Causes of Sulfation
Most cases of sulfation are caused by:
UNDER CHARGING OR NEGLECT OF EQUALISING CHARGE
When a cycled battery is charged repeatedly at low rates but not fully charged, the acid is not effectively driven out of the plates, particularly the lower parts, and sulfation results.
Repeated partial charges which do not effect thorough mixing of the electrolyte also result in sulfation. It is difficult in normal battery operation to determine just when sulfation begins, and only by giving periodic equalizing charges and comparing individual cell specific gravity and voltage reading can it be detected in its early stages and corrected or prevented.
Troublesome sulfation does not occur in less than 30 days.
STANDING IN A PARTIALLY OR COMPLETELY DISCHARGED CONDITION
Permitting a battery to stand in a partially discharged condition for long periods allows the sulphate deposited on the plates to harden and the pores to close.
Batteries should be charged as soon as practicable after discharge and not allowed to stand in a completely discharged condition for more than one month. During freezing weather the battery should be recharged immediately following discharge to prevent freezing.
If the level of the electrolyte is permitted to fall below the tops of the plates the exposed surfaces will harden and become sulphated.
If acid is added to a cell in which sulfation exists the condition will be aggravated.
HIGH SPECIFIC GRAVITY
In general, the higher the fully charged specific gravity of a cell the more likely is sulfation to occur and the more difficult to reduce. If in any battery there exists cells having specific gravity more than 0.015 above the average, the possibility of sulfation in these cells will be enhanced.
High temperatures accelerate sulfation, particularly of and idle, partially discharged battery.
All cells of a sulphated battery will give low specific gravity and voltage readings. They will not become fully charged after normal charging. An internal inspection will disclose negative plates having a slate like feeling, sulphated negative-plate material being hard and gritty and having a sandy feeling when rubbed between thumb and forefinger.
The internal inspection should be made after a normal charge, since a discharged plate is always somewhat sulphated. A good fully charged negative plate is spongy and springy to the touch and gives a metallic sheen when stroked with the fingernail or knife. A sulphated positive plate is a lighter brown colour than the normal plate.
Created by • Last edit by on 25 Jan 2018