12 V starting aid battery

In http://www.myoutlanderphev.com/forum/viewtopic.php?f=9&t=3425 (and probably some others threads), the question of a small, tiny battery was raised that should be sufficient for bringing up the car's electronics when the 12 V battery is down.

I just ran into this situation yesterday after having the car in ACC mode for several hours while working in the garage.
This situation was solved as per the handbook: Starting aid from another car, supplying the 12 V to the contact in the fuse box near the engine.

Replacing this "other car" by a small battery might be attractive. I consider using a battery set that can buffer the 12V and also provides a 5 V USB connection for helping an empty phone or tablet.

Question 1:
What current [A] will be needed for starting up the car? Does anybody have an idea or did anybody meter this already?

Question 2:
As my 12V battery was down (7 V remaining, metered at the contact in the fuse box), a small 12 V device on the socket under the dashboard as still showing an active status LED. When this socket is active under such conditions, it might be that the "small 12V starting aid battery" can simply be connected to the socket under the dashboard. Did anybody try this?

Best regards, Harald

The 12v cabin auxiliary port is disconnected when the car is off ... I have a portable Lithium Ion jumpstart battery for such an eventuality though despite running a dashcam 24/7 no issues.

I have a GX4hs which recharges the aux battery daily, some other models I believe do not do this.

SolarBoy said:

I have a portable Lithium Ion jumpstart battery for such an eventuality ...

Click to expand...

What capacity or size did you use?

Harald said:

SolarBoy said:

I have a portable Lithium Ion jumpstart battery for such an eventuality ...

Click to expand...

What capacity or size did you use?

Click to expand...

It says it can start a 2.5 litre diesel, in reality anything that can get the car computer to boot will work.

It was about £35 a few years ago.

SolarBoy said:

It says it can start a 2.5 litre diesel...

Click to expand...

Thanks. I consider something much smaller than that...

Keep in mind, although the car needs only very little to boot, the 12v battery itself will take a lot, in an attempt to recharge itself from your aid battery. So make sure you use decent wires!

Hook up, hit the power button and as soon as READY comes on, disconnect.