Volts is a simple application that provides a digital readout of the internal battery voltage of your Macintosh Portable or PowerBook computer. Its original aim was to provide a more informative indicator of the voltage than that provided by the Battery desk accessory.
In addition, the present version of Volts also attempts to estimate the amount of battery life remaining from the reported battery voltage. It does this by automatically calibrating the discharge rate of the sealed lead-acid (Pb–H2SO4), nickel-cadmium (Ni–Cd), or nickel-hydride (Ni–H) battery (or any other battery type that Apple may use in the future. The calibration data are accumulated over each discharge cycle of the battery and are stored in the resource fork of the application.
Additional display features include a window with 3 zoom states, a pseudoanalog bar meter for the battery voltage (during charging only), status indicators for the battery and battery charger, CPU clock speed indicator, and an autoscaling chart of the recent voltage history of the battery.
Upon being launched, Volts displays its information in a window in the upper right corner of the main screen. The user is able to choose from one of 3 zoom states for this window and thereby exercise a modicum of control over how much information is displayed and how much desktop real estate is taken up by the window. The user is also able to move the display to a location more to his or her liking. The new zoom state and position will be remembered for future launches of Volts. It is recommended that the Volts application (or an alias to the same) be placed in the Startup Items folder for automatic launching during startup.
Volts is a shareware product. If you use it, please send your shareware payment of US$5 to:
Lawrence Anthony
Keck Laboratories
Caltech 138–78
Pasadena, CA 91125
U. S. A.
Please include your e-mail address with your payment so that you may receive future updates and beta releases. Thanks once again to those of you who have already sent in your shareware contributions.
Display Features:
The main features of the Volts display window are (in approximate order from top left to bottom right):
• The close box, which duplicates the functions of the Close and Quit menu items in the File menu. Clicking in the close box quits the Volts application.
• The battery voltage, which is nominally in the range [5.12 V, 7.67 V]. However, the PowerBook puts itself to sleep (within 10 seconds) if the voltage drops below a certain critical value. This corresponds to about 5.78 V on PowerBooks using a sealed lead-acid battery (the PowerBook 100 and the Portable), about 5.65 V on PowerBooks using a Nickel-Cadmium battery (the PowerBooks 140, 170, 145, 160, 180, and 165c), and about 5.85 V on PowerBooks using a Nickel-Hydride battery (the PowerBook Duos 210 and 230). So a voltage reading below this critical value is rarely registered. The style of the voltage readout is normally plain, but turns to bold when the battery is being charged at the “hicharge” rate (1.5 A).
• The estimated remaining battery life in hours and minutes. This is the estimated time remaining until the “10-second warning” appears (see previous paragraph). The remaining battery life display only shows its face when the battery charger is disconnected from the PowerBook. After all, concerns about remaining battery life are unwarranted when the battery charger is connected to the PowerBook. Therefore, when the battery charger is connected to the PowerBook, the remaining battery life display is replaced by a bar meter indicator of the battery voltage. This meter is linear and indicates a value in the range [V10-second warning, 7.67 V], where V10-second warning is the voltage at which the “10-second warning” appears. (See below for an explanation of how to autocalibrate your PowerBook battery.)
• The zoom lever, which can be in one of 3 states. Clicking on the zoom lever cycles through the 3 states and changes the corresponding size of the display window and the amount of information displayed:
Only the battery voltage and remaining battery life are visible.
In addition to the above, the status of the battery and battery charger as well as the CPU clock speed are displayed.
In addition to the above, an autoscaling chart of the recent voltage history of the battery is also displayed.
• The battery status indicator, which can be in one of 3 states:
Normal battery. I.e., none of the below.
Low battery. The battery voltage is below the low-voltage threshold. This corresponds to about 5.90 V on PowerBooks using a sealed lead-acid battery (the PowerBook 100 and the Portable), about 5.90 V on PowerBooks using a Nickel-Cadmium battery (the PowerBooks 140, 170, 145, 160, 180, and 165c), and about 5.95 V on PowerBooks using a Nickel-Hydride battery (the PowerBook Duos 210 and 230).
Dead battery. Apple Inside Macintosh, Volume VI insists that this should never happen, but it is here just in case.
• The battery charger status indicator, which can be in one of 4 states:
Charger disconnected from PowerBook.
Trickle charge. Just enough juice is being supplied to the battery to maintain an equilibrium fully-charged voltage (about 6.80 V to 6.90 V on the PowerBook 100).
Hicharge. A whopping 1.5 Amperes DC is being supplied to “top off” the battery.
Having difficulty hicharging battery. This could be due to any number of reasons, such as using a battery charger without the requisite power rating or neglecting to plug the A/C adapter into the A/C wall outlet.
• The CPU clock speed in MHz. It should read 1 MHz when in “rest” mode. Otherwise, it should read 16 MHz, 25 MHz, or 33 MHz (or whatever the instantaneous CPU clock speed of your PowerBook happens to be).
• The voltage history chart, which displays an autoscaling chart of the recent voltage history of the battery.
Menu Commands:
See Quit below.
Use this menu selection to quit the Volts application. Preference changes are saved automatically and remembered between sessions.
Use this menu selection to specify default preferences for Volts, including Display Update Period, Chart Update Period, and Chart Type. Factory default settings are 1 second, 5 seconds, and Histogram, respectively (see the dialog box below). The Display Update Period specifies the time interval between updates of the various displays. The Chart Update Period specifies the sampling period of the voltage history chart. Specifying a negative or zero value in either of these two fields causes the corresponding updates or samplings to occur continuously. User preferences are saved automatically and remembered between sessions.
Use this menu selection to erase all calibration data. Caution: This erasure is irreversible and the discharge rate of the battery will have to be recalibrated before accurate estimates of remaining battery life can be obtained once again. Under normal operation, there should be no need to choose this menu item. However, you may wish to do so if the modus operandi of your PowerBook has changed significantly.
Autocalibrating your PowerBook or Portable Battery:
This is easy. Just start Volts running in the background in the usual manner and use your PowerBook or Portable as you normally would as your battery goes through at least one complete discharge cycle. Thereafter, each time you use your PowerBook on battery power, Volts adds to the accumulated calibration data, improving the statistical accuracy of the calibration. The more you use your PowerBook on battery power and the more consistent you are in the use of your PowerBook, the more accurate the estimated remaining battery life.
Known and Potential Problems:
Volts stores its calibration and preference data in its resource fork, not in a Preferences file. (In particular, the calibration data are stored in the ‘DTDV’ resource with ID #128.) This has the unfortunate side effect of one’s having to recalibrate the PowerBook battery with each new release of Volts. This is ameliorated somewhat by the fact that the autocalibration process is automatic.
The more intrepid user may wish to use ResEdit to copy the ‘DTDV’ resource (ID #128) from the resource fork of the older version of Volts to that of the newer version. If you decide to do this, please observe the usual precautions when using ResEdit, i.e., make backup copies of both versions in case the surgery fails. Also, during the copy process, make sure you overwrite the ‘DTDV’ resource with ID #128 in the new version of Volts—when prompted with “Replace resources with the same ID?”, click on the “Yes” button, not on “Unique ID”.
For the reasons mentioned in the previous paragraph, make sure you run Volts from a volume to which you have write access. In particular, do not run it from a read-only file server.
The autocalibration algorithm of Volts may get a little confused if you frequently put your PowerBook to sleep for short periods of time (less than 5 minutes at a time) while operating on the internal battery. This may tend to overestimate the amount of battery life remaining very slightly. This should not be noticeable under normal operation and should be of no concern to all but a very few users.
The Power Manager is only able to directly determine whether or not the battery charger is plugged into the jack in the back of the PowerBook or Portable. It has no way of determining if you have plugged the adapter into the A/C socket or if you have switched on the power to the A/C adapter. It follows that the same of true of all extensions, control panels, desk accessories, and applications that make use of the Power Manager, including Volts. A caveat: I have been informed by one Volts user that the above is not true of the Duos, i.e., the Duos are not fooled by an A/C adapter that is switched off or unplugged from the wall socket. An improved Power Manager, presumably?!
Volts should run on any Macintosh with the Power Manager IC, including but not limited to the Portable; the PowerBook 100, 140, 170, 145, 160, 180, and 165c; and the PowerBook Duo 210 and 230. I have only tested Volts on a PowerBook 100 (the only machine I have access to) running System 7.0.1 and System 7 Tuner 1.1.1. Judging from user comments, Volts also seems to run satisfactorily on the Portable and PowerBooks 140, 170, 145, 160, and 180 and PowerBook Duos 210 and 230 running System 7.x. However, I have yet to hear from anyone using Volts with System 6.0.x. If you fall into this latter category, please drop me a note—otherwise, I may drop support for System 6 in future releases.
If you find that Volts does not work on your battery-operated Macintosh, consider it a bug and please report it to me.
Please send bug reports and suggestions for improvement to:
lza@ulysses.caltech.edu
Please include the following when you do so:
the version number of Volts,
the model number of your PowerBook,
the version number of the Macintosh operating system, and
your e-mail address.
If you do not have internet access, you can contact me by U. S. Mail at:
Lawrence Anthony
Keck Laboratories
Caltech 138–78
Pasadena, CA 91125
U. S. A.
Version History:
1.3.1 (April 4, 1993):
Fixed a problem with underestimation of remaining time on PowerBooks using Nickel- Cadmium batteries and overestimation of remaining time on PowerBooks (Duos) using Nickel-Hydride batteries.
Reduced memory allocation from 100 KB down to 60 KB.
Revised manual.
1.3 (March 12, 1993):
Functionally similar to 1.2ß1 but with minor cosmetic changes and bug fixes.
Revised manual.
1.2ß1 (September 16, 1992):
Completely revamped display layout and many new features, including:
a) plain dialog box window with 3 zoom states.
b) instantaneous voltage displayed digitally.
c) alternate bar meter indicator of voltage level.
d) pictorial status indicators for battery and battery charger.
e) instantaneous clock speed.
f) chart of recent history of voltage level with autoscaling ordinate axis.
g) estimated remaining time of battery charge determined by autocalibrating discharge characteristics of battery and maintaining database of same.
Fixed a bug that prevented Volts from responding promptly to update events.
Other minor bug fixes.
1.1.1 (August 21, 1992):
Fixed a bug that prevented Volts from being switched into the background on some PowerBooks.
Modified the window type from a standard Dialog Box window to a regular Document window.
1.1 (August 14, 1992):
Modified to use standard Dialog Box instead of Movable Modal Dialog Box to display the battery voltage.
Kept track of display position and saved it for future launches.
Distribution of this software product for commercial purposes or monetary gain without prior written permission from the author is prohibited. Permission is hereby granted to distribute this software (together with accompanying documentation) from anonymous ftp sites on the Internet.
This software is provided as is without any warranty, either expressed or implied.
Apple and Macintosh are registered trademarks of Apple Computer, Inc.
Further Reference:
• Apple Inside Macintosh, Volume VI, Addison-Wesley, Reading, Massachusetts, (1991); Chapter 31: The Power Manager (see especially pp. 31-23 to 31-24).
