Flooded Battery Failure

Crown solar batteries

How do you tell if you have a “Bad” battery?

We get these phone calls all the time - “My batteries are bad”

We understand that the battery or batteries appear to be all bad. The reality is this is very unusual and sometimes impossible. We hope to clarify a few things that can assist you in determining what might be the cause of the failure.

The first thing to keep in mind is that your batteries will take the brunt of any failure. If your charger fails, the symptoms show up in the battery. If you leave a load on, the symptoms will show up in the battery. If your solar controller or any other charging source fails, the symptoms will show up in the battery. This is important to know when determining what happened to the battery.

The quick and expensive solution of course is to replace the batteries. We hear it all the time. We put in new batteries and everything works! Of course, it does because you have new batteries. The question still remains, just how did they fail?

A battery itself can also fail. The most common defect is a dead cell. If your 12 volt battery has a dead cell it will not register any higher than 10.5 volts. A dead cell means that the bus connection between one of the cells on the inside has been broken.

The best place to start is to determine the cause of the failure. You can look through the list below of common failures and see if any of these match your symptoms. In the end, you might have to call our battery specialists for tech support. 888-826-0939

Common Battery Failures

Lead acid battery cells commonly fail in several ways. There are Open Cells and Shorted Cells.

Open Cells which are more resistive, suck up charging voltage which in turn steals voltage from the rest of the batteries so the entire battery bank slumps.

Shorted Cells which are less resistive, letting voltage and current pass to the rest of the batteries in the string, causing an overcharge. The dead cell doesn’t take any of the voltage so the rest of the batteries in the string become overcharged.

Specific Gravity

Specific gravity can be viewed in three ways. There is too high, too low, or just right.

Just right. In some cases, all the specific gravities may look great, but when the battery bank is under a load you see the voltage rapidly drop. Many times, this indicates a shorted cell.

Too low. This is where you lose capacity, this will always cause sulfation, which then causes overheating and excessive water use, which then leads to battery failure. This is the most common way an FLA battery bank dies is low SGs (unequal voltages) are not corrected soon enough and the bank sulfates.

Too high. This is where you get great capacity, for a while, but that higher acidity will cause corrosion on the plates which will act a lot like sulfation. In this case, you will very often see a darker electrolyte as the higher acidity/corrosion is eating away at the active material of the plates.

What to do?

  1. Charge the bank to what you think is full or close to it.
  2. Find the 10 Hour Discharge Rate of the bank (C/10 Discharge Current).
  3. Apply load as close as you can get it by running loads in the house. You will be running this test for 2-5 hours depending on test results.
  4. Monitor battery voltages during this test every 30-60 mins.

Individual battery voltages should stay pretty close to each other as they discharge If you start to see one or two batteries sag in voltage before the rest you have weak or dying cells.

Wet Cell Batteries and More

Solar Biz has been in the battery business for 52 years. Even a well-intentioned battery owner, who cares for his batteries religiously, can have problems. Contact Solar Biz today to learn more about wet cell batteries or other battery care and replacement.

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