Why does the phone consume charge faster than the manufacturers say

Phones often run on battery less than what is stated in the specifications. Let's try to understand why the statements of manufacturers and our expectations are not always justified.

Phones of some manufacturers have a long battery life with the same battery capacity and similar operating conditions. Obviously, this is caused by the peculiarities of the “hardware” used - the microcircuits, the display, and other electronic components on which the device is built. But we are trying to understand why real life is different from the promises of the manufacturer. In these conditions, the features of the "iron" fade into the background, because we compare the work of devices built on the same "hardware".
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About banal

First of all, you need to realize that the battery stored energy in the autonomous mode is used to serve absolutely all the needs of the device - the work of processors, receiver, transmitter, display, backlight, GPS, Bluetooth, Wi-Fi, FM receiver, flashlight, and so on. Accordingly, each included energy consumer will reduce the remaining energy available to other consumers, and the possible battery life.

Therefore, if the user wants to talk a lot, or play with toys, he must accept the fact that in standby mode, the phone will be able to stay without recharging the battery much less than it could if it were just turned on without using it.

If you want to charge the battery less often, you’re less likely to worry the phone over trifles and turn off unnecessary internal consumers, which speed up battery drain in offline mode: less backlighting, communication as needed, close maps and turn off GPS, adjust more rare updates.

Battery

The first thing that people usually pay attention to is the capacity of the battery. It is quite obvious that increasing the battery capacity will lead to a longer battery life. But, it is necessary to take into account that “battery capacity” is some “design”, calculated, target parameter of a battery. For a specific design and manufacturing technology, it is indicated “with a margin” to ensure an acceptable yield of products in production.

Typically, when leaving the production capacity of a particular battery is slightly higher than the nominal value, but as the operation due to irreversible chemical processes in the body, the battery is worse and worse able to store energy in the next charge cycles, and in addition, its internal resistance increases. In reality, the amount of electrical energy that a particular instance of a battery can store depends not only on its nominal capacity, but also on the number of conditions in which it operates.

Let's start with the process of charging the battery, which is usually charged without removing the tablet from the device. A strongly simplified diagram is shown in Figure 1.


Figure 1. Simplified power supply and charger connections
E - battery power (EMF)
Ri is the internal resistance of the battery
R - resistance of contacts through which the battery is connected to the phone
R - load resistance (all consumers in the phone)
+ Charger and –ZU - “charger” contacts
CPS - charge control circuit controlled by a phone processor
V - ADC measuring battery voltage

"Charger", which is connected to the phone, in fact, is simply a source of energy, and the charge process is controlled by the device itself (its control module), in accordance with the program embedded in the device software.

If at the time of connection of the charger the battery is highly discharged, and the voltage on it is below the lower limit, then the device starts the mode of charge with a small current - trickle charge. In this mode, the phone usually does not show any "signs of life", despite the connected charger. Such a charge continues until the voltage on the battery reaches the minimum required to start the processor of the phone (in modern devices it is usually ~ 3.0 V). At this point, the phone comes to life, and its processor begins to control the process of charging the battery.

Charging current pulses are applied to the battery, followed by a pause, during which the voltage on the battery is measured. In addition, battery temperature is monitored. If the temperature of the battery exceeds a pre-selected value (usually ~ 40 ° C), the charging process stops for a while so that the battery can cool down.

Battery voltage monitoring is used to determine its charge state. This takes into account not only the voltage value itself, but also the tendency of its change, depending on time. A battery is considered charged if its voltage ceases to increase and there is a tendency to decrease it.

In the process of using the device, the processor during the periods of its activity monitors the voltage on the battery, and when the battery voltage reaches the lower limit set in the phone settings (usually ~ 3.0 V), the phone automatically turns off. It would seem that everything is simple, however, there are several nuances associated with the technical features of the implementation of the processes described above and the design of the phone.

Calibration

To measure the battery voltage in the phones, ADCs are used, which can measure the voltage with a certain discrete step and require calibration. During calibration, a correspondence is established between the actual voltage values ​​at the measured points and the digital values ​​that are transmitted to the telephone software to make decisions - displaying the battery charge level on the display, automatically turning off the phone due to low batteries, or stopping the battery when it is charged.

It is obvious that phones with incorrect calibration of the battery voltage meter may not behave quite correctly - deceive the user with false information about the current battery level, turn off the phone ahead of time, prevent charging the battery until fully charged.

Unfortunately, the parameters of indication, charge and discharge of the battery are not regulated by the standards for the phones, so each manufacturer is free to do as he pleases. It is particularly unpleasant that even in service centers they can not always help to eliminate problems with the calibration of ADCs, since the manufacturers did not provide them with such technical capabilities.

The process of voltage measurement itself usually takes place already in the circuits located on the telephone board, and between the control points and real circuits in the battery there are several other intermediate elements that influence the measurement results.

First of all, it is the resistance of the contacts (Rk in Figure 1), through which the battery is connected to the phone. And in some phone designs there are also additional intermediate contacts between the elements on the phone case and the printed circuit board. Of course, the phone manufacturers are taking measures to ensure that these contacts have minimal resistance, and do not lose their property over time. However, the contamination of contacts, which I already wrote in previous posts, can have a very noticeable impact on the results of work. After all, the increased contact resistance, as well as the internal resistance of the battery, leads to the fact that at the moment of maximum current consumption by the transmitter, the voltage at the measurement points can be below the set limit, as a result, the processor turns off the phone, considering that the battery is very low.

E (Volt)	Ri + R to (Ohms)	I bit ( A)	V ( Volt)	Device action
3.6	0.2	one	3.4	Works
3.4	0.2	one	3.2	Works
3.2	0.2	one	3.0	On the verge of shutdown
3.6	0.5	one	3.1	Works
3.4	0.5	one	2.9	Will disconnect

Table 1. Voltages measured by ADC (V) as a function of battery voltage (E), internal resistance (Ri) of the battery, and contact resistance (Rk).

For simplicity of calculations and clarity, I took round values, but the current consumption close to 1A is not something particularly strange, especially when the GSM900 transmitter is operating at maximum power (2 W).

The table shows that the increase in contact resistance can cause premature disconnection of the phone. This effect is observed at the time of an incoming or outgoing call, sending / receiving SMS, checking balance and other operations when the transmitter is turned on.

The practical conclusion - keep the contacts through which the battery connects to the phone, clean, if you want the phone to work longer offline!

In move

In order for the network to know through which base stations it is necessary to search for a mobile device in case of an incoming call or incoming messages, it must have information about the area where the phone is located with a certain accuracy. To this end, when you turn on the phone is registered in the network, and when you move through the territory of the service area, it performs a re-registration in the new Location Area. Each re-registration requires a short two-way radio session, during which the phone’s authorization (the SIM card installed in it) is checked, and the phone receives a new temporary identifier (TMSI).

Each such communication session causes additional battery power consumption. Consequently, a phone that moves around a lot in the service area will drain the battery faster than if it just lies in one place.

Delivery of scheduled information

The phone in standby mode involves quite a lot of events, usually invisible to the user. In order to be able to receive incoming calls and messages, the phone listens to information transmitted by the base stations of the network.

The GSM network establishes a kind of “schedule” at which times it can transmit information for a specific device. Depending on the number of subscribers staying in a particular territory, engineers can divide the phones into different numbers of PAGING GROUPS, the call of which will be made during different multi-frames. By changing the value of the BS-PA-MFRMS parameter, engineers can force the phone to turn on the receiver to receive signals addressed to it in every second, third, or only in every ninth multiframe.

In addition to the time periods when call signals can be received, the “schedule” can also include the reception of broadcast messages (Cell Broadcast), which are used to deliver location information to phones (MOCKBA - OBLAST, for example) or to implement other services.

It is obvious that the more often the phone needs to turn on the receiver, the greater will be the energy consumption from the battery, and, accordingly, less battery life.
If the user cannot influence the network settings, then you can think about the phone settings that affect the receiver's additional power. For example, you can disable the reception of network broadcast messages (Cell Broadcast), or accept the fact that the use of additional services is worth reducing the battery life.

2G / 3G

Studying the parameters of the phone when choosing a purchase, many probably noticed that the promises of manufacturers regarding the battery life of the same phone in standby mode and talk mode in 3G networks are less than 2G networks. It would seem that technical progress should give the opposite result?

The fact is that 3G uses a fundamentally different way of packing information for transmission over the radio channel and generating a radio signal. Having many advantages over similar operations in 2G networks, information processing for transmission over the radio channel in 3G networks requires significantly more computational resources, as well as the use of continuous reception of a base station signal.

Equipment manufacturers are struggling to reduce the energy consumption of all the physical elements of mobile phones that provide communication. One of the tricks is the ability to turn off the supply of a clock signal and a supply voltage to a SIM card between the sessions of information exchange between the phone and the SIM card. But the implementation of such a regime does not always work flawlessly. As a result, some phones in the intervals between communication sessions with a SIM card cannot fall asleep deeply enough. The result of such errors may be, for example, a meaningless supply of a SIM card with supply voltage and a clock frequency signal, leading to additional battery power consumption and, therefore, the need to charge the battery more often.

Unfortunately, the user can do little in this case. To help fix the problem can only release and use of the new version of the phone software.

So how to evaluate the promises of manufacturers of battery life?
First of all, note that manufacturers usually write carefully - “up to XXX hours in standby mode” or “up to X hours in talk mode”. This means that the data refers to, relatively speaking, the "ideal" conditions for autonomous operation of the phone.

For example, for standby time:

• The phone is used only in standby mode. They do not speak on it, do not press the buttons, do not turn on the backlight, FM radio, player, do not use games or any applications that exchange information over the network, etc .;
• The network has the most “sparing” mode of operation for the phone - the maximum value of BS-PA-MFRMS = 9, because of which the phone rarely turns on the receiver, the network does not need to confirm its location “on schedule” with the LOCATION UPDATE operation.

For talk time:

• The phone is located near the base station, which allows you to set the minimum output power of the transmitter of the phone, and therefore the most economical use of battery power;
• Conversation takes place continuously, thereby reducing the length of the intervals, for example, at the beginning of a conversation, during which the phone must operate at elevated output power levels until the base station with its commands sets the minimum output power of the telephone transmitter.

It is clear that in real life, telephones are never used in such “ideal” conditions, and therefore the actual values ​​of battery life are noticeably less than the stated maximum values.

But after all, phones are bought in order to use the functions provided by them, and not just to compete in the duration of autonomous work?