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This information is to help you to understand some basic principles and to suggest possible systems for your van conversion. It is in no way intended to be a complete or definitive guide to vehicle electrics or your van conversion.
The most common electrical addition to any van conversion is an auxiliary battery and charging system.
A battery is an accumulation of cells each having a voltage of around 2.1 volts. The most common type being lead acid. Our every day vehicle battery is a group of 6 cells connected in series making up a 12 volt battery. If we connected another 12 volt battery (6 more 2 volt cells) in series then we would have 12 x 2 volt cells making a total of 24 volts. This is of no use to us as our vans are 12 volts. However, if we connect another battery in parallel we then still have 12 volts but with the combined capacity of the two batteries (e.g 100ah+100ah = 200ah). When using this method the batteries should be identical in every way. With two dissimilar batteries one will be stronger than the other but will be dragged down by the weaker one.
Other battery types are GEL and AGM where the acid (electrolyte) is in a semi solid form and is impregnated into the seperator plates of the cell. These batteries are generally leak proof but not as ideally suited to vehicle applications as ordinary lead acid as they require a slightly different charging regime to that of the standard lead acid fitted to your van for starting purposes.
As the vehicles alternator is regulated for lead acid batteries we can see that fitting GEL or AGM is not the ideal solution . They are also considerably more expensive and should only be considered where exceptional circumstances exist.
However, with the introduction of intelligent alternators and stop start technology the use of an AGM battery is recommended. This is because the charging system required on these vehicles is more complex than a standard split charge system. More on this later. This information is also different when using a DC-DC (aka battery to battery) charger. This is because these chargers, unlike a conventional split charger, can be configured to suit most battery types.
Modern sealed (maintenance free) lead acid batteries do not need to be vented but can be if you so desire. Ask your battery supplier for a suitable venting kit when you order.
Myth number 1: "My battery measures 12 volts so it must be full". A fully charged battery will measure 12.6 - 12.7 volts at rest and a depleted one will measure 11.8 volts. To gain a true measure of our battery we should observe the charging progress. When the voltage is at 14.4 (at 25 deg C) and charging current has decreased to 2% or less of ah capacity then your battery is truly full.
Unless you fit genuine "deep cycle" open lead acid or GEL/AGM batteries it is not acceptable to discharge below 50% which is 12.2 volts as permanent damage to the battery can result.
For most van conversions a compromise is called for due to the limited space. We call this battery a "leisure battery".
Deep cycle and leisure batteries differ to the standard van battery as they are required to do different jobs. The van battery will be required to supply very large currents but for short periods of time during engine starting. The deep cycle or leisure battery however has to supply much smaller currents for longer periods of time. For example, lighting or TV, refrigerator or sound system.
The most popular battery for this type of work is the 100/110 ah leisure battery. Small enough to accommodate under a cab seat but big enough to hold enough charge for a reasonable amount of use.
So, we have our battery, now we need to be able to charge it and the most popular way is to charge it from the engine alternator in the same way that the van battery charges. This method is known as "split charging". This, as the name implies splits the charge from the alternator and sends it to both batteries. It is important to match the split charge system to the capabilities of the vehicles alternator. The output of a standard van alternator is 90 amps (with some having 120 amp or even 150 amp ones for special applications). It therefore follows that our split charge system should be capable of handling the 90 amps that our alternator can give.
If you don't understand amps then let me make a simple analogy. Amps represent flow of electrical current. The conductors used to carry this flow must be of a suitable size. Imagine that you have a fireman's hose (large diameter conductor) at full flow (alternator charging flat battery) filling a large tank (your battery) and you then introduce your garden hose (small diameter conductor) into this circuit.
You now have have a very large flow being restricted by the smaller garden hose. Not only does this slow down the filling of our tank but there is a serious risk of something bursting.
This is not just idle theory or conjecture. Every month I see at least one van that has been very close to having a fire due to the fitment of an incorrect split charge system. Don't be fooled into thinking that because it is only 12 volts then no harm can arise. Batteries can supply massive currents, enough to melt a large metal object like a spanner. Always err on the side of caution with conductor sizes and always fuse the circuit below the capacity of your cables.
Please note that an alternator is NOT a battery charger and it cannot fully charge a battery, no matter how long you drive the vehicle for! It's primary purpose is to supply the vehicles electrical demands when the engine is running. For the same reason if your van has a flat battery and you jump start it you should charge the battery properly from a mains charger as soon as possible. Failing to do so will harm your battery.
For new vans with intelligent alternators there are special considerations. Please see the section at the end of this page.
Fuse boxes vs Control Panels
Next, for your conversion wiring you will need a fuse box to distribute power throughout your van. Every circuit must be protected by an appropriately sized fuse as close to the battery + as possible. If you want to install a fuse box further away from the battery then that is fine as long you fuse the supply cable to the fuse box. Fuse boxes are available in different sizes (ways). Beware of cheap blade fuses, particularly the higher amperage ones. The market is flooded with cheap fuses made of folded foil rather than stamped metal. These can be a source of problems. Try to buy brand name fuses where possible.
It is at this point where you have to decide whether you want a discrete, functional system or whether you prefer something a little more conspicuous and showy. There are many caravan/motorhome based control panels available and a lot of people, including professional converters go down this route. I think that they are initially seduced by the visual aesthetic and the prospect of a nice easy install. Don't be fooled, you will end up wasting space and not using many features that are incorporated into these panels.
General wiring tips
As we only have around 12 volts to begin with we cannot afford to squander them on poor connections and unnecessary inclusions. It cannot be over exaggerated how important it is to make secure connections. All cable should be of a suitable construction for vehicle use. This should be multi-strand cable in every instance. If you look at the construction of these cables you will see that the strands are slightly twisted in either clockwise or counter-clockwise direction. This is called the "lay".
When preparing the cable for insertion into a crimp terminal you should always twist the strands in the direction of the lay so that they are all tight and tidy. Make sure that all strands are inside the terminal before crimping with the correct tool.
Do NOT solder the wire before crimping. You may solder instead of or after crimping but not before.
Do NOT use switches in circuits that don't need them. Using a switch to control something like a power socket is not only pointless (instead of switching off remove plug) but can lead to as much as 1 volt lost in the circuit.
Cable sizes: The size of the cable used in each circuit will be governed by the amount of current flowing in that circuit and also by the length of cable used. In most instances, apart from things like fridges and high power amps etc, cable length should not be an issue. The cable also has to be of an appropriate size physically for the connected appliance. For example, using a 4 mm cable to supply LED lights would not be very tidy as you have large diameter heavy cables trying to connect to the very small ones attached to the LED lights.
In most instances we have taken the calculation out the equation for you and all cables are listed with suggested applications.
Other areas to watch are: Battery connections should be clean and tight. Do not use battery connectors that are not tinned. Protect the + terminal from coming into contact with any metalwork.
Whenever possible use two core cable and run all negatives to a common point, preferably the battery negative. Grounding circuits locally can cause a lot of problems when trying to fault find. Using a self tapping screw with a ring terminal is not a good connection. If you cannot run to the battery then try to use the vehicles existing earth points. These can generally be found in areas like seats, rear lights, front kick panels.
Remember, every time you make a connection you lose power.
Keep cable lengths to a minimum.
If in doubt err on the side of caution when choosing cable sizes.
Always fuse the circuit at less than the rating of the cable.
Always fuse the circuit as close to the battery + as possible and protect the unfused length from mechanical damage.
LED lighting can appear quite spectacular to look at but you need to choose carefully according to your needs. A very bright white LED may be good for working or reading but is a bit harsh for general background lighting. In this case choose a warmer white or go for a different colour like red or blue.
There are three types of "fridges", the 3 way fridge which can run on gas, 12 volts or 240 volts. This is an absorption type fridge and can only be powered by 12 volts once pre chilled and only during travelling due to the heavy power consumption. They also need to be level to function properly.
The Cool Box. Not strictly speaking a fridge and generally only cools a certain amount of degrees below ambient so if the ambient is 28 degrees you may only be able to cool to 8 degrees or higher. Again quite power hungry and should only be used when the engine is running. Either of these types could empty a 110 ah battery in less than 24 hours.
Compressor Fridge. These fridges are very efficient, tolerate uneven ground and are fairly quiet. From an electrical point of view you must provide a compressor fridge with a substantial supply. This is because the compressor will demand a high current momentarily when starting up even though when running the current draw is quite low. Our fridge looms use high quality
tri-rated 6 mm cable and come complete with connectors and fuse for connection direct to your leisure battery. Again, no switch is required in this circuit. Expect 2-3 days usage on a 110 ah battery taking into account other battery usage.
The most popular kind of 12 volt power socket is the cigarette lighter type. Many appliances like phone chargers and laptops can come ready fitted with plugs for use in these.
However, increasingly we see things that charge from a USB socket. Tablets and smart phones will need a USB socket that can supply at least 1.5 amps to 2 amps.
Power sockets do not need to have switches.
You can find a full range of CBE and C Line sockets and switches on the relevant pages. This is a very popular range of accessories that all match and can be mounted in single, double or triple frames. Used extensively throughout the industry.
230 volt AC equipment.
Installing 230 volt AC in your van is not essential but often desirable.
This is especially so if you frequently stay at camp sites that have hook up facilities.
In days gone by converters would cut a quite large hole in the side of your van to fit the inlet connector. These would often very quickly deteriorate due to the activity of UV and would quickly become unsightly. Fortunately new ideas have developed and this is no longer necessary. The norm nowadays is to mount the inlet under the bonnet or to secrete it behind a rear light.
The big advantage of under the bonnet mounting is that this is usually a dry area and does not require you to get down on your knees in the wet grass to make the connection.
When installing mains cables into your van you should, as with all cables, take care to route them away from possible sources of damage and always use grommets when passing through metal panels.
It is essential to fit a suitable RCD (consumer unit) and earth bond the internal earth bus bar to the vehicle body.
Suitable units will contain the RCD (main switch) and to comply with current regulations, should contain double pole MCBs .
The MCBs will need to be 1 at 5 amps for your battery charger (see next section) and 1 at 10 or 16 amps for your socket outlets.
All internal cable should be Arctic grade 3 core flex and 1.5 mm is adequate. Your earth bonding cable should be green/yellow 4 mm.
It is very important that you do NOT use grey twin and earth as used in domestic installations.
Multi stage intelligent battery chargers.
Another advantage of having a 230 volt AC mains installation is that you can integrate with your 12 volt system by fitting an intelligent mains battery charger. Choose one of a suitable output for your anticipated needs and this device will supply all your 12 volt requirements as well as charge and condition your leisure battery when you are hooked up to the mains.
I recommend the use of one these chargers at least once a month to maintain a healthy charge level in your leisure battery. This will not only give you better performance from your battery but should extend it's service life considerably.
Check with supplier that your chosen charger is also suitable for use as a power supply.
All our Victron chargers now have Bluetooth built in. This enables you to monitor the chargers functions via an app on your phone.
Solar panels are fast gaining in popularity and rightly so. These simple devices can greatly extend your battery time away from other charging sources. (wild or free camping).
There are two main types of panel to consider, the rigid glass panel that you will be familiar with from the roof tops of houses and the more recently developed semi flexible ones.
There are also two major types of solar regulator to consider. The basic one is known as a PWM (pulse wave modulation) and the (arguably in some instances) better one is MPPT (maximum power point tracking).
For a single panel I recommend using a good quality PWM regulator. MPPT regulators come into their own when used with more than one panel connected in series to increase the array voltage to around 42 volts. This is a whole subject on it's own and if you want to research it in more depth there is a huge knowledge base out there. I would just urge you to consider the fact that established producers of quality solar electronics sell MPPT controllers at massively different prices to the ones available widely on the net. There is a reason for this! Do your research first.
What is Intelligent Alternator / Regenerative Braking? The initiative behind the introduction of smart alternators / regenerative braking is to lower CO2 emissions and to improve miles per gallon / KM per litre for EU regulations. These smart alternators are installed on modern European Vehicles (Euro 5, Euro 6 + and newer engine models). The object of this new system is to utilise a vehicles wasted kinetic energy during braking / deceleration cycles experienced in every day motoring and rapidly convert as much of that energy (which is usually wasted as braking heat) into useful electricity and store this energy in the starter battery. Then, during acceleration and cruising release this energy back into the vehicles running system as “free electrical energy“ thus reducing the time where an alternator loads the main engine. This increases MPG/KPLand lowers CO2 emissions. However, in order for this system to be effective, the starter battery must have ‘free space’ to boost the energy into the battery, this requires the battery to be about 20% depleted (low enough to allow more power to be boosted into it but not too low as to prevent the engine from restarting when switched off). To replenish this ‘free space’, during deceleration or braking events, the voltage on the alternator shoots up to 15V or more. This higher voltage fast charges the starter battery to replenish its capacity. As you are using the inertia of the vehicle to charge the battery, rather than fuel, it is seen as ‘free energy’. Then the voltage drops to about 12.4V to allow the free energy to be consumed by the vehicle allowing the battery to deplete itself by about 20% ready for the next speed reduction and so on and so forth. Albeit an improvement in terms of emissions, there are knock on effects regarding the auxiliary charging systems on board commercial vehicles, read on.
Problems with Smart Alternator / Regenerative Braking
The system requires a 20% empty starter battery for the system to work. It needs the space to “dump” the fast energy build up during braking. This is in direct conflict with the auxiliary charging system requirements, why? 1) No charge going into the batteries during the 12.2-12.4V phase (which is totally by primary system design). Therefore, if a simple relay charging system was used to charge the auxiliary system it would not be charged during this time frame. This will be a problem if you require a charged auxiliary battery during travel or at location to location. 2) Very high battery charge rate during vehicle deceleration / braking due to alternator high voltage. This is relatively problem free for the starter battery as it is usually full. However, a large empty auxiliary bank could experience high currents at high voltages (much higher than their recommended level) which would be detrimental to the battery leading to premature destruction. Problem with using voltage sensitive/controlled relays? 1) Most VSR / VCRs have time delays before activating. 2) Even when the relay engages then at low voltages the batteries do not charge but at high voltage the aux batteries will get damaged. Also remember that the inherent software control system prevents the battery from being over 80% charged, so even when the battery is charging it will prematurely stop charging due to the software limitations which must leave that 20% space for the unit to be able to dump the braking energy, so you can never fully charge a battery using a relay or Diode you must use a DC-DC product like the CTEK Dual, Ablemail ABMC 12 12 30, Victron Orion 12 12 30 or Redarc BCDC1240. (other products are available and prices vary hugely)
travelvolts has long been involved in the VW van conversion sector. We offer a no nonsense approach to electrical systems for your conversion. Honest, reliable top quality brands that won't let you down.
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