Solar panel cable question
i want to put a solar panel on my garage roof with a 10amp controller inside (the garage) ,and the run cables to the battery on my Motorhome to keep it charged ,my question is ...the cable run from the controller to the battery would need to be about 5 meters ,would this be ok??
the cable run from the solar panel to the controller would only be about 1metre , there is no electric to the garage ! And I want to use the sun's free power
Comments
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The shorter the better for cables really.
Could you not do what we've done on the caravan and fit a controller in the motorhome with connectors that you can fit the solar cables to?
Hard to explain on here. Drop me an email if you want me to send pics
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It is more efficient to have the long run of cable from the panel to the controller, rather than from the controller to the battery. The panel sends a higher voltage to the controller which then reduces it to a lower voltage to charge the battery. The higher the current the higher the power loss iirc if you double the current the power loss increases by a factor of 4. This is why electricity is sent down power lines at very high voltage and low current.
Whether this would make any noticale difference to your application I have no idea.
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Ideally, you want the controller by the battery it is charging, so near zero voltage drop between it and what it thinks it is controlling. Plus if it is an at all decent controller it will also have temperature compensation. The latter's sensor is typically built in so the controller needs to feel the same temperature as the battery, though remote sensors can sometimes be used.
Remember that current flows in both the positive and negative wires so cable losses need calculating on twice the physical separation. Basically the bigger the wire the better, but when the panels yield is low and you need every bit, then the current and with it so the losses are fortunately reduced; thus going OTT has limited real world benefit. Typically on high-yield there is plenty of energy to be obtained and cable losses whilst also higher are not a big worry, on our mobile installations. Mine is 85 Watts and I used a spare length of 2.5 mm2, EHU cable, routing the return down two of its cores the supply up the other.
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