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Can I use a 9v battery to power usb speakers?

I recently made a mini amplifier out of some usb speakers and at the moment it's powered by usb but I want to make it battery powered so do you think a 9v battery will be fine? I don't want to ruin the amp so I want to make sure but it has a 16v 470uf capacitor on it and that's about all I can tell you about the circuit board. I'd imagine it would be fine but is there any way to tell?

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jlandreth1 (author) 1 year ago

Thanks for all your answers and I'll be considering all of them. Also I might do a bit of testing with different batteries and stuff and see what works best!

I suggest using 4 AA alkaline, or carbon-zinc, batteries in series, using a battery holder made for this. The nominal output voltage for a series stack of 4 AAs is 4*1.5 = 6.0 volts. I think that would be the cheapest and easiest thing.

I mean aside from using a single a single 9-volt battery. I suppose that might work too. The mini amplifier can probably tolerate a pretty wide range of supply voltage. Like you said, you found an electrolytic cap on the board, with a rating of 16 V printed on it.

Although, where I live, a single 9-volt battery usually costs more than a pack of 4 AAs of the same chemistry. And the 9-volt has terrible current capacity (measured in ampere*hours) compared to the AA, so the 9-volt would likely die sooner.

Answerers have also suggested using one of these USB charger gizmos, and usually those are a boost-converter that supplies a regulated 5V output, using a single lithium-ion cell (3.7 V) that maybe even has a included charger, or there are other USB charger gizmos powered by 1x or 2x AA batteries.

A problem you might run into with the USB charger gizmo, is that some of the cheap ones do not do a good job of filtering their own switching noise, which might be in the audible part of the spectrum. You will easily recognize this problem if you have it, by the "weeeeeeeeeeeeeeeeeeeeeeeeeeeeeee..." sound coming over the speakers. In contrast, the DC that comes from a battery is dead quiet.

Link to picture of what 4x AA battery holder looks like:

https://www.instructables.com/file/FQP1WX5GYR36BUZ/

jlandreth1 (author)  Jack A Lopez1 year ago

Thanks and that buzzing noise they can make is very good to know so if I do the usb idea I'll be careful. Also aa batteries might work but 4 of them might not fit in the project box I've made but I'll consider that :)

a 9V battery won't last long as they are not meant to provide good power levels.
Essentially they are 6 1.5V batteries, each smaller and thinner than a AAA.
Go with old style mobile phone batteries instead.
You get them new and dirt cheap on Ebay and often with more than enough power - more mAh the longer your amp will work.

jlandreth1 (author)  Downunder35m1 year ago
Thanks and true didn't think about that with 9volts. Plus I think I have a few phone batteries lying around! Just one thing though. Most phone batteries are around 3.7v would that make my amp underpowered?

You can try the amp on a regulated power supply to see how far down you can take the voltage but as Wired Mist suggested use a boost converter or dedicated USB backup pack.

Use a "boost converter" to bump-up the voltage from 3.7 to 5V. Even a Tiny lipo like a cell batt will have better life then a 9V

Here's a Link...

Unfortunately this is sold out ATM, but many other electronic stores have something similar. This one will also charge you batt too!