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Battery Questions and Answers

Written by William C. Shumay Jr. for Arcon Equipment Inc., published in the Material Handling Wholesaler
copyright © William C. Shumay Jr.
For more articles, please visit http://www.arconequipment.com

Should I make sure to completely discharge my battery prior to recharge?

Not necessarily. Lead acid electric vehicle batteries (known as "deep cycle types") are immune to the "memory effect" seen with nickel cadmium rechargeable batteries used in familiar appliances. Nickel cadmium cells benefit from frequent full discharge (to the point of "0" volts), but the same is not true of lead acid. A "full discharge" of an industrial lift truck battery is actually only 80% of its rated capacity (measured in Ampere Hours, or A.H.), and the battery is charged for a full 8 hours after it has reached this 80% discharge point. Experience has shown this approach to be the best for long battery life. Truck-mounted battery discharge indicators and gauges are calibrated to indicate how a "low battery" condition when the 80% point is reached.

Batteries that are far less than 80% discharged may be recharged without affecting battery behavior, but it is important to keep in mind that the charger causes more wear and tear on the battery than does the truck, and every visit to the charger uses one more cycle of the battery’s expected cycle life. Batteries that regularly receive charge after only partial discharge benefit from a charger with a microprocessor charger control, one that automatically terminates the charge after only a few minutes if it detects a fully charged battery.

Why do some batteries use blue connectors, others use red, yellow or grey?

The most popular battery cable-end connectors in use today are available with plastic housings of a variety of colors. These connectors are "keyed" to mate only with another connector of the same color. This can be used to advantage in plants that have a variety of battery sizes and voltages that must be protected against accidental connection to the wrong battery charger. By making sure that each battery type and charger rating are equipped with their own color, expensive charging mistakes can be avoided. During maintenance checks, do make sure to check that the key tabs in the connector housings have not been filed down to allow cross connection of connector types.

Battery and charger suppliers, unless told otherwise, usually ship their products with the standard grey connector housing.

How hot should my battery cables get in use?

Not hot at all. Cables heat if a poor connection is present, if the cable is undersized for the current load, or if the copper conductor has become corroded by acid seeping through damaged insulation. No damage or heating of battery and charger cables should be tolerated because of the potential for high current arcing and ignition of hydrogen gas vented by the battery when charging. Most battery connectors rely on spring force to hold contact tips firmly together. If cables and tips get hot, these springs will weaken and cause further heating.

Any battery or charger inspection should include a look at cables, tips, and connector housings to detect any signs of heating. Remember, large electric lift truck batteries may charge at rates of hundreds of amps for hours, and this requires good maintenance of all connections.

Exercise extreme caution when changing battery connectors or removing the plastic connector housing from battery cables. If battery positive and negative cable ends, or live connector tips, contact each other, a violent arcing will occur that can literally vaporize the parts that touch. Because of this danger, do this procedure with gloved hands only, and make certain you take care not to work on the connector over top of a battery that may be actively venting hydrogen.

Why is it difficult to find an inexpensive 36-volt battery charger that plugs into a 110 volt outlet?

It’s not, if all you want to charge are golf cart batteries. If you want to charge your lift truck from a 110-volt outlet, you are usually limited to chargers designed to charge batteries sized less than 500A.H., and this is with a full 16-hr. charge period. In practical terms, the 110-volt wall plug rating limits the amount of charging current at 36-volts DC to less than 40 amps maximum to the battery.

Popular, inexpensive, ferro-resonant design chargers, available with a 36-volt DC start rate of approximately 30 amps, can only charge a 330 A.H. battery in 16 hrs. This is because of the characteristic fall-off of current as the battery voltage rises during charge. Other considerations enter here also: the finish rate (during the last 3 hrs. of the charge cycle) should be approximately 4 amps for every 100 A.H. of battery capacity. A small charger, such as that described here, cannot provide the recommended finish rate for a large battery.

A carefully engineered SCR-type charger can overcome some of the above limitations, but you do have to pay for the sophistication.

For more information, contact Arcon Equipment Inc. (440) 232-1422.

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