BT speaker, battery or PCB problem?

Thread Starter

tab a

Joined Jan 14, 2015
47
Not sure how my post ended up in the Datasheets forum, but I think it belongs here.

Working on my Oontz 3 speaker. It suddenly quit playing even though battery charge should have been good. When plugged in to USB charger, charging light does not flash like it should. Took the batteries out-- (2) 18650s in series, which each show a little over 3.7v.

My initial thought was that the PCB is bad, which is way over my pay grade, but then I wondered if the battery management chip on the batteries might possibly cause this? If possible, how to test?

Thanks.
 

Audioguru again

Joined Oct 21, 2019
3,171
An 18650 battery is 4.2V when fully charged so yours are only half-charged.
The manufacturer claims an output of 10 peak Whats that is not true 5 Watts.
Reviews say the tiny speaker has crappy and awful sound with no deep bass.
 

Thread Starter

tab a

Joined Jan 14, 2015
47
I looked at the batteries again and see that I was wrong--they are in parallel, not series. I also can't test them individually.

So my question remains. Could the chip on the batteries cause this? Or could one battery be dead, and the chip doesn't allow the other to charge. I know very little about Li battery management chips.

I've been into ''high-end" (terrible term) audio since it was actually affordable ;) and for the price, think it sounds pretty good. Of course there is no deep bass!
Thanks!
 

Audioguru again

Joined Oct 21, 2019
3,171
Many 18650 lithium batteries do not have protection chips inside. I do not know if the Oontz speaker has them.

I am looking at the datasheet of the PAM8403 bridged class-D amplifier IC, with the battery fully charged at 4.2V the output power when clipping barely begins at 0.1% distortion into 4 ohms is only 1.5W per channel but is 2W at 1% distortion and is 2.9W at a horrible 20% distortion. Maybe they overload the amplifier with 3.2 ohm or 3 ohms speakers for more power and more distortion. Then they say "peak" power which is simply double the real power.

I heard a Bose little speaker at Costco and was amazed at its good sounds until I saw its very expensive price.
I went to a Bose demo and heard two huge speakers producing very deep bass. Then two pretty young ladies came and removed fake covers over two little speakers that made me shiver that they produced such good sounds. I looked all over to see if they hid a sub-woofer but there was none.
 

KeithWalker

Joined Jul 10, 2017
1,778
I am not familiar with the Oontz 3 speakers but from you comments, the batteries are good. That means that the problem is either in the power management circuit, the amplifier or the speaker.
You can easily test the speaker. If you measure the coil resistance, it should be a little under 4 ohms and you will probably be able to hear a click when you connect the meter on the ohms range.
It will be difficult to diagnose an electronic problem without a circuit diagram. All I can suggest is inspect the circuit board carefully with a magnifier to see if you can find any bad solder joints or broken wires.
 

Audioguru again

Joined Oct 21, 2019
3,171
The little circuit hanging on the side of the batteries might be a defective BMS or defective charger since the charging light does not flash anymore.
 
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