Is it OK to replace an AGM Battery with a Lead Acid Battery?

An AGM battery is also a lead acid battery. The only difference is that an AGM battery is a maintenance free lead acid battery with starved electrolyte.

AGM batteries are more widely used nowadays as stationary batteries for standby applications.

All stationary batteries are connected to a charger which gives a trickle current to maintain the batteries within a specified range of float voltage – as and when the batteries are not supplying power to the load. This trickle current ensures that all self discharge losses are compensated for – thereby guaranteeing that the battery is in a state of readiness to deliver the power it is expected to as and when needed in case of an emergency.

This is common for AGM type as well as flooded electrolyte batteries.

However what varies in the charger used for AGM batteries and the conventional type flooded electrolyte batteries is very important as well as critical from the battery life point of view.

The change is in the float voltage setting in the charger for both these types of batteries. There is another significant change which pertains to boost voltage or top of charge voltage.

All AGM batteries need a float voltage setting of the charger to be in the range of 2.20 to 2.25 volts per cell. The maximum voltage setting of the charger meant for AGM batteries is limited to 2.25 volts per cell.

All flooded electrolyte batteries need a float voltage setting of the charger to be in the range of 2.16 to 2.20 volts per cell. The maximum voltage setting of the charger meant for flooded electrolyte batteries is set to be in a broad range of 2.55 volts to 2.75 volts per cell. This is known as boost charge voltage.

Hence it is absolutely necessary to change the charger setting as and when the type of battery connected to the load and charger is changed from AGM type to flooded electrolyte type. The charger setting has to suit the battery.

What happens if AGM battery is replaced at site with a flooded electrolyte battery without taking due care of above mentioned charger setting is another topic altogether –  which merits a long discussion.

In case the physical limitations of size or the environmental demands of safety do not allow such a replacement of AGM batteries with flooded electrolyte batteries then adjusting charger to suit batteries does not serve your purpose.

Flooded electrolyte batteries cannot be used where acid fumes generated during boost charge & vented out through vent holes are not permitted.

Flooded electrolyte batteries are to be kept upright to avoid acid electrolyte spillage unlike the AGM batteries which can be kept in any orientation.

Flooded electrolyte batteries of capacity equivalent to AGM batteries are more bulky compared to AGM batteries and occupy more space.

Based on the above it is possible to come to a conclusion as to whether an AGM battery can be replaced with flooded electrolyte battery or not.

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Ramesh Natarajan Kailad


UNIK Techno Systems Pvt Ltd

Pune India

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