I have a lead acid battery that has a manufacturing date of 2016. Also, I live in Texas.
Recently, the voltage dropped on it to 10v. I was able to drive my car to do some chores the day before. So, there was enough of a charge on the battery for the car to turn over. The individual cells were always topped off with appropriate fluids and I made sure to use a trickle charger if I wasn’t using it for long periods of time. I was fortunate enough to get my hands on a de-sulfator. So I decided to spend 4 weeks de-sulfating it. Now, because we live in Texas, we have temperatures over 90F at least 1/3rd of the year. So, obviously, not an ideal environment for car batteries.
After de-sulfating it outside the first three weeks, I take it inside to let it de-sulfate the last week in an environmentally controlled room. After the last de-sulfation cycle, it initially shows 8v. I wait a few hours and the voltage goes up to 12.8v. Not only that, I install it in my car and I’m able to turn over the car twice. I hooked it up to a trickle charger to see if, overnight, I could get a little bit more voltage out of it and it climbed to 13.1v and the car was still able to turn over. I let the battery sit for a few days because I didn’t need it right away and I’d rather use it for something unimportant if it fails. When I get ready to use it, I find that the voltage had dropped to 8v.
Now, the temperature outside the night I tried out the battery going into the next day when it reached 13.1v was around 80F. Over the next few days I had held off using the battery, the temperature reached over 90F. At this point, I don’t know what is going wrong with the battery internally. Whether the chemical composition of the acid/water mixture had changed or the cells inside of the battery had changed their properties due to 6 years in 90F heat or something else entirely. I just know that the battery was holding a decent enough charge to turn over our car engine for 12 hours before the voltage dropped to 8v.
At this point, in regards to de-sulfating a battery, I’m sure some people might get some success out of doing that. However, considering the fact that the battery was showing 12.8v until I took it from a temperature controlled environment to 90F heat, I think the heat changed the properties of the chemical solution and the individual cells too much for de-sulfation to be of any use in an envitonment that can reach +90F 1/3rd of the year.