As I am involved in rallying, and am a volunteer marshal and radio operator, having recently bought my 2010 Octavia, I need to route the power cable direct to the battery from the cabin. Because of the power drain, I cannot use the cigarette lighter.

 

Is there any access to said battery through the bulkhead, or is it a case of via the passenger door aperture, then through the gap in the top of the wing?

Running a high current cable direct from the battery and then closing the bonnet and door on it I hope you have a fire extinguisher and can bale out quick.

 

The wiring loom and many other service penetrations pass through grommets in the bulkhead, run your cable through one of those that has spare capacity and do not wire it directly to the battery terminal, there are spare fused terminals available on the busbar of the battery fuse tray. You should also use an in line fuse rated to the section of your cable or the maximum that the radio could draw fitted as close to the connection point as possible.

Edited 3 November, 20214 yr by J.R.

Thanks for that.

 

The radio has an inline fuse on the power cable, so that isn't a problem. I wasn't aware of spare fused terminals on the battery, as I have only just bought the car 2 weeks ago, and haven't had a good look around that side of things, concentrating on others. Routing the cable was my primary concern, hence the question.

 

Being a fully licenced radio ham as well, gives me electrical knowledge with power ratings anyhow.

18 minutes ago, Quinny1 said:

 

Being a fully licenced radio ham as well, gives me electrical knowledge with power ratings anyhow.

 

My callsigns M7NPC/2E0NYG/M0NYG 

 

Have a look under the dash drivers side, on the MK1 there was a terminal strip below the relays and one of them was a Live 12v supply so there might be the same on a MK2 if you're lucky

There's quite a few ham's on here.

73 de me. 🎙️

Thats good to know.

 

G8FSO

6 hours ago, Quinny1 said:

The radio has an inline fuse on the power cable, so that isn't a problem. I wasn't aware of spare fused terminals on the battery, as I have only just bought the car 2 weeks ago, and haven't had a good look around that side of things, concentrating on others. Routing the cable was my primary concern, hence the question.

 

The method of cable fire protection, whether in a car, home, or industrial equipment, is to have a fuse rated to protect the cable (not the load) mounted in a protected area between the power source and the cable. If your in-line cable fuse is outside that protected then you have a part of the cable exposed to damage and unprotected.

 

As JR said, you should connect the cable to a correctly rated fuse inside the fuse box that exists for this purpose near the battery.

 

If you need to step down down to a smaller cable at some place (such a smaller flexible cable), then you must add another smaller fuse to protect that smaller cable from the effects of damage too.

 

Sizing fuses and cables to provide protection from overheating and short circuits is not well understood by non electrical design engineers.

 

One final point, do you really have to run the cable directly to the battery? There is a fuse panel on the right hand side of the dash. Pull off the cover and you will see spare positions for fuses - some of which are permanently live.

 

73 de G4***

 

 

Edited 3 November, 20214 yr by pikpilot

I think that its good practice to fit a smaller fuse than what the cable is rated to, sufficient to protect the radio.

 

My explanation could have been misinterpreted by someone who might fit a smaller cable than required.

2 hours ago, J.R. said:

I think that its good practice to fit a smaller fuse than what the cable is rated to, sufficient to protect the radio.

 

My explanation could have been misinterpreted by someone who might fit a smaller cable than required.

 

Yes, that is fine as it will protect the cable. The radio will also have a last resort fuse or on circuit board thinned track to protect itself from internal faults causing a fire.

 

Another situation that causes confusion is the "cigar lighter" power socket. There are two types of plug - one with direct connection to the centre pin and one with a fuse between the pin and the spring. With some of our cars having a supply fuse of 30A  on the supply to the socket, it is clear that if you have a cable rated less this coming out of the plug then again there there is fire risk unless the fused version is used.

We should only used the fused plug. The supplied fuse is usually 1A but you should fit a fuse to match the load cable rating or smaller if the load allows.

 

While on my hobby horse, I am a appalled to see recommendations for high power audio bass amplifiers to be connected directly to the battery - without a fuse. I wonder how many car fires are caused by such cables rubbing through the cable insulation and the grommet as they pass through the firewall.