Electrical charges travel between lead-acid battery plates, during discharging and recharging. Their sulfuric-acid electrolyte transfers a quantity of sulfate to the plates, and recovers it respectively during these alternating phases. Lead battery sulfation impedes the flow of electrical charges when discharging, until the battery is technically ‘flat’. However, sulfation need not be permanent.
Comparing Soft and Hard Lead Battery Sulfation
A lead battery goes through the sulfation / de-sulfation routine numerous times during its active life. This is because the sulfate is still ‘soft’, and almost all of it removes easily.
However, the sulfation gradually ‘hardens’ if recharging does not follow regularly. It could become permanent, if the battery remains in a semi- or completely-discharged state.
The electrical charges can no longer travel as easily between the sulfated plates. The battery no longer charges fully. But it may be possible to loosen the sulfate by applying an ‘over charge’ for 24 hours, according to Battery University.
In summary at this point:
- Lead-acid batteries may ‘hard’-sulfate if they do not recharge in a matter of days.
- This is why lead batteries in storage should ‘trickle charge’ to avoid this.
- Undercharging a lead battery by 10% reduces its capacity by a similar factor.
- The longer a battery is in storage, the greater the chances of ‘hard’ sulfation.
The Consequences of Hard Sulfation
‘Hard’-sulfated lead-acid batteries may signal falsely-higher voltages to battery chargers, according to Rolls Battery Technical Support. This ‘fools’ the regulators into believing their battery is fully charged, when it is not. And as a result, the charger may lower its voltage to the point it never recharges the battery fully.
The remaining sulfate ‘hardens’ further over a period of time. The battery loses more and more of its capacity, until it can no longer perform its task. Always check the manufacturing date on any new battery, to make sure you are not purchasing old stock.
More Information
Lead Sulfation & Practical Steps to Slow the Process
