PPRuNe Forums - View Single Post - 787 Batteries and Chargers - Part 1
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Old 8th Mar 2013, 10:59
  #860 (permalink)  
hAnd
 
Join Date: Mar 2013
Location: Hungary
Age: 46
Posts: 1
Cell balancing in serial connection ?

From the Factual Report:

"These features included thermal protection devices, circuitry to monitor cell and battery voltages and temperatures, circuits to ensure that all cells in a battery are charged equally and within safe voltage limits, and components and circuitry that discontinue charging of the battery when conditions warrant this action."

I wonder how the cell balancing works, if only cell measurements are possible, but no other reaction than stop charging at overall battery level (via message from BMU to BCU or opening the contactor by BMU4).

I see no possibility to charge the cells separately, only in series connection. So I am really curious how they "ensure that the cells ... are charged equally".

Assuming a cell short circuit as primary event, it seems, the BCU manufacturer's patented "voltage monitoring only" cell diagnostics failed to detect or failed to report (to BCU) or failed to open the contactor (as a redundant charge-shutdown path, I guess).

Individual cell temperature measurement at the cost of some cents would have given a higher confidence in cell failure detection, instead of the shaky voltage monitoring, that Securaplane is so proud of.
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