Key Features:
- Smooth body transition
- Reduced noise due to lower temperature
- Perfect fit
- Print-in-place design
Why I Made This:
The M8S has two integrated fans that automatically start spinning at two temperature levels using loud PWM control. Since the internal temperature rises quickly, the fans are active most of the time when discharging above a 10W rate.
An external resistor might mitigate this, but I do not have a suitable setup. Reverse charging is also an option, but I do not always use it. When charging at higher currents, the fans activate as well, so I was looking for a way to reduce fan noise.
Replacing the fans might have worked, but the PWM signal could still cause them to whir loudly. I also did not want to remove the fans entirely, as they help air circulate over the heatsink. Instead, I left the fans in place and removed only the bottom cover. I installed a large fan and ensured enough air could be drawn from below.
Keep in mind:
- I only use the charger indoors
- My charging currents do not exceed 5A
- 4S is the highest voltage I use
- An extension will not be very effective, as the heatsink is on the opposite side of the PCB
Important:
- The screws holding the bottom of my charger in place included three small (3.4mm diameter) screws and one larger (4mm diameter) screw.
- I designed the extension to accommodate this screw size.
- If your charger has different screw sizes, they will not fit.
- Just ask me for a different version or modify the model yourself.
- If you frequently charge at high currents or near the maximum rating, this modification may have minimal impact, as the internal fans will still run continuously.
How I Made This:
The extension was modeled based on the dimensions of the original bottom cover, with slight modifications to fit the fan inside while maintaining a perfect fit.
I also created a simple temperature-controlled circuit using minimal components:
- 10k NTC thermistor
- 2N2222 transistor
- Two 10k resistors
- One 1k resistor
- Diode
This circuit makes the fan spin at a low, silent speed at room temperature and increases its speed as the internal temperature rises.
It also helps supply colder air to the other fans, improving their efficiency. I placed the NTC between the heatsink.
Since there are 5V and 12V solder pads on the bottom of the PCB, you can use a fan that matches the voltage and simply install it without a circuit in between.
Choosing the right fan voltage is crucial for silent operation:
- I use a 12V fan and supply it with 5V, which results in near-inaudible operation while maintaining effective airflow.
- A 24V fan at 12V might also work well.
- A naturally silent fan can be connected to the matching voltage pads directly.
Note:
- The resistor values are based on my fan and voltage setup, so they might not work for all fans.
- I do not know what the current limit on these pads is, but I assume the 5V pad is directly connected to the USB output (2.1A limit).
If you are interested in this circuit, feel free to message me or leave a comment.
You can probably also make a simple speed controller by replacing the NTC with a potentiometer.
What You Will Need:
- 4 M4 bolts (max 16mm thread length)
- Screwdriver
- Soldering iron
- Soldering wire
- 60x15mm fan
- Ensure the mounting holes are 50mm apart
- See the "How I Made This" section for voltage recommendations
- Temperature-controlled fan circuit (optional)
- Printed M8S_Fan_Cooling_Extension
How to Install:
1. Install the Fan
- Angle the fan slightly and slide it into position.
- Secure the fan in place using four M4x20 bolts.
- You might need to insert the bolts in the fan holes first
2. Remove the Bottom Cover
- Remove the rubber feet by pressing on them and pushing outward to loosen the adhesive.
- Keep the rubber feet intact, as they will be used on the extension.
- Remove the four screws hidden beneath the rubber feet.
3. Soldering
- Locate the GND, 5V, and 12V pads on the bottom of the PCB.
- Solder the fan or the temperature-controlled circuit to either the 5V or 12V pad and GND, depending on your fan or control circuit.
Note:
- I noticed the pads had to be heated a bit longer than I normally have to.
- I applied hot glue on top, but this might get loose due to heating up.
4. Install the Extension
- Insert the screws through the extended holes in the extension.
- Secure the extension in place by tightening the screws.
POEPOEFRED
