1. Fusebox with individual power supplies for each circuit

These fuseboxes only distribute power on the +ve side of the circuit and each circuit must be fed with an individual +ve supply cable. These are inexpensive but multiple cables can make installation time-consuming and complex if you have lots of circuits.

The -ve connections for each circuit cannot go through the box so need to be taken back to a suitable common -ve connection point or directly to the battery -ve terminal.

2. Fusebox with common power supply for all circuits

These fuseboxes tidy up the input wiring by having all circuits connected via an internal busbar (essentially a metal plate), so only one +ve power supply cable is required. These make installation cleaner and quicker but they tend to be slightly more expensive than boxes with individual power supplies for each circuit.

Again, the -ve side of each circuit cannot go through the box so need to be dealt with externally.

3. Fusebox with common power supply for all circuits, plus negative connections

These boxes go one stage further and have an internal busbar for the -ve side of each circuit as well as for the +ve. This means that you only need to wire one +ve cable and one -ve cable into the box, keeping the inputs really neat and tidy.

The -ve connections for each circuit can then be taken to the negative busbar in the box, so all your connections are in one place. In this example we've used twin-core cable for each circuit which makes the installation even more tidy.

Conclusion

Although more expensive, fuseboxes with busbars for both +ve and -ve sides of the circuits (example no. 3 above) are the option we recommend for most installations. They keep the number of connections to a minimum, make fault finding easy (no -ve connections hidden behind carpeted linings that are difficult to access) and, when combined with twin core cable, can result in very neat wiring installations. These are available in 6-way and 12-way versions.

One topic that causes a bit of confusion is the concept of wiring batteries together so we thought we'd take a couple of minutes to provide a brief overview.

PARALLEL WIRING

If you want to increase your battery storage capacity by wiring two or more batteries together then you need to wire them in parallel. This means joining +ve to +ve and -ve to -ve. For two 12V batteries of the same size this will double your capacity in Ah but keep the voltage the same.

SERIES WIRING

If you want to increase your battery voltage by wiring two or more batteries together then you need to wire them in series. This means joining the +ve of one battery to the -ve of the other.  For two 12V batteries of the same size this will double your voltage but keep the capacity in Ah the same.