...:::Basic info about Nokia Battery:::...

[ali 4800]

Dear here is Nokia Battery Basics.........


A normal battery has only two terminals brought out of its casing. But the batteries used in Mobile Phones, many times have more than 2, at least 3 or even 4 (at the most) terminals brought out on its casing. You may wonder why so? It is very interesting to go into the details and know more about it. Though the charging circuit inside a mobile phone is generally designed with providing a very very safe charging voltage to the battery, it is made more perfect with the use of this additional terminals provided on the battery casing.

Let us see why it is thought necessary, to provide more than the normal 2 terminals in Mobile Phones Batteries. Take the case of a Nokia phone 3310 or 3315. You may notice that for this particular model of the phone the batteries available are of both the types, Ni-Mh as well as Li Ion types. It is necessary to inform you at this stage that not only the charging current may differ in these two different kinds of batteries but also the voltage level up to which they can be charged safely will also differ in them. To be more specific, the Ni-Mh battery can be charged safely up to 5.2 volts whereas the Li Ion battery’s safe voltage is only 4.8 volts. So the same circuit in the mobile phone will have to stop charging the batteries at different levels of voltages in each case. So how it will know which kind of battery is inserted in the mobile phone and to be charged and so at which level to stop charging in each of the case? This is achieved with the help of a standard, pre-decided or pre-determined by all the battery manufacturers according to which they put extra components inside each battery casing which will bring a certain predetermined voltage level at that point called BSI (Battery Size Indicator), which will help not only to know the type of battery it is but will also let us know it’s capacity in mAH!!!! Isn’t it very intelligent?
Yes, it is a very nice way of letting the charging circuit to know how much charging current it should supply and on reaching which level of voltage, it should stop supplying the charging current to the battery. I am sure, all of you would like to now how this is achieved. The following details taken from the technical pages for the Nokia Model 3310 will help you understand this better.
The type of the battery inserted in the mobile phone is found out by the think-tank of the phone, which is the CPU (Central processing Unit) of the mobile phone. In the case of Nokia 3310-3315 models it is the IC known as MAD IC, which is actually the CPU of the mobile phone. This is done by the CPU with the help of the Charging Control IC of the phone CCONT IC. The CCONT IC reads the voltage at a point on the battery called the BSI line. The Batteries contain a pull-down (connected to either ground or the –ve terminal of the battery) resistor inside the battery casing. Typically, for a BLB-2 type of Nokia battery (Li Ion 650 mAH), it is a 68Kohms resistor. Other values used in other types of batteries are listed in the table below:
Battery Type and it’s capacity
Value of the pull down resistor inside the battery
BMC-2 Ni-Mh 640mAH
3.3K (3.3K=3.3Kohms=3300ohms)
BMC-3 Ni-Mh 900mAH
5.6K
BLB- 2 Li-Ion 650 mAH
68K
BLC- 2 Li-Ion 900 mAH
75K

How would this help identifying the type of battery?
Let us try to visualize the schematic of the Battery related components. This BSI point of the Battery is connected as shown below in the figure via a 10K resistor to a point on the CCONT IC. Also it is connected to 2.8volts supply line via a pull-up resistor of a value fixed at 150K.


The thermistor RT is a thermal kind of resistor, whose value decreases as it’s temperature rises. As above in the case of BSI point, the BTEMP point of the Battery is connected with a pull-up (to pull up the voltage) resistor of 100K.


When the Battery is put for charging in the mobile phone, there is normally a little rise in the temperature of the battery. This will cause a rise in temperature of the Resistance RT inside the battery casing. Now as per the characteristic of the NTC resistor , it’s resistance value decreases as it’s temperature rises. This also changes the voltage at the BTEMP point of the battery as well as the CCONT BTEMP pin. This change is always fed to the CPU which keeps monitoring it continuously. This is always online referred to the Energy Managemant Software loaded in the Memory ICs (Flash & RAM ICs) inside the phone. When the temperature inside the battery increases beyond it’s allowed limit, this change in voltage at the BTEMP point will be processed in the CPU and the Memory ICs and the CPU will then ask the CCONT IC to stop supplying the charging current to the battery and will stop charging absolutely to save the battery from any damage that may occur due to it’s rise in temperature.

Thus, in Nokia 3310-3315-3330-3390 etc. series of Phones, all the functions of charging are achieved very accurately and perfectly with the use of :
(1) Chaps (Charging IC)
(2) CCONT (Charging Controller IC)
(3) MAD (CPU IC)
(4) Memory ICs (Flash & RAM ICs) &
(5) Energy Management Software loaded in the Flash IC.






If u like it Press Thanks Button...