Raspberry pi in car (power issues)

I have an issue of no video when using a USB adapter wired into my car. The HDMI works great when I hook up my portable battery (Ankara IQ) that defaults to maximum charge. So I suppose the issue is the amps I am putting out or something. The wired in usb adapter is 2.4… how much do I actually need? I am using raspberry 3 (wifi, bluetooth, etc) can I turn off some of those services I don’t need? I will want wifi. But Bluetooth has no need.

The minimum suggested by the Raspberry Pi Foundation is 2.5a. Also, depending on your adapter it may not always be giving a steady 2.4a. Also you say “etc”, the list would help, as that is the MINUMUM. It may require more if you start trying to power a portable hard drive from the Pi. Another thing to look at is in MyOSMC, setting the Pi 3 to allow full power from the usb ports. Can’t remember which menu, but shouldn’t be that hard to figure out.

William, thank you so much!

What will be active/needed are wifi (to teather with phone for internet and use as remote control), and video/audio output.

Storage is only on the micro SD (128gb), so no need for external storage.

Things I would love to turn off:
No need for bluetooth.

No real need for USB, so low power mode for occasional need (keyboard in emergency).

No need for Lan/wired connection.

Any suggestions? Can I disable these things in my bios or something?

If this adapter is some unregulated linear converter it might not even put out stable voltage. You might want to get a proper switch mode converter to get stable 5V from the 12-14.5V from your car.

Probably something like this:

All the amps you will ever need.