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What's a wiring sketch?

As part of our solar consultation to help answer your questions about going solar and putting together a complete system we will email you a wiring sketch. This essentially helps to highlight how the main components of your system will connect. Each install is very different to the next and the sketch is designed as a guide rather than a detailed wiring diagram.


Here's an example of a wiring sketch for 2x170W SunPower E-flex solar panels wired in parallel to a Victron Energy 100|30 MPPT charge controller (12V battery bank):


MC4 y-branch connectors


Here you can see the two SunPower 170W flex panels are wired together in parallel by using a pair of the 2-1 Y-branch connectors. In the sketch it shows the fixed connectors but you can easily use the flexible y-branch connectors shown below. These are sold as a pair in our store.


Remember in parallel you are combining the two positive cables (one from each solar panel) so two 'male' positive MC4 connectors will plug into two 'female' ends of an MC4 y-branch connector. This then gives you one positive 'male' end.


The same is true for the two negative cables (one from each solar panel) so two 'female' negative MC4 connectors will plug into two 'male' ends of an MC4 y-branch connector. This then gives you one negative 'female' end.




PV Extension wire


The next step will be a length of PV extension wire to get from the y-branch connectors to the Victron Energy MPPT charge controller. We typically recommend the 10AWG which will mean less wire losses (ie heat build up) as it is easier to send current (amps) over a longer distance with a thicker gauge wire.


The PV extension wire already has a male MC4 connector on one end and a female MC4 connector on the other end. To make things easier we suggest buying a length of PV wire twice as long as the distance of the wire run. For example if you have 20ft between the y-branch connectors and the MPPT charge controller then buy a 40ft length and cut it in half. This will leave you with 2x20ft lengths with an MC4 connector on one end (one male and one female) to click into the MC4 y-branch connectors and bare wires at the other end to connect into the MPPT controller.


Victron MPPT charge controller


Next you have the MPPT charge controller, in this case the 100|30. These are the SmartSolar range with built in bluetooth so from within say 10-20ft of the controller you can 'talk' to it with the VictronConnect app on your phone or tablet. This has two connections for the solar coming in, the positive and negative. These are screw down terminals so with a short amount of the bare PV wire end exposed you poke it in the slot (positive PV wire to + and negative PV wire to -) and then tighten up with a small screwdriver.





You may like to add on some ferrules (sometimes referred to as cord end terminals or bootlace ferrules) which are connectors used to terminate stranded wires. This then gives an improved connection and help prevent multiple stranded wires from splitting/getting damaged by the screw.





Battery bank


From the MPPT charge controller you have a positive and negative wire that is going to go to your battery bank. The positive wire we recommend go via an appropriate circuit breaker (or fuse) in this case a 30A or 35A marine rated circuit breaker.


Connecting to your battery bank will be different for each install so we have shown a very simple connection to a single battery. In reality you will probably have multiple batteries wired together in a bank eg. 2x12V batteries wired in parallel to keep 12V or 4x6V batteries wired in series to get 24V


You will need to source larger gauge battery cable and terminal fittings locally.


We're happy to offer guidance on where to connect your solar charge controller but it should be the same as where your shore power/battery charger is connected. This of course assumes that the shore power/battery charger is wired correctly...which may not be the case! You want to be charging across a battery bank so if we took the 2x12V batteries in parallel battery bank as an example then your positive from the controller would connect to the positive post on battery 1 and the negative from the controller would connect to the negative post on battery 2.


To avoid your battery terminal posts getting overcrowded with a bunch of wires connecting to it you may have a bus bar that you are connecting to.


We will soon have a blog post with more details and examples about how to connect to your battery bank but if you have any doubts please consult with a local marine electrician.




Victron Battery Sense

The other item we recommend is the Victron Battery Sense, which is the small blue box which connects to one of your batteries. This is a battery temperature and voltage monitor and it transmits this data via Bluetooth to your MPPT charge controller. This gives more accurate data for improved battery charging. It also helps when you have multiple charge controllers and as part of the SmartNetwork will help the controller 'talk' to each other.



Other components


As mentioned this is a simple wiring sketch which outlines the main components and each install is unique. We are happy to look at how your system will be set up and offer advice on what else may be needed. Here's a few examples from other installs:


My panels don't all reach the Y-branch connectors. Solution is to add a few short lengths of PV extension wire, say 3ft and not to cut them in half as you need MC4 connectors on both ends this time.


Adding a circuit breaker after the solar panels and before the charge controller, sized appropriately for the current (amps) from the combined solar panels.


Adding a battery monitor such as the Victron BMV-712


The MC4 disconnect tool which is used to help disconnect your solar panels



We can help you go solar


You are bound to have some questions and we are here to help. Maybe you have a custom install and need a wiring sketch unique to you? Feel free to contact us and we will help you on your way to clean & quiet power aboard your boat.