12v stable from a 4S5P li-ion pack

[Ozzyfr]

Hi,
Is there a small module capable of stabelising a 12v output out of a 4S5P battery pack that delivers around 14.8V and drawing at max 20A?
Thank you!

[innkeeper]

Hi,

The problem is that a lipo under that kind of load will likely drop in voltage to 3v per cell and even lower as it discharges depending on the cell.

to handle that, you would need something called a boost/buck converter, that will raise and lower the output voltage depending on need, however, i've never seen one at 20A... it doesn't mean it doesn't exist or that you couldn't design one.

life would be easier if it were 5S then you would be at 18.5v and maybe 15v under heavy load.
There are plenty of circuits out there that could do that by just regulating the output.

[Audioguru]

If your battery can supply 20A continuously then each cell provides 4A. It has 4 cells in series so its fully charged voltage is 4 x 4.2V= 16.8V. The poor voltage regulator will heat with (16.8V - 12V) x 20A= 96W. Do you have a voltage regulator powerful enough and a heatsink large enough?
The voltage regulator has a minimum input voltage of about 14V but your battery will drop to 12V. Then when the battery is 14V each cell is 3.5V which is almost only half a discharge.
   

[sleemanj]

The poor voltage regulator will heat with (16.8V - 12V) x 20A= 96W. Do you have a voltage regulator powerful enough and a heatsink large enough?

The poster didn't say he wanted a linear regulator.

Assuming there is a suitable DC-DC converter found with around an 85% efficiency, which is reasonably typical, the dissipation as heat at 20A 12V output would be, ((12*20)/0.85) - (12*20) = 42W, still a sizeable amount but not that large, although active cooling is probably advisable.

The primary problem to solve though  is finding a suitable SEPIC that can handle the demands.  I'd say that going to a 5S pack would be better then it becomes easier to find a capable buck converter, rather than a SEPIC.

[Audioguru]

The poster didn't say he wanted a linear regulator.

He said, "a small module capable of stabelising a 12v output" which sounds like a voltage regulator. I don't know the dropout voltage of a 20A switching regulator.