DC fast charging stations are being deployed at an unprecedented pace, and metering equipment, as a core component of these stations, is constantly evolving in terms of technology to meet changing market demands.
From early external shunt meters to the more common integrated DC energy meters of recent years, and now to Reallin Electron' latest smart shunt solution, DC energy meters are undergoing a true technological revolution.
Three Generations of Technological Evolution: Which Has Higher "Value"?
The metering accuracy of DC power meters directly affects how much electricity users pay and how much operators collect. In high-power overcharging scenarios, every 1% increase in error represents a significant financial loss for operators.
Currently, there are three main technological approaches on the market:
Shunter-connected Dual-Circuit DC Power Meters
>> First Generation Solution <<
This solution emerged more than a decade ago. It uses two shunts connected to a single power meter, measuring two DC current paths, and was once hailed as a "game-changer" design.
However, problems have become apparent over time: Because it uses external shunts for current/voltage signal sampling, the sampling lines are often 1 meter or longer. In the strong electromagnetic environment of charging stations, these lines act like high-frequency signal receiving antennas, easily causing data distortion and metering errors. External electromagnetic interference can cause sampling voltage fluctuations of 5-10mV, leading to a significant decrease in metering accuracy after long-term operation.
The more critical hidden danger lies in the fact that shunts generally use a 75mV output specification. Calculated at 300A current, the theoretical power consumption of the shunt alone is as high as 22.5VA. This enormous heat generation causes the shunt resistance to drift over time, leading to increasingly inaccurate metering data.
Furthermore, the random combination of some low-quality shunts with electricity meters makes the metering error untraceable, hindering its use in trade settlements.
In addition, the shunt specifications used must match the electricity meter settings, leaving room for meter tampering. Even using lead-sealed shunts is only a temporary fix, not addressing the fundamental source of the metering error.
Integrated Shunt DC Smart Energy Meter
>> Second Generation Solution<<
Reallin Electron pioneered the integrated shunt DC smart energy meter in 2020. This integrated design of the meter and shunt allows for direct access of voltage and current sampling signals to the metering chip, fundamentally resolving electromagnetic interference and error aggregation issues caused by excessively long sampling distances.
The integrated design stably controls metering errors to 0.5 level accuracy, while the theoretical power consumption for a 300A current is only 1.8VA, reducing power loss and heat generation by more than 90% compared to an external shunt.
Reallin Electron' actual factory-delivered accuracy reaches 0.2 level, far exceeding industry standards. Simultaneously, the integrated solution achieves a complete lead seal for the shunt and meter, fundamentally solving compliance challenges related to tamper prevention and meter traceability.
After five years of technological iteration, Reallin Electron' integrated DC energy meter can withstand a maximum voltage of 1500V and a maximum current of 1500A, resulting in dozens of sub-specifications. For the international market, certifications such as the German PTB and the EU MID demonstrate that the products meet the highest international standards for metering accuracy and safety.
However, in dual-gun charging pile scenarios, the integrated solution requires two separate electricity meters, resulting in a slightly higher overall cost and creating a certain barrier for cost-sensitive small charging pile companies.
Dual-Loop DC Smart Energy Meter with Smart Shunt
>> Third Generation Solution <<
Dual-gun charging piles need to achieve independent metering for two circuits while reducing the overall equipment cost. Is it possible to solve the comprehensive cost problem in dual-gun scenarios while retaining the core advantages of an integrated design?
Reallin Electron' answer is smart shunt technology. It integrates precise current and voltage sampling, as well as power and energy calculation capabilities, all within the shunt, forming an independent digital metering unit.
Each smart shunt is equivalent to a complete integrated DC energy meter. It connects directly via ribbon cable, converting voltage, current, power, and energy information into RS485 digital signals, which are then transmitted to the display unit for centralized processing.
This means that installers only need to install two smart shunts in the corresponding DC circuit of the charging pile and connect a voltage sampling line and an RS485 communication line to complete the wiring. Complex long-distance sampling lines are eliminated, and the risks of electromagnetic interference and wiring errors are significantly reduced.
How does the intelligent shunt achieve "installation in three seconds, accuracy for a lifetime"?
The intelligent shunt solution completely changes the wiring method of traditional dual-loop DC meters, as reflected in the following aspects:
| Comparison Item | Conventional Shunt Type | Intelligent Shunt Type |
|---|---|---|
| Sampling Method | Long-distance analog signal wiring, susceptible to interference | Built-in sampling → digital signal transmission, anti-interference |
| Error Factors | Multiple error superposition of meter, shunt, and wiring | Stable error, determined only by the shunt itself |
| Installation Complexity | Requires connection of current sampling lines, voltage sampling lines, power lines, and communication lines; prone to wiring errors | Display unit connected to intelligent shunt via plug-in wiring, simple and error-free |
| Lead Seal Security | Shunt is not lead-sealed, vulnerable to tampering | Integrated lead-sealed shunt, compliant with regulations |
| Dual-gun Compatibility Cost | 1 meter + 2 shunts, uncontrollable error | 2 intelligent shunts + 1 display unit, independent and accurate for each channel |
The function of the display unit has also evolved: it integrates two RS485 interfaces and two power pulse output interfaces, uses DC10-30V power supply, and is mounted on a 35mm DIN rail.
The display screen is equipped with two pulse lights and two buttons. Operators can see all the data of voltage, current, power and accumulated power of the two channels on the screen, and can also interact with the charging pile motherboard and the operation platform in real time.
Optional Configurations for Different Scenarios – There's One for You!
● Single-gun DC charging piles: Ideally, use an integrated DC smart meter. Excellent cost-performance ratio, easy installation, accurate metering, and reliable stability.
● Dual-gun DC charging piles: Ideally, use a smart shunt-type dual-circuit DC meter. Two independent metering circuits prevent interference and are unaffected by electromagnetic interference. The overall cost is more competitive than traditional dual-circuit solutions.
In Conclusion
The intelligent shunt solution precisely addresses a long-standing pain point in the industry: it combines the metering accuracy and anti-interference capabilities of an integrated solution with the installation scheme and cost advantages of a dual-circuit solution, propelling DC metering for charging piles towards greater accuracy and reliability.
Choosing the right technology for your charging pile is far more important than price when selecting a smart meter.
Reallin Electron shunt solutions offer accurate metering, digital communication, multiple tamper-proof features, and extremely simple installation, making them a reliable and trustworthy choice.