Lithium Ion Battery Pack humming / whining when under load

[ii]

I've connected these together, and when I attached the 5V out from the Power 1000, the battery pack begins to whine.
Since I'm trying to put this into a keyboard, I'm looking to keep things as silent as possible.

https://twitter.com/hippiehacker/status ... 2535146496

I had another keyboard based on the same battery and the Powerboost 500 and it didn't whine.
Any thoughts as to why it whines, is that normal?

Products:
Lithium Ion Battery Pack - 3.7V 6600mAh : https://www.adafruit.com/products/353
USB LiIon/LiPoly charger - v1.2 : https://www.adafruit.com/products/259
PowerBoost 1000 Basic - 5V USB Boost @ 1000mA from 1.8V+ : https://www.adafruit.com/products/2030
Raspberry Pi 2 - Model B - ARMv7 with 1G RAM : https://www.adafruit.com/products/2358

[adafruit_support_bill]

I suspect what you are hearing is from the boost converter, not the battery itself. Boost converters work by switching current through a resonant circuit at a high frequency. Higher loads mean higher currents and stronger magnetic fields in the inductor. This creates a vibration whch can be audible under high loads.

[ii]

I put my ear up to the different components and I'm pretty sure it's coming from the battery.

I'll get some second opinions on the audio... its' interesting to note than when using ssh over wifi, I can hear the transmit of each character back to me when using an Intel Edison.:

https://twitter.com/hippiehacker/status ... 1762824193

[ii]

You're right it is the powerboost converter. I think the 500 model doesn't make this sound (that's what I had before), only the 1000 does.
500 seemed enough, but I wanted to be able to boost up.
Is there anything I can do with the 1000 to reduce the noice or should I just go back to a 500?

[ii]

I sent an email to support, really asking for an exchange or a solution, but I got an automated email to post on the forums.
So I'll include it here.

Sender: chris@hippiehacker.org
Date: Mon, 20 Apr 2015 09:43:15 -0700
Subject: Powerboost 1000 whine
To: Limor Fried <support@adafruit.com>

Hi there,

I'm having a terriblly loud (for me) whine coming from my PowerBoost 1000 Basic

It's documented:
viewtopic.php?f=19&t=66337&p=366904#p336409

But not on the purchase page:
https://www.adafruit.com/products/2030

I built another device using http://www.adafruit.com/products/1944
that I didn't quite hear the noise on.

And thought it would be useful to buy a stand alone charger (to have
status pins) https://www.adafruit.com/products/259 and combine it with
a 500/1000 basic, but since my project is a keyboard and I'm noise
sensitive, I was wondering if I could trade out the 1000s for the 500s
if you think the 500 basic would have the same noise levels as the 500
Charger. Otherwise I might need to just forgo the status pins and go
back to a 500 w/ charger.

https://twitter.com/hippiehacker/status ... 1762824193

I'm open to other alternatives as well.

Cheers,
-chris