My battery was fine one day, then down to about 11.7 volts the next. This happened during our first couple of 90 degree days this year. It’s a “five-year” battery that is just shy of four years old. It took 16 hours with a battery tender to get the battery back up to charge.
I removed the battery from the charger and took it to a battery store where it passed the load test. I then read that a battery fresh off a charger will have what is called a “surface charge” that can skew load tester results. There are several ways to dissipate the surface charge, turn on the headlights, or just let the battery rest for several hours. I am going to let the battery sit overnight, then take it to be tested again. It is a nearly four-year-old battery. I am on the fence about doing the test vs just replacing the battery. Are the load tests accurate in estimating battery health? The alternator on this vehicle is under the engine and is no fun to replace, so I don’t want to stress the alternator with a weak battery.
For what it is worth, the battery is used in a vehicle that is driven only during the summer months, and even then it is driven pretty infrequently.