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How to wire a ciruit to charge a lead acid battery when needed and power a audio amplifier?

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I have a small audio amplifier i am trying to power off of a lead acid battery to make it portable.  I want to make it so when you plug in a power adapter it will be able to charge the battery and run the amplifier at the same time. It is a 30 watt amplifier.  Should i connect the power adapter to the charging circuit and the audio amplifier in parralel? And then connect the battery to the circuit in parralel? I was thinking of using a laptop power adapter as the power source. I forgot to put a diode between the battery and the amp to prevent the power supply from charging the battery directly through the audio amp parralel connection.  Would this work? Else what should I do?

3 Replies

Re-design (author)2010-01-03

The battery should be connected to the amp and the charging circuit should be connected to the battery.  Blacks to black and reds to red.  The power supply should be connected to the charging circuit only.

YOu could put a diode on the battery between it and the charging circuit to prevent the battery from discharging thru the charger when it is unplugged.

snowluck2345 (author)Re-design2010-01-03

I was worried that the charging circuit wouldn't be able to charge it and supply power for the amp at the same time. Because If the charging circuit is charging the battery at 1 C, that would be 5 amps for a 5 amp hour battery and if it was trying to power the amp at the same time it would have to supply 7.5 amps, which i think is more than most charging circuits can

so wire it like this, and it won't charge as fast when the amp is on, but it will still charge.  Also do you know how fast you can charge a lead acid battery safetly, as in what amount compared to its capacity?