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Discussion Starter #1
Probably been posted before but I'm struggling with Internet connection, what size cable from my controller to my leisure battery. Thank you please
 

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How long is a piece of string?
Seriously, it depends upon the length of the cable run, but always "thicker is better".

What current does the controller give?

Do NOT go on "cable ratings", ie, you have a 10 amp output, so 1mm cable would "handle" it fine....for 10 amps, you want at LEAST 6mm cable, as long as the run is less than a couple of metres.
 

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Discussion Starter #3
It's a 100w panel, and the leisure battery in less than 1m away
 

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I've a 200w panel, 20a mppt controller, 270amp leisure battery approx 1.5m from controller, i messaged Martyn of Travelvolts from the forum to buy what he recommended - which was 4mm from controller to battery. Bought all i needed as a wiring 'kit' from him.

Would imagine the same would suit you, from what you describe.
 

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Nice one rexy baby!
Thats ok, happy to help.

I have a 20amp fuse between the panels and the controller, and the same between the controller and the battery, although i have 200w of panels to your 100, so this may need to be different in your case. (Please check as i am in no way an electrician) Battery is earthed to the seat belt lower mounting with 16a cable (my furniture layout isn't the norm) 500mm long.

All's been installed for around a month now and works well.
 

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I hope you mean 16mm cable, and not the thin stuff "rated" at 16 amps!

Cable ratings are mostly done for mains voltages, and only concerned about the amount of heat they will withstand.
Voltage drop is the important factor on a 12 volt system.
 

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Thats ok, happy to help.

I have a 20amp fuse between the panels and the controller, and the same between the controller and the battery, although i have 200w of panels to your 100, so this may need to be different in your case. (Please check as i am in no way an electrician) Battery is earthed to the seat belt lower mounting with 16a cable (my furniture layout isn't the norm) 500mm long.

All's been installed for around a month now and works well.
No point in having 20A fuse between panels and controller as the panels will never develop enough current to blow it. All the fuse will do is add unnecessary voltage drop.
 

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Hi, I have a 200w suitcase panel and the cables supplied with that are approx the equivalent of 6mm and came as a 2 metre length.

However these are the finer multistrand cables used in vehicles and not the same as domestic cables.

Cable rating in domestic use have to take into consideration length of run (for voltage drop and resistance) and also the fabric of the building etc. (for heat dissipation) so it's not really practical to try and compare the two.

I would go out and buy a cheap set of jump leads, these are mostly around 6-10mm equivalent and should be more than adequate for your panel. Just make sure your connections are tight as that is where you can get real issues.
 

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No point in having 20A fuse between panels and controller as the panels will never develop enough current to blow it. All the fuse will do is add unnecessary voltage drop.
A fuse is NOT to protect the panel or the charger....it's there to protect the CABLE.

If you don't understand electrics, please don't confuse people.

@SmileyT;

Doesn't matter how many strands the cable has...it's still 6mm csa. (extra strands only make it more flexible)

Voltage drop is the most important factor with 12 volts.....
Drop a few volts at 230, no problem, the cable just gets warm.
Drop a volt on a 12 volt system, and you are 20% down on power available.

I agree about the jump leads....but don't buy the cheap aluminium ones!
 

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A fuse is NOT to protect the panel or the charger....it's there to protect the CABLE.
In order that the 20A fuse can protect the cable it needs some thing in excess of 20A for it to operate. A typical 100W / 18V solar panel has a short circuit current of about 6A which is the maximum current the panel can deliver and is clearly not sufficient to blow a 20A fuse. The controller will not be capable of delivering any current back to the panel. It is quite normal for the connection from a single panel to it's controller
 

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I hope you mean 16mm cable, and not the thin stuff "rated" at 16 amps!

Cable ratings are mostly done for mains voltages, and only concerned about the amount of heat they will withstand.
Voltage drop is the important factor on a 12 volt system.
Oops, my error, and your right T: the cable is 16mm not 16amps. Knowing my electrical limitations i emailed an expert with a detailed description of what i wanted/needed to achieve and went 100% with what he recommended, so am happy and safe.

Always worth paying a little extra for some professional guidance if unsure.
 

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A fuse is NOT to protect the panel or the charger....it's there to protect the CABLE.

If you don't understand electrics, please don't confuse people.

@SmileyT;

Doesn't matter how many strands the cable has...it's still 6mm csa. (extra strands only make it more flexible)

Voltage drop is the most important factor with 12 volts.....
Drop a few volts at 230, no problem, the cable just gets warm.
Drop a volt on a 12 volt system, and you are 20% down on power available.

I agree about the jump leads....but don't buy the cheap aluminium ones!
Quite agree GazM, however stranded has a slightly higher resisitance than a solid core, the voltage is DC and not AC and they have different insulation properties. I was just pointing out the differences to domestic wiring and what those ratings are based on. If in doubt always go for higher and I agree copper over aluminium.
 

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In order that the 20A fuse can protect the cable it needs some thing in excess of 20A for it to operate. A typical 100W / 18V solar panel has a short circuit current of about 6A which is the maximum current the panel can deliver and is clearly not sufficient to blow a 20A fuse. The controller will not be capable of delivering any current back to the panel. It is quite normal for the connection from a single panel to it's controller
TOTAL BULLSH*T!!!!!

The cable will probably be "rated" at something like 60 amps! (to reduce voltage drop)
The fuse is NOT there to protect either the controller or the solar panel!
It is there to protect the high current/LOW VOLTAGE drop cable.

IF there was a short somewhere in the system, the fuse is there to BLOW and stop the wires burning!!!!

Were it there simply for the "components", well, if the fuse blows, they would be FUBAR anyway!

Please STOP making comments about something you obviously have zero experience in! :eek:

THE FUSE SHOULD BE RATED JUST BELOW THE MAXIMUM CAPACITY OF THE CABLE!!!!!!!!!!!!!!!!!!!!!
That applies to ANY fuses....from 1 amp up to 1000!
 

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Or_GazM
For my education please could you explain the failure mode on a 100W solar panel that would result in a 20A fuse in the panel to controller blowing.
Thanks
The controller is a "switched mode device"....basically taking the DC from the panel, converting to a square wave AC signal, and then controlling the width of the pulse to regulate the current/voltage.
This means, should the transistor doing this switching go short circuit, you could have a path direct from the battery to the panel.
No problem with that really....BUT, if what caused the transistor to fail was a cable that had worn insulation and shorted to the chassis, you would have a connection from battery to "ground", which could result in 100s of amps flowing.

Like I stated, the fuse is to protect the cable (and your van from a fire.)
 

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So if I use 6mm tri rated cable I'll be ok?
Forget the "Tri-Rated" part.
Any automotive 6mm cable will be fine.
Tri-rated only applies to mains installations.....the 3 ratings for it's use in different circumstances.

Automotive spec cable tends to have a thinner, but tougher, insulation.
It can be thinner as it doesn't have to withstand 240/415 volts.
It's also usually of a higher temp spec....it's not often "house" wiring lives in an environment like the engine bay!

If you look, you'll see the cabling used to connect a boiler or immersion heater is NOT the same as that used through the rest of the house...this is due to the extra heat it has to endure.

On the inverse, the lead used to connect your van to a mains supply on a campsite, will often have a specific LOW temperature insulation...to allow it to remain flexible and not crack.

Basically, a "cable is never just a cable".
 
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