Custom T-Box Battery Manufacturer in China
A T-Box does not draw power in one steady line. During sleep mode, current may stay very low. When the TCU wakes up, searches for GNSS, connects to a 4G or 5G network, or sends data, the load can rise quickly. If the backup battery is selected only by nominal capacity, the voltage may drop during pulse loads, cold operation or long-term aging.
VTCBATT designs custom T-Box battery packs for automotive telematics control units, connected vehicle modules and TCU backup power systems. We support Li-ion, lithium polymer and LiFePO4 battery packs with custom voltage, capacity, protection circuit, wire, connector and mechanical design.
The right T-Box battery starts with the real TCU load profile. It also depends on pulse current, minimum system voltage, backup runtime, installation temperature and service-life target.
Custom T-Box Battery Pack Solutions
VTCBATT develops custom T-Box battery packs based on backup runtime, pulse current, temperature requirements, service life and available installation space.
Best for: High energy density and longer backup runtime
- Compact pack size with high energy density
- Strong pulse-power capability
- Flexible voltage and capacity configurations
Best for: Thin or irregular mechanical spaces
- Thin pouch-cell construction
- Flexible dimensions and custom pack shapes
- Useful where enclosure thickness is tightly limited
For cold-start requirements, also evaluate low-temperature battery options.
Best for: Thermal stability and long service life
- High thermal and chemical stability
- Good cycle-life performance
- Suitable for reliability-focused TCU designs
Industry / customer-specified option
- Established use in selected automotive electronics
- Good temperature tolerance
- Suitable when the vehicle platform or customer specification requires NiMH
How to Choose a T-Box Battery
Map the full operating sequence: sleep, wake-up, GNSS fix, network registration, data transmission, voice communication and standby.
Cellular transmission can create ampere-level transient loads. The battery must maintain sufficient terminal voltage during these pulses, especially at low temperature and after aging.
Usable capacity ends when loaded battery voltage falls below the minimum operating threshold of the TCU, PMIC or DC/DC converter.
Vterminal = VOCV − Ipulse × Rloop
Validate the actual loaded voltage in the complete pack.
Define discharge, charge and storage temperature separately. A cell that can discharge at low temperature may not be allowed to charge under the same condition.
Account for capacity retention, DCIR growth, high-temperature exposure, high-SOC storage and end-of-life pulse capability.
Battery vs Supercapacitor for T-Box Backup Power
| Design Factor | Battery | Supercapacitor | Hybrid Battery + Supercapacitor |
|---|---|---|---|
| Stored Energy | High | Low | High |
| Backup Duration | Minutes to hours | Seconds to short hold-up periods | Minutes to hours |
| Pulse Power | Good | Excellent | Excellent |
| Repeated Data Transmission | Well suited | Limited by stored energy | Well suited |
| GNSS / Callback Operation | Well suited | Best for short-duration operation | Well suited |
| Charge Acceptance | Moderate | Very fast | Fast pulse-energy recovery |
| Cycle Durability | Chemistry dependent | Very high | High |
| Best Use Case | Longer TCU backup operation | Short hold-up and pulse support | Longer runtime + strong pulse response |
Selection principle:
Choose a battery when backup runtime and stored energy are the main priorities. Choose a supercapacitor when short hold-up and high pulse power are more important. A hybrid architecture can combine battery energy storage with supercapacitor pulse support.
What Is a T-Box Battery?
A T-Box battery is a backup power source for an automotive Telematics Control Unit (TCU). It helps keep critical functions such as eCall, GNSS positioning, cellular communication and post-crash telemetry operating when the vehicle’s main 12 V or 24 V power supply is unavailable.
Selecting a T-Box battery requires more than matching voltage and capacity. Key engineering factors include low-temperature DCIR, cellular pulse current, voltage sag, automotive temperature exposure and long-term standby aging. A battery must still provide sufficient usable energy and peak power after years of service and under worst-case conditions.
Key Information Needed for a Custom T-Box Battery Pack
To recommend the right T-Box backup battery, the following project information is usually needed:
- TCU operating voltage range and minimum cutoff voltage
- Backup runtime target after main vehicle power loss
- Peak pulse current during 4G / 5G communication
- Sleep, wake-up, GNSS, network attach and data transmission duty cycle
- Charge, discharge and storage temperature requirements
- Available battery space, pack dimensions and installation position
- Required chemistry preference, such as Li-ion, LiPo, LiFePO4 or NiMH
- Wire, connector, PCM / BMS and protection requirements
- Service-life target and end-of-life performance margin
- Applicable automotive, eCall or customer-specific validation requirements
Engineering Validation Notes for T-Box Battery Projects
- A T-Box backup battery should be tested with the actual TCU operating sequence, not only with a constant-current discharge test.
- Pulse-load testing should include network registration, GNSS positioning, data transmission and repeated wake-up events.
- Low-temperature testing should confirm both usable capacity and loaded voltage under communication pulses.
- End-of-life validation should simulate capacity fade, DCIR growth and long-term high-temperature exposure.
- The complete pack power path should be checked, including cell DCIR, protection MOSFETs, wires, connectors and DC/DC efficiency.
- Pack-level results should be verified again after PCM / BMS, connector and mechanical structure are finalized.
Cell-Level Validation Data for T-Box Battery Design
These results provide cell-level validation evidence, rather than full T-Box or TCU system validation. Each test identifies the cell model and conditions. Final pack performance requires validation with the actual TCU load profile, pack structure, protection circuit, wiring resistance, cutoff voltage and thermal environment.
- Low-Temperature Cycle-Life Test
- High-Temperature Storage Capacity Test
The INR18650T-3500 cell was tested at -20°C ±2°C with 0.1C charging to 4.1V and 1C discharging to 2.5V. The cycle-life curve shows stable capacity retention through 200 low-temperature cycles for the tested samples.
| Parameter | Test condition / result |
|---|---|
| Test temperature | -20°C ±2°C |
| Charge condition | 0.1C charge to 4.1V, 0.05C cut-off |
| Discharge condition | 1C discharge to 2.5V |
| Criterion | 100th cycle capacity >95% of 1st cycle capacity |
| After 100 cycles | 98.28% to 99.12% capacity retention |
| After 200 cycles | 98.74% to 100.79% capacity retention |
| Recovery after 200 cycles | 98.35% to 99.01% capacity retention |
Cell-level evidence only. Final battery pack performance requires validation with the actual TCU load profile, protection circuit, wiring resistance, cutoff voltage and thermal environment.
The 18650T cells were fully charged, stored at high temperature for 7 days, rested at 25°C, then discharged at 1C to 2.75V. The test checks retained capacity after storage and recovered capacity after one standard charge-discharge cycle.
| Condition | Capacity retention | Capacity recovery | Observation |
|---|---|---|---|
| 70°C, 7 days | 89.35% to 91.26% | 96.02% to 96.53% | All listed samples stayed above the 88% retention criterion. |
| 65°C, 7 days | 83.68% to 93.31% | 96.96% to 97.73% | One sample fell below the 88% retention criterion, while recovery remained above 92%. |
Recovery capacity remained above 92% for all listed samples. At 65°C, sample 23 retained 83.68%, below the 88% retention criterion; its capacity recovery was 96.96%.
Cell-level evidence only. Final battery pack performance requires validation with the actual TCU load profile, protection circuit, wiring resistance, cutoff voltage and thermal environment.
A T-Box can use Li-ion, LiPo, LiFePO4, NiMH, a supercapacitor, or a hybrid energy-storage design. The right choice depends on TCU load profile, pulse current, temperature range, charging strategy, available space and backup runtime. For new custom pack projects, VTCBATT mainly recommends Li-ion, LiPo and LiFePO4 evaluation.
4G and 5G communication can create short high-current events. The battery must keep the TCU above its minimum operating voltage during these pulses, including at low temperature and after aging.
Runtime should be calculated from sleep current, wake-up events, GNSS activity, network attach, data transmission, standby time, usable capacity above cutoff voltage, temperature derating and aging margin. A constant-current capacity test alone may not represent real TCU operation.
A supercapacitor can support short hold-up or pulse buffering, but it stores less energy than a rechargeable battery. For longer telematics backup operation, a battery or hybrid battery-supercapacitor design is usually more suitable.
The required range depends on the actual TCU installation position and project specification. Discharge, charge and storage temperature limits should be defined separately because each condition affects safety and performance differently.
