[ltp] Re: self-made external battery for laptops project

[M. Leo Cooper]

I've had pretty good results using a portable "jumpstart" battery for
a car.  These have a sealed lead-acid battery and include a 12-volt
cigarette lighter socket. They seem to give something like 4 hours worth of
laptop power when fully charged up.

Advantages:
    1) Cheap. Run around $40 new.
    2) Readily available. Can buy them at any auto parts place and many
       hardware stores.
    3) Good for several hundred charge/recharge cycles.
    4) Can use with an inverter, and just plug in laptop.
    5) Can also use them for intended purpose -- jumpstarting your car when
       the battery is dead.

Disadvantages:
    1) Heavy. Around 20 lbs. or more. You can lug them around by their handle,
       but they're not really all that portable.
    2) Big and bulky.
    3) Best to use with an auto adapter (extra $30+).
    4) They go bad if you leave them unused for a few months.