How to Prolong Lithium-based Batteries
Today’s battery research is heavily focused on
lithium chemistries, so much so that one could assume that
all future batteries will be lithium systems. Lithium-based
batteries offer many advantages over nickel and lead-based
systems. Although maintenance free, no external service is
known that can restore the battery’s performance once degraded.
many respects, Li-ion provides a superior service to other
chemistries, but its performance is limited to a defined lifespan.
The Li-ion battery has a time clock that starts ticking as
soon as the battery leaves the factory. The electrolyte slowly
‘eats up’ the positive plate and the electrolyte decays. This
chemical change causes the internal resistance to increase.
In time, the cell resistance raises to a point where the battery
can no longer deliver the energy, although it may still be
retained in the battery. Equipment requiring high current
bursts is affected most by the increase of internal resistance.
Battery wear-down on lithium-based batteries
is caused by two activities: actual usage or cycling, and
aging. The wear-down effects by usage and aging apply to all
batteries but this is more pronounced on lithium-based systems.
The Li-ion batteries prefer a shallow discharge.
Partial discharges produce less wear than a full discharge
and the capacity loss per cycle is reduced. A periodic full
discharge is not required because the lithium-based battery
has no memory. A full cycle constitutes a discharge to 3V/cell.
When specifying the number of cycles a lithium-based battery
can endure, manufacturers commonly use an 80 percent
depth of discharge. This method resembles a reasonably accurate
field simulation. It also achieves a higher cycle count than
doing full discharges.
addition to cycling, the battery ages even if not used. The
amount of permanent capacity loss the battery suffers during
storage is governed by the SoC and temperature. For best results,
keep the battery cool. In addition, store the battery at a
40 percent charge level. Never fully charge or discharge
the battery before storage. The 40 percent charge assures
a stable condition even if self-discharge robs some of the
battery’s energy. Most battery manufacturers store Li-ion
batteries at 15°C (59°F) and at 40 percent charge.
- Charge the Li-ion often, except before a long storage.
Avoid repeated deep discharges.
- Keep the Li-ion battery cool. Prevent storage in
a hot car. Never freeze a battery.
- If your laptop is capable of running without a battery
and fixed power is used most of the time, remove the battery
and store it in a cool place.
- Avoid purchasing spare Li-ion batteries for later
use. Observe manufacturing date when purchasing. Do not
buy old stock, even if sold at clearance prices.