1.0 Introduction
1.1 Battery calibration loss symptoms
In certain instances, the PLM’s battery can lose calibration causing some undesirable effects. The following observable symptoms may indicate a battery that has lost calibration:
- The battery remains at 0% even after extended charging.
- The battery appears to charge up to 100% unusually fast. The battery charge may appear to jump from a low value to 100%.
- The battery appears to discharge (go to 0% charge) too quickly.
- The battery voltage is not in synch with the charge level, such as showing 100% charge while at 7V or lower.
To address these issues, a user initiated battery calibration feature is now available starting with PLM FW V1.14.4.91.
1.2 Calibration loss causes
The 2 most likely causes of battery calibration loss are:
- Battery was disconnected or replaced
- The unit remained shelved for an extended shelf time with no applied power
If the PLM’s battery is disconnected for any reason or replaced, a battery calibration is required.
If the PLM is disconnected from external power for an extended time (such as a lengthy shelf time), the battery can drain to the point where the protection circuit built into the battery pack goes open circuit.
Afterwards, the charge counter chip (LT4015) loses it’s register value for Qcount. Upon power up, the charge counter defaults to half scale which does not reflect the true state of charge. The battery therefore needs to be calibrated again to resolve this.
The battery menu now contains status bit indicators that will show the user that these conditions have been detected.
2.0 The Battery Info menu
To start the calibration, first enter the Battery Info menu as shown in Figure 1. The menu may also be entered by pressing the battery icon on the Main menu.
Figure 1.
For releases prior to V1.14.4.91 that do NOT have the calibration feature, the menu will appear as shown on the left in Figure 2. For releases that have the feature, it will appear as shown on the right with the title, “BATTERY INFO.”
figure 2.
Note that in prior releases, this menu was just called “Battery,” but now is called “Battery Info.”
2.2 The battery STATUS field
As shown, the new battery STATUS field has individual bits which indicate the current status of battery calibration. The function of each bit is described below.
Figure 3. Status Field Definition
| Status Bit Function | Description |
| Is Characterized | Flag is set if the unit has ever had a battery characterization |
| Power Loss Detected | If a power loss is detected (while using v1.14.4.91 or later FW only) this flag is set. This flag is persistent across reboots |
| QCOUNT PRESCALECONFIG+BITS | These bits reflect a check of register values in the charger device. If set, this could mean a bad calibration or a HW problem accessing the charger device. If this persists, contact Technical Support |
| Calibration Out of Order | There was a problem in the calibration attempt sequence, restart the calibration process |
3.0 Starting calibration and the calibration wizard
Inside the Battery Info menu, swipe to the left to bring up the screen to the right. This is the “Battery Calibration” screen. To perform the calibration, the battery must be between 7-8V. Therefore, typically the first notice presented is an indication to either allow the battery to discharge or charge up to reach the required starting voltage. A typical screen is as shown in Figure 4.
Figure 4. Wizard first step: charge or discharge to the required voltage
Once the battery either charges or discharges to the required level, then the Start button is presented to start the calibration as shown below in Figure 5.
Figure 5. Wizard Start Calibration Screen
Pressing Start allows you to continue through the calibration wizard, starting with connecting the wall charger.
Figure 6. Wizard Attach Charger Screen
The battery will then be charged to completely full. Afterwards, the user is prompted to start the discharge phase of the wizard. The user prompt will appear as shown below. This phase can take up to 8 hours to complete. Once completed, the device will automatically shut down.
Figure 7. Unplug to Start The Discharge Phase
After the charger is unplugged, the screen below appears to indicate that the discharge phase has begun. This phase can take up to 8-hours to complete. Once completed, the device will automatically shut down.
Figure 8. Wizard Battery Discharge to Shutdown Screen
Once the unit has automatically shut down and turned itself off, the calibration is complete. Re-attach the charger to restart the device. Note that the battery will be at 0% at this point, so allow some time for it to recharge. It is not required to charge back to 100% before using.
Enter the Battery info menu as shown in Figures 1 and 2. Observe that:
STATUS 1 0 0 0 0
indicates a successful and complete battery calibration. If the STATUS is any other value, reference Figure 3 and the table below it for indications of any problems incurred. If a problem occurred, either repeat the calibration or contact Foresight technical support.
The device is now ready for use after recharging the battery to a reasonable level.
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Appendix 1. FW v1.15.0.92 Hotfix Update
1.0 Changes in the release
The v1.15.092 FW update contains the following changes:
- New Feature: battery calibration health check, on boot
- Detects bad calibrations from older or current releases after FW Upgrade
- Fixed calibration mode log spamming
- fixed a calibration edge case condition where the unit would shut down seemingly due to low charge percentage before presenting the START calibration button
2.0 Calibration Health Check on Boot
On every boot, after battery initialization, a calibration health check is now performed. Afterwards, the flags in figure 3 (above) will be set or cleared accordingly. (Reference Figure for the expected results)
3.0 Calibration Edge Case
In some rare cases it is possible for the battery calibration data base to be corrupted in such a way that the unit has a high battery voltage such as 8.2V, but due to corruption, a low charge percentage such as 10%. In FW V1.114.4, this could cause the unit to automatically shutdown before the START calibration button (see Figure 5) is presented. This required use of the HDT to perform a “battreset” command before the unit could be calibrated.
With the fix in the update, the unit will not shutdown in this case.
Note that the low charge percentage warnings may still occur, but they should be ignored during the “Waiting to Discharge” phase (see Figure 4) of the calibration procedure.