How to maintain the lead acid batteries?


Do you know the main reason why lead-acid batteries fail and lose capacity? The battery is sulfated. This is 80% of the causes of these problems. However, with the right battery maintenance tools and a small amount of time, you can restore the battery to use and make it operate reliably. Learn everything you need for battery maintenance.

Poorly know about batteries, even if life on battery power is off the grid. A better understanding of the inner workings will go a long way in making these batteries happy. Considering that batteries are expensive and they are the main (recurring) cost of the entire off-grid system, battery maintenance should be high in everyone’s off-grid list.

Starter batteries, semi-traction batteries, traction batteries, and even stationary batteries require maintenance to achieve their full potential. Perform the basic maintenance tasks we outline here on a regular basis to optimize the performance and reliability of lead-acid batteries.

Regular inspection and maintenance

Regular testing and inspection will help maximize battery life. It is recommended to check at least once a month to maintain optimal performance.

When examining the battery, please refer to the following:

1. Check the charging status of the battery. Most batteries have a “charging status” indicator on the top of the battery, which can provide you with on-site diagnosis of the battery status. However, a more reliable inspection method is to use a voltmeter to determine the stable voltage, or if the vent cover is removable, use a hydrometer to determine the specific gravity (SG) of the electrolyte. A charged battery will have a stable voltage above 12.5 volts and an SG reading above 1.240.

2. Make sure the battery box is clean, dry, free of dust and dirt. Dirty batteries may drain through the dirt on the top of the battery box.

3. Check whether the terminals, screws, clamps and cables are broken, damaged or loose connections. They should be clean, sealed and free of corrosion.

4. Apply a thin layer of high temperature grease to the terminal and cable connection to provide additional protection.

5. Check the battery box for obvious signs of physical damage or warping. This usually indicates that the battery is overheated or overcharged.

6. If you have a maintainable battery, be sure to check whether the battery has enough electrolytes to cover the battery board. If you need to add liquid, please do not fill it up, because when the battery is fully charged, the liquid level will rise and may overflow. Add water with distilled or dematerialized water; do not fill with sulfuric acid.

7. When repairing sealed maintenance-free (SMF) batteries, check the charging status indicator. This gives you a snapshot of the battery condition and whether the battery needs to be charged or replaced. Although the indicator indicates that the battery is to be replaced, the vehicle may still start the engine. If the charge status indicator suggests “replace the battery”, it is important to replace the battery, because the electrolyte level may be lower than the plate, which may cause an internal explosion.

8. For batteries used for seasonal applications and long-term storage, please fully charge the batteries before storage. Check the charging or voltage status regularly. If the voltage drops below 12.5V, please charge the battery. It is important to check the battery thoroughly before reconnecting to electrical equipment.

Charging batteries

Charging a lead-acid battery is a process of replacing the energy removed during the discharge process, plus EXTRA to compensate for any inefficient charging. The energy required for a full charge depends on the depth of discharge, charging rate and temperature. Usually 110%-150% of the discharge ampere hours (depending on the battery type) must be returned to the battery to achieve a full charge.

Safety first

Before attempting to charge the battery with an external battery charger, it is important to observe safety precautions when charging the battery and follow the instructions outlined by the charger manufacturer.

●Please turn off the charger before installing, shaking or removing the terminal clamp.

●Keep open flames and sparks away from the battery.

●Place the vent cover.

●Please charge in a well-ventilated place.

●Please follow the battery charger manufacturer’s instructions to avoid overheating.

Dangerous explosive gases are generated during charging, which may be ignited by a variety of sources, including sparks, open flames and static electricity. It is strongly recommended to wear PPE (personal protective equipment), including safety glasses, chemical resistant gloves and work clothes.

Choose the right charger

Lead-acid batteries should be charged in three stages; constant current (boost), constant voltage (absorption) and floating charge.

When choosing a battery charger, it is important to choose a charger that can provide the specified charging voltage and current to suit the battery type. Water-filled absorbent glass mat (AGM) and gel battery types require different charging specifications to provide the best performance and longevity.

Charging voltage (for manual charger)

Monitoring the battery voltage during the charging process is very important to reduce the risk of overcharging and to check the battery progress during the charging process. Always retain the parameters outlined in the table below. Otherwise, the battery may be permanently damaged.

Auxiliary charging voltage of battery type

Type Absorption Charging Float Charging
Flooded (Maintainable / SMF) 14.4 to 14.8V 13.2 to 13.5V*
AGM (Absorbed Glass Mat) 14.6 to 14.8V 13.6 to 13.8V
Gel Electrolyte 14.2 to 14.4V 13.6 to 13.8V

The recommended temperature during charging is 25°C. If the battery temperature reaches 50°C, charging must be suspended.

The above specifications apply to 12-volt lead-acid batteries. When charging a 6-volt battery, please provide half the voltage provided.

In addition to following the battery charging voltage guidelines, choosing the correct charging current (Amps) for the battery size is essential to provide performance and longevity.

Charging current (for manual charger)

The recommended safe charging current is 10% of the battery’s 20-hour (Ah) rating. For example, if you want to charge a 100Ah battery, the recommended charger current for this battery is 10A. Slow charging is the best way to charge lead-acid batteries. Fast charging of lead-acid batteries by increasing the recommended amperage may cause excessive stress and shorten battery life.

1. For efficiency reasons, the charging capacity must be more than the discharging capacity. The coefficient factor can be between 110% and 150%.

2. The deeper the discharge, the higher the coefficient.

Note: When the temperature rises above 50°C, the charging must be suspended

Charging time

The time required charging a lead-acid battery to 80% accounts for about 60% of the total charging time, and the remaining 40% of the time will return the last 20% of the charge to the battery.

It is difficult to determine the charging time due to the following factors:

●Discharge depth


●The size and efficiency of the charger

●The age and condition of the battery

●For guidance, please refer to the constant current charging method table

●When connecting multiple 12V batteries in parallel, you increase the capacity of the battery pack while maintaining the voltage. E.g. when 3X12V 60Ah batteries are connected in parallel, a 12V 180Ah group will be generated.

●When connected to a battery charger, the charging current is divided among all the batteries in the battery pack. E.g. a 15 amp charger connected to 3 batteries will provide up to 5 amps for each battery.

●When connecting 12 volt batteries in series, you increase the voltage of the battery pack while maintaining current. E.g. When 3x 12V 60Ah batteries are connected in series, a 36V 60Ah battery pack will be produced.

●When charging batteries in series, you must have a charger with the correct voltage corresponding to the number of batteries in the battery pack. E.g. If three 12-volt batteries are used in series, a 36volt charger must be used.

Important note: Avoid fast charging, as this will only charge the surface of the battery plates and may increase the chance of overheating, which may cause permanent damage to the battery.

Factors Affecting Battery Life

As batteries age, they will gradually lose capacity as their functions perform. Constant charging and discharging will eventually lead to malfunctions. Over time, components can corrode, electrical shorts can occur, and vibration can cause damage; ultimately leading to failure. Overcharging and insufficient battery will affect battery life.

Battery Inspection

Check if the electrolyte level under the top of the partition indicates overcharge or poor maintenance. The overcharge state may be caused by incorrect voltage settings, low voltage or aging caused by heat or internal defects.

●Is there electrolyte on the top of the battery? This may indicate overcharging or overfilling.

●Is the battery loose in the battery box? This may cause vibration failure.

●Are there any signs of damage or misuse of the battery? This can also cause malfunctions.

●Exhausted battery

A flat battery should be checked with a hydrometer. The specific gravity readings of all batteries are lower than 1.220 or lower, indicating that the batteries have been discharged and must be charged for further inspection and testing. The discharge status may be due to a problem with the electrical system (alternator belt slip, regulator or alternator failure, high resistance due to corrosion). Internal short circuits can also be attributed to manufacturing defects, short circuits during aging, or vibration damage.

Share now

Leave a Reply

Your email address will not be published.