Dell BIOS update workaround with no battery.

DELL XPS L501X with no Battery running an old BIOS.

tl/dr
extract bios from official release, phlash it from DOS.
...

running the official Bios phlasher fails because I dont have a battery.
error given -144
to sucessfully use the official phlash the laptop needs to be running off AC AND have battery plugged in.

when this fails it does however usefully extract the bios wph file,
in my case to
/USER/AppData/Local/Temp/WinPhlash64/BIOS1.WPH

USER is my username, which will vary on different systems, and you will also need to view hidden files and folders as Local is invisible.

-- now you need a bootable USB-stick to run DOS,
i used RUFUS https://rufus.ie
-- next a DOS version of WinPhlash
i used version 1.7.0.21 https://www.wimsbios.com/phoenixflasher.jsp

-- copy PHLASH16.EXE to the USB drive.
-- copy BIOS1.WPH and rename as BIOS.WPH to USB drive

-- reboot into DOS,
run PHLASH16.EXE

it beeps a lot and loudly, then is finished !!

** dont forget fucking up the BIOS can brick your laptop **

some of this info was supplied by this now deleted blog
https://webcache.googleusercontent.com/search?q=cache:qyhf_0TE20wJ:https://blog.howlin.se/bypassing-error-144-winphlash-on-a-dell-vostro-1520/+&cd=5&hl=en&ct=clnk&gl=au