How can battery exploded? "case samsung note 7 global recall"

Why do cellphone battery exploded ?

This article simply trying to explain why and how li-ion battery explodes. 

Samsung Galaxy Note 7 Explosion

Basic theory

“A lithium-ion battery (sometimes Li-ion battery, Lion battery, or LIB) is a member of a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge and back when charging.”

Source: Wikipedia Lithium-ion battery

Concept

Electron Ion in lithium will move when discharge and produce lithium oxide. Recharging this cell battery, electron was inserted to this lithium oxide and produce lithium cobalt oxide.

These reactions continuously happen when you are using this battery, Recharge – Discharge.

Cellphone Lithion Ion Battery

Why these batteries explode?

1.   Overcharge

Overcharge more than 5.2 volts. The energy of each gram of lithium related to faraday constant it produces about 41.7 kj at 3 volt. If you charge 1 kg battery li-ion it produce heat equal to combustion of gasoline.

Now a day every cellphone have a voltage regulator in their circuit to keep the voltage stable when charging battery. Their engineer designed the circuit to prevent any unstable voltage during charging but any electronic device has probability to failure.

Solution

Using compatible charger / manufacturer recommendation. Check the specification of your charger.

Use good regulated input voltage , our charger actually have capability to connected either in 220VAC and 120 VAC but when you are using off grid or standalone power generation make sure you got good regulated voltage.

2.   

      Failure to design charging stage

Li-on battery have 3 stages of charging:

Constant Current

Applying constant current until reach full voltage

Constant voltage source

Applying maximum voltage until full and current reach zero

Balance

Too complex , but the key is method to charge many cell of battery

Electronic engineer of each phone manufacturer has their own method. I believe their design were good and had completed many test and review.

Samsung S4 overheat when charged

Note:

The problem is when you are using non compatible battery. Even you had good design in your circuit but when the battery manufacturer failed or not matched in your criteria there is still a problem.

I suspected the case Samsung Galaxy Note 7 battery blast was one of this. Samsung design of charging voltage and Current doesn’t meet with battery maximum limit.

For example : Samsung design 5.2 V and 2 A but the battery capability is 4.8 V and 1.8 A if this is continuously happen there will produce heat because the circuit keep charge the battery even tough battery was already fully. Like you are at full but mom ask you to keep eat food

3.   Extreme Temperature

Li-ion designed to work well in 5⁰C to 45⁰C , when you are using in extremely thermal environment above 45⁰C battery will be degraded impacted in the capacity of battery.

Never place your phone in enclosed non ventilated high ambient temperature. 

Recommended Temperature is 5 degC  - 45 degC

4.   Short Circuit

Many articles in internet said the blast on Samsung note 7 battery caused by short circuit.

Personally I am not agreeing to this statement or let say it’s not in my logic. Because the probability the short circuit happen is low except the case was design failure.

Short circuit in battery can cause thermal runway and lead to blast because there is uncontrolled erratic movement of electron. These are some cases lead to Short circuit.

1.   Design failure

Design of electronic circuit failed to anticipate the electron jump between line. Maybe because the design is not neat, too shallow between positive and negative, protruded edge of board, or bad insulation.

2.   Water ingress

It’s clear when water come in to your electronic circuit its happen

3.   Impact

When you hit your battery with hammer the internal cell anode and cathode will be touching and lead to short circuit.

Those are some of my  humble analysis why battery cell phone could be exploded.

(end of article)

Source ;

1.       Wikipedia

2.       Journal electromechanical society