Charging - Quick Charge Function
lithium-based batteries with a quick charge function is
not as easy as it would seem. The design of the lithium-ion
battery does not permit super-fast charging. However there
are some steps which can be taken to permit lithium battery
charge time to be reduced. Because of strict rules for charging
lithium-ion cells it is important to follow guidelines in
charging procedures provided by the manufacturers.
is an charge technique which permits a faster recharge and
XPower1 has implemented this approach in our design. In
addition we are working on new designs which can be used
in the future which permit batteries to charge in seconds
verses hours. This new technique will work with new lithium-ion
battery material which is going to be released in 2012..
not wait until 2012 however to improve charging. There is
information below regarding implementing steps to a faster
little background on lithium-ion may also help so we have
provide this for your information. We will try not to get
too technical. Lithium-ion batteries are a clean battery
system and they do not need priming as with other batteries
such as nickel-based batteries. The 1st charge is no different
to the 2th charge or the 100th charge. No need with Lithium-ion
batteries to charge the battery for 8 hours or more for
the first time they are used. This just is not required.
cells are charged to 4.20 volts with a tolerance of +/-0.05V/cell.
There is a reason for this level of voltage because charging
only to 4.10V reduces the capacity by 10% but provides a
longer service life. Newer cell are capable of delivering
a good cycle count with a charge to 4.20 volts per cell.
There are charge stages of a lithium-ion battery and it
is how there stages are implemented that can be used in
our technique to charge faster. Increasing the charge current
on a lithium-ion charger does not shorten the charge time
by much. The voltage peak will be reached quicker with higher
current however the topping charge will take a longer period
of time to perform.
what is the typical time it will take to charge a lithium-ion
battery used in a cellphone. Most charges take 1 hour for
a full charge. These are cellphone, MP3 player type batteries
are smaller batteries. The charged is at 1C. Larger batteries
such as a 18650 cell used for laptops will take 0.8C or
less for a charge. The charge efficiency is 99.9% and the
battery remains cool during charge. There is a threshold
for voltage which is normally attained at full charge of
a battery and once this is reached the current drops to
3% of the rated. So it levels off after the threshold is
reached. Increasing the charge current does not shorten
the charge time by very much. If the current is increased
this the voltage peak is reached quicker but the charge
will take longer to complete top off the battery.
fast charge lithium-ion there is a common technique. The
technique is during charging to eliminate one stage ( second
stage of charging) and go directly to 'ready' state once
the voltage threshold is reached at the end first stage
of charging. The charge level at this point is only about
70% of total capacity. To top the battery normally will
take twice as long as the initial first charge stage. But
70% during half the charging stage is good and permits a
user to make a fast charge and have a high level of capacity
quickly. XPower1 uses this technique to charge the battery
as fast as possible during the first stage of charging.
batteries are unable to absorb overcharging so the Xpower1
does not permit this. This overcharging is called a conntinuous
trickle charge. Instead, a brief topping charge is provided
to compensate for the small self-discharge the battery and
its protective circuit consume. Depending on the battery,
a topping charge may be repeated once every 20 days. Typically,
the charge kicks in when the open terminal voltage drops
to 4.05V/cell and turns off at a high 4.20V/cell.