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Auxiliary Battery Systems

According to a leading manufacturer of multiple battery control systems, premature battery failure is on the increase, "BUT DON’T BLAME THE BATTERY", says Rod Street.

With over 30 years’ experience in the industry, Rod Street of Rotronics claims that the major cause of auxiliary battery failure is excessive sulphation.

"Sulphation builds up on the battery plates during the discharge cycle of the auxiliary battery and is broken down by the alternator applied voltage and current, when the battery is recharged. Continuous discharging of the auxiliary battery below 11 volts may shorten the life of the auxiliary battery by as much as 20%."

"Auxiliary accessory equipment, ie fridge etc are not to discharge the auxiliary battery below 11 volts," he added.

Not only is the battery life affected, but the time required by the alternator to recharge the auxiliary battery is longer and in some situations with late model 4WDs (direct sense alternator regulator charge systems), may not recharge at all, as the alternator regulator will sense the over discharged auxiliary battery as a fully recharged auxiliary battery.

"Winches can cause problems too"

Rod went on to say that the alternators on late model 4x4s are not designed to support the high winch currents and may cause excessive over-heating of the alternator. Damage caused by alternator overloads due to accessory equipment is not covered by the vehicle warranty.

If the winch is connected to the main battery and the winch is turned off, high voltage spikes are discharged throughout the vehicle’s electrical circuits and could damage sensitive computer circuits in the vehicle.

Rotronics recommend fitting an auxiliary battery, to connect and operate the winch. Also install a Rotronics charge / isolator to charge the auxiliary batter. The Rotronics charge / isolator design includes Assisted Alternator Protection, to isolate the auxiliary battery and the winch from the alternator and the vehicle electrical circuits, when the winch is operated. The alternator will be protected from the winch current overloads.

"Solenoids may be cheap, but they do not provide assisted alternator protection and they in themselves, unless suppressed, introduce high voltage spikes when turned off."

Solenoids also introduced voltage drop reducing the ability of the auxiliary battery to fully recharge.

The Rotronics charge / isolator design ensures the high voltage spikes from the winch are reduced to a safe level and isolated from the vehicle electrical circuits, before the alternator is reconnected to the auxiliary battery for recharging.

Rotronics Charge / Isolator

Rotronics "closed loop" charge / isolator / monitor systems incorporate a low voltage monitor and cut-out to provide protection of the auxiliary battery, and to ensure the auxiliary battery is recharged and discharged, without introducing excessive sulphation. Rotronics not only provides a three year guarantee, but also after sales technical information on all Rotronics products and vehicle electrical system operation. For additional technical information phone 1800 644 620.

Article reprinted from 4WD PARTS & ACCESSORY NEWS.

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