While making the wiring of a DIY camper, the most straightforward (wrong) solution would be to just connect any 12V appliances directly to the battery, following the scheme BATTERY –> CABLE –> SWITCH –> CABLE –> APPLIANCE.
That is definitely a super dangerous install!
In case of shortcircuit, the current sent by battery would be able to start a fire. That’s all.
I am not going into details explaining you why 12V tension is more hazardous in terms of fire catching compared to 220V, check this external website in case you do not just trust me 🙂
So, how to avoid this risk? How to deal with shortcircuits?
We should always connect the battery to a fused distribution block, where each fuse protects a single electrical circuit. In case of shortcircuit in one circuit, its fuse only will blow off and everything will be fine and safe.
One fuse, one appliance or group of appliances (For example all the interior led lights).
Sounds easy, right? It is! 😉
Let’s go in details and discover how to succesfully install a fused distribution block.
1) Think about what appliances you really need
Dreaming about what kind of electrical equipment we would love to install is great fun! 🙂
I spent so many hours imagining what I would need in my camper, while offroading in Australia and camping in the beaches.
Off course I need lights, 12v and USB sockets to charge mobile devices, water pump, fridge and freezer, inverter and so much more.
Take your time to complete a list of what you plan to install, it will make life way easier during next steps!
2) Just power or power and ground distribution block?
Basically two models of distribution blocks exist.
- Just power, the most common, it distributes only the power. The appliances will receive only the power by the block and will be grounded directly to the chassis. This type of block is used mainly on vehicles where the ground cable coming from battery is soundly connected to chassis.
- Power and ground: the names says it all, they distribute also the ground to each circuit. That is nice where it is difficult or not possible to ground each device to chassis. It is the case of boats and big campers.
3) Where are you going to place it?
Our goal would be to position the block as close as possible to battery, to keep the power cable from it as short as possible to avoid any voltage drop. The ideal location would be somewhere fair easy to access, bear in mind that in case of any circuit’s failure, the first to check would be the distribution block itself, looking for blown off fuses.
4) Choose the power (and ground) cables of correct diameter
Probably the most exciting part of building or renovating our own camper, 4wd or boat, is just thinking about each appliance we would love to add to our system. We plan to buy that nice USB and 12V sockets panel, wondering the best way to install some extra lights or just to manage the wiring of the service battery bank. And for the ones of us that are willing to build theirs overland camper like me, it goes without saying that a large amount of 12V and 24v appliances is required to guaranteed some basic comforts.
Even on the most spartan camper, 4×4 or not, there are at very least half a dozen of appliances to manage: water pump, lights, some extra 12V and USB sockets, fridge or at least a coolbox, 220v inverter…
But how to correctly fuse them and avoid the dangers of short-circuits and fires?
In this post I will do my best to explain you in details how to choose the correct fuse for each appliance and will try to keep it as simple and direct possible.
1) First things first: choosing your Fused Distribution Block!
A fused distribution block basically is feeded by the battery and allows to connect each appliance to one single fuse, providing the maximum level of safety in the install.
Before buying one, you may just put it down all the appliances you want to add, and maybe buying a bigger block than what you need now, allowing room for future expansion. (yes, you will fill it up quickly! 🙂 ). Common blocks are available for 4,6,12 and 24 fuses.
2) Feeding the distribution block
You have to connect the battery positive terminal to the block via an electrical cable of correct diameter (Read “How to choose the correct electrical cable diameter”). Some blocks also provide a busbar to connect the ground terminal – not really a necessity on standard vehicles with ground connected to chassis, but useful on boats and campers.