[ Home ] [ Feedback ] [ Contents ] [ Search ]
Battery Comparison       www.trafficUPS.com
[ Battery Calculator ] [ Battery Comparison ]

From time to time, we are asked about  the differences between the Valve Regulated Absorbed Glass Mat (VR-AGM or AGM) sealed lead acid battery and Gelled   battery.  In the future, we will expand this section with more detail information and test results.  Simply speaking, both batteries are sealed and use regulated valves (vents) to vent any excess gas.   The main difference is how the electrolyte is suspended within the battery.  The AGM battery uses a glass mat between the plates that absorbs acid somewhat like a sponge.  The gelled battery uses a technique that mixes the acid with a silica material to form a gell. Signal Sense TRAFFIC UPS^TM can be used with either battery design.

Based on our experience, Gelled sealed batteries generally perform better at lower temperatures.  However, Gelled batteries do not have the ability to perform as well at higher discharge rates such as 15 minute rates typically used in a large UPS for a large computer room. 

Another issue we find is the amount of electrolyte within the battery jar.  AGM batteries have very little electrolyte stored within the mat (typically referred to as starved electrolyte batteries).  Towards the end of discharge, you will find the battery voltage collapsing at a faster rate as compared to Gelled batteries.  This is due to the loss of acid in the electrolyte.  Under normal conditions, this would note be a problem.  However, with elevated operating temperatures and age, the AGM battery will tend to dry out and loose capacity.

In a real application were the TRAFFIC UPS were to totally be discharged, the AGM battery would have very little acid.  Should power not be returned for an extended time then the plates could become sulfated or possibly damaged.

Below, you find a comparison between a AGM battery (PVX-840T) and a Gelled battery (SG-70).  Each battery was discharged at a one hour rate at 65 degrees and then at 0 degrees.  You will note that the AGM battery voltage drops faster at the end of discharge and at lower temperatures does not perform as well as the Gelled battery.

In designing for an application, we consider more things then just the capacity/time.  We also review the customer's preference and their own experience.

Send mail to support@trafficUPS.com with questions or comments about this web site.