Controller to battery cables (1 Viewer)

Jun 20, 2022
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After a year of procrastination I am finally about to order a solar system for my van. Have pretty much settled on one 295 watt panel from bimble solar. The full kit comes with everything I need but the controller to battery cables are only 1m long. My batteries are situated one under each seat and I would like to mount the controller just inside the whoosh bang at high level. This would mean one cable would be about 2m long and the other nearer three. Is this a problem?
 

Kannon Fodda

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Not a big issue to have the solar controller a distance from the battery. My controller in a PVC is in an overhead locker so just under the roof entry gland from the solar panel. Wires to the battery take a torturous route down the inside of van behind panelling on the shower room wall to emerge into the underbench stowage where the batteries are. That's probably about 4m length.

But do size the cable correctly allowing for voltage drop which you do want to minimise to get maximum charge into the battery.
 

Lenny HB

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If your cable run is under 5m 10 mm sq cable will be OK but it would be better to mount the Regulator nearer the battery.
295w is a hell of a big heavy panel I think you would be better to fit 2 x 150w panels.
 
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Boldly
Jun 20, 2022
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Only 17kg according to their website. So not really very heavy. Was thinking of mounting it in a tilting frame to get maximum benefit.
 

Stealaway

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The size of the cable connection in the controller could be the determining factor.

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Boldly
Jun 20, 2022
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The kit comes with 10mm cable so that should be ok. It also comes with a consumer unit and circuit breaker presumably for a shed or suchlike. Would there be any benefit to fitting this in the van?
 
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Boldly
Jun 20, 2022
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Seems strange as surely if breaker tripped you would have to disconnect panel from controller before resetting or you would have connected panel before battery
 

Kannon Fodda

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The kit comes with 10mm cable so that should be ok. It also comes with a consumer unit and circuit breaker presumably for a shed or suchlike. Would there be any benefit to fitting this in the van?
That implies this is a mains power solar system i.e 240V output. Is the solar controller output with a 12V battery charging profile, and is that profile suited to your 12V van's battery (lead acid / GEL / Lithium)?
 
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Boldly
Jun 20, 2022
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Don't think any solar is 240v this controller is either 12v or 24v which is like all others (I think). To get 240v you need an inverter (again I think). Website says this one is particularly suited to motorhomes that's why I'm interested in it.
 

grasscutter

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Bimble supply a circuit breaker for the panel with their kits.
Itā€™s so you can isolate the panels if work needs doing.
I had one on a previous van.

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Hoovie

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May 16, 2021
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If your cable run is under 5m 10 mm sq cable will be OK but it would be better to mount the Regulator nearer the battery.
10mm2 is very heavy cable for something that is peaking at around 20A. Why are you suggesting such thick cable?
As an example, the Victron 100/20 20A MPPT Controller would not even accept 10mm2 cable. In fact you are hard pressed to even get 6mm2 cable in the connectors.
295w is a hell of a big heavy panel I think you would be better to fit 2 x 150w panels.
I would totally agree. A well as the weight management issue on installation, you have a big panel that is not designed to be shaken around on a van with all the stresses that brings. Smaller panels are better for that. (last install I did, went for a pair of 175W panels for all these reasons).

The kit comes with 10mm cable so that should be ok. It also comes with a consumer unit and circuit breaker presumably for a shed or suchlike. Would there be any benefit to fitting this in the van?
I would be VERY surprised if any solar kit for a van came with 10mm cable.
Comes with a consumer unit as well? This sounds even odder to me. Post a link to the kit you are talking about.
 
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Boldly
Jun 20, 2022
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Craig solar panels are more efficient but also heavier and slightly more expensive. It's because there are so many to choose from that I have been dithering for so long. Still confused about which is best but all are better than the none I have now.
 
Apr 27, 2016
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Don't think any solar is 240v
There is a method of doing solar where each panel has a small 240V inverter, and the outputs are all connected together. It's not common but it definitely is possible, so check the back of the panel for a small box.

Edit, just seen the kit list, it's a consumer unit with a 32A DC breaker, so not 240V.

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Apr 27, 2016
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10mm2 is very heavy cable for something that is peaking at around 20A. Why are you suggesting such thick cable?
As an example, the Victron 100/20 20A MPPT Controller would not even accept 10mm2 cable. In fact you are hard pressed to even get 6mm2 cable in the connectors.
The kit comes with 6mm2 wire for panel to controller, and 10mm2 wire from controller to batteries. In the manual it says 10mm2 is the max for the connections. 3m of 10mm2 wire has a voltage drop of 1.3%, and for 6mm2 it's 2.1%, so it depends on what you decide is an acceptable loss - usually 3% is the target maximum. The manual suggests 10mm2, but that I suppose is for a house roof or a shed roof, where the wire may be longer.
 

Hoovie

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The kit comes with 6mm2 wire for panel to controller, and 10mm2 wire from controller to batteries. In the manual it says 10mm2 is the max for the connections. 3m of 10mm2 wire has a voltage drop of 1.3%, and for 6mm2 it's 2.1%, so it depends on what you decide is an acceptable loss - usually 3% is the target maximum.
well, I would not spec 10mm2 for a circuit that will handle 20A at the absolute maximum. way overkill.

looked at the kit ..... 1M lengths of 10mm2 cable, so even more overspec'ed
 
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Boldly
Jun 20, 2022
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So 6mm will be more than enough if the cable is less than 3m long. Does it make any difference if the +ve or -ve is the longer or do you have to make them the same length as the longest?
 

Hoovie

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So 6mm will be more than enough if the cable is less than 3m long. Does it make any difference if the +ve or -ve is the longer or do you have to make them the same length as the longest?
everyone has their own way of doing things, but if it were me, I would use 6mm2 maximum for panels to controller and controller to battery. And if you were never going to go bigger than 295W, 4mm2 would be ok as well - but may as well use 6mm2 instead of 4mm if running cable.
Look at the breakdown of costs ... they are pricing their 6mm2 cable at around Ā£1.80/Metre and the 10mm2 cable at Ā£4.80M. Just shows how much the price of thicker cable starts to rack up and there is no need to spend nearly 3 times the price for a benefit that is highly marginal (IMO).
 
Apr 27, 2016
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Does it make any difference if the +ve or -ve is the longer or do you have to make them the same length as the longest?
Normally it doesn't make any difference. But since you have the batteries in different locations the wires will be separate all the way to the controller. You could make them equal length to equalise the voltage drops. Alternatively you could use 10mm2 for the longer run and 6mm2 for the shorter run, that would probably just about equalise the voltage drops. Or 6mm2 and 4mm2 if you are taking Hoovie's advice.

If you are using wires for the negatives, ie not connecting to the bodywork, then they should be the same as the positives. If it's a PVC you could probably run the negatives through the bodywork.
 
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Boldly
Jun 20, 2022
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Sorry autorouter think you misunderstood. The two batteries are wired together. So are you saying I would just connect positive and connect negative to the body.(it is a self converted fiat ducato).
 
Apr 27, 2016
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You don't need to bother about equalising voltage drops if the wires connect at or before the branch point where the amps splits to the individual batteries.
 

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