The type of battery used as the “house” battery in van conversions needs to be capable of being discharged more, and sometimes left in a partially charged state. Rather than one that’s designed to give a lot of power for a short period of time, they need one that’s designed to give a little bit of power over a long period of time. As a result they need a different type of battery than the starter battery. These things run all the time, whether the engine is on or off. You’ll probably want some lights, some charging sockets for your electrical devices, and a way of powering a vent fan, fridge, water pump, the electrical control unit for a diesel heater, and so on. Now let’s look at what’s different about the electrical stuff in your van conversion. It’s good at delivering a lot of power for a short period of time, so the starter motor can turn the engine over, but it’s not designed to be left in a partially charged state for any length of time.
The type of battery used in cars is designed to be kept fully charged. Once the car is started, the alternator takes over to provide most of the power that the car’s electrical system needs. The battery has to be able to start the car after it’s been sitting unused for a while, but that’s about it. They tend to specify the smallest battery that will do the job. Obviously, things that take more power will run the battery down faster.Ĭar manufacturers don’t want to add weight or cost to their vehicles.
It’s also why your stereo may turn itself off a while after the engine stops. It’s why some of the 12v sockets switch off when the engine isn’t running. When the engine is off, the battery has to keep providing power to things like the car’s alarm system, parts of the engine management system, the courtesy lights that come on when the doors open, the stereo system (so it doesn’t lose its programmed radio stations), and anything you’ve plugged in to the 12v sockets like your iPhone charger. Because the alternator is attached to the vehicle’s electrical system in just the same way as the battery is, this means that when the engine is running, the voltage in the whole system could be 14 Volts or higher. This “pushes” more charge into the battery. To recharge the battery, the alternator provides a voltage slightly higher than the battery’s regular resting voltage. What we call a “12 Volt” battery might actually provide anything from 11 Volts to 13.5 Volts depending upon what type of battery it is and how charged or discharged it is. They use an alternator that runs from the engine to provide the 12 Volts that recharges the battery and to run all the electrical components (lights, ignition, stereo, engine management system, etc.) while the engine is on. They use a battery for starting the car’s engine. Most vehicles on the road today use a 12 Volt electrical system.
12V DC in a vehicle 12V DC in a van conversion Calculating what size battery you need How battery size is measured Stated battery size is different to usable battery capacity Match battery size to your expected usage Charging the 12V house battery Different charging options Three stage charging Charging voltages Knowing how full your batteries are Linking the battery to the things it powers 12 Volt cables are different to household wiring Choosing the right cable thickness Connecting cables to your devices Protecting the cables with fuses Simplifying wiring with bus bars and distribution panels Safety first Using 12V to make 120V AC versus DC - and why you care Inverters often charge the battery too Inverters are power-hungry What next? It’s worth reading all the way through, but you can jump to the piece you want using this index, too. Consult other sources of information before you start your own build. I made a complex 12v electrical system work in our van without anything bursting into flames, but that doesn’t make me an expert. Although I learnt the physics underlying this stuff back in school, there’s a big difference between theory and practice.
It also covers the most important pieces of adding a house battery and charging system to your van conversion, and the things you need to consider when you wire up your fridge, fan, and electrical outlets.ĭisclaimer: I’m not a professional electrician. If everything that goes on under the hood of your car is a mystery to you, this article might help out. Here’s a basic overview of how a 12 Volt system works in vehicles.