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Old 21st July 2012, 05:17 AM   #1
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Default Running class d amps on batteries...

I have two questions about battery power on class d amps.

1) When using my sure 7498 boards (either 4 or 6 channel) 3 large SLA batteries, I am getting clipping sounds. It sounds better and louder at 24 volts.

2) When using two inexpensive 12v cctv lithium batteries to power a 2050 class d board (at 24v), my batteries seem to automatically turn off. When I toggle the on off switch on the battery it all fires up again for a while, then kicks off again. Are they not able to run in series?

Thanks for the help, sorry if this is already covered, I couldn't find it.

Tor
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Old 21st July 2012, 05:29 AM   #2
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Originally Posted by torclausen View Post
2) When using two inexpensive 12v cctv lithium batteries to power a 2050 class d board (at 24v), my batteries seem to automatically turn off. When I toggle the on off switch on the battery it all fires up again for a while, then kicks off again. Are they not able to run in series?
You're lucky. Your packs have current overload protection.
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Old 21st July 2012, 03:49 PM   #3
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So the cctv batteries can't run that size of amplifier, or they can't run at 24v?

And does anyone know why my sure boards on SLA batteries are behaving that way?

Thanks, T
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Old 22nd July 2012, 06:49 AM   #4
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What type of batteries do I need?
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Old 25th July 2012, 07:19 AM   #5
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It seems that it has nothing to do with the batteries. I hooked up two car batteries, and it did the same clipping sound. So I wonder whats up.
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Old 25th July 2012, 08:53 AM   #6
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Originally Posted by torclausen View Post
It seems that it has nothing to do with the batteries. I hooked up two car batteries, and it did the same clipping sound. So I wonder whats up.
Most probably the input signal is too high. What are you feeding it?
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Old 25th July 2012, 07:37 PM   #7
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Iphone out. I've tries all the gain settings. Its unimpressively not loud. worst at 39 volts. 2050 at 24 is much louder and clear. I feel like I'm doing something wrong, but I don't think its my rather feeble iphone output.
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Old 26th July 2012, 09:49 AM   #8
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The output from iPhones and iPod touches have more voltage swing than most portable devices, but definitely shouldn't be a problem.

Which speakers are you using?

I'm interested in the CCTV batteries - they offer a lot of capacity but the current limiting is an issue. Perhaps some bulk capacitors would smooth out the current demands to something the battery will tolerate?
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Old 26th July 2012, 12:19 PM   #9
marce is offline marce  United Kingdom
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Try a power supply between the batteries and the class D amp, a good SMPS will do the job if you have one. This will isolate the batteries somewhat from the class D switching pulses asnd give you another metric to work with.
Also look at inductances between the batteries and the amp.
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Old 26th July 2012, 07:07 PM   #10
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chris661 - I'm currently using 4 kicker 6x9 speakers, and a DVC infinity 12" sub. All 4 ohm.

I've had great luck with the 25 watt class d 2020 amp and lithium batteries. ONe common one on ebay even has a usb output as well. 3800 mAh. $18 bucks shipped. The size of a deck of cards. The seem to run into problems when set in series to make 24 volts. I wonder if other 12 dvc lithiums can handle it. I don't know what specification I should look for when buying for such an arraignment.

Marce How big does the power supply need to be? Could one of those scooter 24vdc 3amp power supplies work? They are commonly at the junk stores.
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