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Power supply for laptop on robot

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AllanBertelsen

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I got this old IBM Thinkpad that I want to use on my outdoor robot. The adapter has this stupid value of 16 Volt 2.2A. What kind of power supply should I choose? The microcontroller, motor controllers, sensors and the like use 5 Volt. The motors use 6V or 12V. But should I really put 3 times 6V batteries on the robot to be able to deliver enough volts and current to the old laptop?
 
An extra 6V battery would be less expensive than a car adapter. A L78S15 voltage regulator will be sufficient to regulate from 18 to 15 volt.
 
The two typical reasons are 1) laptops are pretty power hungry - for a given wattage, higher voltage means lower current and smaller wires, 2) The battery pack charging voltage is probably just a little bit below the 16V rating. If you don't plan on having two separate battery packs - and don't plan on charging the laptop's battery from your other battery - the laptop will probably work fine off a lower voltage.

Alternatively (and more dangerously) hack the battery and feed the power directly in. Obviously don't do this unless you are *sure* you know what you're doing.
 
I really don't think a L78S15 would deliver enough current!.. not at all!


i think the best idea that have been said here is the "auto/plane adapter", this one i think would work perfectly (even if it will be a litle more power consuming).
 
Search the web for your model, maybe you can find some specs. It's likely somebody has done some modifying for other uses. Laptops are expensive, nobody likes to just throw them away, or sell it for pennies on the dollar when they upgrade. Might take a look on HackaDay.com, the have lots of similar projects. Also MAKE Magazine has a website, great for finding new uses for old stuff.
 
Hi – Thanks for the responses. I have used some time surfing HackaDay.com. Lot's of interesting stuff, but no examples of laptop power supply. Ikalogic – I have also searched the net for "auto/plane adapter", these are expensive. Some did only deliver 15V designed for the same ThinkPad model as my. The L78S15 should deliver 2A. The dead ThinkPad battery has been removed, so the power supply will not use power for recharging as the 2.2A 16V adapter was designed for. I may eventually remove the display from the ThinkPad. A laptop display is very power consuming. The display will be replaced by 2x40 character LCD display for direct interfacing and wireless communication for uploading software etc. I will always have the opportunity to connect an external display for setting up OS and programs.
This is my initial thoughts of my solution. But comments and advice will be very welcome as I am not an experienced robot-builder.
 
well, here are my advices:

- In case you remouve the batt. i think the 7815 is ok.. i think i was wrong about saing it wont work, but use a good heat sink it will help it deliver all the current you may need.

- About remouving the display, i was suggesting, for the sake of your laptop, you can just connect your LCD to the parallel port of your laptop, and leave your screen as it is, as you may need it to start/stop your program, or use this laptop in another projects later...and taking a huge PC screen with you is not that funny! you could just turn off the laptop's screen. most laptop have this feature.

but i think you are approaching to a realiable solution...


good luck.
 
What's the type/rating of the battery pack? NiMH batteries peak at ~1.2V, and fully drain at ~.9V, Lithium ones peak at 4.2V, and drain at ~3V. The battery circuitry on the laptop itself can probably accept down to ~70-%80 of the full battery pack directly.
 
AllanBertelsen said:
Hi hjames
It's a Lithium-ion Battery 10.8 volt 3AH.
https://www.notebook-laptop-batteries.com/IBM/29H9232.HTM
But theres five conectors in the socket. Not as easy to figure out a the adapter socket. I am afraid there could be a fundmental difference in the circutry. ie. the battery has to be charged etc.
10.8 sounds very much like a NiMH battery, although I guess they could estimate it being 3.6V * 3 or something. If it is Lithium, then it should be able to accept 3*3=9V, up to 3*4.2=12.6V without any problems. If you have a 12V supply, stick a fuse or something on it, and it should accept it just fine.

If you still have the battery pack, just snap it apart (destructively if necessary) and look at the wiring. Alternatively pop the computer open and eyeball the connections at the socket to figure out what to wire up.

One thing - if you aren't comfortable doing this level of "hacking", it's probably easier to just buy some adapter. Personally I'd just rip into the hardware for the following reasons:

1) I'm cheap
2) Applying the power to the battery circuitry is likely going to be the most efficient configuration - otherwise you'll end up supplying power to the computer at <80% efficiency by going through another voltage conversion - which means you'll dissipate a bunch more power
3) It'll also be the smallest/lightest setup.

James
 
hjames - It sounds tempting. But could some of the circuitry, in the battery or the computers connection to the battery, be use to verify, that this is a valid battery. The battery is 10.8V. Would there be a risk of blowing the laptop off if supplied by 12V through battery connectors.

1Steveo – Thank you for the link to the dc-dc converter. If I don't dare or don't succeed by supplying the laptop though the battery connectors, then this is what I need.
 
Unless the hardware is exceedingly paranoid - auto shutoff if a "proper" battery isn't detected, I'd guess that the laptop power supply will happily accept any current that is fed to it.

In any case, *you* should look around and and read up on Lithium batteries to convince *yourself* that it will/won't work. From you've said so far, I'd be inclined to try it, but you might not have the tools (current limited power supply for starters) to try this out safely. Like I said before, the easiest way is to open up the battery pack and see if things look reasonable/figure out the pinouts.
 
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