Things I Learned the Hard Way

Building my own Battery Pack

I've been attempting to build my own external battery pack using standard D-size NiCad batteries. I tore apart my dead SupersPORT battery pack, and it had ten batteries that were soldered together in two sets of five. NiCad batteries produce a slightly lower voltage than alkaline batteries: 1.25 volts instead of 1.5 volts. The original unit appears to have been designed to supply 12.5 volts.

I originally tried using fourteen batteries, yielding a total voltage of 17.5 volts. My thinking was that by using more total batteries, I could extend the length of time that the battery pack would last. However, I only got about ninety minutes out of it. Also, two of the batteries were totally dead. They measured around -30 mV. After a couple of hours, they returned to a normal voltage of 1.25 volts, and could be recharged. I suspect that the voltage regulator on the laptop is pulling the voltage down to around 12 volts, and is creating a quasi short-circuit.

I next tried cutting the number of batteries down to ten, matching ZDS's original design. This lasted about thirty minutes, and again I had a couple of batteries go completely dead. I suspect that the batteries I am trying to use cannot deliver enough current. My current measurements on the laptop show that it draws between 0.5 and 1.0 amps, depending on how bright the backlighting is, and whether or not the disk drive is being used. A unit with a hard drive would draw even more current.

The only other thing I could think of was to double the number of batteries. I wired up twenty batteries for 12.5 volts. (See the diagram below.) This setup works quite well. It will run the laptop for around two hours. But it's far from perfect. There are several issues to be aware of if you are trying to do this.

  1. It's bulky. This setup does not come anywhere close to fitting in the original SupersPORT battery case. I'm using a case designed to hold twenty CD's (about 5" x 5" x 8").
  2. I don't know if the SupersPORT charging circuit will work correctly with these batteries. I avoided the issue by using a standard NiCad battery charger from Radio Shack. Each set of four batteries takes about five hours to charge, so it takes a couple days to get them all recharged.
  3. For the best battery life, the batteries should be completely discharged before charging. The SupersPORT doesn't do this. You can either get a charger that discharges before it starts charging, or rig up some sort of discharging circuit yourself. I use a 12 volt light bulb.
  4. I've had one of the batteries pop out a couple of times. I'm using Radio Shack battery holders (they're kind of cheap), and apparently if they're jarred or bumped just right, the batteries can come out. This left me with just ten batteries supplying power instead of twenty, and it ran down in just a few minutes.
  5. Overall, I would call this a failed experiment. It just wasn't reliable. I had several occasions when the batteries didn't last as long as I thought they should. It might work better with Nimh batteries instead of NiCad.

Booting a System with a Dead Hard Drive

The usual symptom of a dead hard drive is the error Can't Reset Drive when you power on the system. If you have a 720K bootable disk in drive A, you should be able to press <Ctrl> <Break> or <Esc> to continue booting from drive A. Several bootable disks are available on the SupersPORT Software page.

On my system I ended up removing the hard drive controller and the bad hard drive. With the controller in, it kept trying to boot from the hard drive. I think it gave me a different error message, but I don't recall what it was. I'll throw the controller back in one of these days and find out. This should also extend the battery life a bit.

Warning! I don't recommend disassembling your system unless you are very comfortable working with hardware, and are willing to take the risk that it will never work again. Some of the inner workings are rather delicate.

I have the DIP switches set to all-on, except switch three. This sets it for one drive, 8Mhz clock. This will allow you use the single floppy drive as both drives A and B. (See switches for a detailed breakdown.)

I'm using DOS 6.22. I'm not sure why, but DOS insists that I have a 360K drive instead of 720K. I had to add the following lines to the config.sys to be able to format disks.

drivparm=/d:0 /f:2
drivparm=/d:1 /f:2

This configures drives A and B for 720K. On a single drive system, DOS can treat one physical drive as two logical drives. This makes it easier to do disk swapping. For example, I have a boot disk with a word processor that I use as drive A, and I have a second disk for drive B that just holds my data files.

Using the SupersPORT on a Network

Yes, it's true. You can really use the SupersPORT on a network. I've done this using a Xircom Pocket Ethernet 3 adapter that attaches to the parallel port. Here's what you need:

  1. A Xircom Pocket Ethernet 3 adapter (PE3). You sometimes see these on eBay or at used computer shops.
  2. A power source for the PE3. Some units came with an external AC adapter. There is also a PS/2 style keyboard adapter that draws power from the keyboard jack. You can plug this into the keypad jack on the right side of the SupersPORT if you use a PS/2-to-AT keyboard adapter.
  3. Network software. I'm using LAN Manager 2.1 to attach to a shared printer on Windows NT, and a shared drive on Windows 98. A disk configured with this setup is available at SupersPORT Software. I chose LAN Manager because I thought it would be the easiest to get working on my home network.

It took a lot of trial and error to get this working. I started by installing the PE3 and LAN Manager on an old 386 system. Having a hard drive and more memory gave me a little more room to maneuver while testing. LAN Manager comes from Microsoft on four 1.44MB diskettes. (This can be downloaded from Microsoft's ftp site.) It takes up about 3MB on the hard drive when installed.

Next came the process of trying to fit this onto a 720K disk. Article Q87672 from Microsoft's knowledge base was very helpful in this process.

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Last modified 1/18/2009