Cable diameter/rating ?

[headlight]

Question for you guys that know about electrickery.
I have bought a 100 watt solar suitcase that came with 10ft wires with crocodile clips to attach to the leisure battery.
I want to do away with the crocodile clips and connect wires directly to the battery clamps.
I want to run the wires from the leisure batteries under the vehicle to a small Anderson plug which I will locate by my grey water waste valve.
I can then plug my solar panels in rather than have wires running across the floor.
This will mean that the wires will be approximately double the supplied 10ft.
Will I need to increase the wire diameter to negate any voltage drop ?
ie if the supplied wires are 20 amp by 10ft, should I increase the wires to say 40amp by 20ft long ?
TIA.

 

[Realist]

Get some SY Protected - Multi-Flex its rated at 24/25amps and its protected and voltage drop should be ok.

But double check for peace of mind.

 

[Coolcats]

Question for you guys that know about electrickery.
I have bought a 100 watt solar suitcase that came with 10ft wires with crocodile clips to attach to the leisure battery.
I want to do away with the crocodile clips and connect wires directly to the battery clamps.
I want to run the wires from the leisure batteries under the vehicle to a small Anderson plug which I will locate by my grey water waste valve.
I can then plug my solar panels in rather than have wires running across the floor.
This will mean that the wires will be approximately double the supplied 10ft.
Will I need to increase the wire diameter to negate any voltage drop ?
ie if the supplied wires are 20 amp by 10ft, should I increase the wires to say 40amp by 20ft long ?
TIA.

www.cable-ratings.co.uk

cable ratings

www.cable-ratings.co.uk

 

[The Wino]

I wouldn't claim to be an expert but would assume there isn't a safety risk the power will be too low to worry about overheating but just a matter of how much power you lose on the way to the battery. Isn't 100w too high a power to use without a controller? If so you could put that somewhere in the fixed wiring part.

 

[headlight]

Yes there is a controller, it's attached to the back of one of the panels.

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[rod_vw]

Rough calculation is that at 13.5v output from a 100W panel you will have about 7.5A flowing and that is IF (very unlikely) you were to get all of the 100W output from the panel. I bet most of the time you will have only about 5A flowing especially in UK sunlight.
It's anyone's guess what the suppliers mean by 20A cable but this table which was gleaned from the link above may give you a clue as to the probable losses dependant on the current/cross sectional area/ length of the cable concerned. At the end of the day your main concern is the voltage drop between the panel and the battery, which should obviously be kept to a minimum.

VOLTAGE DROPS (AMPS PER METRE)

Conductor Cross Sectional Area	Two Core Cable
	d.c.
1.5mm²	31mV
2.5mm²	19mV
4.0mm²	12mV
6.0mm²	7.9mV
10.0mm²	4.7mV
16.0mm²	2.9mV

 

[Lenny HB]

Without known what cables it supplied with difficult to answer.
Providing they are not stupidly thin they will probably be OK. Bear in mind in summer when you have plenty of output a few percent loss is not goi g to worry you & in winter because the output is so much lower the percentage loss will be negligible in terms of current output.

 

[The Wino]

Just a thought if you cut down the wires from the panel to say 5 foot and the wiring fixed on the motorhome is say 10 foot but twice as thick it's quite likely you will have a lower power loss than if you used as supplied

 

[L' Hobo]

There was a very helpful graph on an earlier this year thread on this subject, perhaps could be found in the search box?

or the one in Post #3.

 

[headlight]

The cable that has come with the panels (10ft), to go between the controller and batteries is 4mm2.
Looking online that size cable can carry around 30 amps.
As the max amperage the panels will supply in reality is about 6 amps (probably closer to 5 amps) then maybe I am overthinking this and a 20ft run in the same 4mm2 cable will be fine

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[The Wino]

The cable that has come with the panels (10ft), to go between the controller and batteries is 4mm2.
Looking online that size cable can carry around 30 amps.
As the max amperage the panels will supply in reality is about 6 amps (probably closer to 5 amps) then maybe I am overthinking this and a 20ft run in the same 4mm2 cable will be fine

I think I'd stick with the 4mm but if after using it a couple of times it was clear that it didn't need the full 10 foot the the new terminal which sounds a lot I'd chop some off.

 

[Pausim]

I find the 12V Planet Guide useful, it includes a voltage drop calculator.

Cable Size Calculator - Cable sizing and selection | 12 Volt Planet

Cable Size Calculator - Read our guide to selecting cable of the correct type and size for your automotive, marine or leisure wiring application. Auto and Marine Electrical Components from 12 Volt Planet

www.12voltplanet.co.uk

 

[The Wino]

I find the 12V Planet Guide useful, it includes a voltage drop calculator.

Cable Size Calculator - Cable sizing and selection | 12 Volt Planet

Cable Size Calculator - Read our guide to selecting cable of the correct type and size for your automotive, marine or leisure wiring application. Auto and Marine Electrical Components from 12 Volt Planet

www.12voltplanet.co.uk

Interesting. It suggests for the ops purpose 4mm should be fine as long as the connection socket has a really good negative earth connection so as to minimise the return run.

 

[Sue and Rick]

I get 22 v from my panel on a sunny day.

 

[The Wino]

I get 22 v from my panel on a sunny day.

That would reduce the cable thickness required. The op says though that his solar controller is on the back of the panel so it's 12 v or close to.

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[nabsim]

I did similar but different, I already had spare capacity on a decent mppt controller close to my battery bank so I disconnected the controller on the back of the panels (mine was a cheap PWM controller though) and fitted Anderson connectors. I connected the rest of the cable (approx 4mtrs) to my mppt controller with Anderson connector on the other end. I uncoil the cable when I want to connect the folding panel.

I did find that the 4mtrs limited where I could put the panel without moving the van so added another 5mtr length with Anderson connectors should I need it.

You panel may have a decent controller anyway, I knew mine wasn’t before I purchased. The extra 5mtr length I ran with 6mm sq cable and there is no difference which one I use in regard to voltage drop so you should be fine as is

 

[headlight]

This is the 100 watt solar suitcase I have bought with a 20 amp controller.

 

[pappajohn]

100watt panel direct to the battery will fry the battery.
The solar panel will output around 20 volts so needs a controller/regulator to bring it down to 13.6v -- 14v.
Unless it's a long run 4mm² will be fine.
Some idiot connected direct to battery on my mates van.
The battery was so cooked it wouldn't hold any charge

 

[The Wino]

100watt panel direct to the battery will fry the battery.
The solar panel will output around 20 volts so needs a controller/regulator to bring it down to 13.6v -- 14v.
Unless it's a long run 4mm² will be fine.
Some idiot connected direct to battery on my mates van.
The battery was so cooked it wouldn't hold any charge

It's got a controller on the back it's in the pictures and the op already mentioned it

 

[rod_vw]

I get 22 v from my panel on a sunny day.

That's direct from the panels, the OP has a controller attached to the panels to reduce the voltage to that suitable for charging a 12v battery.