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Building and external laptop power supply? Answered

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.

Discussions

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......

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!

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...

use a jump starter and an inverter to power the charger

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)

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.

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

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.

i dont think so. lets see: battery-40$ approx battery charger-20$ fuse pkg8-2$ voltage regulator- is 18.5 even a standard vreg rating? i think a 20 volt v reg, and a zener diode are better. anywho, 5$ heatsink/fan for vreg-5$ zener diode-5$ max. comes to about 77 dollars or so. however, if you already have a battery, its only 37$. and if you use the same battery as your car (the battery in your car, maybe through the cigarette lighter), you can save another 20 dollars, spending just 20$ or so.

wait, my bad. your car battery is 12 volts, so you would need another battery and charger. so its about 77$.

I'm envisioning a bank of rechargeables. They can be purchased a few at a time to boot.

ohh. so then we get 20 volts that needs to be 18.5. it could be a lot cheaper. as i said, the components of the adapter should cost around 20 doolars. you need an 18.5 or 19 volt regulator, or zener diode capable of handling 4 amps. i think that there are 4 amp zener diodes out there. im not sure about 18.5 zener diodes or vregs.

if its 3.5 amps, a zener diode or standard 4 amp 18.5 volt or variable voltage regulator should work, assuming you attach a heatsink and fan

. 50-60Hz = universal operation (in conjunction with 100-240V~)
. 18.5V = output voltage. Since the input V has the sine wave after it, it is probably DC, but won't swear to it.
. 100-240V~ = universal operation
. 3.5A = probably input current
. 70-90VA = probably rated output. For this situation, VA = W
. Verify before depending on this - I'm no expert.

it's usually like around 10 amps or something I have the same problem with a dell. I'm just trying to find a friend with a dell power cord that's compatible. If it works I'm going to buy 8 16805 batteries or whatever to refil the battery instead of spending 80 dollars.

10 amps. way beyond a zenerd diode. looks like a heavy duty heatsinked vreg with fan is called for then