In the March edition of this magazine we looked at various power generation options open to RV designers. In this article we focus on the battery technology that will drive the hybrid solutions for our RV’s. We also consider options for those solutions and the bus technology propelling them. Finally, we reflect on the emerging hydrogen economy, which has the potential to be a complete game changer for our industry.

Words Terry Owen

Battery tecnology

In an ideal world the perfect battery would be fully rechargeable in minutes and hold a similar amount of power to a tankful of gasoline or diesel. The question is – how far are we from this goal and will we ever get there?

Lithium-sulphur batteries
Lithium-sulphur batteries use a sulphur-carbon anode instead of carbon alone and have energy densities of the order of 500 watt-hours per kilogram (W·h/kg). This is significantly better than lithium ion types, which are in the range of 150–250 W·h/kg. The problem, until now at least, has been poor cycle life and self-discharge, with active material being lost from cathode to the anode. Recently, according to The Engineer Magazine, a team of international researchers led by Monash University’s Department of Mechanical and Aerospace Engineering in Melbourne, Australia, have filed a patent for a lithium sulphur battery with a long cycle life that is simple and low-cost to manufacture, using water-based processes. This means a big reduction in hazardous waste. Testing in cars and solar grids is to take place in Australia throughout 2020.

Solid state lithium
All commercial lithium batteries use a liquid or polymer gel electrolyte. This is the medium through which the ions pass between the electrodes when charging and discharging. In a solid-state battery, the liquid or polymer is replaced by a solid compound. The idea is not new but, up to now, poor conductivity of the solid compounds used has restricted development to small, specialist applications such as pacemakers, RFID and wearable devices. However, research is now producing solid state materials with ionic conductivities close to those of liquid electrolytes. The advantages are huge. Firstly, unlike liquid electrolytes, solid-state electrolytes are non-flammable when heated. This makes the technology extremely safe. Another bonus is reduced self-discharge, which means a longer shelf life. Secondly, solid-state electrolytes, can be made to have high capacitances and withstand high voltages. This results in batteries with a higher power-to-weight ratio, making them ideal for RV use. Despite these advances, it is likely to be a few years yet before such batteries have a significant impact on our market.

Batteries from sand
Referred to by some as ‘sand batteries’, lithium-silicon batteries use silicon-carbon composite anodes instead of carbon. Silicon can store a lot more lithium than graphite as the cell discharges. This means that more lithium can be deployed, resulting in more energy density. So – why don’t all lithium batteries use this technology? The problem is that, during the charge/discharge process, silicon expands by more than three times when it reacts with lithium, before shrinking back again. The overall effect is to cause the anode to disintegrate. This problem is being tackled by combining silicon with silicon dioxide (effectively sand) coated with carbon. In 2016 Elon Musk revealed that Tesla’s lithium ion cells are built that way although to date, amounts of silicon have been minimal. Now, Californian company Sila Nanotechnologies Inc., is producing silicon-dominant anode products that can drop into existing battery manufacturing processes, replacing graphite entirely. It promises an increase in energy density of 40% along with a 20-40% improvement in battery life. Initial deployment will be in consumer devices such as smartphones and watches with larger applications coming later. Costs are expected to be similar to exiting with reductions as economies of scale trip in.

Batteries from seawater
With a long history of innovation in material science, IBM Research unveiled a new battery chemistry at the end of 2019. It uses three proprietary materials that have never before been recorded as being combined in a battery. Apparently, these materials are able to be extracted from seawater so eliminating the need for mining or other intrusive sourcing techniques. The bottom line is that the technology could eliminate the need for heavy metals such as cobalt and nickel, so helping to provide long term sustainability in battery production. Currently cobalt is often found in the cathodes of lithium ion batteries where it helps with thermal stability and energy density. Nickel is widely used in battery production, being found in NiCd and NiMh devices. IBM is naturally being somewhat coy about the exact details of its invention but it seems that lithium is used as the anode material and is combined with a safe electrolyte with a high flash point and a cathode that is completely free of cobalt and nickel. Advantages claimed include lower cost, faster charging, high power and energy densities, 90%+ energy efficiency and low flammability. IBM is now working with others to move the technology from exploratory research to commercial development.

Graphene batteries and supercapacitors
As well as the potential to help improve solar panels, mentioned in our previous article, graphene also has the potential to improve battery performance. So far developments have focused on faster charging and discharging without overheating. This is done by covering the anode and cathode with a single layer of graphene rather than redesigning the whole battery. Typically, a cell phone battery can charge fully in just 20 minutes, compared to 90 minutes with conventional technology. Samsung is also working on a version that will enable a 45% increase in capacity. Initially, development was held back by the extremely high cost of graphene, but this has now reduced significantly so, eventually, we can expect to see many more graphene enhanced products (not just batteries). In the meantime, the first products to benefit are likely to be small devices such as smartphones, hearing aids and the portable charger shown here. Graphene also has the potential to make supercapacitors. These store charge directly without the need for a chemical reaction. As a result, they can be charged and discharged extremely quickly. This makes them perfect for applications such as regenerative braking.

Asymmetric temperature modulation (ATM)
One of the problems associated with extreme fast charging of lithium ion batteries is that metallic lithium can become plated on the anode, severely reducing battery life. Researchers from Pennsylvania State University have found that heating a cell to 60°C before charging eliminates the problem. However, the time needs to be limited to about 10 minutes to prevent cell degradation. Discharge is then at a much cooler temperature, hence the term ATM. Heating has been demonstrated using a nickel structure that preheats in less than 30 seconds. The technology is said to be scalable because the cells are based on industrially available components. Using this technology, it should be possible to add a 200-mile range to a battery in just 10 minutes.

Dual technology solutions

Lithium ion batteries have one big Achilles heel and that is charging below 0°C can result in permanent damage. Lead acid batteries on the other hand have no such problem but, in other areas they don’t perform as well as lithium. The question then arises as to why not combine these two technologies to give a seamless performance in battery behaviour. With this in mind, engineers at Hymer cooperated with German off-grid energy solution company BOS, to produce the Hymer Smart Battery. Launched in 2018, it works by combining the lead acid battery with a special lithium battery in such a way that the lithium battery does most of the work. This is done by ensuring that the lead battery is charged first with any excess energy going to the lithium battery second. When power is consumed, the lithium battery is discharged first, significantly increasing the lifespan of the lead battery. Hymer says the effect is to increase both the capacity and performance of the lead acid battery, whilst simultaneously tripling the efficiency. More details can be found in issue 21 of Aboutcamp BtoB.

Hybrid solutions
With so many exciting developments in both power sources and battery technology, the challenge is to find the best ways of combining these into hybrid solutions offering a high degree of independence for the RV.
Specialist manufacturers such as CBE, Mastervolt, NDS, Nordelettronica, Sargent, Victron Energy and Votronic each produce a wide range of products to fulfil this need. Some also offer bespoke design services to enable vehicle builders to get the best from their products. Here is a bespoke system from CBE, as fitted to a motorhome. There are two battery chargers, various isolation relays, a solar charge controller along with 12- and 230-volt fused distribution panels.
Mastervolt’s Combimaster range of products offer pure sine wave inverter power and multi-chemistry battery charging. They also have automatic AC transfer switching between generator or mains and inverter output, ensuring a constant power supply. Models up to 2600 watts continuous power are available.
Victron Energy goes a step further with this all-in-one solar power solution. The EasySolar-II GX combines a MPPT Solar Charge Controller with an inverter/charger and control hub, in one enclosure. The product is said to be easy to install, with a minimum of wiring. It’s rated at 2400 watts continuous power at 25°C. The unit also features connectivity for Victron’s GX products. These provide comprehensive monitoring of various parameters whilst operating as the communication-centre of the installation. Monitoring can be carried out locally or remotely via a smartphone. The GX-device also provides remote firmware updates and allows inverter/charger settings to be changed remotely.
NDS’s offering includes advanced battery charging from the vehicle’s alternator. Its Powerservice modules make the best use of the alternator power, through charging curves designed for service batteries of any kind of lead-acid technology. They are compatible with Euro 6 engines and can provide up to 40 amp-hours of charge for each hour of travel. Some models also accept solar and grid power sources. Nordelettronica presents a wide range of battery chargers along with advanced bus systems and control panels. Sargent prides itself on offering total design and service support for its wide range of products. These include power supply and distribution devices, advanced bus systems, level measuring, alarm systems, wiring harnesses, centralised management and remote control. Votronic also proffers a wide range of electrical and electronic kit. This includes chargers, voltage transformers, solar systems, level measurement technology, measuring devices and displays, peripheral units and accessories.

Bus communication and control systems

Bus communication and control systems were first developed by Robert Bosch GmbH in the 1980’s for use in automobiles. Their big advantage is a drastic reduction in the amount of wiring required to control and monitor the many components inside an automobile.

Advanced electronics is used to send and receive signals down wires connecting various components together. Each component can decode the signal and react just to those destined for it. In recent years the falling cost of electronics has meant that bus systems have been making their way into caravans and motorhomes. There are two basic types of technology in use – CAN bus (short for Controller Area Network) and LIN bus (short for Local Interconnect Network). In essence CAN bus allows major components to communicate seamlessly with one another via a single pair of control wires. The wires are routed round, visiting each one in turn, a bit like a bus calling at different stops. A microprocessor on each component connects to the control wires via a dedicated CAN controller. These controllers form a series of nodes on the network with protocols determining how they communicate. For example, an urgent signal to activate the ABS system will override other signals. For all its virtues, CAN bus is relatively complex and may be considered overkill for the habitation components inside our caravans and motorhomes.
LIN bus is much simpler, needing only one control wire. It works by sending signals from a master controller to a maximum of 16 slave units (one on each component being controlled). The signals wake up one slave at a time which then communicates with the master to produce the desired effect, such as switching on a heater. Once complete the master can then communicate with other slaves as required. This simplicity makes it cheaper than CAN bus whilst still being well suited to applications that do not need the level of sophistication that CAN bus has to offer. That’s why, in 2011, Europe’s Caravanning Industry Association, the CIVD, adopted the principals of the less complex LIN bus system for its CI-BUS (short for Caravan Industry) standard. This defines a common platform for creating, maintaining and servicing a uniform data bus system in the caravanning sector.
The CI-BUS standard is now widely adopted throughout Europe. Indeed some 67 CIVD members on four continents have signed the CI-BUS cooperation agreement. This underscores the industryís trend towards increasing digitalisation.
As a result, on many RVís, items such as heating and air conditioning can already be operated quite easily via a laptop, tablet or smartphone. This can help to provide both increased comfort and improved energy efficiency.
The CIVD says ìInnovations such as the CI-BUS contribute to the future viability of the caravanning industry and continue to offer enormous innovation potential.î
As more components become equipped with a CI-BUS interface so increasing levels of sophistication will become possible. Of course, much depends on how many functions each individual OEM decides to route to the interface, but the potential is there.
We have already seen an explosion of attractive control panels at the heart of some RVís. As well as sending out control signals these panels are able to receive feedback on things such as temperatures, levels and voltages. Also signals sent down the bus wire from one item can be used by others as needed. For example, a tank level sensor could be used to switch a pump off when the tank gets low.

Emerging hydrogen economy

Since the industrial revolution we have relied heavily on atmosphere-polluting fossil fuels to provide the energy we need for our power-hungry lifestyles. More recently, the use of renewables such wind and solar power, has helped to keep emissions in check but the global trend is still upwards.

Now, further help is on the way in the form of hydrogen, the most abundant element in the universe. Technological developments are nudging this green fuel towards a much greater presence in our lives. Its environmentally friendly nature, coupled with high energy density, efficiency and good technological flexibility mean it holds great promise as an energy carrier.

When hydrogen is burned in air, the only by-product is water. There are no harmful emissions and no greenhouse gases. Of course, hydrogen still has to be manufactured and this process can generate pollution. In an ideal world, all hydrogen would be produced by the electrolysis of water using electricity from renewable sources. Currently this is not the case and the vast majority of the worldís hydrogen is produced by the steam reformation of methane (CH4). The problem is that the process requires heat and produces CO2 emissions.

CH4 + H2O > CO + 3H2      CO + H2O > CO2 + H2

It might therefore seem futile to consider hydrogen as a sensible fuel but, the CO2 can be captured and stored and there are some advantages to using hydrogen.  For example, hydrogen has the highest energy density for its weight of any fuel (about three times that of gasoline) although, when stored as a highly compressed gas in strong cylinders, this is offset somewhat.

However, alternative means of storage, such as those based on material-based technology, are being developed. These store hydrogen through a process known as adsorption and are characterised by high storage densities whilst requiring relatively little by way of a supporting infrastructure. A wide range of adsorption materials is being researched.

Hydrogen comes into its own when used to power fuel cell electric vehicles (FCEVs).  Thatís because a fuel cell driving an electric motor is two to three times more efficient than an internal combustion engine running on gasoline. Whatís more, unlike battery powered vehicles, hydrogen types can be refuelled in about five minutes and have a range similar to gasoline powered vehicles.

Of course, itís perfectly possible to use hydrogen to power internal combustion engines (as demonstrated by BMWís Hydrogen 7 limited production car, built from 2005 to 2007) but the arrangement is much less efficient and produces some tailpipe emissions.

In 2018 Mercedes demonstrated its F-Cell Concept Sprinter van at the Caravan Salon in Dusseldorf. This has a 147-kW motor and a range of 500 km. (More details can be found in issue 21 of Aboutcamp BtoB.)

In October 2019 Groupe Renault announced the launch of the KANGOO Z.E. Hydrogen at the end of 2019 and MASTER Z.E. Hydrogen in 2020. It claims these models have up to three times more range than 100% electric vehicles with a charging time of only 5 to 10 minutes. Toyota, Hyundai and Honda also produce FCEVs for selected markets, although take up is limited by the availability of refuelling stations.

The key to really unlocking the hydrogen economy will be the production of hydrogen cheaply enough to compete with that produced by steam reformation of natural gas, but without the carbon emissions associated with it. To this end various technologies are in development that aim to achieve that objective.

In the meantime, the hydrogen roll out is set to be relatively slow, although many countries are pressing ahead regardless.  Experience is showing that, as hydrogen fuel stations are installed so FCEVs will follow.  Germany, for example, via its H2 mobility initiative, is planning for 400 charging stations by 2025 and estimates they will serve 650,000 FCEVs.

Japan too, is planning for a hydrogen fuelled future, spurred on by the Fukushima incident in 2011. It is planning for 900 refuelling stations by 2030. China, meanwhile is planning for 300 charging stations by 2025.

In the US, as you might expect, California is leading the way. It already has some 6,300 FCEVs and 39 fuel stations. The latter figure is set to increase to 200 by 2025.

Conclusion

With so much global focus on the impact of climate change there is a clear need to reduce emissions and our reliance on fossil fuels. The Covid 19 pandemic, with its resulting drop in global emissions, is already resulting in calls for greener ways to return to normality.

There is no doubt that a key component of clean energy is electricity, especially if it can be generated from renewable resources. Today the race is on to produce ever greener RVís and some notable achievements are already in the bag.

Last year we reported on the launch of the Iridium E Mobil ñ arguably the worldís first all-electric motorhome to go on sale to the public. We also reported that two New Zealand hire companies (Tourism Holdings Ltd and Jucy Rentals Ltd.), had begun to offer fully electric motorhomes and campers for holiday hire. 

Now, the increasing take up of hydrogen power means the day of the hydrogen powered RV may not be too far off. With fast refuelling, an excellent range, independence from the electricity grid, and zero emissions, it will be a complete game changer.