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).

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:

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:

Aluminum Board

Power board contain 6 transistors and 3 screwed terminals for three phases of BLDC motor:

All components are surface-mounted, which important for this aluminum board:

Components

MCU SH79F6413	DC-DC U3018 VIN: 18V-180V IOUT: 0.6A SOP-7	GATE DRIVER FD2103S 180V 1A SOP-8	N-CH MOSFET SKSS055N08N 85V 4.6mOhm 120A

💡 Unique Multiboard Construction (Al+FR4)

Actually I'm thinking about using the same approach for high power projects before:

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

Conclusions