What is a busbar?

6 April 2023

As with everything to do with DIY activities, you will find a lot of information online to help you along the way with your campervan, boat or off-grid build and the 12v electrics side is no different. We get a lot of enquiries from customers regarding wiring diagrams that they have found online and wanting to recreate these, but one thing that often comes up in conversation are busbars. In this article, we will explain what a busbar is and what it can be used for.

A busbar is a metallic strip or bar that used is for power distribution in low and high voltage applications. Focusing on the low voltage side of things, this can be splitting power cables, consolidating ground returns and reducing the number of connections on your battery terminal clamps. Busbars can make your installation look very professional and having all your connections neatly and logically arranged in one place makes fault finding and circuit checking much easier. Separate busbars must be used for the connections on the positive and negative sides.

Busbars come in all different shapes, sizes and with various connection types, but the most important thing to consider when looking for a busbar is the current rating that it can handle and the current that you are expecting to go through it.

For example, if you have a leisure battery and you want to attach a DC-DC charger (30A), MPPT controller (30A), fuse box (total 25A capacity), inverter (85A) and cut off switch to it, a busbar would be a great way to neatly consolidate all of those connections like the below image: 



To work out the current rating of the busbar required you need to consider the maximum current-flow scenario, and in the case above it would be when all the 'loads' are drawing power simultaneously, i.e. when all the circuits connected to the fuse box are on (assume 25A) and the inverter is operating at full capacity (85A), meaning you would need a busbar that was capable of handling 110A as a minimum. In practice, you would probably want to allow for some additional current-handling capacity in the busbar and your final choice might also be determined by the type and number of connections on the busbar itself (stud, screw or push-on terminals are common). The positive (red) busbar used in the above image has stud connections and a 210A continuous rating, and you can find it here.

Some busbars are colour-coded red or black, which we would recommend as it is an excellent visual indicator. However, it is not essential if your cable colours conform to the convention of red for positive and black for negative. As good practice, you should always use a cover on the positive busbar at least, to prevent accidental short-circuits from tools or negative cables coming loose.

A busbar does not replace the need for fusing, as you can see in the image above, the cables going to and from the busbar all have inline fuses, the busbar is just there to consolidate all of the connections meaning that only one feed is coming from the battery terminal. We would always recommend fusing the main feed cable from the battery to the busbar, particularly if it is of any significant length, and you can see that a mega fuse protects this cable in the above image.

Click here to see our new range of busbars.

If you want more information to clear things up around 12v electrics or to help you on your way to getting the electrics finished off in your vehicle, then click here for further information.

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