current into sla battery at fixed voltage

Thread Starter


Joined Oct 13, 2018
I have a 12 volt 7.2 Ah sla battery. Its cycle voltage is given as 14.4-15.0v. I intend to charge it at 14.4 volts.
At this voltage and assuming the initial voltage of the battery is 12v what would be the current flowing into the battery? I don't have the equipment to test this. There will be no resistance between the charger and the battery. The only resistance is the internal resistance of the battery.
Is there an online calculator that gives current into sla batteries at different charging voltages?


Joined Aug 27, 2009
The cycle voltage is the absorption voltage. That's typically the second stage of the charging process. The first stage BULK is current limited to prevent overheating the SLA cells (that can lead to permanent damage from gassing) when the differential between cell and charging voltage is too high. The current limiting might be from the current limit of the charging circuit transformer in a simple circuit with just a rectifier and transformer. With a high current charging source it's highly recommenced to have a current limiter to the battery until the voltage hits and maintains the absorption voltage limit. After that the current to the battery will taper off as it is fully charged.

For a 7.2 Ah battery I would be careful not to push the current more than 2 or 3 amps at the max as the typical recommendation for charge current is 25% of battery capacity in amp hours. As for a online calculator, there are IMO too many manufacturing variables to give exact numbers.