How does solid brass compare in resistance to 8AWG wire?

[PhilipA]

I am rewiring my newly bought caravan.
I have run an 8AWG cable from the rear of the car where it taps off a 4AWG cable to run a Renolgy 20amp DC /Dc charger for my 100AH Lithium battery.

I have now run the same 8AWG cable to the 12v,240v, gas fridge to replace the thin wire which meanders around the caravan wall and is fed by the standard D2 loom through the 7pin plug to minimise voltage drop.

Total amps should be about 35 initially until the Lithium battery is full then drop to 11 amps for the fridge. 2way distance about 5 metres. The feed is via a 70amp relay in the rear of the car energised by accessory position.

The problem I came across is joining the two sets of 8AWG wires under the caravan floor. Currently I have 2x8awg rammed into one end of screw type tube connectors usually used for 240V into 1x8awg at the other end..

I do not really want the "naked" posts under the caravan floor, although I have some on order along with eye fittings for 8AWG.

Anyway, I looked for 8AWG busbars, no joy, and also there are 12v available but they all seem to have 4AWG in and 2x8AWG out and are relatively expensive.

So my solution is to use 3 x threaded 240V screw tubes , cut from a nylon insulated strip with a bit of solid brass shim material between the 2 and the one. The shim material is cut in a Y shape with the Y arms about 6MM wide folded in half to fit the connectors and is 0.5MM thick. There is a solid section about 10x10Mm between the three. The contact area in the connector tube is about 12MM long, so there is a small area between where the brass tube conductor ends and the large bit of Brass sheet which is 6MM wide folded in two. I can maybe fit these into a Jaycar box with holes cut out which can be sealed with Sikaflex.

So 2 wires in, although one is actually "out" to the fridge and one out.( to the 20Amp DC/DC Charger)

I have studied the web and it appears that the setup should be OK , but I just wanted to be sure that this connector would not cause voltage drop. The reason that I want to use this is that I can more easily seal it from the weather and rocks thrown up from the car wheels than 2xpost terminals with 8MM posts and 6 eye connectors.

Seeking opinions from the electrical experts.
Regards PhilipA



.

[reefmagnet]

I'd use a 50 anderson plug to connect input and output to a DC-DC charger. Slap a bit of dual wall heat shrink over the cable crimps and lanolin or silicon grease over the contacts and call it a day. If really nervous about exposure to the environment you could wrap the whole thing in self amalgamating butyl tape, but I wouldn't bother unless driving through really extreme environments.

[Tombie]

I am rewiring my newly bought caravan.
I have run an 8AWG cable from the rear of the car where it taps off a 4AWG cable to run a Renolgy 20amp DC /Dc charger for my 100AH Lithium battery.

I have now run the same 8AWG cable to the 12v,240v, gas fridge to replace the thin wire which meanders around the caravan wall and is fed by the standard D2 loom through the 7pin plug to minimise voltage drop.

Total amps should be about 35 initially until the Lithium battery is full then drop to 11 amps for the fridge. 2way distance about 5 metres. The feed is via a 70amp relay in the rear of the car energised by accessory position.

The problem I came across is joining the two sets of 8AWG wires under the caravan floor. Currently I have 2x8awg rammed into one end of screw type tube connectors usually used for 240V into 1x8awg at the other end..

I do not really want the "naked" posts under the caravan floor, although I have some on order along with eye fittings for 8AWG.

Anyway, I looked for 8AWG busbars, no joy, and also there are 12v available but they all seem to have 4AWG in and 2x8AWG out and are relatively expensive.

So my solution is to use 3 x threaded 240V screw tubes , cut from a nylon insulated strip with a bit of solid brass shim material between the 2 and the one. The shim material is cut in a Y shape with the Y arms about 6MM wide folded in half to fit the connectors and is 0.5MM thick. There is a solid section about 10x10Mm between the three. The contact area in the connector tube is about 12MM long, so there is a small area between where the brass tube conductor ends and the large bit of Brass sheet which is 6MM wide folded in two. I can maybe fit these into a Jaycar box with holes cut out which can be sealed with Sikaflex.

So 2 wires in, although one is actually "out" to the fridge and one out.( to the 20Amp DC/DC Charger)

I have studied the web and it appears that the setup should be OK , but I just wanted to be sure that this connector would not cause voltage drop. The reason that I want to use this is that I can more easily seal it from the weather and rocks thrown up from the car wheels than 2xpost terminals with 8MM posts and 6 eye connectors.

Seeking opinions from the electrical experts.
Regards PhilipA



.

8awg is pretty light on for that length run.

You can get crimp joiners then heat shrink over them.

[Vern]

As an electrician, i have no idea what you are talking about with those materials[emoji1]. Can you post any pics?
Personally i would solder them and heatshrink, or as Tombie said.

[PhilipA]

I have 8AWG joiners and heat shrink , but the problem is fitting 2X8AWG into one end of the crimp tube (basically impossible) and having it stay there on bumpy roads.
That is why I sought out a solution that will enable 2x8AWG in and 1x8AWG out.

I will give it a try and see. . If I see too much voltage drop I can see another solution in a Bussmann midi fuse holder which has a cover . I can replace the midi fuse with a brass bar.

The 20amp DC/DC charger will not worry with say 5% or more voltage drop , say from 13.9-6%, and the fridge will have to have far less drop than with normal 30amp wire that runs around the caravan walls and then through a 7 pin plug into the car loom to the starting battery.!!!! After all that is what they are for.

Remember these only will be active when the car is being driven.
Regards PhilipA

[Blknight.aus]

why not use a fused buss bar?

12 Way Fuse Block with Bus Bar | Jaycar Electronics (https://www.jaycar.com.au/12-way-fuse-block-with-bus-bar/p/SZ2032?gclid=CjwKCAjwruSHBhAtEiwA_qCppkUICh6eYeJ5x ZlxrlfUBRPqZ5pMKRpxh0Q0djYVGi_8FxBmArFKSxoC3wsQAvD _BwE)

[Tombie]

Phillip. The cars loom is what length run/cable?
By the time you factor 10mtrs into the equation you’ll be pulling down on 8B&S

But hey. If you’re happy [emoji41]

[PhilipA]

Blknight.aus

why not use a fused buss bar?



I actually have one much like that as the distributor from my caravan battery to loads but lighter duty .

I would need 2 as I have to join pos wires and neg wires so it gets very pricy.

I already have maxi fuses between battery and DC/DC charger, and at the car after the relay, and one blade fuse at the fridge so I do not need any more fuses!!!

I have found a moderately priced fuse holder in which I could replace the fuse with a brass plate.

https://cdn10.bigcommerce.com/s-ydm181c/products/18087/images/34587/modular-fuse-holder-fuse-module-ILMIFM-7031_std__46311.1598679269.1280.1280.jpg?c=2

I already have these below on order along with crimp eye terminals to suit but I was looking for something less bulky and easier to waterproof and stone proof.
Regards Philip A


https://i.ebayimg.com/images/g/SEkAAOSwKThg~9~3/s-l64.jpg

[PhilipA]

Phillip. The cars loom is what length run/cable?

By the time you factor 10mtrs into the equation you’ll be pulling down on 8B&S

The loom from the second battery (AGM 130AH) positioned in the original battery position of a D2 is 4B&S to the RH rear of the car, into a 4B&S to 8B&S distributor placed in the RH area behind the air grill.


Your input has me thinking about shortening the run a bit as the relay is in the LH behind grill area and is tapped in 8B&S from there. I can reduce the run by shifting the relay to the RH side and tapping from the 4B&S distributor.

Regards PhilipA

[Tombie]

You could also do:

3 crimp lugs,
1 bolt
2 washers
Locknut

Then wrap and heat shrink to seal.

Or make the connection in a box.

[PhilipA]

3 crimp lugs,
1 bolt
2 washers
Locknut

Yes I dig.
Except it is 6 ie 2 bolts..

Yes I thought of that, and I may do it. I have plenty of crimps on order.LOL

The insulated block ones are attractive as I could put them in a box and bolt them down. Thoughts evolving..
Regards PhilipA

[Homestar]

X2 for what Vern said - I’m also an Electrician and I’d solder it.

[Dorian]

Hi Philip,
As a rule of thumb, brass is about 1/2 as conductive as copper.
8AWG is (oddly) 8mm2, so you would need closer to 16mm2 of brass to get the same conductivity. I think from your description, your thinnest section is 0.5 x 10 so you would need to boost this x 3.
While solder is a great solution a half decent crimp joint will out last solder by decades.

Cheers Glen

[Tombie]

Yes I dig.
Except it is 6 ie 2 bolts..

Yes I thought of that, and I may do it. I have plenty of crimps on order.LOL

The insulated block ones are attractive as I could put them in a box and bolt them down. Thoughts evolving..
Regards PhilipA

I only needs one Phillip


***********=
=*****************
***********=


One lug facing down
Single lug doesnt matter orientation
Other lug facing up

Bolt together with shortest bolt whislt retaining bite of Nyloc

[Hoges]

A 50mm off-cut of 1/2" copper pipe flattened in a vise and drilled at each end to take an M6 nut and bolt works well as a buzz bar. Cables terminated with lugs and attached thereto. The whole lot then housed in a small plastic "Systema" housing with the clip on-lid (bought from Woolworths). Can use grommets to seal the housing .... works well ... total cost $5-6

[PhilipA]

Thanks for that .
I have tentatively decided on plan B which is 6x8B&S eye lugs crimped with my humungous crimper, bolted to either insulated towers which have not yet arrived, or just bolted and placed in a jaycar alloy box, as the caravan will see dirt roads such as Great Central etc. along with lashings of Sikaflex where I drill the holes for the wires.
Very similar to your idea.
Regards PhilipA

[superhet]

Philip, You are overthinking this.
The additional resistance of a short piece of brass will be insignificant.
Also don't think of cable coming in and cable going out. Electrically you will be connecting all wires together.

[modman]

Giant connector is your friend here….
NLS 30399 | 2 X 35mm Heavy Duty Double Screw Connector (https://www.sparkydirect.com.au/p/NLS-30399-2-X-35mm-Heavy-Duty-Double-Screw-Connector)

[PhilipA]

Not quite that big ,but that is what I originally made the joint from, but concerned that the two in May fall out with vibration.
regards PhilipA