Status: Need is Closed

Battery Pack with Balancing Electronics

Request Number

Point of Contact
Need was closed on
Jan 3

Siemens is seeking a 24V - LiFePO4-battery pack with balancing and protection electronics in an overall plastic enclosure with approximately 1 … 3Ah

The battery's application is the energy storage in an industrial UPS (uninterruptable power supply) for 24V loads in the field of automation. In the event of a line supply outage the battery will be directly connected to the loads via power transistors, therefore the resulting battery voltage has to remain within the load's operating range over the whole temperature range according to this specification.

The buyer requires the new battery to be integrated into an existing UPS system that offers a widely programmable charging characteristic and undervoltage shutdown protection and can be programmed to the battery´s needs.

The requirements are described as either minimum requirements or stretched requirements with a possible derating (reduction of performance parameters is allowed). Demand is approx. 2000 packs p.a.



Ideally, the battery pack should be close to the dimensions of up to 120 x 80 x 80mm. The electrical connection should be with standard 6,3mm faston terminals. An optional signal connector for communication between the battery-pack-internal electronics and an external HOST system should be located on the same side as the power terminals.



The UPS system kicks in during the event of a power outage when a regular line-fed power supplies cannot continue to provide 24V. At this point, the 24V loads will be supplied directly from the connected battery pack. During the buffering time, the minimum supply voltage has to remain above 21V. This is especially challenging at -10°C battery temperature. The number of charge / discharge cycles is widely depending on the application, since the UPS + battery is sometimes used as a line-independent mobile power supply and can vary from 10 to 2000 over its lifetime. The UPS-system includes a µC controlled charging circuit with adjustable voltage and current limitation, a temperature sensor near the battery and the ability to store charging & discharging instructions in the controller to fully adapt to the battery´s needs. For future UPS developments an optional communication to the Battery Management System (BMS) would be ideal.


Key success Criteria
  • LiFePO4 as chemical system.
  • Minimum voltage of 21V@10A@-10°C for minimum 2min.
  • Maximum charging voltage: 28,8V, UL- transportation test and UL-recognized for the complete battery pack. Approvals should be done by vendor (buyer would cover approval cost)
  • Lifetime rating min 5years @40°C



Possible Approaches

8 pieces of 26650-LiFePO4-cells with 2,5Ah … 3Ah and low internal resistance in series. Cells assembled to a PCB with balancing electronics and protection shut down and optional communication to the BMS, assembled in a plastic housing.

Approaches not of Interest

Other chemical systems than LiFePO4 or high internal battery resistance at low temperatures that would require a power converter to meet the target voltage of 21,5V to 28V

Due Date
Feb 8
Items to be submitted

We are looking for concise, non-confidential proposals. The proposal should:

  • Describe the technical approach
  • Provide information on the performance of the technology (if available)
  • Include a description of the responding organisation or team and their experience.

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Gallery Moderator(s)
Dezarae Carver
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