Unik Techno • August 20, 2020
What happens if lead acid battery runs out of water?
What happens if lead acid battery runs out of water?
A lead acid battery has positive & negative plates fully immersed in electrolyte which is dilute sulphuric acid.
The concentration of electrolyte is defined & specified for batteries of different applications based on the application & in line with national & international standards.
This concentration is expressed as specific gravity.
This specific gravity is usually determined at design stage by battery manufacturers with relation to the volume of electrolyte which can be accommodated in a cell. The specific gravity is always in a defined range with the maximum specific gravity specified in such a manner so that it does not accelerate corrosion of battery components & allows for release of sulphate from the plates when a battery is on charge. The minimum specific gravity is also such that it retains the conductivity of electrolyte so that there are no problems to charge a fully discharged battery. Thus the volume & concentration of electrolyte form part of the design of battery.
As regards battery plates the active materials of the plates are decided in such a manner that the quantity of active materials as well as surface area of the plates decide battery capacity.
When the level of battery electrolyte reduces to an extent that the top portion of the plates are exposed - a situation is created wherein a certain portion of the plates do not take part in the reaction.
This leads to reduction in battery capacity. This is undesirable & hence it is not recommended to allow the battery to run out of water.
Regular topping up with distilled or demineralized water ensures that level of electrolyte is maintained. Evaporation of water component of battery electrolyte has to be compensated by topping up with water on a regular basis at defined intervals.
Another effect of reduction of electrolyte due to evaporation of water is increase in concentration of electrolyte i.e. increase in specific gravity. An increase in specific gravity of electrolyte with plates not fully immersed in electrolyte results in heating up of cell on charge. The battery can get damaged since corrosion of internal components used in battery manufacturing is accelerated in the acidic electrolyte at elevated temperatures.
A physical effect of reduction of water is heating up especially during the last stages of charging or in case of an undesired overcharging. Electrolyte also acts as a coolant though this may not be its main purpose for its presence in a battery. Hence the problems of thermal runaway faced by sealed maintenance free (SMF) or valve regulated lead acid (VRLA) batteries is not a phenomenon faced by designers of flooded electrolyte lead acid battery designers.
Finally coming to the main question as to what happens when a lead acid battery runs out of water – totally i.e. electrolyte has fully dried up or battery has been tilted or stored upside down due to which the electrolyte has spilled. Please note that we must not remove acid completely from flooded electrolyte lead acid batteries once it has been filled with acid & charged.
A lead acid battery consists of a few major components viz. the positive electrode, negative electrode, sulphuric acid, separators & tubular bags.
In charged condition the positive electrodes are lead dioxide and negative electrodes are sponge lead.
Sponge lead is highly reactive in the presence of moisture & oxygen and gets converted to lead oxide. In the process of conversion to lead oxide it gets discharged & heated up.
Hence it is necessary to ensure that the acid is not spilled or drained from a wet battery once it is filled and charged.
As and when a battery filled with acid is drained of acid the wet moist negative electrodes come in contact with atmospheric oxygen. An exothermic reaction takes place releasing an enormous amount of heat thereby discharging the negative plates (electrodes) and oxidizing the sponge lead to lead oxide.
During this exothermic process of heating up of the negative electrodes, the other components within the cell i.e. separators, tubular bags, plastic components like bottom bars, vent plugs, cell covers and rubber bushes fitted to cell covers get deformed, degraded or damaged.
Whilst it is possible to revive such batteries if they are not fully damaged, the life & performance of such batteries do get adversely affected and hence it is very important to ensure that there is no spillage of acid from fully charged batteries. Loss of electrolyte from the top of the plates in the normal course without exposing the electrodes is however different and cannot be equated to spilling.
Sulfation is a widespread yet often overlooked issue in the world of lead-acid batteries. Frequently dubbed the “ silent killer” , it operates without obvious warning signs, quietly reducing both battery performance and service life. Whether used in industrial machinery, UPS systems, or off-grid energy storage, sulfation poses a serious risk to any application reliant on reliable battery power. What is Sulfation in Lead Acid Batteries? At its core, sulfation refers to the accumulation of lead sulphate crystals on the battery’s internal plates. This occurs naturally during discharge as the active material on the plates reacts with sulphuric acid. In a properly maintained battery, these crystals dissolve again during the charging process. However, when a battery is left undercharged, stored in a discharged state, or routinely subjected to deep discharge cycles, these sulphate crystals begin to harden. Over time, they become dense and irreversible, severely inhibiting the battery’s ability to hold and deliver electrical charge. What Causes Sulfation in Lead Acid Batteries? Understanding the root causes of battery sulfation is the first step to avoiding it. One of the most common contributors is infrequent or incomplete charging. A battery that is not brought back to a full state of charge after use may retain a residue of sulphate on the plates. This residue becomes the starting point for permanent sulfation, especially if the battery is neglected over repeated cycles. It is not just charging habits either—environmental conditions also play a significant role. High ambient temperatures accelerate the electrochemical reactions inside a battery, increasing the likelihood of crystal formation and growth. In warmer climates, or in confined battery enclosures without proper ventilation, this risk is amplified. Prevention of Sulfation in Lead Acid Batteries Prevention begins with proper charging practices. Always use a smart charger that can automatically adjust the charging voltage and current based on the battery’s state-of-charge. These chargers typically include bulk, absorption, and float stages that ensure a complete and balanced charge. Some models even include pulse or maintenance modes that help dissolve early-stage sulphate deposits, reducing the onset of crystallisation. Routine maintenance is another critical factor. For flooded lead-acid batteries, it’s important to regularly check electrolyte levels and top up with demineralised water when necessary. Low electrolyte levels expose the upper portions of the battery plates to air, causing oxidation and increasing the likelihood of sulphate build-up. In addition to fluid checks, make sure to clean terminal posts, check for corrosion, and tighten connections to ensure efficient current flow. Equalisation charging is a powerful tool in the prevention arsenal. This is a controlled overcharge applied periodically—usually once every 30 to 90 days that helps equalise the voltage between cells and reverses mild sulfation. Equalisation charges are particularly effective in larger battery banks where cell imbalance is common. However, they should only be performed according to the manufacturer’s guidelines, as excessive overcharging can damage the battery. Storage practices also matter. If a battery is left unused for extended periods, it must be stored fully charged and kept in a cool, dry environment. Batteries in storage should be recharged every 60 to 90 days to prevent the slow self-discharge that can lead to sulphate crystallisation. Even sealed lead-acid batteries are vulnerable if stored improperly. While some specialised de-sulfation chargers claim to reverse sulfation through high-frequency pulse technology, their effectiveness is generally limited to early-stage sulphate deposits. Once the crystals become hard and dense, recovery is unlikely, and battery capacity is permanently reduced. Prevention remains far more effective than any attempted cure. The consequences of ignoring sulfation can be expensive. Reduced runtime, increased charging times, and eventual failure can disrupt operations and require premature battery replacement. For businesses, this translates to higher operational costs, increased downtime, and reduced energy efficiency. At UNIK Batteries, we believe that prevention is the smartest investment. By manufacturing high-quality lead-acid batteries and state-of-the-art charging components, we help customers protect their power infrastructure from day one. Whether you operate forklifts , golf carts , maintain a solar backup system , or manage a unit of UPS batteries , we have the right solution to keep you powered and protected from sulfation. Contact us to explore our range of batteries and charging components today!
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