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Can a car amplifier run off of a 9 volt battery?
Can a car amplifier run off of a 9 volt battery?
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Old 22nd March 2017, 04:08 PM   #11
realflow100 is offline realflow100  United States
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I have a 12v 5AH SLA AGM battery i bought for 12-14$ free shipping no tax on amazon.

I had to take the plastic protective cover off and open all the little rubber valves
and go in to all six of them with an army of q-tips and a plastic bag to put the used q-tips in
because there was lots of excess water/acid everywhere
It was VERY clear so it might of been just excess water
It was all over the caps and underneath the plastic cover and valves

once i dried all of that out and got it all cleaned up i had about 20 q-tips used up in a plastic sandwich bag

There was a bit of free liquid in each cell so i dabbed it carefully with a q-tip till all the excess was soaked up and no longer free liquid.

Now i super glued the plastic cover back on with all the rubber valve caps on each cell vent.
and it works normally.
I had to do that because I didn't want any excess liquid dripping out.
No i did not test it on bare skin or anything or taste it. but it was most likely just excess liquid from the factory.

It works fine and can power a 12v 400W power inverter for plenty length of time startup a blender and run my desktop computer and monitor (235W PSU and 20-25W LED monitor)
I tweaked the power inverter potentiometers and analyzed the waveform to match it to a 60hz sinewave on my computer
also tweaked the voltage so it read a max of 127v and minimum of 110v (higher the input voltage of 12v the lower the output voltage. No idea why its like that.) the reason I tweaked it because its output voltage was excessively high. over 140v AC! It was running really hot like that. especially when running something like a 2A 120v 200W vacuum cleaner. it would heat up a lot more.
Now its immensely more efficient and lasts a lot longer running cooler.

Also installed a resistor in series with the fan so its not going full blast all the time (no need for fan to be screaming. the inverter barely gets even warm while powering my desktop computer the whole time.

I'm not using the 12v battery for anything at the moment. only keeping it topped up for an emergency use with my inverter if the power goes out. (nothing plugged in or running so no power gets wasted)
like lights and stuff.
And yes this forum post is really old
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Old 22nd March 2017, 04:14 PM   #12
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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300W from a 9V battery! This is efficiency! I want two of them :-)
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Old 22nd March 2017, 04:26 PM   #13
realflow100 is offline realflow100  United States
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Well of course its not going to output 300W
More like 1W if your lucky.
but thats still plenty loud enough to be "running" for some small desktop speakers or something.

I'm not trying to run a 24" jackhammer woofer or anything
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Old 22nd March 2017, 04:34 PM   #14
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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Neither in this case it can work pretty fine. The self power consumption is several time greater than the power capability of the cell.

Do not doubt, guy, definitively it will not do its job.
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Old 22nd March 2017, 04:48 PM   #15
realflow100 is offline realflow100  United States
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i've ran a 12v power inverter from a single directly connected 9v battery long enough to make a 1W LED light bulb flicker on then off.
so its got at least some power in it.
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Old 22nd March 2017, 05:26 PM   #16
Johnny2Bad is offline Johnny2Bad  Canada
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You can use a buck/boost supply to get 12V from 9; you lose current in the translation, and you need the current to get decent power output, but it can be done.

Where I see the issue trying to run off a simple 9V supply without such a crutch is that is below the minimum voltage of a 12V lead-acid battery; go below about 9.5V and you have in most cases effectively killed the battery. Some multi-stage "smart" chargers might be able to bring it back to life but don't be surprised if that doesn't work, because it may well not.

So no car audio gear is going to be expecting a 9V supply as such a supply does not exist in the automotive world. Most of it won't expect anything below about 10.5V and is probably happiest at something closer to 14.6V. And that's assuming you are getting a full 9V ... if it's via a battery, let's not forget that this battery is going to be depleted in operation as well. So you are really asking to run on perhaps 8V or even 7.5V.

There might be specific models that will take 9V and go with it (at reduced power output compared to 12V) but how do you know which to choose without spending a lot of money just trying different candidates out?

Maybe it can be done ... somehow. But you are going to be much better off if you try and solve your problem some other way.
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Last edited by Johnny2Bad; 22nd March 2017 at 05:37 PM.
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Old 22nd March 2017, 09:09 PM   #17
realflow100 is offline realflow100  United States
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What about charging a super capacitor from a 9v battery with a boost converter
with 50-100mA current limiter (slowly to keep efficiency up)
up to 12v-ish
then using the super capacitors charged up. to run it for some time?
That way it would get the most energy out of the 9v battery as possible. even if its only for a minute.

I ran a 100F 2.7v super capacitor with a boost converter up to 5v to 12v and it ran for a good amount of time at least several minutes (At medium volume anyways. with some occasional bass beats and various moments of silence)
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Old 3rd February 2018, 02:47 PM   #18
VenusFly is offline VenusFly  Australia
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Can a car amplifier run off of a 9 volt battery?
with a 9v lithium battery you can extend the time even further.

But they are not much better being single use only. What you should be looking for are LSD 9v NiMH batteries. That way you can recharge it again and again for even longer runtime per charge.

I would however power a rasberry pi with an integrated power supply (dc to dc converter) and amplifier from a single 9v battery. That way you will get more use out of it.

Last edited by VenusFly; 3rd February 2018 at 02:58 PM.
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Old 8th February 2018, 05:35 PM   #19
realflow100 is offline realflow100  United States
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I got a 9.6v type 9v LSD NIMH battery now.
its 230mAh but quite durable giving out over 6 amps if shorted and easily sustaining an amp or two without heating up.
on my 5v to 24v wide voltage range class D stereo audio amplifier it lasts for quite a while and when I like i'm able to easily push my speakers loudly and the voltage doesnt drop much either when its fully charged i'm able to make the speakers flex with some decent excursion and have some pretty impressive bass no one would expect such a tiny compact battery being so powerful sounding.

Imagine if bluetooth speakers were like that with rechargeable NIMH LSD 9.6v type 9v batteries instead of generally using a single lithium battery.
good battery life. and hard hitting bass when its needed. and rechargeable with fast charging time (ive charged it very quickly and it barely gets warm)
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