Campervan electrics
Terminology
Volts (v) voltage can be thought of as the pressure from an electrical circuit's power source that pushes charged electrons (current) through an electrical circuit, enabling them to do work such as illuminating a light. (common voltage in the UK is 230v AC for houses and 12v DC for normal cars and vans)
Current is the flowing of electric charge. AC is Alternating Current. DC is Direct Current.
Amps / ampere is the unit used to measure that flow of current over a given time period. (We use Amps per hour to indicate battery capacity)
Watts / wattage is the amount of power any electric device consumes or produces.
Example
A typical leisure battery setup in a VW Transporter would be a 12 volt, 100Ah battery powering a fridge, USB/phone charging sockets, diesel heater, lighting and a water pump for the sink.
If we assume the 12v lighting has a total load of 50 watts we can calculate how long our battery will be able to provide power for in between recharges.
Capacity (Ah) x Voltage (V) x Efficiency / Load Power (W).
So 100 Ah battery at 12v with 90% efficiency powering a 50w load would have a runtime of (100 Ah x 12V x 0.9) / 30w = 36 hours.
However, not all loads are constant, for example a fridge will draw high wattage when first switched on while it cools down, then it will consume only a small amount of power to maintain temperature.
Lets begin
There are a few things to consider when it comes to your vans electrical installation.
12 volts
Vehicle main battery
The vehicles main battery (also referred to as the starter battery or car battery) is what starts your vehicles engine. This main battery always remains in the campervan after the conversion.
Leisure battery
A leisure battery, sometimes called a house battery, runs on a deep cycle and is designed to efficiently discharge a low and stable current over a long period of time.
Constructed using thicker battery plates and a denser active material than the vehicles main battery, a leisure battery can withstand repeated charge and discharge cycles throughout its lifetime.
The leisure battery is an additional battery installed usually below the driver or passenger seat in a van the size of a VW Transporter, it allows the use of the ceiling lights, phone chargers, 12v TVs, fridge/cool box etc without the worry of flattening your vehicles battery.
Battery types
Pretty much all conversions have a 12 volt (12v) leisure battery system installed as a minimum.
Some deep cycle battery types have a Depth of Discharge (DoD) rate as high as 80% before they require re-charging.
There are 4 main types of chemistry used for deep cycle batteries. Below is a brief summary of each.
Lead-Acid batteries use wet lead-acid technology containing lead plates housed in a sulphuric acid liquid electrolyte.
Gel lead-acid batteries have a gel electrolyte which offers greater safety should the battery suffer damage.
AGM batteries use lead-acid technology and the liquid electrolyte is contained in Absorbent Glass Matts (AGM). This provides greater protection against vibrations and offers a greater DoD.
Lithium batteries use Lithium Iron Phosphate (LiFePO4) technology and, whilst more expensive than the other types of battery, offer a number of advantages over lead-acid technology. Weight saving and a DoD as high as 80% being very advantageous features of a lithium battery.
Charging
For a campervan a Lithium battery is the best option with the AGM battery another excellent choice. All batteries will require charging up, the amount of use you can get out of a battery before it requires recharging is determined by the batteries chemistry (as shown above) and its capacity, this is usually expressed in Ah e.g 100Ah, 150Ah etc.
A traditionally installed leisure system will recharge the leisure battery whenever the vans engine is running, this is done via a DC-DC charger or voltage sensitive relay.
To further understand why the engine must be running to charge the battery it should be noted that whenever the engine is running the system voltage rises, sometimes as high as just above 14 volts (thanks to the alternator) depending on the the state of charge.
Additionally an electrical hook up (EHU) point is installed in the van along with a mains charger, the mains charger takes the incoming 230v AC and converts it to just over 14v DC and adjusts the current to safely charge a 12v battery.
Solar panels can be installed to charge your leisure battery up if you planning on parking up and not starting the engine for a few days. Solar panels are great but cannot be relied on for all of your power needs, to get most out of a solar panel setup a large battery bank (400+Ah) is required along with large solar panel(s) (600+w). This is not really possible in a small van from a cost or size point of view, so we use solar as a supplementary charging system to help the engine and mains chargers.
Conserve energy
Items like a water pump, water immersion heater, fridge and an inverter should always be switched off when not in use as the power (wattage) consumption can be quite high even in standby mode, this can lead to a flat battery and also shorten the usable life of the battery if the voltage is allowed to drop too low.
As current is directly proportional to voltage and inversely proportional to resistance we can assume a leisure battery voltage of less than 12 volts is flat and requires charging back up.
To keep thing easy to understand. A simplified regime to follow is when your leisure battery has been discharged (taken below 12v) it should be fully charged back again before its next use to maximise longevity. The best way to fully charge the leisure battery is via the electrical hook up EHU connected to a main charger for a few hours, the mains charger will output around 14.4v
Part of campervan life is learning to use the battery as necessary and switching off non-essential items when not in use.
230 volts
The next thing to consider is weather you require 230v in your van or not. In the UK we have 230v in our houses, so some people like to have household items in their van like a toaster, kettle, coffee maker or hairdryer. The problem here is the van only produces 12v, the household items require 230v.
How to overcome this?
On-grid camping: This means you are visiting a campsite with a 230v EHU This allows you to connect your van to the campsites 230v supply.
This supply is used to power up your vans 3 pin plug sockets and also (via an onboard charger) powers all of the vans other systems including the 12v leisure battery. This allows 10 to 13 amps of 230v power and will also provide all of the 12v power you need. You have no worries of 'running out' of electricity with this method. It is the simplest setup.
Off-grid camping: This means you are wild camping or at a site that does not have an EHU. The 230v system will not work when off grid. The only way to enable your vans 3 pin plug sockets to work when off grid is via the use of an inverter - An inverter takes power from your leisure battery (12v) and steps it up to the 230v that the sockets require.
When off-grid your van will be using the 12v leisure battery only. The leisure battery will eventually go flat, however by either running the engine or using a solar panel (given enough sunshine) the leisure battery can be recharged.
So can you combine the OFF-GRID and the ON-GRID electrical systems?
Yes, our solution is to use a Clayton Power LPS II power unit.
Simply put, the LPS II gives huge capability to your vans electrical system, providing ample power both on and off grid.
It features a powerful lithium battery, a 12v to 230v inverter along with EHU charging, alternator charging and a built in mppt solar charger ready to accept a solar panel.
click here read more about the Clayton Power LPS II
Another option is to use a standalone inverter connected to a leisure battery. Care must be taken when using an inverter to avoid fully discharging and damaging the battery so this is not suitable for everyone.
Even if you are On-grid a lot of campsites in the UK limit their 230v EHU supply to 10amps this equates to a supply of 2300 watts(in comparison, one single socket in your house is 13 amps)
To put this in context a microwave draws around 700 watts and a 2 slice toaster draws around 900 watts so some care must still be taken to ensure you do not overload the site and trip the circuit breaker.
A normal household kettle can draw 2000 to 3000 watts so buying low wattage appliances will help. There are low wattage versions of most appliances.