Budget Boominator "lite".

mr. doom · 4th August 2010, 03:04 PM

I have acquired the components for a mobile mini PA and am about to start construction on the works. My design parameters have centered around trying to balance cost/weight/SPL but I still have to choose a battery, any suggestions?

Lead acid is very cheap ($30 for 24v 7ah) but kind of heavy.

What is the cheapest lithium battery that will drive the Sure Amp at full power for 4-6 hours?

Components:

Amp Sure Electronics 2X100 board $40

Speakers Peavey Pro 10 neo $40 X 2 = $80

24 piezo tweeters $24

5' of 10" sonotube (Free)

I also have a case of these 5" neo drivers I can array, although the lower efficiency might not add much to the project, at $3 each with grill I could not pass them up!

8 X $3 = $24

This will be the second "boom bike" I have constructed and be used to promote the local science museum.

Trying to keep the project under $225, that gives me about $60 for a battery.

mr. doom · 5th August 2010, 12:49 AM

Bump to any in the know.

gfiandy · 5th August 2010, 08:49 PM

Hi,

A very rough and ready calculation.

Full power music = approx 1/8th of max power (otherwise it will be so clipped you can't listen to it due to crest ratio of music)

Assume amp efficiency is 80%

Power = 100W / (8 * 0.8)

=> 15.6W per channel

2 channels

=> 31W

24V supply

P= IxV => I = V/P

=> I = 24 / 31 = 0.77A

playing time 6 hrs

=> 6 x 0.77 is required capacity => 4.6 amp hours required

Cheaperst lithium Ion I could find (with no charger) £138 but I didn't spend long looking.

I'd recomend you go with the SLA or even a slightly smaller one.

I can't guarantee this calculation it has some pretty rash assumptions in it, you didn't give me much to go on.

Regards,
Andrew

AdamThorne · 5th August 2010, 09:12 PM

Just a note for refinement on gfiandy's estimate:

80% efficiency on that amp sounds about right, but it only outputs 30-40 watts per channel at reasonable distortion levels into 8 ohms.

If he's using the amp I'm thinking of, anyway.

2*100W@ 4ohm TK2050 Tripath Class-T Audio Amplifier Board, Upgraded of AA-AB013 Buy Two Get One Free_Audio Amplifier and other Audio Boards_RF and Audio, Video Equipments_Sure Electronics' Webstore

so -- no promises here! -- 4.6 amp-hours might be more than you need to hit your target.

mr. doom · 6th August 2010, 01:15 AM

Thanks, it looks like I am on track and will share pictures soon!

mr. doom · 24th August 2010, 12:20 AM

Just needs to be wired up!

r0b · 24th August 2010, 09:10 AM

Sweeeeeeeeet

You could make it steampunk style, taht would fit with the science museum thing.

4th August 2010, 03:04 PM	#1
mr. doom diyAudio Member Join Date: Mar 2006 Location: glacier	Budget Boominator "lite". I have acquired the components for a mobile mini PA and am about to start construction on the works. My design parameters have centered around trying to balance cost/weight/SPL but I still have to choose a battery, any suggestions? Lead acid is very cheap ($30 for 24v 7ah) but kind of heavy. What is the cheapest lithium battery that will drive the Sure Amp at full power for 4-6 hours? Components: Amp Sure Electronics 2X100 board $40 Speakers Peavey Pro 10 neo $40 X 2 = $80 24 piezo tweeters $24 5' of 10" sonotube (Free) I also have a case of these 5" neo drivers I can array, although the lower efficiency might not add much to the project, at $3 each with grill I could not pass them up! 8 X $3 = $24 This will be the second "boom bike" I have constructed and be used to promote the local science museum. Trying to keep the project under $225, that gives me about $60 for a battery.

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5th August 2010, 12:49 AM	#2
mr. doom diyAudio Member Join Date: Mar 2006 Location: glacier	Bump to any in the know.

5th August 2010, 08:49 PM	#3
gfiandy Audio Engineer diyAudio Member Join Date: Jul 2003 Location: Cambridge UK	Hi, A very rough and ready calculation. Full power music = approx 1/8th of max power (otherwise it will be so clipped you can't listen to it due to crest ratio of music) Assume amp efficiency is 80% Power = 100W / (8 * 0.8) => 15.6W per channel 2 channels => 31W 24V supply P= IxV => I = V/P => I = 24 / 31 = 0.77A playing time 6 hrs => 6 x 0.77 is required capacity => 4.6 amp hours required Cheaperst lithium Ion I could find (with no charger) £138 but I didn't spend long looking. I'd recomend you go with the SLA or even a slightly smaller one. I can't guarantee this calculation it has some pretty rash assumptions in it, you didn't give me much to go on. Regards, Andrew

5th August 2010, 09:12 PM	#4
AdamThorne Rebel Samurai! diyAudio Member Join Date: Oct 2006 Location: Minneapolis, MN	Just a note for refinement on gfiandy's estimate: 80% efficiency on that amp sounds about right, but it only outputs 30-40 watts per channel at reasonable distortion levels into 8 ohms. If he's using the amp I'm thinking of, anyway. 2*100W@ 4ohm TK2050 Tripath Class-T Audio Amplifier Board, Upgraded of AA-AB013 Buy Two Get One Free_Audio Amplifier and other Audio Boards_RF and Audio, Video Equipments_Sure Electronics' Webstore so -- no promises here! -- 4.6 amp-hours might be more than you need to hit your target.

6th August 2010, 01:15 AM	#5
mr. doom diyAudio Member Join Date: Mar 2006 Location: glacier	Thanks, it looks like I am on track and will share pictures soon!

24th August 2010, 12:20 AM	#6
mr. doom diyAudio Member Join Date: Mar 2006 Location: glacier	Just needs to be wired up!

24th August 2010, 09:10 AM	#7
r0b diyAudio Member Join Date: Sep 2009	Sweeeeeeeeet You could make it steampunk style, taht would fit with the science museum thing.

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