🛠 TEARDOWN: Brushless Motor Controller 48V of the Chinese Electrical Bike (Ebike)
Introduction
This motor controller installed in the Chinese electrical 🚲 bike (ebike) with 750W motor. It failed due to water ingress, so let's analyze board and construction in overall.
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Specification
Brushless DC Motor Controller
- Model: JH4AQ6585DZMN
- Voltage: 48V
- Low Voltage Protect: 40V±1V
- Current Limit: 25A±1A
- Throttle adjustment voltage: 1.1V-4.2V
- Date: 20-03-2024
- Manufacturer: Dongguan jing hui Controller Co;LTD
- Transistors: 6PCS
- Chassis connection: isolated from GROUND
Teardown
Aluminum housing + heatsink
Aluminum board screwed to the case-heatstink with using thermal paste.
Cable input doesn't have good water protected input (some transparent sealant).
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Combined Construction
This is a multiboard, so we can see heating components on the aluminum board (bottom) and logic components on the FR-4 board (top):
It's pretty easy to detached them, because it uses 2mm pitch pin headers for signal lines:
FR-4 Board
Control board has additionally two electrolytic capacitors 1000uF 63V:
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The holes has only bottom side, so screwed not electrically connected to any of spacers:
Wires soldered directly to the board without proper mechanical retention. Silkscreen labeling not clear:
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Aluminum Board
Power board contain 6 transistors and 3 screwed terminals for three phases of BLDC motor:
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All components are surface-mounted, which important for this aluminum board:
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Components
MCU SH79F6413 | DC-DC U3018
| GATE DRIVER FD2103S
| N-CH MOSFET SKSS055N08N
| NPN BJT MMBT5551 (Marking G1 SOT-23 package)
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💡 Unique Multiboard Construction (Al+FR4)
Actually I'm thinking about using the same approach for high power projects before:
| 1 | Top FR-4 board for control components (microcontroller) |
| 2 | Metal spaces (standoffs) or screwed terminals |
| 2 | Bottom aluminum board for power components (transistors) |
And that's interesting that this miniature commercial controller already made like I want to do 😮
 | Effective High-Power Multiboard Design using Aluminum and FR-4 boards |
Wiring (Update from 09/04/2025)
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The end (2026/08/23)
After another water ingress controller totally died. I tried to replace FETs and drivers but it didn't helped, so I have to buy a new one.
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Tips (How to prevent water damage of controller?)
Place controller upside down, so water residuals can't easily ingress into internal space through gasket and cover. However, connectors are still in dangerous. 
Add drainage hole for frame space where controller is placed.
Check controller + connectors after rainy rides.
Conclusions
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Hello, I have one of these boards it got a little water now shorted can't find exact one out there it's from a 2024 bluvall b1 ebike
Hi. After riding at heavy rain I left it for a week.
On the next weekend I tried throttle, but display showed Error message.
I removed controller board, cleaned it and replace two big aluminum electrolytic capacitors 1000uF 63V (their pins was damaged).
In your case the situation could be another, who knows how much the board is damaged.
Hi. Is there a way to bypass display of the scooter with this type of controller? I have a scooter with same controller and display with NFC tags for «keys», but it's not working anymore. At first display turned on, but not always reacted to NFC tags, so i had to dial password almost every time, but now display doesn't turns on at all. And the controller do not have single thin red wire, near thick red and black battery wires, like other controllers do, which i could connect to a switch and use the scooter until new display arrives. I saw in some YouTube video that in the same case with ebike, you can connect red and blue wires that goes to display, and still use the bike with pedal assist, but it didn't work in my case, because my scooter doesn't have PAS censor and pedals. It only have a throttle which don't do a thing until you switch any «gear», which i can't do without display turned on.
Hi.
If NFC integrated into display I don't think so.
If NFC connected to the display with like with 3 wires (GND, VCC, SIGNAL) it should be possible.
It worth to check if wires and connectors from display to controller are fine and consider buy new/try to repair existing display.
Yes, NFC is integrated into display, and it wouldn't be that much of a problem if display would at least turning on, so I could just use a password, but it just completely died and was blinking like crazy before it happened. Anyway, new one comes in a few days, so it's doesn't matter anymore, but thanks for the answer.
Hi. Do you, by any chance, know what communication protocol this controller uses? I bought a new display in UART2 protocol and it shows «communication reception failure» error(E10).
No, I don't know.
BTW, this controller from Crosser CR2 ebike.
Ok, thank you.