The Forklift Lead-Acid Battery takes a lot of abuse during heavy loading and severe discharging. In order to maintain long life and peak performance there are a few general preventative measures to be taken. Keeping it clean and free from corrosion goes without saying. Frequent checks for proper electrolyte level is a must. Preventing the battery from being discharged below its working level not only protects the battery but also the major current carrying components on the lift truck. A battery controller is the cheapest insurance any forklift owner/operator can purchase to prevent destructive deep discharging of the battery.
Battery controllers come in a variety of shapes, sizes and features. They are commonly referred to as Battery Discharge Indicators (BDI), Battery Protection Indicators (BPI) or simply Battery Gauges. All units give some form of warning or visual indication to allow the operator to monitor battery charge status. The simplest controllers use a lamp mounted on the dash which will begin to flash, warning the operator to return the vehicle for charging. If the vehicle continues to operate at this low voltage the lamp will come on steady to warn that the battery could be permanently damaged by further use. More expensive devices come complete with a "Fuel" Gauge and a lamp, typically an LED, built into the face of the gauge. The added gauge feature provides the operator with continuous battery status, from "Full" to "Empty", much like an automotive gas gauge.
Adjustable features range from none at all to full adjustment for "Discharge" and "Reset" levels. The "Discharge" level is the volts/cell setting at which the gauge and/or the lamp indicators will register a low battery condition. The "Rest" level adjustment sets the volts/cell level required for the battery controller to "Reset" or accept the battery being applied. As an example if a "Reset" level is set at 2.07 volts/cell and the battery is charged only to 2 volts/cell the battery controller will not reset and will indicate a discharged battery level. This particular feature becomes a problem if the battery is well into its life cycle, very old, and will not charge to full capacity. Also, if the "Reset" adjustment is set incorrectly problems will arise with the controller not resetting. The newer units overcome this weakness by providing "Opportunity Charging". This feature allows the battery to be charged slightly, with results of the charging showing up on the gauge as soon as the battery is connected.
At first thought you may wonder why it is so important for the battery controller to "Reset". Most controllers incorporate a "Disable" or "Interrupt" feature, which as its name implies will disable a selected vehicle circuit by de-energizing the contactor coil circuit. The hydraulic pump circuit is the most common vehicle operation to disable. Some vehicle manufacturers may also disable the Forward or Reverse directional circuits. In any case the idea is to provide a definitive measure to insure the operator will return the vehicle for charging before any significant damage to the battery is done.
Voltage selection is yet another feature to consider when selecting a battery controller. The best controllers come in multi-voltage packages, meaning they may be adjusted or used on vehicles with 12 to 72 volt batteries. Other units may come with a limited voltage range for the most popular vehicles such as 36 and 48 volts. Still others may be specifically manufactured for a single voltage.
Up until this point we have been discussing add-ons or external controllers, some complete vehicle systems employ battery controllers from within the main control card itself. Systems like the newer General Electric controls use an external dash display to show actual battery percentage, as monitored via the main control card. So the electronic part of the controller comes complete with the system and the vehicle manufacturer can use this information and send it to a gauge if he wishes to incorporate this feature.
There are many different types of battery controllers with features to please just about any situation. Next time we'll look at the two most popular devices, the Curtis 933 and the Flight Systems Model 204. Hookups, troubleshooting and how they "Disable" circuits will all be explained.