An Automatic Sealed-Lead-Acid Battery Charger - as described in the May 2001 QST, page 43.
Printed Circuit Boards for this project are now supplied by FAR Circuits.
Note: If an SLA battery is left sitting around in a discharged condition it can go into a "high impedance" condition where it will no longer accept a charge. As soon as the charger applies voltage, the battery voltage immediatly goes to 14.5 volts causing the charger to cut off for 4-seconds. This will be indicated by a RED LED which pulses a quick GREEN every 4-seconds. Since the pulses are a very short duration the battery may take a long time (if ever) to recover from this condition. Success in recovering the battery has been had by placing the battery directly across a 13.8 volt power supply for a period of time while monitoring the charging current. Once the battery starts accepting a charge as indicated by an increased current, it can be placed back on the SLA Charger to complete the charge.
Construction Details
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