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Building and external laptop power supply?

I have an old Dull (not a typo) Latitude XPi that I would like to use as a field journal.
Problem/s:
The 14.4 battery is dead.
Refurbished and used batteries cost $80.00 usd and up with zero guarantees.
I fear trying to replace the cells because opening the battery is not straight forward plus the electronics inside my be frelled any way.

My solution is do do what I have done in the past and make an external supply.
battery X n = desired voltage.
In this case 18.5v is what I need to power it from the external supply input and the numbers don't add up.

Now I am brain dead when it comes to basic electronics so my question is how do I resist 21v to the required voltage?
Or better yet 24v to 18.5v so I could use alkaline or rechargeable batteries.


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Big Bwana8 years ago
Staples they have this battery recycling box and people honestly, use it and in there attempt to be green they throw away perfectly good batteries for laptops, some may have one bad cell, if your by me they will already be broken open and all the good stuff will be missing, Just go in there and ask ((( Nicely ))) if you can borrow some for a few months and either wait till you find a good cell (( I've gotten several dull CPi one's over the years )) or make a good one from a few packs... I just beat the cell against a counter on the edges, not to hard and they crack open and you just measure each cells output to find the bad cell and replace it and I tape the cell back together but you can glue them with some abs pipe glue if you don't like tape......
Sandisk1duo8 years ago
Use a voltage regulator!
make sure you get an adgustible one, also make sure it doesn't put out too much current, or it's bye bye laptop!

you don't mind a little wieght, right? Here is a link for a mega, ultra battery!
V-Man7378 years ago
Fear not! I am developing an instructable that will fix this exact problem with much more ease, simplicity, and frugality than what is being speculated. It'll take some time, though... And then I hope it doesn't disappoint anyone if it isn't so spectacular... oh great, setting high expectations for myself...
LinuxH4x0r9 years ago
use a jump starter and an inverter to power the charger
Vater Araignee (author)  LinuxH4x0r9 years ago
Hmmm, I have said it else ware "I'm no expert" but.... The problems with that are, Waisted power, I.E. DC to AC to DC Size and weight, May as well just carry around a car battery. Immediate cost, I can buy parts one at a time and rechargeable D cells 2 at a time, which incidentally are extremely lighter then lead acid. £337 XD right...sorry
actually I got that and a spotlight and tire pump for only $15 (USD)
Vater Araignee (author)  LinuxH4x0r9 years ago
Full capacity charge time? How large is it? It weight? How long will the charge last with just the inverter plugged in and running? Inverter plugged in running a load? Where? I wont mind increasing my in/out load by about 20-30 lbs. but my daily load cant be increased by more then 10 or my trips will be cut short by exhaustion.
look here for the size
it is a 200w inverter, and it depends on the battery.
tech-king9 years ago
24 to 18.5. hmmm. do you have any idea how many amps you need? you ay be able to use a zener diode or Vreg if its a reasonable ammount of amps. otherwise, an industrial strengh Vreg may be the only option
Vater Araignee (author)  tech-king9 years ago
On the power supply 50-60Hz 18.5V 100-240V~ 3.5A 70-90VA And I am completely lost by every thing but the 18.5V & 100-240V~ Plus every thing you said.
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