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c0reyl 17th April 2012 05:21 PM

Velleman K4003 battery powered?
okay so I bought the Velleman K400 at radioshack assuming it would be DC and found out it's AC. I tried powering it with a 12v 7800MaH battery across the left channel only and it would only make the speaker driver push out like if you were to hook the battery directly to the voice coil, then when I put the ac adapter I had laying around which is like 12v 2A, it worked like a normal amp.

I need to power this thing with a battery so I can make my ipod dock with quality amplification. How do I power this amp with a 12v 7800MaH Li-Ion battery?

c0reyl 17th April 2012 06:50 PM

Oops typo, I meant to say K4003 :(

Pano 17th April 2012 06:52 PM

:cop: Thread title fixed.

Mooly 17th April 2012 06:53 PM

Do we have a circuit we can look at ?

c0reyl 17th April 2012 07:35 PM

Pano 17th April 2012 07:42 PM

This uses a dual supply - positive and negative. You'll need 2 batteries to make it work. You can see how to connect them in the PDF you linked.

c0reyl 17th April 2012 07:55 PM

damn I don't have enough batteries to make this work :[

if I were to use 6 volts at 3900 MaH on each side, would it work? I could mix a 13.2V Ni-Cd battery but I think that's a bad idea

c0reyl 17th April 2012 09:35 PM

update: it worked fine with both the Ni-Cd and the Li-Ion batteries.

So, since I don't have a quality source for audiophile speakers without messing with my home theater setup, I found out I can bridge this little amp, and hooked it up to my Velodyne ULD 18 subwoofer, and with a 10 ohm load, which means it's even less than the 20 watts it would've been if it were 8 ohms :3

and basically, this sub gets really loud for such a small amp, when it's a 400 watt subwoofer, and it definitely goes below 20Hz on this amp. I might just build a new amp instead of trying to fix my servo controller :o

How would I have a battery charging system to charge both the 13.2V and 12v batteries? have a 25-30v DC charger attached to positive of one battery and negative of other to charge while it plays? I'm kind of new to building amps and I'm not sure on how charging while you play works

Mooly 18th April 2012 07:14 AM

L-ion batteries have different (and extremely strict for safety) charging requirements.

To charge two different battery technologies in circuit would be very difficult to implement. If you want battery power then the best route is two small 12 volt SLA (sealed lead acid batteries) which are not that expensive. They could be charged in circuit with the amp still playing with a simple "constant voltage" and "current limited" supply. That means a supply that outputs around 30 volts DC in total (for cyclic duty as opposed to float charging) and that has a current limit of say 1amp. The charger would have to be isolated from "ground", in other words floating and is connected across the two series connected batteries for charging.

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