How to tell if batteries are sulphated or corroded?

[somawheels]

I have a bank of batterries, and the SG on the batteries is uneven. The batterry capacity seems to be much less than what it used to be.

How would you find out whether this was caused by grid corrosion on sulphation?

[Mike90250]

You remove loads for 24 hours and charge everything well for a day, measure the voltage and SG every 3 hours during the day while charging.

What has your water usage been like the last couple years ? Lots of water weekly = overcharge and grid corrosion (rare) Not much water every other month = undercharge/sulphation (common)

[somawheels]

Thanks alot for you answer Mike. Water usage has become extremely high over the past few months. So I suppose it must be grid corrosion. Regarding the first part of you awnswer, What would you expect to see in these measurements if the batterries were corroded vs sulphated?

[Mike90250]

How old, and what kind are the batteries ? Older batteries use more water.

[somawheels]

3 year old lead acid batteries. So not that old. The batteries require water every few weeks now.
I was expecting at-least 5 years of use out of them, so am trying to figure out what went wrong.

Bellow, is a run down of the issues i have noticed over the years. Perhaps you know which of these is responsible for grid corrosion?

1. Batteries hardly ever equalized.

2. Undercharged and over drained in the winter.

3. The cheap chinese inverter/charger used to charge them via generator didnt seem to charge them properly. It finished charging in less than an hour, and the batterries would not last long after this charge.

4. The water level in the batterries was allowed to go too low on a few occasions. It wasnt bellow the plates, but it was bellow some metal parts in the battery.

5. Some of the cells have become murky or brown, some have stayed clear.

6. Also About 2 years after installing the system, the batteries seemed to be charging too fast, so I increased the absorb time by a couple of hours more than recommended.



Thankyou so much for your help.

[Mike90250]

1. Batteries hardly ever equalized.

2. Undercharged and over drained in the winter.

6. Also About 2 years after installing the system, the batteries seemed to be charging too fast, so I increased the absorb time by a couple of hours more than recommended.

Those are killers
#1 & 2 can easily lead to sulphated batteries
#6 charging too fast - means you lost capacity and your 100ah battery is now a 50ah battery, which would charge up quickly. And longer absorb times will start plate corrosion, so your batteries are failing both ways.

Now you know what to watch for with your next set.

[somawheels]

mmm, Im still unsure what caused the early plate corrosion. At https://www.solarpaneltalk.com/forum...13-absorb-time, Sunking seems to be saying extra absorb time is not an issue.

Unlike my solar charger, My inverter charger does not give me much control over its charging functions. It allows me to set the bulk voltage, and nothing else. So im not really sure whats going on with that. But I do know the inverter charger it limited to a 30 amp charging current, and never charged for very long before saying the bank was full. The battery bank is 400 amphours.