Harman Kardon portable speaker charging circuit problem

Thread Starter


Joined May 26, 2021
Hello everyone,
I have a problem with the battery playtime of my Harman Kardon Onyx studio 4.
On max volume it lasts barely 1h30min whereas it used to last at least 3h (it should last a theoretical 8h of playtime on normal volume).
Thinking that the battery life had ended, I replaced it with a new one and charged it as recommended but the problem persisted.
I replaced the battery with another new one thinking that the other may be defective but the problem is the same.
When plugged to a wall outlet, the speaker works for as many hours as needed, it charges as well, so I don't think there's a problem in the power input. The battery lasts for more than 3 hours on normal volume.
I have another same speaker but newer and the battery lasts for more than 3h on max volume.
What could be the problem? Could it be the charging circuit ?
Many thanks!


Joined Nov 6, 2012
It could be any number of things.
These little Speakers are built to satisfy a "Price-Point" so
the Engineering and Quality-Control is sometimes limited.
I'm genuinely surprised to hear that they withstand full volume for hours-on-end.

You can take the old and the new speakers apart and compare the
Battery-Voltages while they are being charged.
Unfortunately you'll spend more Money and Time trying to fix it,
than the actual cost of a new one,
that is,
if you are ultimately successful at finding the problem and fixing it.

An extension-cord is cheaper and more reliable.

Audioguru again

Joined Oct 21, 2019
I think the newer one uses a more efficient class-D audio amplifier but the old one used a class-AB amplifier that wastes more current. The newer battery also might have a higher rated and actual capacity than the old one.