12 Volt Wiring Question - Voltage Drop

Yes

Chassis earths cause more problems than anything else so it always pays to run both power and earth for all accessories and batteries.

Second would be incorrect selection of wire gauge.

Regards
David

Cram it pays in the long run to install earths from the battery to all assesories & never use the body. In particular the tow hitch & trailer chassis should never be used as an Earth from the car. Both the negative & positive wires need to be the same size & to avoid voltage drop heavy wiring should be used for large loads (like fridges) or for long lengths. Additionally I'd toss the Cig lighter plugs away & replace with high amperage plugs (like Anderson or Clipsal) that can't rattle loose.
Cheers Craig.............

Hi Cram

In my opinion yes. I always run a earth wire. I have found chassis earths to be unreliable due to corrosion of the connection to the chassis. Some will say it is overkill but I also solder and heatshrink all connections. it takes longer but i never have lighting problems on my trailers. Cig sockets are notoriously bad for voltage drop especially if drawing anything more than a couple of amps. If you are drawing more, say for a fridge, use andersen plugs for a good connection. A formula I found for calculating Voltage drop is length of run including earth return x max amperage x 0.017 divided by cable wire size in square mm. This is from one of Collyn Rivers books which make excellent reading if you intend to do more wiring. Hope this helps.

regards Kc

Cram,
You most probably already know this.
When you get your thicker cable, don't go by the mm size on the sticker.That is the overall thickness of cable and insulation.
There should be another size indicated. ie 16/0.25. showing the actual wire thickness is a 1/4 of a ml. It might also show an amperage. This has a big question mark.
Overall it may look like this:-
3mm 10amp 16/ 0.25mm
go to this site it should give you all the answers :-
http://www.kayjayco.com/wiretables.htm

Tony

Cram,

I would rethink trying to do the wiring job whilst camping, especially for the the Anderson Connectors.

Run both positive and negative wires from your battery and fuse the positive side close to the battery.

The connection of the wires to the Anderson connectors can be either crimped or soldered, but if crimping, you need a "professional" crimping tool.

I "wire wrap" the cable ends with a single strand of copper wire to increase the diameter if necessary, tin and then solder the joint using a butane torch, but I do this in the workshop. I have never had a joint fail.

These are the two methods, recommended by the Manufacturer.

Bill

Hi Marc,
Where are you going for the cable?

I was in Bambach Cables at Lambton before Christmas and they had multi-strand cable well suited to your needs at 70% off list.

It wasn't saleable any more as new stock due to the change in rules regarding the insulation. Older PVC insulation oddly enough has a small lead content.

The addition of lead is now illegal.

I'd give them a call and see what they have left,

Bambach Wires & Cables Pty Ltd
Specialist Industrial Cables

(02) 4956 204464
Orlando Rd
Lambton NSW 2299

1800 333 291FREECALL

Bambach Cables

Note: The cable they sell will be sized in SI units (metric), ie, Something like 2.5sqmm, 4sqmm, 6sqmm, 10sqmm, 16sqmm etc. This is the cross sectional area of the copper, the only way to measure a cable if you actually know what you are talking about.

This bizarre and dangerous notion of measuring the OD of the copper and the insulation then declaring a blanket current carrying capacity should result in the perpetrators being shot with a ball of their own droppings.

Geoff

If your gonna make the anderson connections away from home you will need a couple of soldering irons ( big ones ) to get enough heat into the lugs !!

When I was an apprentice auto electrician, we were taught that current carrying capacity for automotive wire was for a distance of 3 and one third yards... or in other words 3 metres.

Once you go over this length, you go up to the next size.

It was an interesting thing because every auto electrician I knew at the time knew this (including our tech teachers) but I never actually saw it in print in any of our text books.

When I was wiring my own CT for a battery to run lights etc, my neighbour came over for a gander. He told me I shouldn't use heavy cables as it took "more electricity" to fill up the extra strands in the wire and so my battery would go flat faster.

He was very serious. Also told me that headlight realys worked by "transformer action" to boost the power to the lights.

All very interesting stuff! I wonder how many other people he has imparted his "knowledge" to!!

Cheers

Mark T

Always. Run positive and negative cables of the same diameter.

As suggested, welding cable for the full length of a vehicle.

When wiring for an accessories battery, always use same thickness or greater cables between batteries.

If you're ever stuck with a flat main battery, the accessory battery can be used for an emergency starter battery. This assumes that the accessory battery is large enough capacity and you have a solenoid/relay in the circuit.

If your accessory battery is fitted on your trailer/caravan, suitably hefty connectors across the towing link are a must.