Adding a second battery for parking mode

[AaronIE]

I have my A139 hardwired with voltage cutoff at 12.2v, this only really gives me 6-8 hours of parking footage.
I've researched a couple of different options, i.e. buying a blackvue battery pack, but it's far too expensive.

I have a 14ah sealed lead acid lying around, and I decided to put it in my car's boot and tap it into an accessory fuse. The dashcam then feeds directly from the second battery. The battery charges while driving and is isolated from the main battery (I think / hope) through the accessory fuse.

Question is, it's so simple, but is it safe? I have heard of people installing battery isolators, but I don't think it's necessary?

I am having some problems getting the dashcams third wire (yellow accessory) to activate the parking mode, and I'm not sure whats going wrong with this.
I have this yellow wire tapped into a different accessory fuse, but it doesn't seem to be activating the parking mode. (It was working before when I didn't have this second battery fuse). I wonder is the second battery providing power to ALL accessory fuses, and thus the parking wire cannot detect engine shutoff... Any simple way around that?

 

[AaronIE]

I think my issue with the yellow wire is because I have introduced a second circuit. When the car is shut off, the circuit from my second battery is still closed. Trying to figure this out, where should I connect the yellow cable..?

 

[VIOFO-Support]

Hello,

Could you provide a picture of the connection between the accessory fuse and the lead-acid battery?

The ACC cable would switch as long as there is a power signal of 5V.

 

[AaronIE]

Hello,

Could you provide a picture of the connection between the accessory fuse and the lead-acid battery?

The ACC cable would switch as long as there is a power signal of 5V.

Hey there, I think the easiest way to show it to you is with a simple Paint diagram!

I have confirmed that both fuses are not live when the ignition is switched off, however dashcam does not go into parking mode until i physically disconnect the yellow cable from fuse box. My theory is because the battery is keeping the circuit alive. Trying to figure out an alternative solution for the ACC cable to identify that the ignition is off.

 

[VIOFO-Support]

Hello,

I'm attaching a PDF file about how to install the ACC hardwire kit. That maybe can help. Please make sure there is a voltage signal change when the ignition is off.