Hokay, I don't usually offer advice in here as I'm new to RVs and learning.But I have to share this with you folks. Recently I watched a guy on you tube regenerate a car battery. After watching his video I couldn't wait to try it out. Take your dead 12 volt car battery,( wearing eye protection and using gloves of course) pop the tops, drain the battery acid out. Pour in a mixture of 8 ounces of baking soda in one gallon of distilled water to flush out the remaining battery acid. The baking soda cleanses the battery acid out of there. Then flush the battery with distilled water.Then add 8 ounces of food grade Aluminum Sulfate into one gallon of distilled water.Mix well.Pour into the battery.Enough to cover the plates in the battery, don't overfill. Then replace caps, put battery on charger overnight. SURPRISE! You can start your car or truck with it. I've done this with a small 12 volt car battery and a large deep cell 12 volt battery. I had enough to do three batteries and only spent 20 dollars for the supplies. The distilled water I bought at Walmart,88 cents per gallon, the baking soda came in a one pound box, and since I only needed 8 ounces I have enough to do it again. The ALUM I found at orchlins hardware store, sort of a rural farm type hardware store. Comes in a small green envelope of 1.9 ounces.I bought them all.Look on the back, make sure it says aluminum sulfate.And it needs to be food grade, the same stuff women use for pickling. I'm not sure how long these batteries will hold a charge, so we shall see. I'm sure the deep cell will at least hold a charge for the summer giving me time to save up the hundred dollars to buy a brand new one.Bottom line, if anyone out there is hurting for money( aren't we all?)and needs to deal with a dead battery but cant swing the cash for a new one, try this out. I gain no monetary benefit from posting this, just trying to help others with the info.The one small car battery I had laying around a good two years. The deep cell battery came with my RV and when I popped the caps was surprised to see it was empty ( not a good sign)But I decided to try it anyways.From what I've read, there will be some car batteries this trick may not work with, so don't be discouraged. I've got more than one dead battery lying around here, so it's no big deal for me if one doesn't take. Anyhoo, try this trick out and good luck to ya, just remember to wear eye protection and use gloves. :-)
Pretty interesting! Being in the alternative energy business, I've worked with large deep-cycle batteries for > 30 years and only heard of people trying this a few times. Like you said, sometimes it works and sometimes it doesn't.
On the other hand, when you say "pour out the battery acid", how do you do this without contaminating wherever it is you pour it? We are talking about sulfuric acid and lead here, aren't we? Maybe if you flush with LOTS of water to dilute it down to a non-hazardous level it would be OK? I personally would empty and flush the cells into a poly container to allow the really bad stuff to precipitate out and then let the liquid evaporate. Considering the dangerous, poisonous and persistent nature of the lead particles left at the bottom, I would carefully gather them up and take the crud to an approved hazardous waste disposal site. Many landfills have a place that takes it for free.
Most battery failures happen through vibration or when enough lead oxide sloughs off of the battery plates to form a partial or full bridge between plates, which causes an internal short. The oxide particles are formed as a natural by-product of the charging and discharging process so battery cases have an area below the plates dedicated to accommodating this oxide buildup that eventually fills up to the point that a short can occur. Since the plates lose mass in the oxidation process, they can eventually become thin enough that holding a charge is impossible, or they can crumble and cause a short. Either way, the battery is toast.
Deep-cycle batteries have extra thick lead plates to stretch out the number of charge/discharge cycles possible. They also (should) have extra capacity in the sump beneath the plates and a strong plate separator (non conductive, of course) that prevents any oxide flakes from bridging the gap and lengthens the number of cycles to far more than a typical starting battery is capable of handling.
One reason that batteries go dead after sitting around for a long time is that the lead oxide on the surface of the plates, which creates a barrier to the movement of electrons, remains intact instead of sloughing off and falling into the sump through charge/discharge cycles. It also often happens that attempting to fast charge a really dead battery can cause an internal short, so the best approach is to never let the battery get that dead to begin with.
Another approach is to use an electronic "desulfator" that sends strong pulses through the cells, which can actually stimulate the sloughing process and "fix" batteries.
I suspect that what you are doing with the "alum" is change the batteries from lead-acid to lead-alkaline batteries, which if done right, can actually be *better* than lead-acid. Still, the actual process is quite dangerous and could lead to acid burns, an explosion or the end of the world as we know it. So I would be VERY CAREFUL.
How are they working now? I might have to try this out soon.