Braun Oral-B Sonic Complete 4729 Battery Replacement

Written By: TheFixaholic

Comments: 2

Braun Oral-B Sonic Complete 4729 Battery Replacement

Difficulty

Moderate

Steps

Time Required

30 minutes

Introduction

The device has to be opened and partly disassembled. The battery has to be unsoldered from the logic board and can then be replaced.

Tools

Parts

Battery (4/5 AA-Cell 1,2V NiMH, capacity arbitrary - 2000mAh should do it)

Step 1

Take the device and place it on top of its charger.
Now hold down firmly the charger and pull the top of the toothbrush backwards.
Just above the lid there is the induction coil, so don't pull too much, or it could get damaged!
When the lid at the bottom opens, stop pulling and take it off manually

Step 2

Take the screwdriver (or the plastic opening tool) and go under the ring at the top of the gummed area.
Now rotate it slightly so the ring comes loose.
Be careful not to damage the gum under the ring, as it assures that no water gets inside!

Step 3

Push the point of the device down onto the table and take out the inside.

Step 4

First take away the metal sheet of the start/stop button.
Then pull the center of the black metal connection of the pressure sensor slightly upwards until the hook holding it to the sensor comes loose.
Now it has to be desoldered from the logic board.

Step 5

Now you have to desolder the sensor connection and both the connections to the red led at the top.
The white plastic pins left and right to the led connections can easily melt!
Then desolder the connections to the charging coil.
Be careful not to touch nearby electronic components, as they could get damaged!
And keep the soldering time short and remove the soldering iron as soon as the solder has become liquid, so there is no overheating risk!

Step 6

First pull off the white plastic support for the red led.
Then push the plastic casing of the battery together to pull of the coil.

Step 7

Now the connections to the motor have to be desoldered to take the battery casing of.

Conclusion

To reassemble your device, follow these instructions in reverse order.

2 comments

A good guide but I found removing the bottom quite troublesome. Levering against the charging base felt like it would break the base. I needed to lever it in stages, wedge it and grab and pull it with mole grips. This damaged the plastic a little, but I got it off.

Cone - 26/03/22

Hmm, maybe they changed the construction. When I created the guide the bottoms (of the 2 toothbrushes I repaired) opened quite easily, but that's good to know.
Also I do not think you need to worry about breaking the base: as most chargers that you plug in the mains, it should be completely filled with a hard resin, and thus be almost indestructible.

TheFixaholic -