Rubenzer, vice president, sales and marketing at industrial
battery manufacturer Storage Battery Systems LLC. Even at
50 degrees internal temperature, a 1,000-ampere-hour battery will act more like a 600–700 amp-hour unit, according
to Tony Amato, executive vice president of battery distributor Industrial Battery Products Inc.
When the battery temperature falls below 40, the voltage
will appear artificially high and a battery discharge indicator (BDI) will show more power available than there actually is, says Steve Spaar, marketing director–Americas for
the battery manufacturer EnerSys, which also owns
Douglas brand batteries. At low temperatures, the charger
will also see the voltage as artificially high and will shut off
too soon, which leads to shorter battery life.
There are ways to counteract the effects
of frosty temperatures. One option for
extremely cold environments is to insulate the battery compartment. Another
is to use a battery with a high amp-hour capacity. It’s possible to raise
that capacity in an existing battery by
increasing the acid content in the
electrolyte solution (the mix of water
and acid that governs the battery’s
electrochemical reaction and thus, its
voltage). However, Amato warns,
there’s a trade-off: You’ll get more run
time per shift, but you’ll also be shortening the battery’s useful life by
potentially as much as two years.
A battery with tubular positive plates will have more
usable capacity than an equivalent flat-plate-construction
battery, and so should be considered for cold applications,
Rubenzer says. Not just batteries but also chargers should
be specifically designed for low temperatures, and battery
discharge indicators should be adjusted for cold conditions.
Sustained high battery temperatures can do serious damage. Battery life can be reduced by as much as 50 percent for
every 15-degree increase over 77, based on average temperatures. As a battery’s sustained temperature increases,
moreover, the loss of battery life accelerates.
Battery heating is caused by the resistance of the intercell
connectors while a vehicle is in use, according to
PowerDesigners, a manufacturer of battery chargers and
monitoring systems. Additional heating due to this same
effect occurs during charging, and the higher amperage
used during opportunity and fast charging exacerbates the
problem, the company says. Because there’s no cooldown
period following the charge, as in a conventional charging
application, the battery remains hot.
Hot air temperatures can also lead to overheating, especially in fast and opportunity charging operations.
PowerDesigners explains it this way: While it is in use (i.e.,
being discharged), a battery usually will be warmer than
ambient temperatures. As the ambient temperature rises,
the air becomes less effective in cooling the battery, and
the battery’s internal temperature will rise. Charging will
further raise the battery’s internal temperature—possibly
to the point where the battery could suffer damage if
you’re not careful.
For example, discharging typically adds about 15 degrees
to the battery temperature. At an ambient temperature of
75, then, discharging will add enough heat to raise the battery’s temperature to 90. Charging will add another 10
degrees, bringing the battery’s temperature to 100. When a
battery reaches 130 degrees, the charger will issue a “battery
over temp” fault and will stop the charge to prevent battery
damage. In this case, the battery has a margin of 30 degrees
before that happens. But at an ambient temperature of 90,
Making sure battery charging areas
are well ventilated to provide good air
movement will help to minimize average battery temperatures, according to
and use a first-in, first-out (FIFO) rotation. For opportunity charging, consider using ventilated battery trays or some
type of active cooling, such as blowing air.
Temperature will affect cells differently depending on the
battery layout or position in the lift truck, causing some
cells to be overdischarged while others are underdischarged,
notes Ken Sanders, director of motive power battery engineering for East Penn Manufacturing Co. Inc., maker of
Deka brand batteries. A weekly equalizing charge—an
extra-long charge that brings each cell in the battery up to
the same, maximum capacity—will allow battery and cell
temperatures to reach a state of equilibrium, thus minimizing cell-to-cell temperature variations and improving battery performance and longevity, he says.
▪ Failing to equalize. Batteries should be equalized once a
week, says Amato. Unfortunately, that doesn’t always happen as scheduled, due to poor maintenance tracking or
because with chargers that are set to automatically do an
equalizing charge, users tend to assume everything is happening as planned. But that’s not always a safe assumption,
Amato warns. In a facility that rotates multiple batteries,
“the batteries don’t always get on that charger the right day
or time,” he says. A battery tracking and monitoring system
that alerts managers when a particular battery has not been
equalized is one possible solution.
