Hardwiring dash cam - what size fuse?

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David321

486 posts

Ultimate Geek

#306571 4-Aug-2023 12:13

Hi all,

I have just ordered a 70mai m300 dash cam off aliexpress, I also selected the option to have the hardwire kit included.

I am looking to buy those car fuse adapters so I can wire the kit directly into the fuse box, for those of you who do not know what they are they are a bit of wire with a car fuse plug at one end that has a slot for two fuses on the back of it, the idea is you remove a car fuse, plug this wire in, then put the car fuse in this adapter and then whatever size/amp fuse you want for what you intend to power into the other slot.

I am curious though, what size fuse should I use, I can not seem to find the answer anywhere, as pictured th hardwire kit does not seem to have a fuse in it, just a black box where I assume the voltage conversion happens.

_David_

Trunks2

224 posts

Master Geek

#3111762 4-Aug-2023 12:17

Depends on your car, pull a fuse and have a look, some cars use more than one size.

David321

486 posts

Ultimate Geek

#3111764 4-Aug-2023 12:22

Trunks2:

Depends on your car, pull a fuse and have a look, some cars use more than one size.

I don't think the size of the fuse I pull to get power from really matters, its just to get 12v dc power. What matters is what size fuse I put in to protect the camera.

Unless i've understood you wrong and you meant something else?

_David_

Senecio

2712 posts

Uber Geek

ID Verified

Lifetime subscriber

#3111771 4-Aug-2023 12:41

It doesn't come with a fuse as you reuse the same fuse that you pull out. Don't over think it. Find a fuse that is switched (or permanent if you want parking mode), pull the fuse, pop the tap in and put the fuse back in. That fuse will protect the dash cam and whatever else is on that circuit. Be careful using parking mode unless you have an external power source. Most of them cut-out at ~11.7V which will harm your battery over time.

Bung

6488 posts

Uber Geek

Subscriber

#3111791 4-Aug-2023 14:01

The tap has 2 fuses, the original and 1 for the camera wiring. The output is 5v 2.4a so 2a on 12v side should be ok.

RunningMan

8960 posts

Uber Geek

#3111803 4-Aug-2023 15:02

You have to get the same size as what the car has - nobody here can tell you that, you need to check your car. The automotive blade fuses come in 2 common sizes, but they are not interchangable, so if yours are the small ones, and you get the large plug it won't fit.

concordnz

474 posts

Ultimate Geek

Trusted

EMT (R)

#3111809 4-Aug-2023 15:17

@bung Has it right,
He knows what he is talking about. 👌👍

A 2amp should be fine.

trig42

5814 posts

Uber Geek

ID Verified

#3111812 4-Aug-2023 15:26

I did exactly the same thing (maybe even the same camera) in my car.

I tapped off a 10A fuse and put a 5A in for the camera. I had read somewhere that all I needed to do was to put a lower value fuse for the camera than the tap.

Was very easy, camera has been in the car now for about 2 years.

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Senecio

2712 posts

Uber Geek

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Lifetime subscriber

#3111818 4-Aug-2023 15:44

Bung: The tap has 2 fuses, the original and 1 for the camera wiring. The output is 5v 2.4a so 2a on 12v side should be ok.

Correct, just had a closer look at the photos. Interesting as the fuse taps I've bought before just reuse the original fuse to protect both the dash cam and the original load.

RunningMan

8960 posts

Uber Geek

#3111833 4-Aug-2023 16:52

There's 2 seperate discussions going on here - fuse size, and fuse current rating.

1) Fuse size - OP has to determine this by checking the car
2) Fuse current rating - 2 parts to this

a) Original circuit needs to be protected by the same rating fuse.
b) New circuit needs a fuse of suitable rating for the new cable run to the camera.

The fuse's primary role is to protect the wiring loom from an overload or short circuit condition and would be related to the cross sectional area of the conductor - the thicker the cable, the higher the fuse rating. It's OK to go lower for fuse rating as long as it's not so low you get nusiance blowing. As a starting point, 10 amp fuse for 1mm^2 cable is a good starting point.

David321

486 posts

Ultimate Geek

#3111863 4-Aug-2023 18:35

Hi just to confirm, its not the physical size of the fuse I am asking for, its the current rating. For example 2.5amp (as a few are suggesting here) or 10 or 15amp etc

_David_

Bung

6488 posts

Uber Geek

Subscriber

#3111938 4-Aug-2023 21:39

It's the 5v output of the power adapter that has the 2.4a rating (5x2.4=12watts ). You need a bit more than 12w in so 2 amp on 12v side would be enough but you might find that 5 is as small as Supercheap etc sell in small packs.

MikeAqua

7785 posts

Uber Geek

#3112582 7-Aug-2023 08:08

The fuse should be rated to protect the wire. For example: If the wire is rated to 5A, then a 3A fuse would be suitable. The fuse will fail before the wire overheats and lets all the smoke out. Ideally the ampere rating of the wire will be printed on it.

Another suggestion: if you're using those double ended crimp sleeves as pictured, put a piece of heat shrink twice as long as the crimp over each one. Those crimps can be bit unreliable on their own.

Mike

Bung

6488 posts

Uber Geek

Subscriber

#3112617 7-Aug-2023 09:03

Good luck with trying to be too fussy about fuse value. I don't think many vehicles use low value blade fuses that fit the wire tap. The lowest rated in our car is 7.5A. That affects your chances of finding one stocked locally. The smallest wire size in the circuit is likely to be the input to the power converter. There'd be more choice in glass fuses for an inline holder.