Battery Backup Unit (BBU) - SETsafe

Battery Backup Unit (BBU) Circuit Safety Protection SETsafe | SETfuse Solutions & Products

Overview

A BBU (Battery Backup Unit) is a device that provides temporary power when the main power supply is interrupted. It is typically used in data centers, servers, or high-performance computing equipment (such as AI servers). The BBU uses a built-in battery (e.g., a lithium-ion battery) to quickly switch power during a main power failure, sustaining device operation for a few seconds to several minutes. This ensures data is saved or the system shuts down safely, preventing data loss or hardware damage. BBUs are usually used in conjunction with PSUs (Power Supply Units). Compared to traditional UPSs (Uninterruptible Power Supplies), BBUs are more compact, more efficient, and particularly suitable for servers in high-density computing environments.

Why BBU Needs Circuit Protection

Circuit protection is required to ensure safe, reliable operation and compliance with regulatory requirements. The main reasons include:

Preventing Battery Failures:

High energy density batteries like lithium-ion batteries can overheat, catch fire, or explode under conditions of overcharge, over-discharge, or high temperatures. Circuit protection (e.g., over-temperature, over-voltage, over-current protection) can mitigate these risks.

Protecting Load Equipment:

BBUs provide emergency power to servers, AI equipment, and other devices. Abnormal voltage or current can damage this equipment, so protection circuits ensure a stable power supply.

Improving System Reliability:

Environments like data centers demand high reliability. Circuit protection prevents data loss or system crashes caused by power interruptions.

Compliance with Regulations and Standards:

Circuit protection is a mandatory requirement for meeting safety certifications (e.g., UL, CCC), which ensures that products can legally enter the market and reduces legal and financial risks.

Mandatory Standards and Numbers Involved

The following are common safety standards related to BBUs, covering circuit protection requirements (including over-temperature, over-voltage, over-current, and other protections):

UL Standards (USA)

UL 1973:

Standard for Batteries for Use in Stationary and Motive Auxiliary Power Applications. Requires the BMS to have overvoltage, overcurrent, over-temperature, and short-circuit protection.

UL 1642:

Standard for Lithium Batteries. Tests for overcharge, over-discharge, short-circuit, and other protections for battery cells.

UL 60950-1 / UL 62368-1:

Safety Standards for Information Technology Equipment. Requires BBU power systems to have overload, short-circuit, and over-temperature protection.

CCC Standards (China, Mandatory)

GB 4943.1-2022:

Safety of Information Technology Equipment. Equivalent to IEC 60950-1/62368-1, requiring overvoltage, overcurrent, and short-circuit protection.

GB/T 31241-2014:

Safety Requirements for Lithium-ion Cells and Battery Packs for Portable Electronic Equipment. Requires overcharge, over-discharge, and short-circuit protection.

GB 40165-2021:

Safety Requirements for Lithium Batteries for Fixed Equipment. Covers BMS protection functions.

International Standards (IEC)

IEC 62133 / IEC 62133-2:

Safety standards for lithium-ion batteries. Requires overcharge, over-discharge, over-temperature, and short-circuit protection.

IEC 62619:

Safety for secondary lithium cells and batteries for use in industrial applications. Applicable to data center BBUs, requiring comprehensive BMS protection.

IEC 60950-1 / IEC 62368-1:

Safety standards for Information Technology Equipment. Covers power protection for BBUs.

Other Relevant Standards

UN 38.3:

Safety requirements for the transport of lithium batteries. Tests for overcharge, over-discharge, and short-circuit protection.

IEEE 1625:

Standard for rechargeable batteries for portable computing devices. Emphasizes BMS protection functions.

BBU circuit protection is a necessary measure to ensure battery safety, equipment protection, system reliability, and regulatory compliance. Standards such as UL 1973, UL 1642, GB 4943.1, GB/T 31241, IEC 62133, and IEC 62619 explicitly require protection mechanisms for over-temperature, over-voltage, over-current, etc. In China, CCC is mandatory; in North America, UL is critical for market access; and IEC serves as a universal international reference.

Based on the needs for battery safety, equipment protection, system reliability, and regulatory compliance, BBUs must incorporate circuit protection design. These designs, through mechanisms for over-temperature, over-voltage, over-current, and active protection, address issues like thermal runaway, equipment damage, system failure, and standard requirements, ensuring the stable operation of BBUs in high-load environments (e.g., AI data centers).

The following are common circuit protection types in BBUs and their primary targeted issues (for reference only)

Over-Temperature Protection

Battery Thermal Runaway:

Lithium-ion batteries may experience electrolyte decomposition or catch fire at high temperatures.

Equipment Safety:

Prevents high temperatures from damaging the BBU or nearby equipment.

Service Life:

High temperatures accelerate battery aging; protection can extend service life.

Function:

Monitors the temperature of the BBU battery or circuit. When it exceeds a safe threshold (e.g., 60-70°C, depending on the battery type), it cuts off charging and discharging to prevent overheating.

Over-Voltage Protection

Battery Damage:

Overvoltage can lead to electrolyte decomposition or structural damage to the battery.

Load Equipment Protection:

Prevents high voltage from damaging sensitive equipment like servers and GPUs.

Electrical Safety:

Avoids abnormal voltages from causing short circuits or fires.

Function:

Limits the BBU's input or output voltage, preventing it from exceeding a safe range.

Over-Current Protection

Short-Circuit Risk:

Prevents large current surges caused by a line short circuit.

Battery Overload:

Avoids excessive current from causing battery overheating or damage.

Equipment Safety:

Protects load equipment from current shocks.

Function:

Limits the BBU's output or charging current, preventing it from exceeding a safe value (e.g., tens of amperes, depending on the design) due to a short circuit or overload.

Active Protection

System Stability:

Intervenes early on anomalies (e.g., voltage imbalance, slight over-temperature) to prevent them from worsening.

Battery Lifespan:

Optimizes charging and discharging to extend the battery's service cycle.

Smart Safety:

Uses predictive management to reduce potential risks, surpassing passive protection.

Function:

The BMS (Battery Management System) monitors the battery's real-time status (e.g., voltage, current, temperature, State of Charge - SOC) to dynamically adjust charging/discharging strategies and predict/prevent faults.

Other Common Protections

Short-Circuit Protection:

Addresses line short circuits to prevent large currents from damaging batteries or equipment.

Over-Discharge Protection:

Prevents the battery voltage from dropping too low (e.g., below 2.5V/cell for a lithium battery), avoiding irreversible capacity loss.

Reverse Polarity Protection:

Prevents circuit damage caused by incorrect wiring.

SETsafe | SETfuse Solutions, Protection Types, Products, Series

For detailed product specifications, please click "Learn more" to view the product detail page.

Protection Type: BBU Overcurrent Protection

Product: Chip Fuses (SMFL)

Series: