Roidmi Smart Car Charger 3S BFQ04RM

DSC_3927

Official specifications: I got it from gearbest.com

DSC_3887 DSC_3888

It arrived in a white box with specifications on the back.

DSC_3926

In the box was the charger and a instruction sheet.

DSC_3925 DSC_3929 DSC_3930


When I unpacked it there was a label telling about the control application. Below it was the two usb connectors and a very discrete 5V 2.4A marking.

DSC_3931

DSC_3932

The markings on the charger is also very discrete being black print on a black charger.

DSC_3933 DSC_3934



Measurements

Load%20sweep%2011.6V%20%231

Overload protection is slightly above 2.5A, this is very good for a 2.4A charger.

Load%20sweep%2014.6V%20%231

Load%20sweep%2024.0V%20%231

Voltage do not really change output voltage or overload protection.

Load%20sweep%2011.6V%20%232

The second output has the same limit.

Load%20sweep%2011.6V

But when used together the output is much higher and well above the rated 3.4A

Voltage%20sweep%203.4A%20input%20current

Voltage%20sweep%203.4A

The charger works down to about 7V

No%20load%20voltage%20sweep

The idle current is fairly high due to Bluetooth and FM transmitter.

Load%20test%203.4A

There was no problem running 1 hour with 3.4A load.
The temperature photos below are taken between 30 minutes and 60 minutes into the one hour test.

Temp6290

M1: 44.7C, HS1: 66.8C

Temp6291

M1: 48.0C, HS1: 68.0C

10ohm

At 0.5A the noise is 3mV rms and 50mVpp.

5ohm

At 1A the noise is 3mV rms and 52mVpp.

2ohm

At 2.5A the noise is 6mV rms and 67mVpp.

1.5ohm

At 3.3A the noise is 3mV rms and 55mVpp, all very very low values.



Bluetooth & FM

Spectrum

The FM radio is at selected frequency.

WhiteNoise

And white noise shows a horizontal level as it is supposed to do.

S1s S2s S3s

Roidmi has more than one Bluetooth product and they all share the same application, here I selected "Music Bluetooth Car Charger" and got a couple of simple setup screens. The application did require a lot of access to the phone: Phone, location, pictures, etc.
This application is not required to use the charger, the charger will connect to the phone and play music on 96.4MHz without it. The application is required to change FM frequency or read the battery voltage.

S4s

This is the default screen for the charger.

S5s

The frequency select looks similar to the initial frequency select.

S7s S8s S9s

The voltage display will give an alarm when battery voltage is out of tolerances. It is fairly precise, 12V is shown as 11.997V and 24V is shown as 23.94V. It cannot measure all voltage, but only the valid range for 12V and 24V batteries.

S6s

It also includes an explanation of the different voltage ranges for a car.

S10s

The about information is missing. This screen was selected on the welcome screen.



Tear down

DSC_4123

I could not get it open and used some dramatic cutting to do it.

DSC_4124

When I got it open I could see it was assembled from the front with two small screws to hold the electronic in place. The screws is first accessible when the front is removed.

DSC_4125

DSC_4126

The construction is two layer, one is radio, the other power supply. The front do also have some parts.

DSC_4127

DSC_4128

DSC_4129 DSC_4130

DSC_4131

Some soldering and the two layers was apart.

DSC_4134

This circuit board is the switcher with a switcher controller, a power mos and two current sense resistors (R040: 40mOhm), one for each output. At the input is a fuse (Green part with a T) and about 80uF in five ceramic capacitors.

DSC_4135

The other side is the inductor and a smoothing capacitor for the usb output voltage.
This board has 3 connections to the usb connectors: common 0V and a 5V for each output.

DSC_4142

DSC_4143 DSC_4145

DSC_4144

DSC_4151

DSC_4136

This circuit board has a FM transmitter (QN8027), some flash memory (BoyaMicro) and a processor with build in bluetooth, the bluetooth antenna is marked WTC.

DSC_4137

On this side is a 3.6V voltage regulator (Marked 65KH). The connector to the front is marked GND, RGB, MIC and 5V. The 3 of them is obvious, but what about MIC, is there a microphone in the front?

DSC_4146

DSC_4147 DSC_4152

DSC_4148

DSC_4149

DSC_4138 DSC_4139

The damaged chip was from trying to pry the circuit board out, it is a 3 channel (i.e. RGB) serial controlled LED controller. The other chip must be a auto coding chip.

DSC_4154

Here is the RGB led, below the usb connector. There is no microphone.

DSC_4140 DSC_4141

DSC_4150

The FM antenna is a coil placed around the USB connector.


Being a 12V device there is no need to test with high voltages.



Conclusion

The charger has two output, each with a good overload protection, very low noise and auto coding. In addition to this it is also a FM transmitter that can link to a phone with Bluetooth and transmit music to the car radio (This is most useful in older cars).

This is a very good car charger, but it cannot fast charge two power hungry device simultaneous.



Notes

There also exist a version with microphone, this is used for a hand-free function with the phone.

Index of all tested USB power supplies/chargers with DC input
Read more about how I test USB power supplies/charger