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Symmetra PX 250/500 Battery to Power Module Ratio

Issue:
Symmetra PX 250/500 Battery to Power Module Ratio

Product line:
Symmetra PX 250/500

Environment:
All Product models, all serial numbers

Cause:
Required battery to power module ratio for a Symmetra PX 250/500

Resolution:

Ratio between numbers of battery shelves and power modules (PM)

Maximum recommended discharge level on the batteries used for Symmetra PX 250/500 is 3CA, where CA means the current (Amps) by which the battery is charged or discharged divided by its Amp-hour (Ah) rating.  The 250kW runtime ratio is 10 PMs to 16 battery shelves resulting in a ratio of 1.6 battery shelf per 1 PM. Need to always round up the number of shelves

Results if ratio is not maintained

In some situations, the Power Modules will attempt to draw power from the batteries and if the ratio is not observed, you will potentially clear fuses in the battery modules and (less likely, but it happened before) burn traces on the battery backplane boards due to the DC inrush current.

 

 

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