The best treatment for old batteries is to wash the cells out to clear the debris that collects at the bottom of the cells and shorts them out, then refill with fresh acid. I found that doing this with a bank of large lead acid cells on a wind turbine system (the cells were 900 Amp hour each, every five years the battery bank lasted twenty five years and were still good when the property and system were sold. I have washed out large truck/tractor batteries as well and found that they recovered 80 to 90% of original capacity. But you need to do this before the cells are damaged from being internal shorted.