The critical part of a battery’s life cycle is the time it spends on charge. During charging, a battery is exposed to the most vigorous workout that the active material in the plates receive, and it is during this time that the battery experiences the most wear.
Abnormal charging conditions expose the battery to accelerated wear, and may bring about premature battery failure. But what is the normal charge cycle, and how does one ensure that the battery is consistently charged properly?
The norm is a full-shift (8-hr) charge for an 80% discharged battery, with an 11–hr. charge (equalizing charge) once every five to seven charging cycles (once a week for batteries that receive a charge every day).
Anytime that a battery doesn’t seem to last its full work shift, the temptation is to charge at every available opportunity, even though these may be short breaks or lunch periods. Short charging sessions are not recommended as a daily practice. Batteries require a full shift of charging to ensure that all cells equalize. Through short charge cycles, these cells will tend to be over–discharged in use, will not deliver their full capacity, and may fail prematurely.
If a lift truck battery does not make it through a full shift without a “boost” charge, take the following steps to determine the cause:
- Make certain that the battery always starts the day with a full shift of charging “under its belt”. (Not necessary for those who operate their truck for just an hour or two, and can get away with charging much less frequently.)
- Take a hydrometer reading of all cells after an equalizing charge. Minimum specific gravity readings of 1.275 (higher for some batteries) for all cells should be seen. Variation among cells by 0.025 or more is grounds for battery service.
- Make certain that the battery charger is properly adjusted and that its output approximates the following: A starting current of l8-20 amps for each 100 ampere hour of battery capacity, and a rate of 4 amps/100 A.H. for the last 3 hours of charge cycle.
- Determine, if possible, the age of the battery. Rarely can a battery make it to ten years old with much capacity left. As a rule, after a couple of years a battery gradually loses running capacity with advancing age. Is your battery too old to do the job? Keep track and budget ahead to replace aging batteries
If the above conditions are satisfactorily met, and the battery still does not provide uninterrupted service for your needs, consider the following alternatives:
- Add a new or good used battery to your fleet, and change batteries when necessary. A fully charged battery on the rack is excellent insurance against production delays.
- Trade up to a higher capacity battery. Today’s batteries may offer longer running time in the same physical size case as that of your old battery. Also: If your truck compartment can take a larger battery, get the biggest that fits. You might add an hour or two more running time.
Whatever battery upgrading you do, consider upgrading the chargers from mechanical timers to full auto control. Not only will you get automatic start and stop features, but if you select an auto control with advanced algorithmic programming, you will find that older batteries as well as new always receive a full charge without the danger of overheating. Virtually any timer-controlled charger can be supplied with an aftermarket microprocessor-equipped auto control. They are easy to install. Do find a control that uses advanced algorithms to monitor state of charge rather than simple dv/dt measurement.
Large material handling operations have found the following tactics very cost-effective in the long run:
- A uniform battery monitoring/maintenance plan. This has a major impact on extending the battery life, giving advance warning of battery problems before they significantly affect truck fleet performance.
- Large, stenciled I.D. numbers on all batteries to provide positive identification of battery type and age at a glance. This simplifies monitoring of individual batteries that have caused operator complaints, and helps point out which batteries are candidates for warranty claims.
- Battery discharge indicators mounted on each electric truck. These units prevent battery abuse as well as reduce low-voltage damage to truck motors and controls. Recent advances in this technology have brought the cost of these units down to very reasonable levels. Discharge indicators allow users to get the most out of a battery without over-discharging. The economic ideal: Bring the battery down to 80 percent discharge, then provide a full 8-hr. charge. Any departure from this protocol raises battery life-cycle costs
- State-of-the-art controls on all chargers. As already mentioned, this is the single best way to ensure maximum battery lift: by minimizing abuse on charge.
Posted guidelines and supervision of charging areas. Expend a few man-hours a week to review electric truck and battery operations, record anomalies, and follow up on operators. A part-time battery room supervisor can tag problem batteries for follow up, and monitor truck operator compliance with charging guidelines, such as:
- Connect proper charger to battery (color-keyed connectors can help here).
- No boost charging (new auto-controls can be set to block this practic).
- Adhere to proper equalizing charge schedule.
- Water batteries properly.
- Have chargers checked for proper adjustment at least on an annual basis, or whenever unusual charging behavior is seen. Battery heating or excessive water consumption for example, are indications of overcharging.
For more information, contact Arcon Equipment Inc. (440) 232-1422.
