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I need to power three laptops off a 24V battery.

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Hi, I am currently working on a robotics project that requires a fair deal of computing power. Normally we would be using embedded stuff for this, but we've found it is much easier to prototype with laptops since they are fairly robust and it is very easy to debug and test.


Right now the robot is powered by ~24V LiPo packs. The laptops do not have sufficient battery life so we are powering the laptops as follows:

24V battery -> Dc-Dc converter -> Car inverter -> ac power brick -> laptop

Obviously this is disgusting, but I'm having a hard time finding a dc dc converter that can output ~20A at 19-19.5V.

Do you know of any commercial solutions that can meet our needs? I'd rather not build something.
 
Howdy, sure seems this should be simpler... Take each laptops requirement of voltage & current: most modern ones are 18-20+V @ 1.5-3A. Think diode drops as "spacers" 1N5400s are ~ .8V @ 3A, 1N5420s are ~ .2V @ 3A (schottky).

I'd start with a couple more 5400s (And one set of 4X5420s) than it should run on... the lowest reliable voltage / current yields lowest power (duh). Hook it up to one of laptops, then behave as a ladder: step up each 5820, then after 4 5820s, jump a 5400.

Try to boot the system on each voltage point, but do yourself a favor and hold F8(?) to keep it from trying to run Windows :: marginal voltage may (WILL) corrupt the hard drive.

Once reliable boot to menu occurs, let it go to Windows. Do this for each system....

It's just an idea, doesn't mean it's good G.H <<<)))
 
easiest solution...install a battery, consider using chinese made ones as these could be quite cheap, but make sure they are from a reputable manufacturer...

I tried to achieve something similar and my laptop got fried...I think its much easier and safer to run them off the standard chargers/batteries...sure batteries may be expensive but then you have a fully functional laptop.
 
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I would be wary about using diodes to drop voltage, as the voltage dropped will vary depending on load. This will result in a noisy voltage going to the laptop - eg when the laptop's switched off and there is very little load, the voltage will be significantly higher (which may cause damage).

The best option will be a variable voltage regulator with a high current pass transistor.

Andrew
 
You should definitely be using biscuit PC's rather than laptops, do you seriously need that much processing power? There has to be a simpler way to address this. The amount of power you're wasting on the laptops alone is a crime!
 
From what I can see I believe it will be best to sit down and design a Step-Down Switching Regulators that would be to your specs. MAXIM-IC has a wide range of ICs that can be used to suit your particular application. **broken link removed**
 
You can get 19v laptop supplies to run a laptop from a HGV's 24v dc power source, you'd need 1 per laptop but thats the best solution I can think of without resorting to expensive supply modules.
 
maybe some of these little guys if you can wait for the shipping.

**broken link removed**
 
i do not know what was meant by "bisquit pcs", i would think you could get for the cost in money and power of one laptop you could get 4 atom SBCs... in you are insisting on using windblows crap.

you can do twice as well with ARM powered linux SBCs.
 
Bisquit PC's == SBC
 
what is the point of investing in expensive hardware, when clearly this project is not intended for mass production ?? The advantage of using laptops is that..

1. They are easily replaceable..
2. Easy to debug and program, as they use standard software easily available and commonly used by many developers.

3. Documentation and debugging of these software is easy as support and help should be available in internet user forums...

3. Developers can easily outsource the development effort to other developers..
4. Development of interfaces for standard laptop is easily accomplished using serial port/USB ports etc.

thanks
a
 
I don't know about bisquit pc, but there are a few different sizes of the ITX single board computers. The pico ITX and the nano ITX boards can pack a good deal of computing power in a fairly small space. Power supplies to run them from 12 or 24 VDC are readily available.
 
Biscuit PC is just a nickname for any PCboard that has all the components of a PC in a small form factor.
 
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