How Do You Charge a Lead-acid Battery? 5 Methods

How Do You Charge a Lead-acid Battery? 5 Methods

To help you get the most out of your battery and extend its life, we’ve covered the best lead-acid battery charging techniques below.

  • Method 1: Constant Voltage Charging
  • Method 2: Constant Current
  • Method 3: Constant Current Constant Voltage (CC/CV)
  • Method 4: Taper Current
  • Method 5: Two-Step Constant Voltage

The most popular battery type, lead-acid batteries are 100% recyclable, require little maintenance, and might provide the best value for your money. Do you, therefore, understand how to charge a lead-acid battery? A continuous float voltage of typically 13.7 volts can be supplied to lead-acid batteries to safely charge them; this process is referred to as trickle charging.

These are the ideal procedures for charging a lead-acid battery.

Method 1: Constant Voltage Charging

Battery capacity and life are both maximized by using a constant voltage charging method. The discharged battery is charged using this method using a high charge current until the power supply reaches a specific voltage. Once the battery starts to charge and the pre-set voltage is reached, the current then decreases to the minimum value.

Your lead acid battery can remain charged until you are ready to use it, so there is no issue with that. The battery’s “float voltage” will remain constant as trickle charging continues to compensate for normal battery self-discharge.

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While the battery’s capacity is increased by 20% and the charging time is reduced, its efficiency is decreased by 10%. Despite this, constant voltage chargers enable the charging of cells with various capacities and levels of discharge. The cells are not harmed by the initial, high current flow, which lasts only briefly.

How Do You Charge a Lead-acid Battery? 5 Methods

Since the battery voltage eventually approaches the supply circuit voltage, the current flowing from the charge eventually drops to almost zero. It is crucial to set the charge voltage for the constant voltage method in accordance with the specified charge and temperature characteristics. You could overcharge or undercharge your battery if the incorrect voltage settings are used.

Method 2: Constant Current

Using the constant current charging technique is an additional efficient way to charge batteries. Lead-acid batteries are connected in groups by series connections in this charging technique. Through the use of a loading rheostat, each group charges from the primary direct current (DC) supply unit.

Each group’s charging rate is dependent on the charging circuit voltage, which should be higher than 2.7 Volts per cell. The circuit resistance is reduced as the battery charges to maintain a constant charging current. Battery voltage increases as a result.

Constant current charging can be accomplished in two steps to prevent gases or overheating. The battery receives a high initial charging current followed by a low final current.

Typically, this charging method’s current charge is about one-eight of its ampere rating. Any excessive voltage is absorbed back into the series resistance. For the batteries to fully charge, they must be connected in a way that the series resistance takes a limited amount of energy.

The lengthy battery charge time associated with constant current charging is a drawback. That implies that if the battery is overcharged, it may overheat and need to be replaced sooner rather than later. As a result, the battery needs to be removed, or else you should use the timer feature.

Method 3: Constant Current Constant Voltage (CC/CV)

Combining the aforementioned charging techniques is the constant current constant voltage charging technique. The battery charger in this case restricts the current to a pre-set level until the battery reaches the pre-set voltage level. The current then decreases as the battery is fully charged after that.

How Do You Charge a Lead-acid Battery? 5 Methods

The terminal voltage is raised during this charging process by a controlled current. Because of saturation, the current decreases once the upper charge voltage is reached. 12 to 16 hours are frequently needed to fully charge a battery. Large stationary lead-acid batteries, however, can require 36 to 48 hours to fully charge.

The charge time of lead acid batteries can be shortened to between 8 and 10 hours, though, by using higher charge currents in conjunction with multi-stage charging techniques. Lead acid battery systems are slower than other battery systems. That explains why charging takes a while.

Method 4: Taper Current

Taper current is a low-cost battery charging method because of its simplicity. However, the technique sacrifices the battery’s life cycle. Through transformers, a battery is charged by delivering a constant voltage or current.

Due to the way the transformer is built, the charge current that can be used to charge the battery can be restricted. As a result, the voltage applied to a battery drops when a taper charger is used, reducing the amount of current that is available. The demand for battery current decreases as battery voltage increases. In addition, as the battery charges to its full capacity, the charger’s applied voltage rises.

However, only SLA batteries—not VRLA batteries—can be charged using the taper current method, despite the latter’s effectiveness. That’s because it offers no voltage regulation, plus the applied current is variable when the battery reaches a full state of charge. This may result in early drying out, gassing, and battery capacity loss.

Method 5: Two-Step Constant Voltage

Utilizing two constant voltage devices constitutes the two-step constant voltage charging method. A higher voltage is applied to the battery at the start of the charge stage. The charger switches to a low-voltage setting when the battery voltage rises to a particular level.

Even after a prolonged charging period, this charging method enables quick charge cycles without overcharging the battery. Read More: Can Lead-acid Batteries Explode?

Tips for Charging Lead Acid Batteries

How Do You Charge a Lead-acid Battery? 5 Methods

Lead acid battery maintenance includes watering the batteries. To maximize run time and extend the battery’s life and the number of charge cycles, proper charging procedures are equally important. Here’s what you need to know:

  • Monitor the water levels: Never allow the water to get low enough to touch the plates.
  • Use the correct water type: Always use distilled or deionized water when topping off the fill well in your battery. Commonly found in tap water are minerals that can shorten the lifespan and/or cause damage to lead acid batteries.
  • Start the day fully charged: After use of at least 15 minutes per day, lead acid batteries need to be recharged. The device must be plugged in and charged until the charger indicates the batteries are FULLY charged before use the following day. The lead-acid batteries’ lifespan will be shortened if they are not given time to fully charge before their subsequent use.
  • One full charge per day: To extend the life of your battery, don’t fully charge lead acid batteries more than once every 24 hours. The batteries’ lifespan can be adversely affected by opportunity charging, which is when a device is plugged in for a brief period without fully charging. (Batteries from TPPL are not covered by this.)
  • Fully charge batteries before storing: Never store lead acid batteries that are fully discharged. Some modern machines put parasitic loads on the batteries. Even when the machine’s key is in the “OFF” position, there are electrical components drawing upon the battery’s energy.
  • Check fluid levels: The flooded (wet) lead-acid batteries need to be regularly watered. Weekly electrolyte level checks for the battery before charging, the electrolyte level should be just a little bit above the battery plates. If needed, add distilled water. The electrolyte will expand when charged and may overflow if you overfill the container. After charging, you can add distilled water up to a depth of about 3 mm (0.12 in) below the sight tubes.
  • Use the correct charger: The battery charger is set to charge the battery type supplied with your machine. To prevent battery damage, the charging profile of the charger needs to be changed if you decide to switch to a different battery type or capacity.
  • Seek out new charger technology: Older lead acid battery chargers require careful monitoring to avoid “over-charging.” On the other hand, modern charger technology enables the batteries and charger to be connected for a weekend or longer. As soon as the batteries reach their maximum charge, the charger will turn off. Some more modern chargers have the ability to keep track of the batteries and restart them as soon as a charge is needed.
  • Ideal charging conditions: Charge the batteries in a well-ventilated space that doesn’t get hotter than 80 degrees Fahrenheit to avoid the possibility of gas buildup. It is never a good idea to keep batteries or charge them in an area that is subject to freezing temperatures, intense heat, or other temperature extremes.
  • Follow your operator manual: These battery charging recommendations are generally applicable to all lead acid battery types. To learn about the precise charging procedures for your Tennant cleaning machine, read the operator manual.

To keep your lead acid batteries last long, here is what you need to know:

Conclusion: Charge a Lead Acid Battery Properly

The two most common ways to charge lead-acid batteries are probably constant voltage and constant current. The other charging techniques, on the other hand, are just as efficient.

  • Method 1: Constant Voltage Charging
  • Method 2: Constant Current
  • Method 3: Constant Current Constant Voltage (CC/CV)
  • Method 4: Taper Current
  • Method 5: Two-Step Constant Voltage

The right charging technique aids in maximizing battery capacity and enhancing performance and lifespan. However, take into account the intended use of your lead acid battery (float or cyclic service), economic consideration, and recharge time before choosing any charging technique.

Avoid letting your lead-acid batteries discharge too far, charge them with a three-stage charger, and keep them fully charged in between uses if you want to take good care of them.


How Do You Charge a 12V Lead Acid Battery at Home?

To charge a 12-volt lead acid battery (six cells) to a voltage limit of 2.40V, set the voltage to 14.40V (6 x 2.40). Depending on the battery size, choose the charge current. Between 10% and 30% of the rated capacity applies to lead acid. A 10Ah battery that is 30% charged takes about 3A to complete the cycle.

How Do You Charge a Lead Acid Battery for the First Time?

During initial filling & charging, the batteries should be charged at the Constant Current rate as specified in the catalog, up to 2.75 volts per cell. Even after the battery reaches 2.75 volts per cell, charging should continue until neither the voltage nor the sp increase.

How Long Will a Lead Acid Battery Last If Not Used?

Generally, a battery can last 6 months to 1 year on a shelf with mild temperatures.

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