How much current should I pass through battery to break through sulphate deposits?
I have extensive experience on desulphating lead acid batteries.

The success rate depends greatly upon the level of contamination in days or months and after 1yr, the success rate depends greatly on the resting voltage and ambient temperature which both cause  aggressive  degradation and plate erosion/diffusion.


  The design in electrical terms must excite the piezo-electric effect to vibrate crystal growth and slowly break down and settle to the bottom without self heating which aggravates the cause.


You must have an idea or know how to compute and measure Pd with pulses with a model of the battery condition before and after and can minimize \$E=I^2*ESR*t(PW50) *f \$ f=rep. rate  for 50% Pulse Width by knowing the approximate temperature rise of the plate junctions, not the case, you can restore a dead battery that worked a month ago. Only low degraded or high quality motive power flooded batteries and ceramic 230kg 2V cells can be rejuvenated after 2 years to 100% . Others will be a small portion of this. 

The battery ESR is a combination of SoC and sulphation which may be >100x greater initially so sensing V/I pulses will tell you if it is improving.  I have tested 25KHz 10A flyback pulse 1W types and have seen test results on 1kA pulse rejuvenator with CPU automation for automotive batteries work well up to 1.5yrs of aging.