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Most of the news that's fit to print! The Kussmaul Times •• • • • • • • • • • • • • • • • • •• • • • • • • • • • • •• • • • • • • • Weather: Sunny skies ahead. • • • SPECIAL CUSTOMER EDITION • ••••••••••••••••••••••••••••••••••••••••• WEST SAYVILLE, NEW YORK EDITION 2 2009 DANGERS OF 3 STEP CHARGING Batteries are a storage medium for energy. When they are charged, energy is stored for use at some future time. A battery charger converts alternating current to direct current and supplies it to the battery. The charger is preferably automatic, controlling the current to the battery to recharge the battery as rapidly as possible and then stop charging when the battery is fully charged. In order to quickly charge a battery a method known as "3-step charging" has.been developed. The first step, "Bulk Charge", supplies a constant current until the battery terminal voltage rises to 14.5 to 14.7 volts. At this pOint the charger output voltage is reduced to the "Absorption" voltage, 13.7 to 13.8 volts and charging continues. As the battery becomes charged it accepts less current. When near full charge, at a current from 1 to 3 amperes the charger output is reduced to 13.25 volts. This is the 3"' step known as the '110at" step. Three step charging is preferred for rapid recharging in applications such as golf carts, electric vehicles, fork lifts or any application that has no parasitic loads. Parasitic loads are those accessories such as radios, medical equipment, air compressors, lighting, computers or any devices in a vehicle which require constant electrical power. When a battery is being charged these devices are a load on the charger and will interfere with the 3-step charging process. THIS IS THE DANGER OF 3-STEP CHARGING It is often possible that the parasitic loads will prevent the charger from completing the "bulk mode" step or returning to "bulk mode" when accessories are turned "ON". Thus the charger would continuously supply 14.0 to 14.6 volts to the battery for an extended period of time . This results in overcharging the battery, boiling and out gassing. A preferred method of charging batteries on emergency vehicles is to use a "float charger". This type of charger has a controlled, constant output voltage of 13.25 volts and is current limited to the rated charger output. The batteries are charged when their state of charge is low. Charging continues until the battery voltage rises to the float voltage level. The parasitic loads receive the same voltage and do not affect battery charging. Kussmaul Electronics Co. , Inc. manufactures both 3-step and float chargers. For installation in emergency vehicles only the float chargers are recommended. KUSSMAUL FLOAT CHARGER 091-53-12 KUSSMAUL 3 STEP CHARGER 091-128-12E-20 Authored by Ernesf A. Kussmaul the /ounder a/Kussmaul Electronics Compa,,}', Inc. , 41 years ago in /96 7. He is a degreed engineer, pilot and a licensed PE who has writ/en numerous artides and technical papers in his fong career, He continually educates the emergency vehicle markel nof only with articles bul also as a much sought afier speaker and instructor al pre academie.~ throughout the Country. KUSSMAUL ELECTRONICS CO., INC. WEST SAVVILLE, N.V. 1-800-346·0857 POOR CONNECTIONS CAUSE HIGH HEAT Heat in electrical circuits is caused by current flow through a resistance. The greater the current the greater the heat produced. Also, the higher the resistance the higher the heat. This characteristic is used in electrical heaters, coffee pots, space heaters and the like. Sometimes, however, this heating is not desirable. In wires, switches, and connections, heating is a sign of trouble . Often we find that battery chargers are returned for repair because they no longer charge the battery due to a "burned out" terminal strip. When installed , the screws of the terminal strip must be tight. The wire must be clean and the insulation stripped to the proper length . Anything on the wire at the point where it enters the terminal strip can create a poor connection. The poor connection is a high resistance to the current and the resistance creates heat. Poor connections ca n be a particularly insidious problem because they may not show up immediately. The heating over time creates corrosion of the copper wire. Corrosion of the wire and the terminal increase the electrical resistance . Higher resistance causes more corrosion, more heating, more corrosion and more heating. Eventually the terminal strip insulating material chars and melts and the individual terminal becomes so corroded as to be a virtual insulator. At this point the charger output current drops to zero. The photos show examples of overheating. How long does it take for this to happen? Sometimes it can occur in 2 weeks while at other times it may take 6 months. It all depends on how hard the . charger is working. A vehicle with low utilization that requires maximum charger output infrequently will not exhibit the overheating problem as quickly as one with large batteries that must be frequently recharged. To prevent the overheating problem it is absolutely imperative that the wires are cleanly stripped and inserted the full length of the terminal. Then the wire clamp screw must be securely tightened. Periodi c inspection to ascertain that the screw is tight is also helpful. At the first sign of heating the wire should be removed and cleaned and if necessary the terminal strip replaced. A little preventative maintenance will go far in ensuring continued charger operation.