Practicality of 12 Volt Battery/Inverter for Bass Amp (1 night only)?

[winston]

This is a somewhat random question:

I'm submitting a proposal for an audio/visual art installation that needs to be as self-contained as possible. I'm thinking of either using one of my bass heads (GK400RB / EdenWT400) or a stereo receiver into my Bergantino or EA 1x12 cabs.

This is not a long-term thing, just for 5 hours on 1 night. It only needs to be loud enough to be heard over conversation & cut through ambient noise.

Is this something I could do with a car battery & inverter?
If an inverter, should it be rated for the power draw listed on the back of the amp, not the RMS rating?
How do I estimate battery life...would a bass amp draw too much current to last 5 hours?
Should I just use battery-powered boomboxes instead?

Thanks!

[T-Bird]

Hi.

The basic guideline I use when using inverters (or generators for that matter), is to have at least 100% "reserve" power, IOW double the wattage of the appliances. 3 times if the rig is small/cheap.

The simplified math is relatively easy if You can determine the draw.

Let's assume the average draw is 100W. Restrict the below 100Hz material and You can at least halve that.

Since the inverters efficiency plays the next role, You'll need that.
Again, let's assume it being 80%, and so we get 125W draw from the battery.

That divided by the battery voltage 12V or 24V, we'll get 10.4A and 5.2A, respectively.

Whether the battery can take that or not, and for how long, that depends of the battery.

Edit:Forgot one thing. You shouldn't use a car battery, it'll either be ruined, or at least it's lifespan will be severely reduced on a deep cycle application in which it's not intended to.
Use a deep cycle battery, used on el. wheelcairs, 12/24V power systems etc.

Regards
Sam

[Bassmec]

Originally Posted by T-Bird

Hi.

The basic guideline I use when using inverters (or generators for that matter), is to have at least 100% "reserve" power, IOW double the wattage of the appliances. 3 times if the rig is small/cheap.

The simplified math is relatively easy if You can determine the draw.

Let's assume the average draw is 100W. Restrict the below 100Hz material and You can at least halve that.

Since the inverters efficiency plays the next role, You'll need that.
Again, let's assume it being 80%, and so we get 125W draw from the battery.

That divided by the battery voltage 12V or 24V, we'll get 10.4A and 5.2A, respectively.

Whether the battery can take that or not, and for how long, that depends of the battery.

Edit:Forgot one thing. You shouldn't use a car battery, it'll either be ruined, or at least it's lifespan will be severely reduced on a deep cycle application in which it's not intended to.
Use a deep cycle battery, used on el. wheelcairs, 12/24V power systems etc.

Regards
Sam

Listen this guy must know, after all he can probably still start a Diesel in january where he lives.

[winston]

Thank you very much--makes sense.

Think I'll ixnay the bass amp idea--it's overkill.
I'll do either the battery-powered power boombox, or a low-powered stereo with deep-cycle battery + inverter.

[totem]

You could also rent a small generator. Honda has a line of quiet, small (1000 - 2000 watt) generators. I own one that I've used for outdoor art installations using video projectors, and rented them when I've travelled. I looked at my local rental place and they rent them for $28 a day. The tank on mine holds about a half gallon, which will run it for about 4 hours at a moderate load. I've experimented with batteries and inverters, and a generator is much easier and more reliable.

[Jerrold Tiers]

If you can use a class-D unit, then it's possible, with a battery that is at least a "marine deep cycle", which is neither deep cycle not marine, really, but better than a car battery, and not too expensive. AKA "trolling motor battery".

obviously a tube amp is a non-starter. Too much continuous draw. A small SS amp maybe.

Even a large class-D amp draws relatively little during "no sound" conditions, and there really is a good deal of "no sound" or 'low power" time in music.

if you can do a boom box, they are made for the purpose. the average battery life is probably in the specs somewhere.

[winston]

Thanks again for the helpful replies!

Generators are prohibited so that's not an option.
Interesting about the Class D.
Battery-powered boombox definitely looks like the way to go for this one.