How Long to Charge the Lead Acid Battery? Charging Time of Lead Acid Batteries

How Long to Charge the Lead Acid Battery? Charging Time of Lead Acid Batteries

This is a quick guide to lead acid battery charging times. You will also hear from us regarding some charging instructions for lead-acid batteries.

The lead acid battery is charged using the CCCV (constant current, constant voltage) method. Up until the upper charge voltage limit is reached, a regulated current increases the terminal voltage. At that point, however, the current decreases due to saturation. For large stationary batteries, the charge time ranges from 12 to 16 hours to up to 36 to 48 hours. The charge time can be decreased to eight to ten hours with higher charge currents and multi-stage charging techniques.

Read this blog and you can learn more about the charging time of lead-acid batteries.

How Long to Charge the Lead Acid Battery?

For a variety of uses, there are numerous charger variations available. When choosing a charger, speed is always a plus, but it’s important to keep in mind that every charger type has different advantages that should be considered.

There are times when speed must be sacrificed in order to achieve other goals. Before making a purchase, speak with a charger supplier to learn their thoughts on which charger will work best for your circumstances.

Float Charger

A float charger is the most basic and affordable sealed lead acid battery charger. Nearly indefinitely can be spent connecting a float charger to an SLA battery across the output. A float charger uses an output voltage of roughly 2.25V per battery cell and comes with a typical DC power supply.

How Long to Charge the Lead Acid Battery? Charging Time of Lead Acid Batteries

A 6-volt battery having 3 cells would amount to 6.75V of output power whereas a 12-volt battery having 6 cells would amount to 13.5V of output power.

An average sealed lead acid battery float charger charge takes 16 hours. Your SLA battery will be able to operate at its maximum efficiency with the help of the float charger. If you can live with a slower charge time, this is the least expensive alternative.

Two Stage Charger

To achieve a faster recharging time, a lot of people use a more expensive two-stage charger. A bulk charge phase with a constant current initialization and a top-up phase with a constant voltage are combined in a two-stage charger.

This charger will automatically monitor the charging process switching between the phases and shutting down the charge. It will take this charger 5–6 hours to fully charge.

Three Stage Charger

There are also three-stage sealed lead acid battery chargers. Essentially, the three-stage SLA charger adds a second step for the charger to monitor and finish. The charger enters a low float charge mode and keeps the battery in a fully charged state rather than shutting down after the second phase.

Read More:

Simple Guidelines for Charging Lead Acid Batteries

How to Charge a Lead Acid Battery Correctly - News about Energy Storage,  Batteries, Climate Change and the Environment
  • Charge in a space that has good ventilation. Explosive hydrogen gas is produced while charging.
  • Choose the proper charge cycle for flooded, gel, and AGM batteries. Verify the manufacturer’s recommendations for voltage thresholds in the specifications.
  • For the purpose of avoiding sulfation, recharge lead acid batteries after every use. Don’t store with a low charge.
  • The plates of flooded batteries must always be fully submerged in electrolytes. Fill the battery with distilled or de-ionized water to cover the plates if low. In some areas, tap water might be suitable. Do not ever add electrolytes.
  • Fill the water level to the designated level after charging. When the battery is empty, overfilling can result in acid spillage.
  • The formation of gas bubbles in a flooded lead acid indicates that the battery is reaching the full state of charge (hydrogen on the negative plate and oxygen on the positive plate).
  • Reduce float charge if the ambient temperature is higher than 29°C (85°F).
  • Lead acid shouldn’t be allowed to freeze. A battery that isn’t fully charged will freeze before one that is. A frozen battery should never be charged.
  • Never charge your device at temperatures higher than 49°C (120°F).

Read More: Lead Acid Battery Care: How to Maintain Lead Acid Battery?


Watering is the most crucial maintenance procedure for flooded lead acid batteries, but it is far too frequently skipped. Use, charge method, and operating temperature all influence how frequently to water. Additionally, excessive charging results in water usage.

Every few weeks, a fresh battery should be inspected to determine how often it needs to be watered. The top of the plates is never exposed thanks to this. A naked plate will experience irreparable oxidation damage, which will result in decreased capacity and performance.

Fill the lead acid battery with distilled or deionized water right away if the electrolyte level is low. In some places, drinking tap water is acceptable. Filling to the proper level before charging could result in an overflow during charging, so avoid doing so. Always top off to the desired level after charging. Never add electrolytes because doing so would alter the specific gravity and encourage corrosion. Low electrolyte levels are removed by watering systems, which automatically add the proper amount of water.

Conclusion: How Long to Charge the Lead Acid Battery?

The battery charges to 70 percent during the constant-current charge in 5–8 hours; the final 30 percent is filled during the slower topping charge, which takes an additional 7–10 hours.

Please select the proper charge program for flooded, gel, and AGM batteries when charging your lead acid battery, and check the manufacturer’s specifications for suggested voltage thresholds.


How Do I Know When My Lead Acid Battery is Fully Charged?

Use a battery hydrometer to read the relative density (specific gravity) of sulfuric acid in the electrolyte and check how charged the battery is. A fully charged battery has a density of about 1.28, while a discharged battery has one of 1.15.

Can You Leave a Lead Acid Battery Charging Overnight?

Even though there is no risk of overcharging with the use of a high-quality charger, the battery should not remain connected to the charger for more than 24 hours.

How Long Does It Take to Charge a 100Ah Lead Acid Battery?

Thus to fully recharge a 12V 100Ah battery using a 12V/10A charger will take a nominal 10 hours if the battery is fully discharged.

What Happens If You Charge a Lead Acid Battery Too Long?

At high rates of overcharge, a battery will progressively heat up. As it heats up more, it will take in more current, increasing the temperature. A battery can be destroyed by this phenomenon, known as thermal runaway, in as little as a few hours.

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