I spent the morning yesterday swapping out my batteries – all 16 of them. While this may not seem like a big deal, you have to consider that each battery weighs 121 pounds, and I had to move 32 batteries (the 16 old ones out, and the 16 new ones in). In addition to the pain in the back, I was without power for a couple of hours.
Why did I have to go through this? The old batteries failed after only 12 months, and were not able to provide the amount of power they were supposed to. When we first got the batteries, we were able to go a day or two with no sun recharging them. At the end, we could not even go overnight without the generator kicking on. A battery bank with a capacity of 180 amp-hours (20 percent of the rated 20-hour capacity of the batteries) could not even give us 50 amp-hours.
I was alerted to a potential problem when I measured the specific gravity of the electrolyte in the batteries. A healthy fully-charged battery will have a specific gravity of around 1.265 to 1.275. Some of ours had specific gravity measurements between 1.300 and 1.315. When the acid is this strong, it starts to eat away at the positive plates, resulting in lower storage capacity.
Fortunately for us, our supplier recognized this as a manufacturing issue and replaced the battery bank free of charge. In talking to our supplier, I learn a lot about batteries and how to treat them. Lead-acid batteries do not like to run out of liquid, nor can they be drained too low for extended periods of time. This will dramatically shorten the life of batteries. For the most part, however, lead-acid battery technology is very robust and forgiving, but once in a while you run in to an issue that is not related to owner treatment. In these cases, it is good to have a supplier you trust and that has the experience to know when a battery has failed as a result of a manufacturing defect.
How are your batteries doing?