"Why is that big forklift battery only 36 (or 24, or 48, etc.) volts?" Of course, I insist that there are no silly questions, but this one comes close. Voltage is a consequence of the number of cells (2 volts each) connected in series in a battery, and size of the cells reflects the active material surface area they contain. Hence, at the same voltage (same number of cells) a larger battery has more active material and provides more run time— as would a larger fuel tank for an engine-powered vehicle. Larger batteries also produce higher currents on demand to provide instant response under heavy loads. A forklift battery is usually sized to provide a full shift of operation before it requires a charge. For a big forklift doing heavy work this can be a very big battery.
As you may be aware, even though a golf cart battery charger may have 36-volt output, this does not make it appropriate for a 36-volt forklift battery. The forklift battery may require ten times more current output (measured in amperes) than the golf cart battery charger can provide.
Voltages of 12, 24, 36, and 48 volts became convenient standards as industrial electric vehicles evolved. In many instances the operating voltage planned for a new vehicle was selected based on the availability of economical off-the-shelf components in that voltage that could be used in the manufacture of the vehicle. These low voltages are easy to electrically insulate, and represent little danger of electrocution to operating personnel who often have contact with the batteries for maintenance or changeout.
Interestingly, because most proposed electric highway vehicles are high-voltage systems (200 volts or more), we may see high-voltage fork lift designs in the future— designs that take advantage of the components economically available as the result of mass production of electric cars.
"Why do today’s batteries need replacing more often than they did years ago?" This question is also usually asked in concert with: “Aren’t batteries treated more gently by modern charger and lift truck controls anyway?” Well, they do and they are. Because batteries are automatically monitored at every stage of their operation, never get overcharged, and infrequently overdischarged because of charger and lift truck safeguards, they should live significantly longer than ever before. The puzzler is that lead acid batteries of today don’t. They can’t hold a candle to the cycle life of many batteries made 30 years ago. Batteries were made years ago that operated in daily service many years longer than today’s batteries— some twice as long.
You can point to a few differences in the conditions under which lift trucks operate today, perhaps higher average stacking heights in modern warehouses, a larger number of frozen food facilities (which are tough on batteries) and such, but it doesn’t seem to account for the dramatic differences in battery life over the years.
A few things that we do know are a matter of record:
- Battery manufacturers industry-wide put their batteries on a crash diet a generation ago when lead prices rose abruptly. Lead content in batteries dropped as a result of redesign aimed specifically at reducing lead costs. Since lead is used as an internal structural material as well as an active electricity-producing material, it is understandable that long-term battery survival may have suffered as a result.
- Battery prices have stayed low, reflecting stiff market competition, and have not increased along with other industrial product pricing. So batteries are an even bigger bargain than they were years ago— considering the value of today’s dollar. This does mean that manufacturers make less money on each battery today, hence the necessity of trimming manufacturing costs as in point #1, and in other ways as well that could have an impact on long-term battery life.
- Higher output batteries are now being sold that squeeze more daily run time out of the same amount of active material. These batteries run hard, hot and long into the workday, but they just don’t do it for as many years as lower-rated capacity batteries used to. Higher sulfuric acid concentration in many of today’s high capacity batteries is more corrosive to the battery internally, and requires "by the book" charging to avoid shortening battery life drastically through a phenomenon known as "electrolyte stratification".
- The "battery maintenance man" who monitored battery temperatures, maintained proper water levels, and limited battery abuse in a plant’s charging room is long gone. Along with so many other in-house maintenance personnel across industries countrywide, the battery man position has been cut. Battery experts are now called in only when problems become so severe that plant operation is handicapped. This does not always do enough to correct abusive practices – situations that an in-house maintenance man would have routinely handled— his daily presence and expertise halting progressive damage that whittles away at battery life.
For more information, contact Arcon Equipment Inc. (440) 232-1422.