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starburst
12-01-2013, 19:54
cable from solar controller to battery
I have A solar kit on its way but have
been informed that the cable from solar
Controller to battery is not included,
can anyone tell me what cable i will
need, the kit is 2 X 85w panels to the
controller.

northernspirit2001
12-01-2013, 21:04
I dont know what the experts will say when one comes along but i've just bought some 16mm2, cheapest i have found is earthing cable 2.30 per metre 16mm 16.0mm Green Yellow Earth Cable *ORDER PER MT* | eBay (http://www.ebay.co.uk/itm/300350729196?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649)

If that's not big enough nothing will be!

outtolunch
13-01-2013, 16:01
minimum 6 mm sq up to a 20 ft run

How to Convert Watts to Amps Simplified -- Converting Amps to Watts the easy way (http://www.powerstream.com/Amps-Watts.htm#watts-amps)

Amps and Wire Gauge - 12V Circuit (http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html)

maingate
13-01-2013, 16:06
I take it you mean the short run of cable from the regulator to the battery terminal. Most regulators can not handle large wire diameters. 2.5 mm sq should be sufficient.

wildman
17-01-2013, 10:39
I take it you mean the short run of cable from the regulator to the battery terminal. Most regulators can not handle large wire diameters. 2.5 mm sq should be sufficient.
If loads are being taken from the regulator (which they be should to protect the battery) or the cable run from the regulator to the battery is more than a foot then 6mm2 is the cable you need, whilst not all regulators will allow a cable of this size to be connected a decent one up to the job should, besides the cable can easily be reduced in size to fit the regulator by removing a few strands. this will not compromise the ability of the rest of the cable to withstand cable losses. Bigger cable the better.

maingate
17-01-2013, 11:00
If loads are being taken from the regulator (which they be should to protect the battery) or the cable run from the regulator to the battery is more than a foot then 6mm2 is the cable you need, whilst not all regulators will allow a cable of this size to be connected a decent one up to the job should, besides the cable can easily be reduced in size to fit the regulator by removing a few strands. this will not compromise the ability of the rest of the cable to withstand cable losses. Bigger cable the better.

Totally disagree unless you have around 500 Watts of solar.

sparrks
17-01-2013, 11:07
500w of Solar is approaching 30A

Sparks
17-01-2013, 11:29
Post Deleted

maingate
17-01-2013, 11:40
My Schaudt 1218 regulator can handle 18 Amps from the panels. The wiring supplied with it is nowhere near 6 mm, it is not even 2.5 mm sq. If the manufacturers do this then I would totally ignore any information from amateurs on forums. They may be well meaning but do not have any idea what they are talking about. They are probably confusing the cable size needed from the panels TO the regulator rather than that needed FROM the reg to the battery/ies.

Anyway, my setup is installed and working fine so I will bow out of this discussion before an argument starts. Bye bye. :wave:

sparrks
17-01-2013, 13:05
They are probably confusing the cable size needed from the panels TO the regulator rather than that needed FROM the reg to the battery/ies.


Like you, I'm not wishing to get into an argument but why would the cable be a different size from the panels to the reg than from the reg to the batts? The reg is to drop the voltage, it shouldn't be dropping the current. I'm intrested in this because it may be a route I shall go down.

shortcircuit
17-01-2013, 13:20
Cables designed for domestic fixed wiring installation should not be used as they are too rigid which will result in cores breaking due to vibration. Cores should not be cut off in order to make a connection fit. The current capacity of a cable is with all cores terminated and used.

Wooie1958
17-01-2013, 14:09
So what size cable will be needed on this ?

shortcircuit
17-01-2013, 14:36
The size of cable required will depend on the current to be carried and the length of the run.

Beemer
17-01-2013, 14:57
cable from solar controller to battery
I have A solar kit on its way but have
been informed that the cable from solar
Controller to battery is not included,
can anyone tell me what cable i will
need, the kit is 2 X 85w panels to the
controller.

I have calculated my set up thus:

100w Solar panel =
Watts to amps (A) conversion calculator (http://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.htm)
This says I would get 8.3333333 amps.
Using the Wire Gauges table
Amps and Wire Gauge - 12V Circuit (http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html)
For 15 to 20 feet is 12 AWG
Using another table
Wire Gauges (http://www.engineeringtoolbox.com/wire-gauges-d_419.html)
This then tells me I requires 3.3mm sq cable.
Always go to the nearest higher cable for your installation.

Having calculated the above, I have been using 2.5mm Sq for the past two years.

maingate
17-01-2013, 15:01
I have calculated my set up thus:

100w Solar panel =
Watts to amps (A) conversion calculator (http://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.htm)
This says I would get 8.3333333 amps.
Using the Wire Gauges table
Amps and Wire Gauge - 12V Circuit (http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html)
For 15 to 20 feet is 12 AWG
Using another table
Wire Gauges (http://www.engineeringtoolbox.com/wire-gauges-d_419.html)
This then tells me I requires 3.3mm sq cable.
Always go to the nearest higher cable for your installation.

Having calculated the above, I have been using 2.5mm Sq for the past two years.

With all this present day talk about huge cables, it's a wonder you and I ever got any charge in our batteries. :p :lol-049:

shortcircuit
17-01-2013, 15:13
Just to add to topic, have not seen any mention of an inline fuse in the feed from the regulator to the battery, as near to the battery as possible. Hope you have fitted. :)

sparrks
17-01-2013, 15:18
I have calculated my set up thus:

100w Solar panel =
Watts to amps (A) conversion calculator (http://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.htm)
This says I would get 8.3333333 amps.
Using the Wire Gauges table
Amps and Wire Gauge - 12V Circuit (http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html)
For 15 to 20 feet is 12 AWG
Using another table
Wire Gauges (http://www.engineeringtoolbox.com/wire-gauges-d_419.html)
This then tells me I requires 3.3mm sq cable.
Always go to the nearest higher cable for your installation.

Having calculated the above, I have been using 2.5mm Sq for the past two years.

Another fly in the ointment - isn't the ouput from the panels around 18v? hence the reg to drop it to around 14.4v in this case a little over 5A, or am I way off the mark?:)

maingate
17-01-2013, 15:19
Just to add to topic, have not seen any mention of an inline fuse in the feed from the regulator to the battery, as near to the battery as possible. Hope you have fitted. :)

Certainly have an inline fuse. Not only that, I have my Maplin Car Current Tester plugged into it so I can see the input without getting out of my seat.

Bigpeetee
17-01-2013, 15:37
Another fly in the ointment - isn't the ouput from the panels around 18v? hense the reg to drop it to around 14.4v in this case a little over 5A, or am I way off the mark?:)

Correct, the solar panel output is at the output voltage 18-19 volts ish so as you say the max current is say 5.5A

If there is a slight voltage drop between panel and regulator, so what?? It makes the regulators job easier, as long as you get say 15volts at the input of the regulator then everythings OK.

What is more critical is the distance between the regulator and the batts, as close as possible. A couple of foot of wire at 5A won't give much of a volt drop, so in modest configs a 2.5mm cable is prob OK.

NB, The negative from the solar panel is not always the same potential as the negative of the battery, many regulators use the negative supply lead for regulation. (N channel MOSFETS have lower ON resistance than P Type).

rebbyvid
17-01-2013, 17:55
here's a couple of websites with the info
Cables and Connectors (http://midsummerenergy.co.uk/buy/cables_connectors/)
Solar Panel PV Cable | From 1.10 per Metre >> (http://www.solarpanelpvt.com/pv-accessories/solar-pv-cable-and-connectors.html)

maingate
17-01-2013, 18:17
here's a couple of websites with the info
Cables and Connectors (http://midsummerenergy.co.uk/buy/cables_connectors/)
Solar Panel PV Cable | From 1.10 per Metre >> (http://www.solarpanelpvt.com/pv-accessories/solar-pv-cable-and-connectors.html)

The OP has said that he has a solar panel kit on its way, he just needs details of cable from the reg to battery.

starburst
19-01-2013, 08:52
Thank you all for your feedback, I now have the info i need.




Please do not adjust your mind.....
there is a fault in reality......

wexldted
24-03-2013, 02:25
In low voltage application, the size of the cable is important to minimise voltage drop. I have 300 watts of solar panels on the roof of my motor home, use 4 mm to link the panels together and down to my MTTP Regulator, then 6 mm from reg to batteries. From panels to reg voltage around 17, from reg to batt, around 14.4 but higher amps. On a bright Sunny day clear sky, I can get up to 14 amps if the batteries are down, even this size cable with crimps terminals will get slightly warm. If a cable gets warm it is using power in the form of heat generation. If you have too smaller wire you will loose amps.

El Veterano
28-05-2013, 22:16
I've just fitted a 20amp controller with one 80w panel going into it (may expand later) and the instructions for the controller state that 'the cable from controller to battery should be no bigger than 4amp/MM2' any bigger than this will result in voltage drop. Also you should keep this cable as short as possible and incorporate an in-line 5amp fuse. So I just used 4amp twin white sheathed regular household cable. No probs, and battery is up to full charge in no time in good sunlight, and no overheating at battery terminals or the cable itself.

maingate
28-05-2013, 22:24
It's only a matter of time before criminals stop nicking lead off Church roofs and target motorhomes with solar panels fitted.

All that thick heavy cable will be a tempting target. :lol-049:

sparrks
28-05-2013, 22:34
I've just fitted a 20amp controller with one 80w panel going into it (may expand later) and the instructions for the controller state that 'the cable from controller to battery should be no bigger than 4amp/MM2' any bigger than this will result in voltage drop. Also you should keep this cable as short as possible and incorporate an in-line 5amp fuse. So I just used 4amp twin white sheathed regular household cable. No probs, and battery is up to full charge in no time in good sunlight, and no overheating at battery terminals or the cable itself.


the instructions for the controller state that 'the cable from controller to battery should be no bigger than 4amp/MM2' any bigger than this will result in voltage drop.



That should read 4mm - 4mm cross sectional area any smaller will result in volt drop


So I just used 4amp twin white sheathed regular household cable.

You should not use twin and earth cable in a van it is too rigid and will eventually fail, they don't make 4amp cable in T&E the smallest is 1.0mm which is good for a max of 15.5A in optimum conditions

Firefox
28-05-2013, 23:10
3mm2 cable maybe.

The higher the current, the more power loss.

The currents on the battery side of the regulator are higher as there is a voltage drop from typically 20v at the panels to 14v to charge the batteries and a corresponding increase of current.

I think I have 2mm2 on the panel side and 3mm2 on the battery side. But bigger cables will mean less power loss, no harm in 4, 5 or 6mm2.

El Veterano
29-05-2013, 09:53
That should read 4mm - 4mm cross sectional area any smaller will result in volt drop


You should not use twin and earth cable in a van it is too rigid and will eventually fail, they don't make 4amp cable in T&E the smallest is 1.0mm which is good for a max of 15.5A in optimum conditions

Hi thanks for your input, I was hoping that posting would shed some light on the black art of solar! No, it's not twin and earth it is white round sheathed cable and just twin, no earth and is very flexible. I was also concerned that a 5amp fuse was not correct as well?

MATS
29-05-2013, 11:09
Has anybody experienced a pulsing regulator. My 80w panels works fine but they pulse when sunlight is really strong ie my needle on the current gauge pulses between 4amps and 0 amps?

shortcircuit
29-05-2013, 11:25
I would suspect this will only happen when the LB are fully charged??? The regulator will look at the battery and see it fully charged and switch off, 0 amps. After a preset time it will look again and if voltage down will switch back on resulting in 4 amps.

Experts can confirm, but not a problem.

Firefox
29-05-2013, 11:52
Both regulators I have had pulse slightly and do so when the battery is fully charged.

Wooie1958
29-05-2013, 12:53
Has anybody experienced a pulsing regulator. My 80w panels works fine but they pulse when sunlight is really strong ie my needle on the current gauge pulses between 4amps and 0 amps?




P W M Regulators........ Pulse Width Modulation.......That`s what they do.

Andy75
29-05-2013, 13:00
hmmm not quite, the pulse in PWM is the on/off fast switching that gives a certain current duty cycle by turning the fixed voltage supply on and off quickly.
Pulse-width modulation - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Pulse-width_modulation)
The pulsing from the reg is as already mentioned - the LB's are on the very cusp of being fully charged and the controller may well cycle on and off a little as it over-corrects. More fancy controllers will have some PID control built in where they can predict the need for voltage or not from a feedback system to a microcontroller.

MATS
29-05-2013, 13:08
hmmm not quite, the pulse in PWM is the on/off fast switching that gives a certain current duty cycle by turning the fixed voltage supply on and off quickly.
Pulse-width modulation - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Pulse-width_modulation)
The pulsing from the reg is as already mentioned - the LB's are on the very cusp of being fully charged and the controller may well cycle on and off a little as it over-corrects. More fancy controllers will have some PID control built in where they can predict the need for voltage or not from a feedback system to a microcontroller.
Ok makes sense - yes the LBs are normally near full charge as sometimes it is a steady 2-3a then the pulsing begins after about 3 hours on charge.
Cheers all

El Veterano
29-05-2013, 17:59
My controller is pretty basic so just has a few LED's, the 2nd one in line pulses slowly green when the battery is fully charged. The same thing I would imagine.

wildman
30-05-2013, 13:39
Cables designed for domestic fixed wiring installation should not be used as they are too rigid which will result in cores breaking due to vibration. Cores should not be cut off in order to make a connection fit. The current capacity of a cable is with all cores terminated and used.
Domestic wiring is not flexible enough agreed. as to reducing the number of strands to fit the regulator nothing wrong with that as the length involved is too short to exhibit any heating losses. Over a long distance the greater the dia of the cable the better overkill does no harm whatsoever, generating leccy in the winter when there are only milli amps charging a battery losses need to be absolute minimal. There is more than one right in this world. I think an HNC in electrical and electronic engineering
is sufficient for me to give an informed opinion.

El Veterano
02-06-2013, 10:24
Update:
After everybody's learn'd input, now replaced my flexible household cable from controller to LB with two 4mm solar cables courteously provided by my electrician mate who had some left over from an installation. Seems to to be working exactly the same as the household stuff so far, but there again if it's putting more oomph into the LB then I'm all for it:dog:

shortcircuit
02-06-2013, 11:41
Domestic wiring is not flexible enough agreed. as to reducing the number of strands to fit the regulator nothing wrong with that as the length involved is too short to exhibit any heating losses. Over a long distance the greater the dia of the cable the better overkill does no harm whatsoever, generating leccy in the winter when there are only milli amps charging a battery losses need to be absolute minimal. There is more than one right in this world. I think an HNC in electrical and electronic engineering
is sufficient for me to give an informed opinion.

I also have an HNC in electrical engineering which has no relevance to installation work. I was also an Approved Certifier for Electrical Installations which covers the nuts and bolts which does provide informed opinion. Cutting cores off reduces the current carrying capacity of a cable

sparrks
02-06-2013, 12:31
Cutting cores off reduces the current carrying capacity of a cable

Scenario:

I have a 10A 12v load which requires a 4m long cable, 1.0mm will suffice (fused 10A). To ensure minimal volt drop I choose, say, a 10mm cable and because the cable ends will now not fit in the terminations I would fit bootlace ferrules or wire pin crimps. Now if not available, I could cut the end conductors down to say 4.0mm, this would still be 4 x larger than the original cable, and whilst the overall current carrying capacity of the cable is reduced it is still greater than the design current of the circuit.
So whilst it may not be the correct way to terminate the cable it can be done without reducing the current carrying capacity below the design current of the circuit.

Byronic
02-06-2013, 12:50
Scenario:

I have a 10A 12v load which requires a 4m long cable, 1.0mm will suffice (fused 10A). To ensure minimal volt drop I choose, say, a 10mm cable and because the cable ends will now not fit in the terminations I would fit bootlace ferrules or wire pin crimps. Now if not available, I could cut the end conductors down to say 4.0mm, this would still be 4 x larger than the original cable, and whilst the overall current carrying capacity of the cable is reduced it is still greater than the design current of the circuit.
So whilst it may not be the correct way to terminate the cable it can be done without reducing the current carrying capacity below the design current of the circuit.

But is a waste of 6mm sq. of conductor. The whole 4m @ 4mm sq. would be best. Unless of course you have a spare 10mm sq. roll and just want to use it up.
Copper cable is expensive these days, vehicle manufacturers size their cables with only very small safety margins in the interests of economy, and they make savings by earthing runs to the vehicle body in situations where use of twin core earthed back to somewhere where you can see the earth point might be preferable.

shortcircuit
02-06-2013, 12:50
Scenario:

I have a 10A 12v load which requires a 4m long cable, 1.0mm will suffice (fused 10A). To ensure minimal volt drop I choose, say, a 10mm cable and because the cable ends will now not fit in the terminations I would fit bootlace ferrules or wire pin crimps. Now if not available, I could cut the end conductors down to say 4.0mm, this would still be 4 x larger than the original cable, and whilst the overall current carrying capacity of the cable is reduced it is still greater than the design current of the circuit.
So whilst it may not be the correct way to terminate the cable it can be done without reducing the current carrying capacity below the design current of the circuit.

Please do not confuse capacity with load. I made a simple statement that does not change, "Cutting cores reduces the current carrying capacity of the cable" I make this statement in order that it is understood that if you use a suitable length of cable to carry the load you require which may be near the cables maximum current carrying capacity you cannot cut cores off just to make it fit a terminal

maingate
02-06-2013, 12:55
I agree entirely with sparrks. There seems to be a hysteria about fitting heavy cables, for solar panels especially.

I have happily used 2.5 mm sq domestic 3 core cable for well over 2 years. When I changed to mostly 4 mm sq dedicated solar cable, there was no difference at all in input to my batteries. Some people are horrified that I did not use 6 mm sq and predict doom, gloom and flat batteries. :wacko:

There are websites which, if you feed in a few bits of information, will give you the percentage voltage drop over a given length, at a given voltage for a given cable diameter. The difference for 6 mm, 4 mm and 2.5 mm for most solar installations is insignificant. The cost between 6 mm, 4 mm and 2.5 mm cable prices however ARE significant. The newbie to solar asks on forums for info but usually gets the wrong info.

If they took the time to look at the wiring used by the likes of Fiat, Ford and motorhome converters, they would see just thin a cable needs to be to work OK.

sparrks
02-06-2013, 13:16
Volt drop, Ref method C 70C thermoplastic 2 cables dc

csa mm (mV/A/m)

1.0mm 44
1.5mm 29
2.5mm 18
4.0mm 11
6.0mm 7.3
10.0mm 4.4
16.0mm 2.8
25.0mm 1.75

Just a quick indication of the volt drop in various cable sizes in mV x A x m

Byronic
02-06-2013, 14:45
I've used 2.5mm sq. multifilament twin core rated @ 27 Amps for my 2X60W (c.8A max. output) panels, installed 16 years ago with no problems, nor should there be. Solid conductors, as has been mentioned should never be used in a vehicle...... vibration work hardens the copper and naturally it will eventually break.

1978lovebus
08-06-2013, 10:33
Domestic wiring is not flexible enough agreed. as to reducing the number of strands to fit the regulator nothing wrong with that as the length involved is too short to exhibit any heating losses. Over a long distance the greater the dia of the cable the better overkill does no harm whatsoever, generating leccy in the winter when there are only milli amps charging a battery losses need to be absolute minimal. There is more than one right in this world. I think an HNC in electrical and electronic engineering
is sufficient for me to give an informed opinion.


I agree, But dont forget to check to see if their are diodes fitted whether inline with the + of the cable from REG to Panel or on the control box of the panel, as this will result in reverse feed at night, also make sure the connections on the joints are good as you may result in some resistance (Ohms Law) which will result in loss.. My qualification in vehicle electrics and electronic principles BTEC 2 with distinction gives me sufficient room to add to the thread :lol-049:, there is some good advice on here that has been given.. I have myself fitted solars, regs, fuses, BIG batteries, Inverters, Wind turbine, consumer box, connecters that can handle the amperage and all the wiring to go, if you need help PM me....

I know you were asking about the REG to Batt and size of wire, select cables and connecters that will continously carry a minimum of your REGS output amps with a max lenght of 1.5mtr.. I used AWG12 30amp 79 strand wire at a couple of foot in length with an inline fuse to match output of the REG....

Dont forget the flux capacitor when it hits 88mph, how much current will be used when the solars are at that speed... lol


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