Comment 66 for bug 1765363

Yes. I win.
I install new systemd service with timer for power off NVidia after startup.

Problem:
New laptop Lenovo S540 (2020-made) + Ubuntu 18.04 LTS with NVidia 435 driver eats battery for 2-3 hours.

Result:
12 hours on battery.

Before that the actions from comment #43 have been taken (thank, tom (tombuntus))
(I don't install nvidia-prime. I use nvidia-prime, installed with nvidia-driver-435)

$sudo apt install bbswitch-dkms

add "bbswitch" to /etc/modules

add "options bbswitch load_state=0" to /etc/modprobe.d/bbswitch.conf

And i have don't change kernel parameter nouveau.modeset

Steps for make service:

1 - create file /ets/systemd/system/nvidia-off.service
##########################
[Unit]
Description=OFF unused NVidia chip (20W->5W)

[Service]
Type=simple
ExecStart=/usr/local/bin/nvidia-off-on-start

[Install]
WantedBy=multi-user.target
##########################

2 - create file /ets/systemd/system/nvidia-off.timer
##########################
[Unit]
Description=OFF unused NVidia chip (20W->5W)

[Timer]
OnStartupSec=1min

[Install]
WantedBy=multi-user.target
##########################

3 - create executable file /usr/local/bin/nvidia-off-on-start
##########################
#!/bin/sh
modprobe bbswitch
echo "OFF" > /proc/acpi/bbswitch
date >> nvidia-off-on-start.log
cat /proc/acpi/bbswith >> nvidia-off-on-start.log
#########################

4 - enable and start service
$systemctl enable nvidia-off.timer
$systemctl status nvidia-off.timer

RESULT:

- Power of NVidia adapter stay OFF after reboot and login to any user.
- $ sudo tlp-stat -b | grep power_now
   shows 4000-6000 milliWatts
- On-Battery time is up to 10-12 hours
- Bonus: all coolers stay off.

If i select NVidia in Prime-Select (GUI) and reboot, execute "echo "OFF" > /proc/acpi/bbswitch" no have "off" effect and NVidia ready for gaming.