Algae/Corrosion buildup on the low side negative terminal (24V) (1 Viewer)

[LandLocked93]

Experiencing a respectable amount of algae buildup on the negative terminal.
This is opposite what many see on the positive terminal of your average system.
Any suggestions as to why are welcome.

Background - 12V native LC with twinned D4 AGM batts in series maintained by a RedArc 2420 BCDC.
It's not really an issue electrically, (though it looks ugly and requires occasional scrubbing to remove) just thought I'd throw it out here in case someone might surmise the cause of it.

 

[sdnative]

Algae? You mean corrosion?

Probably due to undercharging if on the negative terminal.

 

[LandLocked93]

Algae? You mean corrosion?

Probably due to undercharging if on the negative terminal.

Yes corrosion ... which reminds me of algae. lol

I've heard undercharging, overcharging, too high equalizing, and terminal seal breakdown.
I can monitor voltage and current to the bank and haven't seen a low charge situation. The RedArc is capable of ~31V charge tho I haven't used that profile more than twice. The AGM profile maxes out at 29.2V before going into float.
My inverter is also capable of ~30V of shorepower charge (tho limited to ~28.9V in AGM settings).
Like the RedArc, it too cycles thru bulk, float, and balance as normal.

FWIW at next cleaning this week going to try resealing the base of the terminal with vaseline as suggested by an outlet online and see what happens. The corrosion normally resurfaces w/i a couple weeks after each cleaning.
I wonder if RTV would be a better option over vaseline?

It would be more permanent anyway.

 

[bj70bc]

drop of oil

 

[LandLocked93]

drop of oil

Read that too.
But will the oil will stay put over distance, temperature, and AoA compared to vaseline or RTV?

 

[peesalot]

if you can spot the crack where the post & plastic have separated I have used a wood burner to melt the plastic over the crack to seal it up.

 

[LandLocked93]

Ok, so here's my findings from the clean.
Background, I can monitor voltage(E) and current(I), in(charge) and out(discharge), from the dashboard. When this batt bank was first installed, I took some baseline measurements so that I could spot deviations if/when they happened. Leading up to this post there were no abnormal indications of the corrosion being an issue.
But it is ugly and demands the aforementioned regular cleaning, so thought I'd just zoom in on the issue hoping to resolve with the forums help.

Initial condition.

Pulled the contacts apart and noted that none of the corrosion made it between the shunts and the terminal, which is good and why charge and discharge readings didn't change from the baseline readings of 'nominal'.
One side:

The other side. Didn't get a pic of the terminal itself, but it was clean.

After cleaning up the gunk, noticed this (red circle). It can be felt with a fingernail, and I cleaned it out a little with a pick. This area also corresponds with the largest buildup of corrosion in the first pic. Did I find the culprit? At least on this side of the terminal anyway.

On the other side of the terminal, found this (red circle). Again, it can be felt with a fingernail and again cleaned it out a little with a pick. The green area - the top mark not sure how that got there. The bottom mark is just surface scratches. Covered them both as well, regardless (see below).

Applied RTV by just smearing it on in a thin layer and let dry overnight. Left and right sides of the terminal:

Vacuumed up all the crud and put back together:

Ran a few charge and load tests to make sure it's all back together correctly. No issues.
Will report back if I see corrosion reappear. Really hoping it's done for tho.
Prob looking at new batts for the bank if not.

 

[LandLocked93]

Just a data point:
After the final pic and subsequent load/charge tests I charged the bank to ~27.5V and walked away, leaving it to sit for 10 days.

Today I checked the voltage of the 24V bank and saw 23.4V. Waaaay lower than I've ever seen before.
Naturally I figured I screwed something up.
Checked the terminal in question and it's as clean as it was in the my last posted pic.
Decided to shore charge the bank.
Plugged it all up and began charging (displayed 18A charge @ 24.6V) meanwhile noticed a .5A draw on the bank from the dash display, even while charging (yes, proper shunt position location has its advantages).
I couldn't figure out what this was, so went looking for LED notifications (indicating an energized component) and eventually found it.
There is an N/C solenoid that - when powered (opened) - enables air to flow out of the air tank and into the lines to Milton quick connects (F&R).
There are two LED switches - one at the dash and one in the rear - that light up when the solenoid is powered, regardless of which switch is 'turned on'.
The LED in the dash had burned out (tested after the fact, presumably due to the 24V source even tho it is supposedly rated to run 24V) and I couldn't tell from the drivers seat that the solenoid was actually ON (powered) as a result.

Bottom line is that the solenoid was powered since my last post (.5A, for ~10 days - constant load).
And even still, ZERO corrosion at the batt terminal in question.
Shore charged the batt bank to get it to ~ 25.8V.
Will check the terminal again in a couple days.
But I think the issue might be resolved (albeit possibly to the detriment of the batts in the bank )
Will update when I know more.