Inquiry regarding RDBESS774A3EVB - Board Damage due to Swapped Connectors (J1_1 and J1_3)

[WcrTh]

Hi,

I am currently evaluating the RDBESS774A3EVB Cell Monitoring Unit (CMU) board (which features the MC33774A Battery Cell Controllers) connected to a 50-cell battery pack setup.

Recently, an accidental misconnection occurred during our testing. We mistakenly swapped the cell connector sets between J1_1 (upper set) and J1_3 (lower set).

The following behaviors were observed during the incident:

1. Initial Event: Immediately upon swapping the connectors, a heavy short circuit occurred at Cell 36, causing an external wire/trace to burn out and break.

2. Subsequent Action: After discovering the mistake, we reconnected the battery packs to the same board using the correct connector positions.

3. Secondary Behavior: As soon as the correct connection was established, multiple balancing resistors (R_balance) on the board began to overheat and burn out.

Based on this scenario, we would highly appreciate your engineering insights regarding the following questions:

• Q1: Did the initial connector swap between J1_1 and J1_3 cause catastrophic internal damage to the MC33774A ICs or related circuitry during the first event?

• Q2: Is it correct to assume that the multiple balancing resistors burning out during the second (correct) connection was a direct consequence of internal damage inside the MC33774A ICs (e.g., internal FET breakdown or gate drivers stuck in an ON-state) caused by the first incident?

• Q3: If we replace the damaged MC33774A ICs and all the burned balancing resistors, can the RDBESS774A3EVB board be restored to a fully functional and safe working condition? Are there any other critical companion components (such as ESD/Zener protection diodes or isolation circuit elements) that we should inspect or replace alongside the main ICs?

[guoweisun]

Do you mean you mistake to add the 50*3.6V voltage between C17 to ground in the MC33774 first part?

[WcrTh]

Hi @guoweisun,

We did not connect the entire 50-cell pack into a single connector. Instead, our 50-cell system is divided into three separate segments with three distinct cell connectors.

1 Initial Event ERROR: CONNECTOR SWAP2 Subsequent Action: NORMAL CONNECTION