Charger settings for AGM batteries

Posted by Peter Kennedy on 10/19/2017 to Battery Chargers

AGM batteries are expensive so you want to make sure they get charged in the optimum way. We looked up the specs from a major battery manufacturer, Lifeline, to get their recommendations.

Lifeline have a Detailed Technical Manual for their batteries and chapter 6 covers charging. The charge voltage is based on battery temperature but it uses 25 Deg C, (77 Deg F) as the default temperature and then has compensation tables for higher or lower temperatures.

Lifeline recommend a Bulk and Absorption voltage of 14.3 Volts at standard temperature. For a float voltage they recommend 13.3 Volts at standard temperature. Here is the table showing how these numbers change with temperature:

How does this compare with other battery manufacturers?

All AGM batteries are going to have roughly the same charging parameters but there will undoubtedly be minor differences between manufacturers. I chose Lifeline for the example above because they have a particularly well detailed battery technical manual.

Victron AGM: Bulk and Absorption 14.2 - 14.6 volts (standard service) or 14.6 - 14.9 volts for fast recharge

Float 13.5 - 13.8 volts

Storage 13.2 - 13.5 volts

Trojan AGM: Bulk 14.4 volts

Absorption 14.1 - 14.7 volts

Finish 14.7 volts

Float 13.5 volts

So you see how everyone has some minor variations as to what they recommend

How does this compare to Wet Cell Batteries

Trojan Batteries have a good Users Guide that includes both wet cell and AGM batteries. The recommendations for deep cycle flooded wet cell Trojans are as follows:

Bulk 14.82 volts

Absorption 14.1-14.7 volts

Finish 16.2 volts

Equalize 16.2 volts

Float 13.5 volts

1 Comments

KEN SHIVELY

Date 5/13/2019

My Volvo engine in my boat says do not use deep cycle batteries on EFI engines. I like AGM batteries and was advised AGM batteries are only deep cycle if plates are in a specific pattern, however it seems most that i see on the web if AGM are deep cycle. Any advice here??

Peter Kennedy

AGM is a chemistry type and doesnt specify whether a battery is deep cycle or not. It is the depth and thickness of the plates that determine whether a battery is deep cycle. Deep cycle batteries will have less surface area on the plates as a proportion of their overall mass. That means less cranking amps than a similarly sized starting battery, and longer charging times than a similar sized starting battery.

Charger Settings for AGM Batteries

1 Comments

KEN SHIVELY

Peter Kennedy

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