Multi-temperature

Measuring the temperature of a block of cells in parallel in more than one spot

The judges of student competitions (such as the Formula Hybrid in the US and the Formula Student in the UK) require that at least 30 % of the cells have temperature monitoring.

A battery may consist of:

• A) A single string in series
• B) Multiple strings each with small cells, which are then connected in parallel
• C) Small cells directly in parallel, which are then connected in series

In case (A) the requirement is easily met: a distributed BMS (such as the Lithiumate) has a temperature sensor per cell board.

In case (B) the requirement can only be met with the Lithiumate Pro, the only off-the-shelf BMS that can be configured for multiple strings in parallel, or with a custom designed BMS.

In case (C), the requirement can only be met with the Lithiumate Pro, the only off-the-shelf BMS that can be configured for multiple cell boards per clock of cells in parallel. This application note shows you how.

Instructions:

1. Get enough cell boards to measure the temperature in multiple points (for example, for a 6P10S battery, and a 30 % coverage requirement, get 20 cell boards)
2. Install one string of cell boards along one side of the cells
3. Connect the end boards to Bank 0 of the BMS master
4. Repeat with the next string of cell boards, along a different side of cell boards
5. Connect the end boards to a different bank of the BMS master (in that example, Bank 8)
6. Configure the BMS for the number of string of cell boards as if they were multiple strings in parallel (in that example, configure it for 2 strings in parallel)

Example: 6 cells in parallel form a block, 3 blocks in series, 2 cell boards per block

If using 3 cell boards per block of parallel cells, use banks 0, 5 and 10, and configure the BMS for 3 strings in parallel

If using 4 cell boards per block of parallel cells, use banks 0, 4, 8 and 12, and configure the BMS for 4 strings in parallel