DIY laptop external battery pack?

Have any of you ever tried to create an external battery pack for their laptop using Ni-MH cells? If so, how well did it work?

This is just something I'm thinking about for a possible future project involving a cheap and/or old laptop (I probably wouldn't do this on an expensive laptop). Maybe pair a netbook or cheap refurb with a homemade battery pack full of low self-discharge Ni-MH AAs as a relatively cheap supplementary battery. Not a terribly portable one, but one that can run through extended periods without power but mostly because it seems like it would be kinda cool to do.

Provided the output voltage is correct (example: pairing 10 Ni-MH batteries for a laptop that uses a 12 volt power adapter), would simply chaining together 10 batteries in series work? Or would I have to worry about making parallel chains (perhaps AA batteries don't provide enough current?) or putting in a voltage regulator circuit (laptop's DC input jack might not like sudden voltage drop when the battery dies?).

 

Hell why not push the boat out and use a car battery!

 

a good ups with automatic voltage regulation will give you portable 120v house current. just disconnect the beeping or warning signal coming off the ups.

yea, and if you wanna use an automotive battery, just hook it up through an inverter. you could recharge your laptop battery with it, to boot.

 

Avoid using Automotive Battery.
If you want to use it to power a laptop, you want deep cycle battries like marine battery.
Also, sealed gell lead acid batteries using on UPSs are generally not deep cycle battery. They will go bad just after few deep cycle drain.
My UPS battery went bad just after about 5 power outages. (Still works, but only last as half as long.)

Using Ni-MH can be done, but you will going to need lots of cells to give enough voltage and current.
Using Li-Ion is best, but you really need some knowledge about Li-Ion battery and must have protection circuit. Otherwise, you might end up with a pack of explosive.

 

When it comes to carbatteries i don't see a problem with any of them, as there is several ciggarettelighter-adapters (and the ciggarette output is powered straight from the battery) providing correct voltage, so if you can get the correct output, i don't see a problem Do you?

 

All batteries will need changing. Batteries are consumables. You can change the batteries in your UPS too. You probably need to.

As far as using deep cycles (which you can also use in your car/truck if you like)...

First off, you don't want to spend twice the money and carry around twice the weight instead of using something you might have in the garage lying around.

Secondly, you're not using it to weld, winch a vehicle out of the water, nor to power up a boat. This is low draw. It's just a laptop battery, a few volts, a couple of amp/hours. Then trickle charge it.

 

Aren't you supposed to use the UPS only when the there is a powerloss?
AFAIK an UPS shouldn't be used as a battery to test out how long the computer runs with it! Sounds like you've been testing it like that

 

Exactly. That is why I'm not recommending it to be used as power source.

I hooked up UPS for my in house network. (Router, switch, AP, modem etc ...)
The UPS will power the network upon power outage until the battery voltage drops to certain voltage and UPS cuts power. Thus, deeply draining the battery.
I used to get over 2 hours on 550VA UPS I have, but the last time I lost power few months back, it only lasted like an hour.

 

Probably best thing would be to use a marine "gel cell" battery.

 

UPS batteries, the actual batteries themselves, are used in many different applications and do get cycled usage. You change them just like any other battery. They may even be used in wheelchairs iirc.

If you want to use an Optima Bluetop marine battery, you can.

You can also get grandma a 17' moving truck to get groceries every week.