User Guide

Practical Theory: Understanding How Data is Stored
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11. Understanding How Data is Stored
This section describes how the BMDM processes data and how the MPM or BDS stores the data.
For details about how the BMDM creates and backs up database files, refer to Understanding
Polling, Extraction and Backup.
11.1. Data Storage in the MPM
Data in the MPM is stored in nonvolatile E
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memory, which retains about a year's worth of
typical data. Collected data is stored until transferred to the Central or Local computer. This
same memory stores setup and calibration data, which is backed up to the Central or Local
computer during initial setup; this process is called synchronizing. Flash nonvolatile memory
stores uploads of new MPM firmware. You can upgrade the firmware on-site or remotely.
The MPM stores these kinds of data:
Alarms - 100 records that show when a parameter went into alarm and left alarm, and
maximum alarm level. Older records in memory are overwritten with more recent events.
(Older records uploaded to a computer are not overwritten.)
Discharge - 20.5kb of nonvolatile memory are allocated for discharge data. Memory size and
the number of cells monitored limit the data stored: many short or a few full discharges.
Each data point requires ten bytes of memory. If the discharge storage threshold is 10mv, and
a typical discharge for 24 cells was to discharge 1.875 volts per cell, and the cell voltage was
to drop to 1.96 volts with load applied, you would calculate the memory required as:
20,500 bytes / ( ( ( (1.96-1.875) / 0.010 volts) x 10 bytes) x 24 cells) = 10 discharges
This worst case assumes all cells discharge to 1.875 volts. Increasing the discharge storage
threshold can raise the number of discharges the monitor can store. Time stamped data allow
a full analysis of battery performance during the event.
Resistance - 1.6kb of nonvolatile memory are allocated for resistance data. Memory limits
the number of resistance tests stored. To calculate the number of resistance records available,
use the formula:
1600 bytes / ( (Number of cells x 2) + 10)
For a string of 24 cells, there is enough memory for 27 records.
Historical Data - With 1.65kb of nonvolatile memory available, historical readings of cell
voltage, temperature, overall voltage, and current are taken at intervals set under Battery
Setup. To calculate the number of historical records available, use the formula:
1650 bytes / ( (Number of cells x 2) + 18)
For a string of 24 cells, there is enough memory for 25 records.