DIY Series 102: Handheld Megaphone Speaker From School

Handheld Megaphone Speaker From School

Received 2 units of Handheld Megaphone Speakers from a primary school. Provided free debugging and free repair service to the school.

Symptoms: 

• Upon power on, there is no sound output

Analysis:

• Checked the battery, it is using a customised Battery Pack (18650 Li-Ion, single cell, 3.7V, 2000mA)
• Battery pack comes with USB port for charging, but unable to charge when insert to a USB port for charging.

Photos:

• Unlatch and open up the back cover of Megaphone

• Unplug the battery pack from USB Port

• Unscrew a screw at the battery pack housing

• Take out the old 18650 Battery from its housing (terminals joint by spot welding)

• Disconnect the old 18650 Battery from +/- terminal wiring (spot welded)

• Prepare nickel strip to make 2pcs of nickel plates for +/- terminal wiring spot welding

• Clamp the nickel plates onto +/- terminal wiring using wire cutter

• Spot welding a nickel plate onto the new 18650 Battery positive (+) terminal

• Spot welding a nickel plate onto the new 18650 Battery negative (-) terminal

• Reinsert the new 18650 Battery into its housing

• Screw the housing and turn on the switch to check Battery Pack. The Red colour LED is on upon switched on, means battery is fine. Take the Battery Pack for USB charging, charge until LED turn into Blue colour.

Tools Involved:

• Screwdriver
• Multimeter
• Spot Welder
• Wire cutter
• Tweezer
• Scissor

Cost Involved:

• 18650 Li-Ion Battery (4800mA): US$0.80

Note:

• Current lithium-ion technology for the standard 18650 form factor (18mm x 65mm) has a physical maximum capacity limit of approximately 3500mAh to 3600mAh. 
• Any 18650 battery claiming more than 4000mAh, including ProDIY, is generally considered by experts to be using inflated marketing specs.
• ProDIY claimed to have 4800mAh but it is estimated the battery capacity < 2500mAh.