The charge time is 12–16 hours and up to 36–48 hours for large stationary batteries. With higher charge currents and multi-stage charge methods, the charge time can be reduced to 8–10 hours; however, without full topping charge. Lead acid is sluggish and cannot be charged as quickly as other battery systems. (See BU-202: New Lead Acid Systems)
Test show that a heathy lead acid battery can be charged at up to 1.5C as long as the current is moderated towards a full charge when the battery reaches about 2.3V/cell (14.0V with 6 cells). Charge acceptance is highest when SoC is low and diminishes as the battery fills.
This mode works well for installations that do not draw a load when on standby. Lead acid batteries must always be stored in a charged state. A topping charge should be applied every 6 months to prevent the voltage from dropping below 2.05V/cell and causing the battery to sulfate. With AGM, these requirements can be relaxed.
Lead acid batteries are actually the most complicated of all the common rechargeable battery types. They have lots of little quirks you have to pay attention to if you want to get the best possible life out of them. However, they do reasonably well in float service and are much cheaper than any lithium or nickel chemistry battery.
Apply a saturated charge to prevent sulfation taking place. With this type of battery, you can keep the battery on charge as long as you have the correct float voltage. For larger batteries, a full charge can take up to 14 or 16 hours and your batteries should not be charged using fast charging methods if possible.
We’ve put together a list of all the dos and don’ts to bear in mind when charging and using lead-acid batteries. Apply a saturated charge to prevent sulfation taking place. With this type of battery, you can keep the battery on charge as long as you have the correct float voltage.