HP Prime Battery consumption analysis
12-13-2013, 06:23 PM (This post was last modified: 01-24-2014 08:05 PM by eried.)
Post: #1
 eried Senior Member Posts: 744 Joined: Dec 2013
HP Prime Battery consumption analysis
Code:
HP Prime - Battery Consumption Tests Valid for Software version: 2013 8 13 (5106)

Baseline test
This test relates the graphical on screen battery indicator with the time the calculator can operate powered on continuously.

Setup
The setup consists in a camera watching the calculator, while a servo pushes one key every second to keep the calculator on. Brightness level is minimum possible in the current software version, default screen used is the Home.

Video of the test/setup is available here:

Conclusions
A new fully charged HP Prime should last about 24.66 hours constantly powered on, with minimum use of the CPU. The warning message about the low battery appears 2.31 hours before the charge gets completely depleted.

Electric consumption measurement
Using the Baseline test as reference, we can relate this result to the real consumption of the device.

Setup
Since the mA sensing circuit is pretty poor performing in most of the multi-testers, I will assemble the excellent board available freely here: https://bitbucket.org/jmedved/usbamps

Video of the assembly:

The boards has to be modified because some small bugs in the PCB, but it is already fixed in the main website.

Results
Using the baseline test, all the data is extrapolated using the captured data from the average consumption over a minute.

Standby/Off consumption
Measuring the standby consumption is tricky. The calculator goes to a very low power consumption state (under 1 mA) with eventual spikes (every couple minutes).

Setup
Going back to the first approach, the calculator will be fully charged and then checked every 1 hour until the device does not power on anymore to get the real standby current consumption over time.

Results

Conclusions
Battery in standby will last for about 1141 hours (47,5 days). The warning about low battery will appear after 43,7 days of standby.

Charging the calculator/Charger efficiency
After discharging the battery we can now test the charging procedure. Using the same energy consumption meter USB dongle from Electric consumption measurement section we can monitor the charging stages until it goes to the same Standby/Off consumption pattern.

Setup
Image is captured thru a webcam. All the images are aligned and processed using ManyCam (to emulate a webcam from images) into WebCam Laboratory Universal Logger (to do OCR over the LCD displays):

Results

Conclusions
The optimal charge rate occurs in the first 100-110 minutes (less than 1:50 mins) of charge. The calculator is fully charged after exactly 198 minutes (3:18 mins).