Specific Gravity as an indicator
The SG quantifies the amount of **Sulfuric Acid** (H<sub>2</sub>SO<sub>4)</sub> to the **water** (H<sub>2</sub>O) in the battery electrolyte. Water has an SG of 1 so anything higher indicates some solvent.
> The next time your batteries don't seem to be taking or holding a charge, check the specific gravity with a hydrometer. If all cells are low even after a long time on charge, chances are you've got some hardened sulfate that has accumulated on the plates. By following the instructions outlined above, the problem may be corrected.
<a href="http://support.rollsbattery.com/support/solutions/articles/5964-battery-sulfation" target="_blank">Rolls Batteries' View</a>
**Lead (Pb) is sulfated** as it takes the place of the Hydrogen (H) atom. So lead becomes <strong> lead sulfate (PbSO<sub>4</sub>)</strong>: <em>Plumbum: Latin</em>
The general level of acid gives the electrolyte an SG of around 1.28 and could well be 1.3
**If the level is high** it would in normal circumstances indicates that the battery is fully charged. However if water has been lost during charging this will also show as an increased SG.
**If the level is low** Hopefully this is part of the normal cyclic sulfation process that occurs as the battery discharges and the SO<sub>4</sub> transfers from the electrolyte to the the lead plates back to the water when charged. Only when the plates have been left discharged for 'quite a while' does the sulfation become difficult to undue and the battery looses capacity, then even with charging the SG stays low.
If despite fears of hardened sulfation it is possible to restore the SG to 1.28 or more then then there is no significantly hardened sulfation.
Longs periods of overcharging are often used to force the sulfate to migrate from the lead plates back to the water. There are other methods such as elctro-vibrations and chemicals that are used, but they are not something I am familiar with.
Created by • Last edit by on 17 Jan 2018