safety - What would be the safest method to power a laptop (IdeaPad 510 15isk) from a 14.8v battery pack?

Looking at my existing power jack and measuring it crudely with a cm ruler it looks like 3mm diameter x 1 cm length. The laptop bottom and charging adapter both say 20v @ 3.25 A max. What would be the best way to deliver that power and have it remain smooth as the battery pack voltage drops from 16.8v to 11v (fully charged to dead)

It looks like a chinesium boost/buck module would be my best bet once I set the voltage via a multimeter and epoxy the adjustment knob so their is no way it could possibly get turned or rotate its self slowly due to thermal expansion or something. I do not favor this idea though mostly because of the fact that most of those crappy boards look poorly put together and I highly doubt that the output is very well regulated and I fear that if one of those does break it may send to much or to little voltage to the laptop.

Are their any other options? If the boost/buck is my only option are their any safeguards I could use (besides a fuse ofc)?

Answer

Non isolated buck convertors powering something valuable, often had a crowbar circuit on the output. When over voltage occurs, the SCR is turned hard on, and stays on, until the fuse has blown. (if you use a triac it will also crowbar on reversed battery)

^{simulate this circuit – Schematic created using CircuitLab}

When the switch of a buck convertor fails, the input flows straight through the inductor to the output. If the load will be destroyed by this, then a crowbar (+fuse) is cheap insurance, and very simple to make.

For example my ebike battery has a usb 5V output, powered by 42V of lithium cells, and a shitty little buck convertor pcb. You bet I added a crowbar, cos I don't trust the regulator.

Transformer coupled power supplies don't have this issue as a fault generally results in no output. However most types of power supply are susceptible to the adjustment pot going open circuit, or being fiddled with. A hard crowbar remains cheap insurance if the load is valuable.

FYI, trimpots can fail where the wiper does not contact the track (permanently or momentarily due to shock). They should always be wired with 3 pins used, so that they don't go open circuit when this happens.

^{simulate this circuit}

This is something to inspect and correct on cheap CN modules. You can always add fixed resistors to limit the max output voltage to something safe.