USB 9V rechargeable battery

[Cuki79]

Originally Posted by dnf777

My understanding from other Li-ion applications is that they all have an internal circuit to monitor and prevent overcharging, as where ni-cad andvothers do not. Perhaps this generates noise in susceptible situations. Maybe simply some shielding foil in the battery compartment would fix it?

Li-ion have nominal voltage around 3.7-3.8 volts. There is no combination of cells that makes 9V.

They are paired with a Boost DC-DC converter to reach 9V.

Such a circuit will involve a switch that is turned on/off at a high speed, producing noise. If the switching is made at frequencies far from the audio-range and well filtered then you are good. However, if you have non-linearity bringing switching noise in the audio-range that is not filtered... Your're doomed.

Companies like Songbird FX main selling argument is for example to produce noise-free operation from USB powerbanks. You can find similar devices for a third of the price on ebay/amazon... But you can not be sure about the quality of filtering in the audio range.



https://www.songbirdfx.com/

[lkingston]

Originally Posted by Cuki79

Li-ion have nominal voltage around 3.7-3.8 volts. There is no combination of cells that makes 9V.



They are paired with a Boost DC-DC converter to reach 9V.



Such a circuit will involve a switch that is turned on/off at a high speed, producing noise. If the switching is made at frequencies far from the audio-range and well filtered then you are good. However, if you have non-linearity bringing switching noise in the audio-range that is not filtered... Your're doomed.



Companies like Songbird FX main selling argument is for example to produce noise-free operation from USB powerbanks. You can find similar devices for a third of the price on ebay/amazon... But you can not be sure about the quality of filtering in the audio range.







https://www.songbirdfx.com/

Thanks for that Cuki! I never had an issue with noise when I tried 9V lithium batteries. My only issue was that they would go immediately from reading full three bars to dead with no warning.

[shufflebeat]

Originally Posted by Cuki79

Li-ion have nominal voltage around 3.7-3.8 volts. There is no combination of cells that makes 9V.

They are paired with a Boost DC-DC converter to reach 9V...

That might be very interesting, cheers C.