RV travel is increasingly gaining popularity among young people. In such recreational vehicles, electricity is primarily supplied through 12V, 24V, and 48V battery systems, each having their own unique characteristics and advantages. It is difficult to determine which one is unequivocally better as they serve different purposes. Therefore, the following is comparison of each system across various aspects.
Voltage Safety:
According to IEC (International Electrotechnical Commission) regulations, the maximum safe limit for DC voltage is 60V, whereas NEMA (National Electrical Manufacturers Association) regulations stipulate a maximum DC voltage limit of 50V for safe operation. Exceeding the voltage limit and coming into contact with direct current can result in electric shock accidents, which can pose a significant threat to personal safety.
In general, DC voltages of 12V, 24V, and 48V fall within the safe DC voltage range limit, ensuring their reliability and safety. Thus, users can confidently employ them without any concerns.
Wire Heating:
Under equal power conditions, the 48V system requires the smallest current, the thinnest wire, and faces least resistance losses, thereby avoiding any potential safety hazards due to wire heating. On the other hand, the 12V system witnesses the highest current demand, the largest wire diameter requirements, and experiences the highest loss caused by wire internal resistance, which could result in wire heating. The 24V system falls in the middle, with average current, wire diameter requirements, and tolerable wire heating parameters.
A 12V power system can experience wire heating due to high currents, causing some to claim that it is the least safe option when compared to 24V and 48V systems. However, this is an inaccurate conclusion.
However, the 12V power system has a significant history of development, spanning over a century, the issue of wire heating, resulting from high current flow, can be effortlessly resolved through wire thickening. This specific wiring section spans a brief distance between the battery and the inverter. Placing the inverter in close proximity to the battery can reduce the wire length, typically at a maximum of 50cm. Correctly utilizing wires of an appropriate thickness and ensuring natural heat dissipation proves more than satisfactory.
Inverter Efficiency:
The conversion of DC to AC is vital, and the efficiency of the inverter's output is greatly influenced by the voltage difference. It's worth noting that an inverter will achieve the highest output efficiency when the voltage difference is at its lowest - the 48V power source is the most optimal. The next best option is the 24V power source, whereas the 12V power source is the least efficient.
DC Appliances:
This metric is of great concern to everyone as it offers the most immersive user experience. Presently, DC appliances on the market, such as TVs, air conditioners, refrigerators, water heaters, rice cookers, electric kettles, toilets, ventilation fans, lighting fixtures, electric mats, etc., most of them are 12V, and can be directly used without an inverter. The 12V system was initially designed for passenger cars, which has remained in use to date, creating a massive user market.
Additionally, there are many 24V DC electrical devices, particularly those used in large trucks, with a considerable user market. Furthermore, many DC appliances can be used universally for both 12V and 24V systems.
In contrast, 48V DC electrical equipment is exceedingly rare and not as widely used as the 12V/24V systems. Market demand determines product availability, and the RV market is a smaller niche market. Therefore, the wide adoption and application of 48V DC electrical equipment are still a distant future event.
Recharge on Driving:
The 12V car DC generator is highly efficient and can directly charge a 12V battery while driving. If both the battery and the car DC generator are 24V, charging can be done directly. However, if the car DC generator is 12V, it is necessary to boost the voltage in order to recharge the 24V battery.
For 48V batteries, due to the limited number of 48V DC generators available on the market, 12V/24V DC generators are commonly used to recharge the 48V battery after boosting the voltage. The difference between direct charging and boost charging is reflected in the energy loss of the boost module. The larger the boost voltage difference, the greater the loss and the lower the efficiency. A 48V battery charging system that does not use a 48V DC generator is known as a "pseudo 48V system".
Recharge on Parking:
There are fewer portable DC generators that run on 12V, with a majority running on 24V and a larger number on 48V. When charging a 12V battery with a portable generator, voltage reduction is usually necessary, which could result in energy loss due to the use of a voltage reduction module.
Costs:
As far as the battery technology itself is concerned, the differences in cost for batteries of the same energy (watt-hours) are negligible. Take lithium iron phosphate batteries, for example, from the same manufacturer, using the same battery cell. The 12V 5 kWh, 24V 5 kWh, and 48V 5 kWh batteries are similarly priced, with no significant discrepancy.
The main contributing factors to cost variation stem from the control circuit and packaging process. The 12V and 24V power systems have undergone extensive, reliable development. Battery-related equipment and appliances have achieved economies of scale, rendering complete product support, exceptional quality, and cost-effectiveness.
The newly developed 48V power system is more intricate than traditional 12V and 24V systems. It requires additional protection measures and advanced control technologies, resulting in higher equipment and equipment costs. Consequently, the 48V power system incurs higher expenses than the 12V and 24V power systems.
Fault Risk:
For RVs, the electric power system mostly uses a 12V system, which includes the front car of a towing RV. However, if a motorhome or the front vehicle of a trailer does not have a 48V generator and uses a 48V power system, adaptations are needed to boost and lower the voltage. This increases complexity and, although boost and lower modules are reliable and safe, there is no guarantee of zero faults. With more modules, the failure rate increases, making the probability of a 48V power system failure higher than that of a 12V or 24V power system. The construction of 48V power systems is more complex, making them more prone to problems. Therefore, in terms of fault risk, 48V power systems are higher than 12V and 24V power systems.
Fault Risk:
The battery pack itself is composed of many battery cells in series or parallel. A single lithium iron phosphate cell has a voltage of 3.2V, and when four cells are connected in series, it becomes a 12V battery (12.8V). Similarly, with 16 cells (some 15 cells) in series, a 48V battery (51.2V) is achieved.
With fewer series connections, a single battery failure has less impact on the entire battery string, resulting in greater fault tolerance, stability, and reliability. 48V batteries are designed with more series connections and fewer parallel connections, while 12V batteries have more series and parallel connections.
It is worth noting that theoretically, 48V batteries have a higher failure rate than 12V and 24V batteries. The more the batteries are connected in series, the higher the requirement for individual battery consistency. This means that connecting more batteries in series amplifies the differences between individual batteries, requiring better battery management systems. As the usage time of the battery increases, there is a greater risk of insufficient charging and discharge.
Unfortunately, a single damaged battery in a pack cannot be detected, repaired or replaced for individuals, and the consumer has to bear the cost of scrapping. Furthermore, forcibly charging a damaged battery can lead to overcharging and increase the risk of damage or danger. Thus, the scrapping risk caused by damage to 48V batteries is higher.
Remain Energy after Damage:
Assuming that four 25Ah battery packs are used to assemble three batteries with varying voltages of 12V, 24V, and 48V, each of the same capacity. A problem arises when one battery pack is damaged and its capacity drops from 25Ah to 10Ah. In such a scenario, computing the current battery capacity is not a straightforward task.
For instance, the 48V battery is a series connection of four identical 12V 25Ah battery packs. If one battery pack is faulty and not the other three, how much capacity is left? A common misconception is that losing one battery pack is identical to losing one-fourth of the battery capacity. In reality, it is similar to a bucket of water with wooden boards of varying lengths. The amount of water held is limited by the shortest board. Similarly, the remaining storage capacity of a damaged 48V battery pack depends on the other good battery packs' status.
That said, the 48V battery calculation is 0.48kWh (48 x 10 = 480wh), while the current storage capacity of the 24V battery is 0.84kWh (24 x 10 + 24 x 25 = 840wh). In a similar vein, the remaining storage capacity of the 12V battery is 1.02kWh (12 x 10 + 12 x 25 x 3 = 1020wh).
Overall, these calculations demonstrate that when a battery or battery pack is damaged, the remaining storage capacity is generally better in a 12V battery than a 24V battery and better in a 24V battery than a 48V battery.
Maintenance:
The electronic components and technologies utilized in the 48V power system are relatively novel, resulting in maintenance, repair, and component replacement becoming more intricate and specialized. Certain repair shops may not have the capabilities to handle these systems, and finding suitable repair facilities and components can be challenging in certain regions, leading to heightened difficulties in maintenance and repair.
In the case of a 48V system malfunction, conventional electrical engineers are unable to troubleshoot it. Conversely, 12V and 24V power systems have the advantage of easy access to accessories and convenient maintenance services.
Additionally, for circuits with the same likelihood of failure, repairing more intricate circuits becomes increasingly burdensome. It is apparent that the 48V power system not only has a higher failure rate than the 12V and 24V power systems but also lacks the convenience of maintenance and repair in comparison.
Upgrade:
Switching to 48V from 12V or 24V power systems that are already in use or planned for future use is a simple process as the wire diameter meets the necessary requirements. However, the wire resistance may be slightly higher, which should not impact usage.
Conversely, for those who already use or plan to utilize a 48V power system in the future, switching to 12V or 24V may not be feasible due to the thin wire diameter not meeting the requirements. This would necessitate the complete rerouting of the entire vehicle. Given that most RV power system lines are concealed, this undertaking would be quite challenging.
Conclusion：
The electricity consumption for RVs is much more complex than that of typical household life. It involves a variety of aspects, including strong and weak electricity, power generation, energy storage, inverters, boosting and reduction of voltage. Because of this, it has a specificity that's difficult for people to understand. However, by making a broad comparison, one can get a sense for the advantages and disadvantages of 12V, 24V, and 48V power systems.
To summarize my personal views on the matter, I suggest the following:
Sunpack is a Chinese company with more than 10 years of experience in the production of lithium batteries, we provide a range of 12V RV batteries with different capacities, which offer the flexibility to be combined in series for 24V or 48V systems or connected in parallel to increase overall capacity.
