As times advance, AI has already impacted various industries. In the battery industry, with the continuous expansion of data centers, increased electricity price fluctuations, stricter carbon emission regulations, and the development of microgrids in industrial parks, data centers are undergoing a structural transformation–the shift to lithium-ion batteries. The shortcomings of commonly used lead-acid batteries, such as their large size, short lifespan, and low energy density, are becoming more pronounced. Lithium-ion batteries, with their high energy density, long lifespan, and rapid discharge capabilities, are gradually becoming the new favorite for data centers. The adoption rate of lithium-ion batteries is expected to accelerate in 2025-2026, potentially even becoming the standard for UPS systems. However, while lithium-ion batteries are superior, there are significant differences between lithium-ion UPS and lead-acid UPS in terms of battery characteristics, performance parameters, and usage scenarios. Lithium-ion UPS systems have evolved from the traditional "battery + charger" model to an "electrochemical energy storage system," which directly changes the current detection scenario. This means that current sensors play a crucial role, including CHIPSENSE current sensors.
I.Differences between Lithium-ion UPS and Lead-acid UPS (System Level)
In traditional data centers, UPS systems use lead-acid batteries. Their function is to act as a backup power source, providing power to the servers for a short period only after the main power supply is interrupted. In this system architecture, current sensors are primarily "protective devices," and accuracy, bandwidth, and zero drift are not the most critical factors. CHIPSENSE current sensor are also.
The load of AI computing centers (GPU clusters, servers) is characterized by large instantaneous power fluctuations, continuous high-load operation, and zero tolerance for power interruptions. With the advent of the lithium-ion battery era, this data center UPS architecture has gradually evolved into: Mains power → AC/DC ↔ DC bus ↔ DC/DC ↔ LFP battery + BMS
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DC/AC → Load.
Several key changes have occurred in this architecture:
1. The current becomes bidirectional, allowing charging during off-peak hours and discharging during peak hours, and participating in power support during grid disturbances.
2. The battery transforms from a "passive load" to an "active power source," requiring BMS to monitor the current in real time, and requiring the UPS and battery to collaboratively control power flow.
3. The current is no longer smooth but highly dynamic. High-frequency switching power supplies (especially SiC) introduce a large amount of ripple, server load fluctuations are superimposed on the DC side, and scheduling strategies may lead to rapid power changes. This means that the current is no longer just about "whether it exceeds the limit," but rather a core input variable for how the system operates.
The performance differences between these two UPS systems can be summarized in the table below:
| Comparison Dimensions | Lead-acid UPS | Lithium-ion battery UPS (primarily lithium iron phosphate) |
| Power density and scalability | Low power density and limited single-unit capacity (generally ≤200 kVA); capacity expansion requires significant additional data center space, making it difficult to adapt to the high-density layout of computing centers. | The power density is 2-3 times that of lead-acid batteries, with a single unit capacity exceeding 500 kVA; it supports modular stacking for capacity expansion, saving data center space and matching the power supply requirements of data center racks. |
| Instantaneous peak current handling capacity | The instantaneous peak power of computing loads can reach 2-3 times the rated power (e.g., during GPU startup or batch data processing), and lead-acid UPS systems have a slow discharge current response, which can easily lead to voltage drops. | It supports high-rate discharge (2-5C), capable of instantly outputting large currents to stably handle peak load surges from computing equipment with no significant voltage fluctuations. |
| Parallel operation and redundancy capabilities | The number of parallel units is limited (generally ≤4 units), and the redundancy switching time is long (milliseconds), posing a risk of power outages. | It supports parallel operation of multiple units (no quantity limit), with a redundancy switching time of less than 1ms, meeting the zero-interruption power supply requirements of data centers. |
| Charging and discharging cycles and lifespan | The computing center operates 24/7, and the lead-acid UPS undergoes frequent float charging/discharging cycles, shortening its lifespan to 200-300 cycles, requiring frequent replacement. | The cycle life can reach 3000-5000 cycles, supporting deep charge and discharge. Even under high-frequency cycling conditions, the lifespan can still be maintained for 5-8 years, reducing operation and maintenance costs. |
| BMS dependency | It lacks a complex BMS, only requiring basic over-current protection. | It relies on a clustered BMS (Battery Management System) to monitor the charging and discharging current and cell balancing status of the entire battery pack in real time, preventing local overcharging/over-discharging that could lead to thermal runaway. |
| Adapted to meet green and energy-saving requirements | The charging and discharging efficiency is low (85%-90%), and the float charging loss is significant, increasing the PUE value of the computing center. | The charging and discharging efficiency is as high as 95%-98%, supporting peak shaving and valley filling (charging during off-peak hours and discharging during peak hours), helping data centers reduce PUE (Power Usage Effectiveness). |
II.Differences in Electrical Characteristics Between Lithium-ion and Lead-acid UPS Systems
The following electrical characteristics are the ones that have the greatest impact on current detection.
1.Dynamic characteristics of charging and discharging current
Parameters: Lead-acid UPS Lithium-ion battery UPS
Charging current Relatively smooth, low ripple May experience pulse charging, segmented charging, and high current during the fast charging phase
Discharging current Relatively stable May experience transient high currents (millisecond range)
Current change rate Slower (low dI/dt) Higher dI/dt
Impact on current sensors:
* Higher bandwidth is required (an increase from the traditional tens of kHz to the 100 kHz range is more reliable).
* Better transient response capabilities are needed.
* Improved resistance to spikes and EMI is more important.
2. Changes in DC bus voltage level
Scenario Lead-acid UPS Lithium-ion battery UPS
Common busbars 192V / 384V Common architectures include 384V, 512V, and even 700–800V
System power Primarily for small and medium power applications Evolving towards higher power (data centers, edge IDCs, industrial UPS)
New requirements:
• Higher insulation voltage rating for current sensors
• Improved common-mode rejection capability
• Stricter requirements for creepage distance and electrical safety ratings
III.Why Data Centers Are Particularly Concerned About Current
In typical industrial UPS systems, current detection is primarily used for: over-current protection and simple monitoring.
However, in data center lithium-ion battery applications, current data is given more responsibilities:
1. The "eyes" of the BMS: SOC calculation relies on current measurement
In lithium-ion battery systems, SOC (State of Charge) estimation is mainly based on Coulomb counting, i.e.:
SOC ≈ Initial SOC + ∫ I(t) dt
If there is a deviation in current measurement:
SOC will gradually drift
May lead to overcharging or over-discharging
Affects battery life and even safety
This means that the zero drift, temperature drift, and long-term stability of the current sensor directly determine the reliability of the BMS.
2. The "Measuring Stick" of Energy Management
In data centers, lithium-ion UPS systems are often used for:
Peak shaving and load shifting
Demand management
Power dispatching in campus microgrids
All these functions rely on accurate bidirectional current measurement:
Does the charging power conform to the strategy?
Is the discharge reaching the target?
Are there any abnormal power fluctuations?
If the current sensor has poor linearity, slow response, or offset, the decisions of the entire energy management system will be "distorted." Therefore, the CHIPSENSE current sensor meets high standards.
3. The "Last Line of Defense" for Protection
Even in the era of lithium-ion batteries, the fundamental role of a UPS remains the protection of critical loads.
Under extreme operating conditions:
Short-circuit currents can be extremely high.
Transient current changes are very rapid.
In this case, the current sensor must:
Have a sufficiently high bandwidth.
Have a fast response capability.
Be able to withstand transient shocks without distortion.
Otherwise, the protective action may be delayed or even fail.
CHIPSENSE current sensor is highly accurate, has a fast response time, offers sufficient bandwidth, and is an excellent choice.
IV.What new requirements does lithium-ion battery technology impose on Hall current sensors?
Based on data center scenarios, these can be summarized into four key dimensions of upgrade requirements:
1. Higher bandwidth: From "visible" to "clearly visible"
In the lead-acid battery era, sensors with a bandwidth of tens of kHz were usually sufficient.
In the era of lithium-ion UPS + SiC converters, the DC side current contains significant high-frequency components. Therefore, it is recommended that:
Bandwidth ≥ 100 kHz
Possess good transient response capabilities
Otherwise, the current "seen" by the BMS and UPS control algorithms will be severely smoothed, affecting control accuracy.
CHIPSENSE current sensors have excellent accuracy. CHIPSENSE CR1A H00 current sensor can be used as a good example.
2. Bidirectional Accuracy is More Important
Lead-acid UPS systems primarily discharge in one direction, while lithium-ion UPS systems operate frequently in both directions.
This requires the Hall effect current sensor to have:
• Linear consistency in both positive and negative directions
• Stable zero point
• Usable accuracy even in low current ranges
Otherwise, systematic errors will occur in SOC calculation and power management.
This situation has never occurred with CHIPSENSE current sensors before, so the quality is guaranteed.
CHIPSENSE HK4V H00 current sensor can serve as a typical example.
3. Upgraded Insulation and Anti-interference Capabilities
The DC bus voltage of data center lithium-ion UPS systems is increasing:
384V → 512V → 700 →800V
At the same time, high-frequency switching power supplies generate stronger EMI.
Therefore, Hall effect current sensors require:
Higher insulation voltage rating
Better common-mode rejection capability
Superior anti-interference design
This is not only a performance issue, but also a safety issue.
CHIPSENSE current sensors have always prioritized safety.
4. Long-term stability becomes a "hidden barrier"
The lifespan of data center equipment is typically 8–10 years or more.
This means that current sensors cannot simply be "accurate at the time of manufacture," but must:
Have low temperature drift
Have low long-term drift
Maintain consistency during long-term operation
Otherwise, while seemingly fine in the short term, they will suffer from "chronic inaccuracy" in the long run.
CHIPSENSE current sensors have consistently received positive feedback from customers regarding their performance.
V.Which locations are most critical?
In a data center lithium-ion UPS system, Hall effect current sensors have three main core application locations:
1. Battery main circuit
Functions:
• BMS SOC calculation
• Battery health monitoring
• Overcurrent protection
Requirements:
• High accuracy
• Low zero drift
• Bidirectional measurement capability
This is the first point that affects the system's "critical performance." This is the aspect that CHIPSENSE current sensors focus on the most.
2. DC Busbar
Functions:
• Monitoring overall power flow
• Supporting power dispatch
• Critical protection node
Requirements:
• High current measurement capability (hundreds to thousands of amperes)
• High insulation level
• Suitable for busbar mounting
3. Bidirectional DC/DC Module
Function:
• Controls power exchange between the battery and the busbar.
Requirements:
• High bandwidth
• Low latency
• Good anti-interference capability
VI. Why do we say that Hall sensors determine the "life and death" of a UPS?
Returning to the question in the title, this can be understood from three aspects:
Safety aspect:
* Inaccurate current measurement can lead to protection failure.
* The consequences of failure are unacceptable in a data center.
Performance aspect:
* Unstable current measurement renders the BMS "blind."
* Inaccurate SOC (State of Charge) leads to distorted system scheduling.
Economic aspects:
• Current errors can affect peak-valley arbitrage and demand management.
• In the long run, this directly impacts the operating costs of data centers.
In other words, in lithium-ion battery-powered data centers, Hall effect current sensors are no longer peripheral devices, but rather the cornerstone of the UPS sensing layer. CHIPSENSE current sensors have always played an important role.
VII. Conclusion: From Supporting Role to Key Player
The wave of lithium-ion battery adoption in data centers has only just begun.
In this transformation, batteries, power electronics, and energy management systems are all evolving, and current sensors—especially Hall effect current sensors—are moving from behind the scenes to center stage.
In the future, the performance of excellent data center UPS systems will depend not only on the converters, BMS, and the batteries themselves, but increasingly on whether the current sensing is reliable, accurate, and stable enough.The CHIPSENSE current sensor can achieve stable and accurate measurements.
In this sense, Hall effect current sensors are indeed at the heart of the UPS system's critical functionality. CHIPSENSE current sensor will be the best choice for customers.
CHIPSENSE is a national high-tech enterprise that focuses on the research and development, production, and application of high-end current and voltage sensors, as well as forward research on sensor chips and cutting-edge sensor technologies. CHIPSENSE is committed to providing customers with independently developed sensors, as well as diversified customized products and solutions.
“CHIPSENSE, sensing a better world!
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