Simultaneous battery and DC jack power

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1

Hi, a friend of mine recommended this forum as a place to get answers about a project I’m working on.

I’ve modified a simple usb-powered plasma globe I bought off the internet to run off a (rechargable) 9-volt battery, so I can take it around with me. However, when it’s stationary, I’d rather preserve the battery by plugging it into the DC jack, which I have so far left intact.

I’m honestly an electronics novice, though, and I have no idea what would happen if I plugged in the DC power while the battery was still connected. Would it overload the circuits? Would it work as normal? Best case, would it charge the battery?

The mod I did was very basic - I just desoldered the DC jack, twisted the wires together with a 9-volt cap, and resoldered them back into the same place, so the battery and DC jack are connected to the same contacts on the board. The two sources of power work fine alone but I have been afraid to try plugging in the power cable while the battery is connected.

I realize that the way I’ve connected the battery may not be optimal, and I’m prepared to redo it and/or change the wiring structure if I’ve done it improperly. Any insights or advice?

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It is likely that if you connect the DC Jack and the battery at the same time it will damage one or the other or both. Assuming the globe can take a slightly lower voltage and still work (specs would be useful here) you could use diodes to isolate each power source. That wouldn’t charge the battery but would at least protect the two power sources from each other. If you use schottky diodes you lose less than half a volt going to the globe. Another alternative would be to put the correct mating plug onto the battery and just plug in battery or DC Jack as needed.

Good luck with your project.

  • Chip