Do I need to change my cables

[Spade]

Hi all.
As part of a project to upgrade my solar set up.
I just bought an victron mppt controller

I have an 100 watt panel and the roof already with this controller

I won't be changing the solar panel or adding more for the time being,
So can I use the existing wiring in the photo and just swap out the controllers?
T.i.a

 

[Phill D]

Don’t see why not you are not going to get any significant more current by changing the controller.
Is the current wiring the best for the job is a different question and depends on the size of you current cables .

 

[Spade]

The cables,panel and controller are there for 8 years, since I bought the van.I am hoping to change the panel for some larger wattage ones,when funds allow.
I assume I'll need to upgrade the cables then?

 

[Phill D]

It will depend on what size your current cables are.
4mm or 6mm cross section cable is normal.

 

[jumar]

I kept original cables when I fitted my Victron...and the difference was quite noticeable and having the app on the phone made an accurate view on what's happening....and we all need to know how much free energy is being harvested...

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[autorouter]

Be very careful you don't accidentally reverse the positive and negative connections. I've never seen that colour scheme before: black = positive, blue = negative

 

[Stealaway]

My 100W solar was wired in 2.5 mm rated at 27amps. I added another 125W panel, changed to a dual battery controller and simply connected them together inside the new dual wire roof box. The controllers maximum output is 20amps well within the limits of the cable.
The highest charge I have recorded is 13 amp's with flat batteries and bright sunshine

 

[Mixyblob]

Be very careful you don't accidentally reverse the positive and negative connections. I've never seen that colour scheme before: black = positive, blue = negative

You've never worked on a German van then. They don't seem to have any set colour coding, just use whatever comes to hand.

 

[autorouter]

If you change the controller, the cables will work just the same, the small increase in power won't be a problem. If you are upgrading the cable, there are two issues, safety and voltage drop. You'll want to maximise the yield from the panels, so you'll want to minimise the voltage drop. The rule of thumb is to keep the voltage drop less than 3%. If the cables are within that limit for voltage drop, then they will be well within the limits for safety.

Voltage drop depends on the amps, cable length and cross-sectional area (CSA) of the cable. As already said, 4mm2 or 6mm2 is likely to be suitable, if they are not too long. There is an explanation of this, and a Voltage Drop Calculator, here

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

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[Mr Mousy]

Don’t change the cables at the moment.

It’s a fair amount of work - do it when you update the panels.

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[rod_vw]

You've never worked on a German van then. They don't seem to have any set colour coding, just use whatever comes to hand.

German convertors should be wiring to the DIN standard as far as possible. Google it if you must but it takes some getting used to.

 

[Lenny HB]

For a single 100 watt panel the cables from the panels are OK the one to the battery are bit on the small side. If the controller is next to the battery that's OK but if some distance away I would increase the size of them.

 

[Lenny HB]

The controllers maximum output is 20amps well within the limits of the cable.

What is more important is the length of cable run and the volt drop which why on 12v systems where we can't aford much of a loss the cables are always well oversize compared to the current they have to carry.

You've never worked on a German van then. They don't seem to have any set colour coding, just use whatever comes to hand.

There is some logic to it, Brown is always earth/negative, Blue is always Positive & when they use Red & Black Red is pos & black earth.

Yanks are more confusing on AC circuits black is live & white neutral and DC circuits black positive & white negative.

Don't know what they currently use on Brit caravans but it use to be blue positive & white negative & green for a switched live from the car for battery charging.

All good fun.

 

[WESTY66]

What is more important is the length of cable run and the volt drop which why on 12v systems where we can't aford much of a loss the cables are always well oversize compared to the current they have to carry.

There is some logic to it, Brown is always earth/negative, Blue is always Positive & when they use Red & Black Red is pos & black earth.

Yanks are more confusing on AC circuits black is live & white neutral and DC circuits black positive & white negative.

Don't know what they currently use on Brit caravans but it use to be blue positive & white negative & green for a switched live from the car for battery charging.

All good fun.

Eh?

 

[autorouter]

There is some logic to it, Brown is always earth/negative, Blue is always Positive & when they use Red & Black Red is pos & black earth.

No there isn't That 'Blue positive' is negative, and the black is positive.

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[Bessy765]

Our Burstner 12 volt, blue is positive, brown is negative

 

[Stealaway]

No there isn't That 'Blue positive' is negative, and the black is positive.

You could be right. Give it a try and report back.

I would be interested in what the voltage drop increase there will be between 2.5 mm and 4 mm cables over a distance of 3.5 meters

 

[Just smiffy]

Oh to be a bomb defuser…. Cut the red… no wait..

 

[Lenny HB]

I would be interested in what the voltage drop increase there will be between 2.5 mm and 4 mm cables over a distance of 3.5 meters

At 10 amps 2.5mm sq it is 4.43%, 4mm sq 2.75%

At 20 amps 2.5mm sq it is 8.83%, 4mm sq 5.49%

It is recomended to keep the volt drop below 3%, I like to aim for 2%.

 

[Spade]

For a single 100 watt panel the cables from the panels are OK the one to the battery are bit on the small side. If the controller is next to the battery that's OK but if some distance away I would increase the size of them

Hi Lenny
The batteries are about 3 metres from the controller.
Is that too far

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[Lenny HB]

Hi Lenny
The batteries are about 3 metres from the controller.
Is that too far

It is a bit you really should have at least 4 mm sq but if you fit 6mm sq it will future proof it if you add another panel.

When buying cable bear in mind auto thin wall cable the size often incudes the insulation so a 4 mm cable is really only 2.5.

 

[Stealaway]

At 10 amps 2.5mm sq it is 4.43%, 4mm sq 2.75%

At 20 amps 2.5mm sq it is 8.83%, 4mm sq 5.49%

It is recomended to keep the volt drop below 3%, I like to aim for 2%.

Wow Lenny once again I'm impressed.
I hope I didn't keep you up
So the difference at 10amps is 0.12v and Is that per metre or at 3.5metres?
Whatever, I can live with that, I really don't want to change the cables.
My controller is inches away from the batteries.

 

[Lenny HB]

Wow Lenny once again I'm impressed.
I hope I didn't keep you up
So the difference at 10amps is 0.12v and Is that per metre or at 3.5metres?
Whatever, I can live with that, I really don't want to change the cables.
My controller is inches away from the batteries.

I make 0.2v doesn't sound a lot but at 12v you are losing 1.68% again not a lot depends what are trying to get out of your system.
Cables from the panel aren't so much of a problem as they are at 17 to 20 volts with less current flowing.

Also in sumer when you have plenty of solar you can afford a bit of a loss, conversely in winter when a 100 watt panel is only producing 2 amps the loss in terms of cuttent is so small its not worth worrying about.

In your case Alex you would get far better gains by changing your cheap controller for a decent MPPT one. Once you have changed the the controller the gains by using the correct size cable are more noticeable as MPPT controllers can make better use of the power avalible.

Yes I know I've contradicted myself but trying to give a view from both sides.

 

[Stealaway]

I make 0.2v doesn't sound a lot but at 12v you are losing 1.68% again not a lot depends what are trying to get out of your system.
Cables from the panel aren't so much of a problem as they are at 17 to 20 volts with less current flowing.

Also in sumer when you have plenty of solar you can afford a bit of a loss, conversely in winter when a 100 watt panel is only producing 2 amps the loss in terms of cuttent is so small its not worth worrying about.

In your case Alex you would get far better gains by changing your cheap controller for a decent MPPT one. Once you have changed the the controller the gains by using the correct size cable are more noticeable as MPPT controllers can make better use of the power avalible.

Yes I know I've contradicted myself but trying to give a view from both sides.

Thanks for that and I've just realised that the 3.5 metres distance was from the solar panels at 19+v.
I can make it work because we only use the van in summer and that my system easily achieves all I ask of it.
If it didn't I would be making changes not matter what the cost ----- Did I actually say that

 

[Dave Scadding]

I think you should ask Gadget John from John & Mandy, he seems to know his stuff.

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[Lenny HB]

If it didn't I would be making changes not matter what the cost ----- Did I actually say that

Nooooo, not possible for you to say that Alex, all a figment of your imagination.

 

[Spade]

Hi
Well I have upgraded the cables and fitted the new solar controller (victron mppt 100/30).
I've downloaded the victron app and all seems grand.
On reading the manual and checking on line,there seems to be different charging profiles for different types of batteries

I've 2 x110 ah lead acid batteries and just want to be sure that I'm on the right profile or am I better off just to let the controller do its own thing.

Would appreciate any pointers Lenny HB

 

[Phill D]

The controller should be set to the profile of your leisure battery type.

 

[Steve and Denise]

When I upgraded the controller and panels in our Carthago the factory had fitted the wiring in the cupboards above the tv in the lounge but the batteries were in the rear some 6 mtrs away.
this caused some Very strange behaviour on the Victron controller, going into float or absorption before the battery was fully charged, we even doubled up the cables to the battery as an experiment still not behaving as it should.
then we moved the controller to within a mtr of the battery and all worked as it should.

 

[Reallyretired]

You've never worked on a German van then. They don't seem to have any set colour coding, just use whatever comes to hand.

Absolutely agree. A meter is essential to investigate the polarity every time any change is made.

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