Let's start by understanding how the massager is constructed inside

1. Front part of the case
2. Rubber sealing (anti-vibration) gasket
3. Shaft guide
4. Metal shaft (where the attachment is inserted)
5. Crank mechanism
6. Plastic adapter holding the motor in the case
7. BLDC motor with built-in control board

The shaft guide consists of two parts: an outer (plastic) casing and an inner metal cylinder, connected by press-fitting. The solution is interesting but not entirely reliable. The metal cylinder pops out of the plastic casing, causing a knocking noise.

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There are no questions regarding the quality of the crank mechanism. It is an interesting solution to use bearings, and I think it is appropriate in this situation. The operating principle is simple: the offset of the center of the axis on the motor shaft creates an up-and-down reciprocating motion

Disadvantages: due to vibration, the bearings will eventually fail due to natural wear and tear. This was observed in one unit.

Error E3 - motor error

The motor has its own logic (control), a typical solution for different BLDC motors. Most often, power switches (field-effect transistors, MOSFETs) fail.

Such motors typically have three phases.
Each phase is controlled (in terms of power) by its own MOSFET. MOSFETs tend to fail (burn out).

Why? Defects/High load (exceeding peak value and/or higher current and longer duration than the nominal value).

Solution? If the problem becomes widespread, install MOSFETs with a higher current margin, possibly a different motor.

Explain to the consumer that blocking the motor's vibration with force for an extended period is harmful.

Below, where we will disassemble the electronics, there will be a photo of the burned-out component.

The following case:The plastic fasteners broke.

What could be the solution? Make more reliable motor mounts. Competitors use a metal plate.

The screws holding the plate were not fully tightened or loosened due to vibration.
This occurs on all devices, with varying degrees of tightness.
This could be the cause of the knocking noise during operation. A lock washer can be used to prevent the screws from loosening due to vibration.

Next problem:
The wires are loose inside the case => you can hear the rear part of the mechanism hitting the wires.

I checked 30 units, and in all but one or two massagers, the wires were twisted.
This is a factory oversight.

The twisting solution seems to work, but it is also a poor solution.
In my opinion, the wires should be separated from the moving metal parts, ideally with a plastic casing. Alternatively, at least with a fabric sleeve.
The chance of a short circuit is extremely low. But such a technical solution makes me frustrated.

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So, we have dealt with the mechanical part and identified the culprits. Let's talk about the electronic components.

The battery is connected to the battery charging board.
The battery charging board is connected to the controller, which, in turn, controls the motor and dictates its speed.
And the board directly on the motor manages the entire power section

So, let's take the case with the battery, error E1 or it simply doesn't turn on.

Battery configuration 4s1p. What does this mean?
4 cells connected in series, 1 such assembly in parallel.

Everything is fine, quite a common configuration for this device.

So why doesn't the assembly work?
The voltage on each of the four cells is marked.
Ideally, they should all be the same. But we have a maximum difference between the cells of almost half a volt! (0.43).
Imbalance, however.

Why does this happen?
Because CQTH is the manufacturer.
And who is that? I don't know, it's the first time I've heard of them.
Personally, I think it's low-quality production.

And what is low-quality production?
It's when they take random cells, repackage them in their own film (if they have the budget for it), and assemble them into packs. And then, it's a matter of luck.

Usually, it looks like this.

This is soldering from a low-quality factory, I'm sure no one tampered with it because externally it was in a nice wrapper with a nice paper listing the specifications.

So, what controls all this battery protection?
The CM1041 chip, a fairly common budget solution.
It can protect, but it can't balance the cells.
They did the bare minimum, and for that, we should be thankful.
If only they used decent cells, it would be priceless.

The solution is to negotiate a change of the battery cell assembly manufacturer.

Charging board.
Primitive to the extreme.
It's like a Mosin rifle: the fewer parts, the less chance of breaking.
A 5-volt converter, a couple of diodes, a charge controller in the form of a single chip with a scattering of resistors and capacitors.
Cheap and cheerful.

Main controller.
Built on the basis of some sophisticated chip, without any markings.
A dozen resistors, about 5 capacitors, a voltage converter to power the chip.
The funniest thing is that the touch sensor chip with 3+ contacts is already embedded in this chip, along with the driver for an 8-segment display with 4+ digits and some motor control. It also handles all the main functions related to charge level, etc. Bravo, fitting all this into one chip is impressive. I don't know how they could have made this circuit any cheaper.

Well, it's time to show the most expensive part of the device - the BLDC motor.
They certainly didn't skimp on this (at least not noticeably).

3 power MOSFETs, one for each phase (couldn't find the datasheet for the markings)
Controller without markings
And a whole bunch of discrete components.
It's quite well-made for this class of device. Although, it couldn't have been done any other way.

Weak point - MOSFETs. I mentioned them above, explaining why this happens. Attaching a photo of the burnt one.

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So, let's move on to the most interesting part.
What about the competitors?

Our review opens with a massager under the brand: FitPulse.

The casing is somewhat different from ours, with screw covers and a semblance of a button that doesn't press

Looks more solid inside:

1) Metal bracket instead of a plastic one.
2) There is a lock washer under the shaft screw (on the left) to prevent accidental unscrewing.

The shaft guide looks the same.

All the other components, including the electronics, are identical.

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Next, we have MDHL:

Significant differences in the casing, 2 screws for the cover instead of 4.

Slippery handle without texture

Type-C charging, which is undoubtedly a plus.

The cover from our massager, for comparison.

Washer and good bearing on the motor side - a plus.
Lock washer on the shaft - a plus.

But they saved a lot on the motor - it's a regular brushed one.

Above, for comparison, ours is brushless

And on the controller board, accordingly, components for controlling the cheaper version of the motor are soldered

Well, and here is the same simple control board. Although, okay, it's a bit more advanced. It supports a different range of input voltages.
And they didn't skimp on two switches to disconnect when charging is connected.
Well, everything is good except for the cheap motor

And the battery is a bit poorer.

There are no differences in the shaft guide

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And the last massager, without a name or label, is absolutely the same MDHL clone, down to the screw

Summary:
**Differences from competitors are as follows, here are the main ones:**

1. Metal motor holder instead of plastic.
2. Competitors' massagers have lock washers. This prevents screws from loosening due to vibration.
3. Competitors' models use higher quality bearings.
4. Motor mounting on top or bottom, as I understand, depends on the type of motor.

Advantages of our massager:
1. Good motor.
2. 4-cell battery instead of 3 (different motors are designed for different voltages).

Regarding failures:
1. The shaft guide becomes unpressed, the metal bushing pops out - knocking sound.
2. The bearing wears out - grinding noise.
3. Screws become loose - extraneous light knocking sounds, vibrations.
4. High load on the motor - motor board switches fail.
5. Poor battery - goes out of balance - stops charging.