I have an amp board that runs on a 3way ac but I would like to run it using a 18650 battery pack.
Ive heard of rail splitters but I just don't know how to calculate what size capacitors and resistors I would need
I would really appreciate it if someone could help me out

This is the amp
https://www.ebay.com/itm/HIFI-200W-...Stereo-Module-Development-Board-/333179527153

 

I do not recognise the term "rail splitter" in the context of converting 3 phase AC to DC.

Can you please describe rail splitters or provide a link to a reference?

 

I do not recognise the term "rail splitter" in the context of converting 3 phase AC to DC.

Can you please describe rail splitters or provide a link to a reference?

Thanks for replying
Well this is where I found out about it

Just to let you I have no experience in electronics

 

hi mv,
Depending upon the OPA circuit application, the Passive splitter is very limited..
The Active OPA based splitter is a better choice, but again it has some limitations.

What are the required 3, voltages and current that you Amp requires.

E

 

It says 15 to 24v ac
So I was planning on using a 38v 18650 battery pack

 

hi mv,
Depending upon the OPA circuit application, the Passive splitter is very limited..
The Active OPA based splitter is a better choice, but again it has some limitations.

What are the required 3, voltages and current that you Amp requires.

E

It says 15 to 24v ac
So I was planning on using a 38v 18650 battery pack

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hi,
Looking over that PCB image, I would say that the 'black' rectifier and the two large capacitors, suggests a dual power supply of approx +/-18V
I would say that a Active splitter is not going to be a solution.
Divide your 36V battery pack into two 19V supplies, one as +V and one as -V. do you know how to do that.?
E

 

hi,
Looking over that PCB image, I would say that the 'black' rectifier and the two large capacitors, suggests a dual power supply of approx +/-18V
I would say that a Active splitter is not going to be a solution.
Divide your 36V battery pack into two 19V supplies, one as +V and one as -V. do you know how to do that.?
E

Oh ok
Thank you very much
One last question
Would it work just plugging it in straight like that???
Being that the battery is DC and the board requires ac

 

hi,
Confirm that the AC connector has 3 pins and the centre pin is the Amps 0v/Common reference.

I need to see clearer images of the PCB, front and back.
E

 

It is ok, but you will loose 1 to 2 volts in the rectifiers, or if you are real careful to always connect the batteries in the correct polarity you can remove the diode bridge and connect the batteries directly to the bridge's outputs marked + and - .

Keep in mind that as you use the batteries the voltage will drop and the specification in the listing says " - Working voltage: double AC18-24V " so maybe you want to start at a higher voltage so you can get more running time out of your batteries.

To get much volume (the amplifier is rated at hundreds of watts!) you will probably want to use a much larger battery than the 18650 unless you plan to run at very low volume.

 

hi,
Confirm that the AC connector has 3 pins and the centre pin is the Amps 0v/Common reference.

I need to see clearer images of the PCB, front and back.
E

Hey
Here it is

 

It is ok, but you will loose 1 to 2 volts in the rectifiers, or if you are real careful to always connect the batteries in the correct polarity you can remove the diode bridge and connect the batteries directly to the bridge's outputs marked + and - .

Keep in mind that as you use the batteries the voltage will drop and the specification in the listing says " - Working voltage: double AC18-24V " so maybe you want to start at a higher voltage so you can get more running time out of your batteries.

To get much volume (the amplifier is rated at hundreds of watts!) you will probably want to use a much larger battery than the 18650 unless you plan to run at very low volume.

I see

Initially this is what I was planning on doing since it seemed like the easiest thing to do
Being that I don't really know much about electronics
I just don't know what size capacitors and resistors I would use
Thanks for your help I really appreciate it

 

Hey
Here it isView attachment 202292View attachment 202293

hi,
Confirm that the AC connector has 3 pins and the centre pin is the Amps 0v/Common reference.

I need to see clearer images of the PCB, front and back.
E

Thank you for helping me

 

Why would anybody want to buy that cheeep, no-name-brand audio amplifier that has no detailed audio spec's??
An 18650 battery pack is rated for about 3A max then the 38V x 3A= 114W where half (57W) can be used for the 3 audio amplifiers and the other 57W is heating.

The Chinglish spec's say 80W, 100W and 120W. Whats? If the total supply voltage is 38V - 2V for the rectifiers then the total is 36V and the stereo amps will probably produce 33V maximum peak output which is 23.3V RMS. Then the stereo output max power per channel is 23.3V squared/8 ohms= 68W and the subwoofer output is probably bridged for 108W output.
Then the total maximum output power is 68W + 68W + 108W= 244W and the heating is another 244W so the battery must produce 488W. Don't even think about 4 ohm speakers.
488W from a 38V battery is an average maximum current of 488/38= 12.8A and the peaks will be 18A. The little 18650 3A battery will explode.

 

Your resistor divider will not work for this kind of circuit. That is because the current needed to flow from the positive power supply to "ground" will not be the same amount that is needed from the negative supply. The currents are constantly changing when the speakers are being driven and much higher than what will be drawn by the 100 ohm resistors.

Eric gave a very good solution

(Some text removed for clarity)
I would say that a Active splitter is not going to be a solution.
Divide your 36V battery pack into two 19V supplies, one as +V and one as -V. do you know how to do that.?
E

And by that I am pretty sure he meant to make two battery packs, one for the positive supply and one for the negative supply.

Going back and looking at the specification, it says " - Working voltage: double AC18-24V ". When an AC voltage is referred to without otherwise specifying the type of measurement, it is taken to mean RMS (root mean squared), which is 0.707 less than the peak voltage. Your DC (battery) power supply should therefore be ±18V/0.707 to ±24V/0.707, or 25 to 34 volts DC, so the battery pack supplies DC that is the same voltage as the peak. Is that right @Audioguru again ?

 

Your resistor divider will not work for this kind of circuit. That is because the current needed to flow from the positive power supply to "ground" will not be the same amount that is needed from the negative supply. The currents are constantly changing when the speakers are being driven and much higher than what will be drawn by the 100 ohm resistors.

Eric gave a very good solution



And by that I am pretty sure he meant to make two battery packs, one for the positive supply and one for the negative supply.

Going back and looking at the specification, it says " - Working voltage: double AC18-24V ". When an AC voltage is referred to without otherwise specifying the type of measurement, it is taken to mean RMS (root mean squared), which is 0.707 less than the peak voltage. Your DC (battery) power supply should therefore be ±18V/0.707 to ±24V/0.707, or 25 to 34 volts DC, so the battery pack supplies DC that is the same voltage as the peak. Is that right @Audioguru again ?

Ok Thanks again for your help

 

hi m,
Look over this marked up image clip.
1. Check that rectifier pins, ie: my marked +V goes to the +V pin of the rectifier.
2. My -V marked pins goes to the -V pin of the rectifier.
3. My 0V marked pin goes to the centre junction of the two 19V battery blocks.

E.
IF in doubt ASK!

 

I agree that resistor rail splitter will not work and if the amplifier was made properly then a DC supply of +34V/-34V can be used but probably then it might explode with its very cheap price and tiny heatsink. The fan will blow the smoke around. Its main filter capacitors are shown as 40V ones so they might be OK.

 

hi agu,
Where do you see +/-36V on that drawing.????

Perhaps a little more helpful advice would be order instead of the over the top rhetoric.

E

 

hi agu,
Where do you see +/-36V on that drawing.????

The spec of dual 24VACmax has peaks at 34VDC.