Nearly all industrial batteries have type information as well as a serial number stamped on top of a lead intercell connector. The battery type is identified by a code such as 18-75-25. This example represents an 18-cell (36-volt) battery with a plate capacity of 75 ampere hours (for each positive plate), and 25 total plates (both positive and negative) within each cell.
Nominal battery capacity can be determined from this code. It is equal to plate capacity multiplied by the number of positive plates in each cell. Positive and negative plates are interleaved within the cell, and there is always one less positive plate than the total of negative plates (12 positive plates and 13 negative in the 25 plate example). Multiplying 75 ampere hours by 12 equals 900 ampere hours of battery capacity.
Battery plate capacities commonly available today include low-profile, 55 A.H. plates in 17.5" high cells; 75, 85, and 100 A.H. in standard 23" high cells; 100 A.H. in 27" high cells; 100, 110, 125, 140, and 155 in 31" cells; and up to 170 A.H. in 31" tall wide-plate cells. Of course, battery capacity drops with age and battery condition, so used battery capacity is described as a percentage of the new nominal rating as determined through a discharge test.
As can be seen, there are two ways to improve a lift truck’s running time: specify a higher ampere-hour capacity plate, or obtain a battery with more plates per cell. Battery size does not increase, and weight rises only slightly if a higher-rated plate is chosen within a certain cell type. Stepping up from the 75 A.H. plate in the 25 plate example to a 100 A.H. plate (also available in 23" high cells) increases nominal battery capacity from 900 A.H. to 1200 A.H., while battery size remains the same.
To achieve that same capacity increase without going to a higher plate rating, it would be necessary to fit a 33 plate battery in the truck (16 positive plates x 75 A.H. = 1200 A.H.). Battery width would increase 9" from 29.5" to 38.5", and weight would rise 900 lbs., from 2600 lbs. to 3500 lbs.
It is important to remember that the charger used for the larger capacity battery must be larger also. Always make certain that the charger nameplate rating matches the battery’s capacity rating. This is especially critical when higher-rated plates are used. Field data show that some high performance batteries rapidly become impaired if the charger is not properly matched.
When selecting a battery for an electric lift truck, the battery’s role as a counterweight must always be kept in mind. In the above example, if a 25 plate, 36-volt battery is substituted for a 33 plate battery, the truck may operate fine, but the 900 lb. difference will significantly reduce the lifting capacity of the truck. Stick to the battery weights recommended by the lift truck manufacturer to ensure safe operation.
When buying a used battery, always obtain test information that reveals the percentage of original battery capacity. Note that a used 100 A.H. plate battery with only 75% remaining capacity is equal in capacity to a new 75 A.H. plate battery of the same physical size. Of course, other factors such as remaining years of battery life also enter into the purchase decision.
For more information, contact Arcon Equipment Inc. (440) 232-1422.