How Many Cells Are in a Battery?

Question from a reader: "How many cells are incell identified as 18650 is one of the most
the Toshiba Satellite M105-S3041 Laptop Battery?common battery cell on the market for laptops.
The battery is for a Toshiba Satellite M105-S304118650 is manufactured by many manufacturers
and its technical ratings are 10.8 volts 8800 mAh,including many private branded companies to
Lithium Ion."public companies like LG, Sony, Sanyo, Samsung,
The question from the reader is a great questionand Panasonic.
for it gets to the heart of battery manufacturing18650 is a 3.6V cylindrical Li-Ion cell. 18650 has no
and begins to unravel the power of a battery.memory effect (distinguish between digital
The answer is simply: 12 cells. But what does thememory effect) and longer storage life than NiMH
answer mean and how does the number of cellsbattery cells. 18650 is light weight and has a high
relate to the overall value of a battery? Let's findenergy density. It is in effect perfect for building
out...batteries for laptop and other portable power
How Does A Battery Create Energy?devices.
A battery is a device that converts chemicalThe additional technical specifications for the
energy into electrical energy. Batteries create18650 battery cell include:
electrochemical energy by a chain of events that- Nominal Voltage Average 3.7 V - the concept of
have to occur prior to the creation of electricalnominal voltage is that voltage range exists
energy. Electricity is introduced into a battery viadepending on the number of cells in the battery.
a charger. The charger acts as a conduit of the- Nominal Capacity - 2200 mAh (above 2200 the
pushing electrons that are forcing their way intostability of lithium based cells is called into question)
the chemical lithium. This charge process involves- Max. Charging Current - 2.4 Amps Max.
intercalation where electrons join with other- Max. Discharging Current - 4.6 Amps max.
molecules in the lithium's minuscule spaces- Dimensions (DxH) 18.3 mm (Max 18.4) x 64.9
between the the lithium's crystallized planes.mm (Max 65.1)
Electrons are in essence ionizing lithium which loads- Weight 46.5 g (1.64 oz)
the crystal planes to the point where they are- Internal Impedance Internal Impedance: less or
forced into a current flow. Intercalationequal to 90 ohms
replenishes, in effect, lithium but the net result of- Cycle Performance is 80% of initial capacity at
ionization is the ultimate depletion of the lithium300 cycles
reactive property.Now as stated above the reader asked how
But what makes lithium good for batteries is thatmany cells were in the Toshiba Satellite
lithium is a highly reactive metal. Lithium has aM105-S3041 Laptop Battery? The battery is rated
very high electrochemical potential. In someat 10.8 volts and a capacity of 8800 mAh.
lithium-based cells the electrochemical potential canAs I mentioned above the nominal voltage
be five times greater than an equivalent-sizedaverage is 3.7V. Some manufacturers may use
lead-acid cell and three times greater than alkaline3.6V and some may use 3.7V. In the case of a
batteries. Lithium is also pliable and bendablelaptop battery with 10.8V the nominal voltage
allowing lithium to fit in tight configurations (perfectrating used is 3.6V. Thus if we divide 10.8V by
for in small cell designs in PDAs. Laptops, Cameras3.6V we get 3. Thus 3 cells in a series. We also
etc...).know that the batteries capacity is 8800 mAh.
What Type of Lithium Cell is Used in LaptopsWe know the nominal capacity is 2200 mAh.
Now this brings us to battery cells and our originalTherefore if we divide 8800 mAh by 2200 mAh
question from the reader. Lithium based batterythen we get 4 in parallel.
cells are good but there are a variety of lithiumTherefore we have: 3 cells in series multiplied by
based battery cells. For example the lithium based4 cells in parallel equals 12 cells in total.