Directly powering from the battery?

Aximilation · 06-26-2008, 01:11 PM

Hey everyone, I've been lurking around for a while and am starting to collect components to make my own carpc and have some great plans for some real-time gps nav stuff I'd like to have people help out in the beta testing of.
But I digress...
I was wondering about power supplies. Given that computers take 12v or 5v, and the battery outputs 12v, there are power supplies (M2, etc) that will distribute power, etc etc. What I would like to know is if anyone has considered directly powering their computer from the battery. Obviously you would have to take into account voltage regulation, etc etc so you don't fry stuff when you start the car, when the alternator kicks in, and stuff like that, but I was thinking that it was theoretically possible to hook in using some homemade circutry (which I'm sure someone could come up with to share) and work with that. Thoughts anyone? The main issues I could see with this idea is A: relliability of homebrew stuff, and B: getting power to the motherboard, they tend to have more wires, but if you knew what is what, then why not?
Thoughts, objections, pointers to another thread this has already been addressed? (I couldn't find anything through search)

Thanks!

2k1Toaster · 06-26-2008, 01:15 PM

That is the whole point of a DC-DC power supply. No inverter needed.

And if you mean directly wiring the PC to the battery, then forget it right now.

The battery does not provide 12v. The power in your car delivers between 6v and 13.8v/14.4v and fluctuates quite a bit. A computer needs the correct voltage to get the correct timings to actually work.

Also a PC does not only take 12v and 5v. It needs 3.3v, and older models need negative voltages too.

Aximilation · 06-26-2008, 01:18 PM

Ok, I was thinking as much, I thought it was a bad idea, but still an idea worth mentioning. I was mainly wondering if you could still make it work, essentially building your own power supply in the end, probably a *lot* more work than is worthwhile. :-P

2k1Toaster · 06-26-2008, 01:30 PM

Quote: Originally Posted by Aximilation

Ok, I was thinking as much, I thought it was a bad idea, but still an idea worth mentioning. I was mainly wondering if you could still make it work, essentially building your own power supply in the end, probably a *lot* more work than is worthwhile. :-P

Sure you can make one. But if you dont know what you are doing, I would not even consider it. Most of the dc-dc's on here started because of a hobbiest making it, and then it was so successful, it is now being sold all over. But if you dont know what you are doing, you are playing with fire... in the most literal sense.

miko55 · 06-26-2008, 03:02 PM

Than you need a power regulator. we to get a scheme for one?

2k1Toaster · 06-26-2008, 03:58 PM

You can buy regulators for pennies everywhere. The good ones cost more. Good being stability and efficiency. Then you still have the whole rest of the circuit to build.

If you are fuzzy on this, just spend the $50 and buy a M2 or something. Because if you dont know now, you wont know when you get the parts in, so you will be lost and out money for parts, and you still have to buy one.