Missing components on a bluetooth speaker pcb from overvoltage

Thread Starter

anodyne3

Joined Oct 10, 2018
1
Hey all,

A friend of mine brought me his bluetooth speaker which he had broken by plugging in a laptop charger (19v) when he couldn't find the actual ac charger (9v 1.3A) for the device. This burned some components to dust as well as melting the housing (purely cosmetic).

The main board still works and was powering on from the battery (18650 7.4v 2000mAh 2s, no balancing, with (I believe) integrated protection), until the battery charge dropped to 6.1v. I can't read or discover what components were destroyed. Maybe a relay and a resistor.

IMG_20181010_113052.jpg

There's a USB input that supplies 4.2v to the battery, but the device won't power on with the USB plugged in. Once powered on by the battery I was able to plug in the USB and unplug the battery, and keep the device on. This USB port is not accessible ordinarily, once the housing is assembled.

IMG_20180912_175757.jpg IMG_20180913_184231.jpg

I'm looking for a way to charge the battery at least, and wondering if using the 9V charger is safe to do so. I believe that 8.4v is the right voltage for charging a 7.4v battery.

I'm also wondering what I would need to be able to power the device and charge the battery at the same time.

I actually don't have that much experience with electronics, so I'm learning as I go. Any help would be appreciated, before I go ahead and learn things the hard way.

Thanks for reading
 
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