from Amazon, since the last time I saw the old one was on the sailboat before I sold it).

And by the way, there are quite a few cables which run to the positive terminal of the house battery. From what has been said earlier in this thread, it appears that putting them on a common bus and then running a heavy duty cable from the terminal to the common bus would be a better way to do it. Trouble is, I am not certain what to look for in order to buy such a bus. Is there a standard name for it???

Blue Sea Systems PowerBar 600A BusBar with Four 3/8 terminals.


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