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electrical confusion

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KamikaziFreak

PostPosted: Thu Jul 09, 2009 3:43 pm
At the house that I live in, we have a solar panel that charges a ~12V sealed lead battery, which is then hooked to a power inverter and used to power some household devices. One of those devices was a boombox, which had the ability to be powered by 8 'C' alkaline cells in series.

I got the great idea that it would be more efficient to avoid converting from DC to AC then back to DC inside the boombox. I checked the voltage on the battery (almost 14V, but that's to be expected), then used my voltmeter leads to join the battery to the boombox, paying attention to the polarities. When I clipped the second lead in place, it started to melt within two seconds, and smoke was coming off it. The boombox's internal components had noticeable heat rising off them; it doesn't work anymore.

While I do view almost starting a fire as a sign of success in any experiment, the fact remains that it didn't work and worse, I don't know why. Anyone have some insight?  
PostPosted: Sat Jul 11, 2009 8:52 pm
Was there anything else connected to the same leads? If the solar panels were, then since they are current sources, it's no wonder that something that expects a voltage source instead would not work correctly. A constant current is fine for charging batteries, but a boombox would likely not be designed to handle anything but a constant voltage as input.  

VorpalNeko
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KamikaziFreak

PostPosted: Mon Jul 13, 2009 12:06 am
Nope, the battery was downstairs, and I'd unhooked the inverter. It was just the battery and the boombox.  
PostPosted: Fri Aug 14, 2009 3:00 pm
KamikaziFreak
Nope, the battery was downstairs, and I'd unhooked the inverter. It was just the battery and the boombox.

Power is volts times amperage. But the circuit in the box should handle the pressure (voltage) fine. Perhaps the battery was overcharged, or it was in series with the solar panels from outside, and it was bright daylight, and so there was greater voltage going to the box?  

O1OO1OO1O1OO1111


KamikaziFreak

PostPosted: Sat Sep 05, 2009 10:50 am
Dr_Improveourselves
KamikaziFreak
Nope, the battery was downstairs, and I'd unhooked the inverter. It was just the battery and the boombox.

Power is volts times amperage. But the circuit in the box should handle the pressure (voltage) fine. Perhaps the battery was overcharged, or it was in series with the solar panels from outside, and it was bright daylight, and so there was greater voltage going to the box?


The solar panel was unhooked, upstairs. The battery was at 14V, slightly higher than the device was expecting, but not unusual for a lead battery like that.
Still, a 2 volt difference should not equal melting components in 1-2 seconds.  
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