Battery Acid

What is battery voltage reading.
You would need to charge up as much as possible first.

Before changing electrolyte get a hygrometer to check specific gravity.

Changing electrolyte rarely helps.  

A discharged battery has lead-sulfate on plates where sulfate came from electrolyte sulfuric acid that gets converted to water making specific gravity of electrolyte low and must be returned to electrolyte or water.
If it is hardened lead-sulfate because it was left in discharged state for some time, it is hard to get rid of crystals.  Best case is to recharge with high current and try to knock it off plates. Knocked off crystals will sink to bottom of battery but electrolytes specific gravity will still be low because sulfate needed to covert water to sulfuric acid has been captured in crystalized lead-sulfate.   

That fact it is cloudy may imply someone tried to fix battery with Epsom salt.  Epsom salt can dissolve harded sulfate but it contaminates electrolyte and is not good for positive plates.

Then drain electrolyte after charging as much as possible.  Replace with distilled water and try to hit it again with high recharge current.  Pure water provides more opportunity to combine with sulfate from plates.

Then drain and replace wih fresh battery electrolyte.

Like I said, usually a waste of time and money for replacement electrolyte.

I don't know your situation, but would consider doing some seriously heavy duty equalizing. Rolls was suggesting some very high voltages for Equalizing Something like 65 volts for a 48 volt system (temperature controlled)... Might do some searches here for how some have been able to recover a good bit of capacity on old Rolls batteries.