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SLA Gel Cell and Wallstreet powerbook - Mac Portable

I have sucessfully run my 233/512 (384 ram, 30g hd, OS 9.2) Wallstreet off a 12v, 7.2 amp-hour gel cell battery: [url]http://www.ibsa.com/estore/view_product_detail.asp?mscssid=7NAV3TTLCWN18JUFAE 4M9F[/url] 6U9L0V9NF9&part_number=SLA1075&category_id=0&find_ spec=power%20patrol&js=1 The battery cost $26 at an Interstate Batteries store (they had it in-stock in Omaha, NE) and weighs 6 pounds. Instead of buying a bunch of soon-to-be-defective replacement wallstreet batteries at $200 apiece, I will carry this battery inside my hard-shell foam-lined case which I keep my wallstreet in. It's a perfect fit in the side pocket. [url]http://images.canadiantire.ca/media/images/Workshop/ToolStorage/HandBoxes/Metal/0[/url] 580925_450_CC_ba96.jpg Usage in the field is not too often, but when I do, it's basically to unload ...

  1. #1

    Default SLA Gel Cell and Wallstreet powerbook

    I have sucessfully run my 233/512 (384 ram, 30g hd, OS 9.2) Wallstreet off a
    12v, 7.2 amp-hour gel cell battery:

    [url]http://www.ibsa.com/estore/view_product_detail.asp?mscssid=7NAV3TTLCWN18JUFAE 4M9F[/url]
    6U9L0V9NF9&part_number=SLA1075&category_id=0&find_ spec=power%20patrol&js=1

    The battery cost $26 at an Interstate Batteries store (they had it in-stock in
    Omaha, NE) and weighs 6 pounds. Instead of buying a bunch of
    soon-to-be-defective replacement wallstreet batteries at $200 apiece, I will
    carry this battery inside my hard-shell foam-lined case which I keep my
    wallstreet in. It's a perfect fit in the side pocket.

    [url]http://images.canadiantire.ca/media/images/Workshop/ToolStorage/HandBoxes/Metal/0[/url]
    580925_450_CC_ba96.jpg

    Usage in the field is not too often, but when I do, it's basically to unload
    photos from my digicam during a photoshoot, so a dead battery is an annoyance.
    My original wallstreet battery is one of those that dies after ten minutes, even
    after all the tricks - new power adapter, power manager reset, pram zap,
    PowerBook G3 Battery Reset application, etc. Can't bring myself to spend $200 on
    a replacement, which would probably fail in the same way.

    With regard to the plug configuration, since I had a spare older power adapter
    that came with the wallstreet (still works fine, but I got the free upgrade to
    the yo-yo) I took off the outer ring, which revealed the center portion of the
    plug to be simply a 3-conductor 3.5mm miniplug.

    The outer ring on the original plug does nothing but keep the plug firmly in
    place. Not needed if you're free of kids, dogs, carelessness, and other things
    which may the plug out of the machine. Then again, maybe if you do trip
    over the power line, it's probably better if the plug comes out easily, rather
    than put a bunch of force on the power manager card.

    The center portion was physically identical in every way to a 3.5mm diameter
    stereo miniplug, except that the power adapter's miniplug is about one
    millimeter shorter at the shank. This required fabrication of a thin flat
    plastic ring shim which I slid down onto the 3.5mm stereo miniplug purchased at
    radio shack. I used the modified stereo miniplug for the power connector.

    The arrangement of power in the plug is as follows (measured with a DVM on the
    Wallstreet's original power adapter):

    Tip: Nothing, nada. Probably just trips a switch that lets the powerbook know
    that it's plugged in.

    First ring: Negative conductor.

    Second ring, furthest from tip: Positive conductor (24v from the adapter, but
    12v runs the powerbook, what gives here? Is the extra 12 for charging the
    onboard battery?).

    The battery came with spade lugs, and I soldered on a short two-conductor lead
    attached to a polarized molex connector. I assume that reverse polarity would
    destroy the computer, so be diligent in this regard. This lead I will only leave
    on for testing, as I plan to put a fuse block inside this short lead for obvious
    reasons. If this battery was shorted, it would melt the lead in a very short
    time.

    Probably also a good idea once the lead is secured is to glob the exposed
    portions of the spade connectors with epoxy or cover them in plastic, so that it
    will be practically impossible for the battery to short itself if it manages to
    turn upside down on a metal surface, shorting the spade connectors. I would not
    take it on a plane until I was SURE it could not short itself.

    From there, I made an 8-foot lead which had at one end the other half of the
    molex connector, and at the other end the 3.5mm miniplug. This way, if I decide
    to power anything else with the battery, I merely need to make another lead to
    hook to the molex. I also made another molex lead to plug into the 12v battery
    charger I got at Wal-Mart. Takes about 7 hours to charge it.

    Testing:

    I made the first endurance test last night, and it was not as good as I had
    hoped, but then again I had not topped off the battery's charge when I bought
    it. The battery started off with about 12.4 volts (measured across the leads
    while powering the wallstreet) and the powerbook's screen started doing some
    weird flickering when the voltage got down to about 11.1 volts, so I unhooked it
    then and put it back on its power adapter. It appears to be unharmed. The
    voltage appeared to descend from 12.4 to 11.1 at a smooth rate, but in the ten
    minutes leading up to this flickering, the voltage started fluctuating fairly
    randomly from 11.1 up to 11.4 volts.

    The time elapsed was 3.5 hours for this change in voltage while powering the
    wallstreet, which had no power-saving functions engaged at all. I was doing
    basic websurfing. Also did at least one reboot.

    Maybe it will last a good while longer after I get a full charge on the battery,
    and engage some power-saving features when running from the SLA.

    I'll post pictures later if you want, and let you know how long it runs on the
    SLA after a full charge and engaging some mild power saving features.

    Is there any way to physically damage the powerbook by running it with
    undervoltages? I don't see any way I could exceed 24 volts with this
    arrangement. I could see instability and crashes happening, but real damage?

    Comments welcome.
    XXX Guest

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  5. #5

    Default Re: SLA Gel Cell and Wallstreet powerbook

    Compliments on the initiative of trying this experiment.

    I did something similar with my 1400, but used an auto adaptor to
    bring the 12 volts up to 24. You can get these pretty inexpensively
    as airplane laptop adaptors. The powerbook regulates the 24 volts
    down to whatever values the electronics and charger circuit needs.
    I'm surprised the wallstreet doesn't just shut itself off at low
    voltage, the lithium-ion battery it uses is nominally 14.4 volts.

    With the adaptor you can probably run your lead-acid battery down
    further, and get a little more running time, but probably not much more.
    The Li-ion battery for the wallstreet is rated at 4.0 amp-hours,
    as a point of comparison. Both lead-acid and Li-ion batteries will
    last longer if kept fully charged.

    A new third-party Li-ion battery for a wallstreet can be obtained
    on ebay for around $100, and less for a used battery, though of course
    you're taking your chances.

    Good luck!

    rob shaw
    rob Guest

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