Rearview mirror power limit

[Angus66]

Does anyone know how many amps/volts can be safely pulled from the auto dimming rearview mirror?

I ask because I'd like to - at least temporarily - run 2 cameras off this power source at the same time for comparison purposes.

One of the dash cam install kits came with the adapter pictured - but I don't for sure if this is safe or not.

Any knowledge and/insight would be greatly appreciated!

 

[Nigel]

I am pretty sure that there is no standard connection for rearview mirrors, so the safe amount of power will depend on which vehicle it is, and you will never get a specification from the vehicle manufacturer, so taking any amount of power is risking damage to the vehicle.

There are a lot of people who have plugged one dashcam in using that method, so presumably that doesn't normally cause any damage.
If you want to take the risk of plugging two in, then let us know the results...

Looking at that connector, I assume those are two USB sockets at the top. The cables look a little thin for powering two cameras, so if you do try it, I suggest you monitor the temperature of the common part of the cable for a while, if it starts to smoke, stop using it! Probably it will be OK, but I don't recommend it, especially if they are multi-channel cameras.

Presumably those USB sockets contain a 12V to 5V convertor, which may also get rather hot if they don't get good ventilation, and that might affect the dashcam performance.

I think it is safe to say that using that cable, even for one dashcam, will invalidate any car warranty that you have. You use it at your own risk, not at the risk of the car manufacturer, or of anyone giving advice from here!

 

[mentadent]

Check the fuse it runs off., and subtract what you estimate other devices on that fuse also use.
Also cars on fire suck.

 

[Angus66]

Thank you both for the suggestions, insight & warning(s.)

Even though I've been a car guy for decades, some of the rules/limits/hazards of electrical systems (both 12 & 110 volt) have always eluded me.

Just to satisfy my own curiosity, I took some measurements this morning for both dash cams I'm currently comparing, .

As I don't have the adapter pictured above installed currently, I just measured each cam separately using the single outlet version already wired to the rearview mirror.

Neither camera has a rear camera plugged in. I've also added an image of a different dual USB-A to 12V kit that I have, which has larger gage wire to both ports + actual specs on them.

So if both cameras were installed, would the USB-A sockets have to pull a total of 5V, 2A & 6W from the auto dimming rearview mirror wiring?

 

[Nigel]

So if both cameras were installed, would the USB-A sockets have to pull a total of 5V, 2A & 6W from the auto dimming rearview mirror wiring?

5V, 1.2A, 6.2W

However, that is measured after the voltage converters in your USB sockets, so the car wiring, which works at 12V, would supply:
12V, 0.6A, 6.2W

I've also added an image of a different dual USB-A to 12V kit that I have, which has larger gage wire to both ports + actual specs on them.

That looks more decent wiring.

Given that those dashcams are quite low powered, I wouldn't worry about plugging both in.

Just remember that you don't know how much power can safely be drawn, so you are taking a risk, I wouldn't plug in 2x 4K 3 channel dashcams, I would actually be a little concerned about 1x 4K 3ch dashcam, it would probably be fine, but better to hardwire that into the fusebox.

 

[lufa6977]

If you find you want to wire straight to the fuse box, both cameras can be wired to a dual fuse tap. You will need two of these in the model for your fuse type.

Lumison Dual Fuse Tap

Lumison list of fuse taps at Amazon.

Lumison FT list