Batteries do not exhibit visible changes as part of usage;
they look the same when fully charged or empty, new or old and in need of
replacement. A car tire, in comparison, distorts when low on air, shows signs
of wear, and indicates end-of-life when the treads are worn. Batteries should
receive the same treatment as a critical aircraft part, a medical device and an
industrial machine where wear and tear falls under strict maintenance
guidelines. A battery behaves like a living organism that is swayed by
conditions such as state-of-charge (SoC), charge and discharge events, rest
periods and age. In addition, a battery with low SoC behaves similarly to a
pack exhibiting capacity loss and these two symptoms become a blur.
The leading health indicator of a battery is capacity; a
measurement that represents the actual energy storage. A new automotive battery
delivers (should deliver) 100 percent of the rated capacity. Lead acid starts
at about 85 percent and increases in capacity through use before the long and
gradual decrease begins. Lithium-ion starts at peak and begins its decline
immediately, albeit very slowly, while nickel-based batteries need priming to
reach full capacity when new or after a long storage.
Manufacturers base device specifications on a new battery,
but this is only a temporary state and does not represent a battery in real
life situations. Performance will decrease with use and time, and the loss caused
by battery handling will only become visible after the shine of a new device
has worn off and daily routines are taken for granted.
Few people know when to replace battery; some are replaced
too early but most are kept too long. When asking battery users: “At what
capacity do you replace the battery?” most would reply in confusion: “I beg
your pardon?” Few are familiar with the term capacity as a measurement of
run time, and even less as a threshold when to retire them. Performance loss
only becomes apparent when breakdowns begin to occur and the battery becomes a
nuisance.
Battery retirement depends on the application. Organizations
using battery analyzers typically set the replacement threshold at 80 percent. There
are applications where the battery can be kept longer and a toss arises between
“what if” and economics. Some scanning devices in warehouses can go as low as
60 percent and still provide a full day’s work. A starter battery in a car still
cranks well at 40 percent. Engine-starting only requires a short discharge that
is replenished while driving, but letting the capacity go much lower may get
the driver stranded without warning. No one gets hurt if a battery cuts off a
phone call, but a failing medical device can put a patient at risk. Running out
of power in an industrial application can also incur high logistic costs.
The best indicator for battery retirement is checking the
spare capacity after a full shift. A
battery should have 10 to 20 percent spare at the end of a day to cover
unknowns and emergencies. If the lowest performing battery in the fleet comes
back with 30 percent, then the target capacity can safely be lowered from 80
percent to 70 percent.
Battery manufacturers like SF Sonic provide car batteries
online to prevent any inconvenience to the users. So once you understand that
it’s time for a replacement, you just have to login for your online car battery.
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