Help about battery

Thread Starter

Dzoro

Joined Feb 1, 2019
137
So i want to build a power cell with lithium batteris and i want it to be bipolar with +12 and -12 volts to power an amlifier and i don't know how to build it to be bipolar.
I was thinking of using lm7812 for +12 volts and lm7912 for -12 but the regulators can only give 1 amp of max current and i need more so i need help of achiving this.
Thanks
Dzoro
 

Reloadron

Joined Jan 15, 2015
4,749
Unless you really need regulation all you need to do is configure two 12 Volt batteries in series and make the junction your common or ground. Like shown below:

12 V Series.png

Now if you really need a +/- 12 VDC supply things get a little more complicated depending on how much current your load will draw. Most amps I have seen really do not require a regulated plus and minus 12 volt supply.

Ron
 

Audioguru

Joined Dec 20, 2007
11,251
Power amplifiers for speakers usually do not need voltage regulators.
Three lithium cells in series produce 12.6V when fully charged and drop to 11.1V at half charge then drop to 9.6V when the battery should be disconnected. The amplifier should work fine at any of these voltages but the maximum undistorted output power will be reduced a little.
 

Thread Starter

Dzoro

Joined Feb 1, 2019
137
How much current does the amplifier draw and how long do you want the batteries to run it for?
The amplifier draws about 1.8 amps at medium and 2.5 amps at max and for the running i want it to run at least 5h but i don't know if its possible beacose i don't have many cells
 

Thread Starter

Dzoro

Joined Feb 1, 2019
137
And also i don't know how can i charge them
Does it need to be 24 volts and 400-500 mA for the charge like normal battery or something different
 

Audioguru

Joined Dec 20, 2007
11,251
Powered from +12V and -12V, an ordinary single amplifier has a peak-to-peak output of about 20V which is 7.1V RMS. Then the power into 8 ohms is (7.1V squared)/8= 6.3W. If it is class-AB then it heats with about 4W so the power from the battery is 10.3W and the maximum current is 10.3W/24V= 430mA. If the speaker is 4 ohms then the amplifier output power, its heating and the battery current are almost doubled.
Amplifiers play music and speech with an average output power of 1/10th the maximum, they usually do not play continuous tones at full blast.

Dzoro did not say if the amplifier is stereo or a quad. He also did not say if each amplifier is bridged.
 
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