Amateur Radio WB3GCK The Care and Feeding
of Gel Cell Batteries

Craig LaBarge, WB3GCK

[The information provided here was originally compiled for use by the Chester County (PA) ARES/RACES organization. -- Craig]

Introduction

Gel cell batteries are commonly used in amateur radio emergency communications. Being maintenance-free and spill-proof, they are ideal for portable operation. Properly cared for, a gel cell battery can provide many years of reliable service. Failure to use a charging method specifically suited to a gel cell battery's internal chemistry will dramatically shorten its useful life.

This article will provide some general guidelines and precautions that can be applied to any gel cell. You should, however, check with your battery's manufacturer for information on charging. If the manufacturer has specific recommendations, you should follow them.

Charging Basics

There are several methods for charging gel cell batteries, however, constant voltage charging is the best way. For this type of charging, a fixed, regulated voltage source is used to charge the battery. Special attention must be paid to the exact charging voltage and the initial charging current.

There are two modes for constant voltage charging: fast charging and float charging. Smart chargers, which are available commercially, automatically switch between these two modes. In addition, the most sophisticated chargers will monitor the ambient temperature and adjust the charging parameters accordingly.

Fast Charging (aka Cyclic Charging)

In this mode, the battery is charged with a fixed charging voltage until the terminal voltage reaches 2.40 to 2.45 volts per cell (14.4 to 14.7 volts for a 12-volt battery) at 20 C. The battery is then held at this voltage until the charging current drops to a value of 0.01 x C amps (where C is the battery's amp-hour rating). At this point, the battery is fully charged and you must either stop the charging or switch to the float-charging mode. Continual charging in the fast charge mode will overheat the battery and damage it. Do not let the battery voltage exceed 2.45 volts per cell or allow the charge current to exceed 0.20 x C amps.

Float Charging (aka Standby Service)

In this mode, the battery is connected to a constant voltage source of 2.25 to 2.30 volts per cell (13.5 to 13.8 volts for a 12-volt battery) at 20 C. Provided that the charging source is regulated at the proper float voltage, the battery will establish its own current level and will be maintained in a fully charged condition. Gel cell batteries can be left in the float charge mode for extended periods of time without damage. This mode is often used to maintain gel cell batteries used in backup power applications.

Precautions

 

References

Sealed Lead-Acid Batteries - Technical Handbook. Power-Sonic Corporation, San Diego, CA. (Available for download at www.power-sonic.com)

Sealed Lead-Acid Battery Chargers (Spec Sheet). Power-Sonic Corporation, San Diego, CA. (Available for download at www.power-sonic.com) Dated January 2000.

The ARRL Handbook for Radio Amateurs (1995). The American Radio Relay League, Newington, CT. Chapter 11, pp 11.20-11.23.

 

 

Disclaimer: This material is provided for general information only. Always follow the manufacturer's guidelines for the proper use, charging, handling, and safety of your gel cell battery.


2001 Craig A. LaBarge

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