Forklift Battery Maintenance


Establishing Requirements

The number of forklift batteries required for service depends primarily upon the number of 8-hour shifts in effect. Normally, for operation on a single shift basis, the minimum number of forklift batteries required will be the same as the number of items of operating equipment and the forklift batteries need not be removed from the truck for charging. With a need for multiple batteries per piece of equipment, even just one malfunctioning battery can lead to serious setbacks. Our forklift battery maintenance guide can help you keep your equipment running as smoothly as possible so that your business can thrive.

For operation on a 2 or 3 shift basis, the minimum number of forklift batteries required will be twice the number of items of operating equipment and it will, therefore, be necessary to exchange discharged forklift batteries for charged forklift batteries at the end of each work shift. Whenever possible, it is recommended that more than the minimum number of forklift batteries be available for multiple shift operation. This will provide at least 8 hours of rest, after charging, as a cooling period.

In an emergency any one forklift battery can be used for two 8 hour shifts during a 24 hour period, but if this is repeated regularly it probably will cause high electrolyte temperatures and could seriously affect service life. Therefore, where 3 shift operation is normal, 3 forklift batteries will be required per item of equipment. Following this guide will help you reduce the amount of forklift battery maintenance needed.

Unpacking Upon Receipt

A. It is important first to examine the exterior of the packing for wet spots on bottom or sides which may indicate leaking jars which could have been broken in shipment. Inspect also for physical damage to forklift battery package which could mean that the forklift battery was effected as well. Report any damage to the superior officer in charge.

B. Make certain that the package is rightside up with skid mounts resting firmly on floor.

C. Use a forklift truck or crane of sufficient capacity to remove the packaged forklift battery from the truck or freight car. If a crane is employed be sure the sling is secured against the bottom of the skid and not around the skid mounts.

D. Move the crated forklift battery to the uncrating area and remove packaging, including any wrapping or other protection provided to the forklift battery terminal cable connectors.

E. Inspect forklift battery and report any damage to the superior officer in charge.

F. A properly insulated lifting beam of adequate capacity should be used to lift the forklift battery, by means of an overhead hoist, from the forklift battery skid.

Handling Forklift Batteries

If you’re preparing a forklift battery for maintenance, you need to know about the following safety procedures. At all times, when lifting forklift batteries, use a device which exerts a vertical pull on the lifting eye or tab. If a chain must be used, it should be in combination with a lifting beam with provision for adjusting lifting hook centers to the exact length of the tray. Any method of lifting which tends to “squeeze” or “stretch” the forklift battery tray may distort it and could damage jars or disturb cell seals. A piece of rubber sheet, or other insulating material, temporarily laid on the forklift battery while lifting, will prevent any possible short circuits from chains or hooks. As an additional precaution against accidental shorting, the lifting beam hooks should be electrically insulated from each other.

Preparing Forklift Batteries for Use

Forklift batteries are shipped either “charged and dry” or “charged and wet.” They vary considerably, of course, in their preparation needs.

Charged and Dry Forklift Batteries

Charged and dry forklift batteries are shipped with plates which have been charged and dried, dry separators and without electrolyte in the cells. The vent openings of all cells are sealed and must remain so until the forklift battery is being prepared for service. Charged and dry forklift batteries must be properly activated. Prepare these forklift batteries for use as follows:

(1) Remove all vent caps and destroy the sealing device, red tape or other material used to seal the vent cap holes. Make certain that all vent openings will permit free passage of gas.

(2) Fill each cell to the proper level with electrolyte and having a specific gravity 15 points (.015) lower than the designated fully charged specific gravity unless otherwise specified by the manufacturer.

(3) Clean the cell tops if any electrolyte was spilled. Neutralize with soda solution (one pound of baking soda to one gallon of water), rinse with water and dry thoroughly.

(4) Give the forklift battery a freshening charge. Be sure to continue the charge until the specific gravity remains constant for three consecutive hourly readings.

(5) Recheck electrolyte levels after gassing of electrolyte has stopped and take and record specific gravity reading, electrolyte temperature and open circuit voltage of each cell. If irregularities in specific gravity readings exist, they should be adjusted . Adjust electrolyte levels so they are 1/8” to 1/4” below vent well skirt.

(6) Each forklift battery manufacturer’s instructions will provide additional detail. Follow these instructions to assure compliance with any special requirements.

Charged and Wet Forklift Batteries

Charged and wet forklift batteries are shipped with cells filled and fully charged. Prepare these forklift batteries for use as follows:

(1) Examine forklift battery to see if electrolyte has been accidentally spilled. If so, clean and neutralize any spillage with a cloth which has been dipped in a soda solution. Rinse with clear water and dry forklift battery thoroughly.

(2) Remove vent caps and check the electrolyte level in each cell. Take and record the specific gravity reading, electrolyte temperature and individual open circuit voltage of each cell. Note any irregularities.

(3) Check to make sure that all cells are properly connected and that terminal connections are tight. If there are irregularities in the electrolyte levels or specific gravity readings or if the forklift battery has been in storage for more than 30 days, it should be given a freshening charge.

(4) Recheck electrolyte levels after charging and after gassing has stopped. Again take and record specific gravity readings and electrolyte temperatures. After the forklift battery has been standing for at least one hour, also take and record the open circuit voltage of each cell. If irregularities in electrolyte specific gravity readings still exist, they should be adjusted.


The modern industrial forklift battery is designed to give an average of 1500 cycles of charge and discharge during its life, depending upon the application and the operating environment. The exact length of the service life will depend, to a great extent, upon the care the forklift battery receives. Following these procedures and making sure you carry them out at a proper time when preparing a forklift battery for maintenance will do much to prolong the life of the forklift battery and provide efficient, satisfactory service.

Charger Adjustment

Make sure that the charger adjustment, for control of charging rates and cut-off are correct. This will assure that the forklift batteries are properly charged with no excessive over-charge. Forklift batteries that are overcharged regularly will need water more often, and cell temperatures will be higher than normal. If either condition is evident, adjust the charge rate downward, in those chargers which have provision for adjustment, so it is between a normal finish rate and one-half normal finish rate. Also check the adjustment of the ampere-hour meter and temperature- voltage relay, if either are used, as well as the timer switch.

Cleaning a Forklift Battery

Inspect the forklift battery at least once each month to make certain terminal connections are tight. Remove dirt or electrolyte accumulation from the tops of the cells. Wash with clean water and dry. Using a solution of baking soda and water (one pound of baking soda to one gallon of water) neutralize any acid which may be collected at cell or forklift battery terminals to keep them free from corrosion. Use the solution until all fizzing stops. Work the solution under the connectors with a clean paint brush. To remove all traces of soda solution and loose dirt, rinse the battery down with clear water from a low pressure hose. Whenever the forklift battery top is being cleaned or rinsed, vent caps must be tightly in place.


Control of Gassing

Gassing is the evolution of gases from one or more of the electrodes during electrolysis. It is a natural phenomenon which takes place when a forklift battery on charge can no longer accept all of the current being applied to it. Gassing is evidenced by bubbling of the electrolyte. The gases liberated are oxygen, evolved at the positive plates, and hydrogen, evolved at the negatives.

The point at which significant gassing begins is determined by voltage, but the amount of gas depends upon the portion of the charging current that is not being absorbed by the forklift battery. Normally, noticeable gassing will begin when the voltage exceeds 2.30 volts per cell. At 2.40 volts per cell gassing will be normal and at 2.50 it will be rapid. The amperage at which gassing becomes excessive depends primarily upon the state of charge and electrolyte temperatures. As the forklift battery approaches full charge, it is necessary, therefore, to reduce the charging rate to a point at which excessive gassing is prevented. This safe rate is the finishing rate. When proper charging equipment is used the tapering of the charging current to the finishing rate is achieved automatically.


Adding Water

A certain amount of water loss in cells is normal and it should be replaced with “pure” tap water or distilled water. In some geographical areas tap water may contain chemicals or other impurities harmful to forklift batteries. The NEMA recommendation for forklift battery replacement water lists the following maximum allowable impurities (parts per million) :
Total solids 350 PPM
Chlorides as C1 25 PPM
Nitrates as NO 3 10 PPM
Iron as Fe 4 PPM

Most industrial forklift battery manufacturers provide water analysis service. A minimum sample of one quart is required

Check the height of the electrolyte at least weekly and, if water is needed, add just enough to bring the electrolyte to proper level. Do not overfill. Never fill cells to above the bottom of the vent well or skirt. To avoid overfilling, it is best to add water at the end of a charge.

Water should be added often enough to prevent the electrolyte level from dropping below the perforated separator protector. Ideally a watering schedule should be established. This would assure adequate watering while taking into consideration those factors which control water consumption, such as:
(1) frequency of charging,
(2) water storage capacity of the specific cell type and
(3) age and condition


Taking Hydrometer Reading

A. Squeeze the syringe bulb and then slowly release it, drawing into the cylinder or barrel just enough electrolyte to permit the hydrometer float to ride free. The float stem must not touch the side of the cylinder nor the top of the syringe. If the float stem touches the upper area of the syringe, too much electrolyte has been drawn up; if the float still rests on the bottom, too little electrolyte has been drawn up.

B. Read the hydrometer float scale with eye at same level as electrolyte. The reading should be taken at the surface of the liquid disregarding any slight curvature. This reading will be the specific gravity of the electrolyte uncorrected for temperature. See Table 2-2 for correction factors.

C. Return all electrolyte to cell.

Record Keeping

Facilities with more than just a few forklift batteries will find that records of battery cycles, maintenance and repair are indispensable for an effective forklift battery maintenance pro- gram. In addition to those monthly records referenced in Paragraph 1-2d, which require the posting of data each time a forklift battery is charged, the following procedure will be helpful:

A. Establish a forklift battery identification system giving each forklift battery a code number. A multiple-digit system is sug- gested such as 1201, 1202, etc., for all 12 volt 375 ampere-hour forklift batteries, and 3601, 3602, etc., for all 36 volt 750 ampere-hour forklift batteries etc.

B. Record specific gravity of the pilot cell or cells before and after each charge. Pilot cells should be selected from those nearest the center of the forklift battery and identified by differently colored vent caps. They should be representative of the balance of the cells in the forklift battery.

C. Record the number of cycles on a cumulative basis plus maintenance and repair information. Note any irregularities. The use of a “Battery Cycle and Maintenance Record” form such as shown in Figure 2-6 is recommended. If variations in specific gravity readings exceed 20 points (.020) and on-charge voltage, after an equalizing charge, varies by more than .15 volts, contact the manufacturer’s service representative. When the forklift battery is new, and on at least an annual basis thereafter, read and record the specific gravity and open circuit voltage for all cells of the forklift battery.