Why the battery power percentage is incorrect? It will affect our use of iPhone. What's worse? It reboots frequently. We need to investigate the cause of the faulty and find the excellent solution.
First test the charging function, it shows
normal, but the battery power percentage jump frequently. Base on repair
experience, this phenomenon should be a reboot frequently caused by battery
failure, so we should repair the battery power percentage inaccurate first.
Connect iPhone to i4 tool, the position of
battery information shows no data, this failure is the CPU doesn't recognize the battery, so i4 tool
can't read the battery data. As shown in picture 4-5-1.
The main reasons for not recognizing
battery information as follows:
1. The battery is damaged
2. The circuit from middle pin BATTERY-SWI
of battery interface J2523 to F2 of charging chip U1401 is broken and the U1401
was damaged
3. The problem of circuit from U1401 G1 #
to CPU AG4 # and problem with the CPU itself.
Replace the new battery and test it, i4
tool still can't read the battery information. Then measure the diode data of
battery middle pin with Multimeter, the diode data is 380 which is normal, so
the line from battery to U1401 is normal. Next we remove the U1401 IC, and then
measure the line from G1 pin to SWI of CPU, the diode data of G1 is 450, its normal.
Now, we can judge U1401 or CPU is damaged.
After replace the U1401, it still can't
read the battery. This fault is not caused by the CPU welding, but because the
CPU damage pulls down the voltage of the SWI line, so we can increase the SWI
voltage by connecting the resistor externally.
Connect a 2.2K resistor on PP3V0_TRISTAT,
the other end of the resistor is attached to U1401 G1 pin (also can connect to
middle pin of battery). The picture of solder jump wire is shown in 4-5-4.
After soldering jump wire, the picture is
shown in 4-5-5
Finally, turn on iPhone 6 Plus and connect
to i4 tool, now it can read the battery information, the fault has been
repaired. As shown in picture 4-5-6.
Tips: you can use 3U tool to replace the i4
tool.
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