The MP3car.com Store  

Welcome to the MP3Car.com forums.

You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. Registering will also remove advertisements. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

If you have any problems with the registration process or your account login, please contact contact us.

Go Back   MP3Car.com > Mp3Car Technical > Power Supplies

Reply
 
Thread Tools Display Modes
Old 01-08-2007, 09:46 AM   #1
Newbie
 
Join Date: Oct 2006
Posts: 7
My Photos: (0)
Connecting AC Power Source to Car Battery

Hello everyone. I have a CarPC implementation using the CarNetix P2140 power supply to great effect. However, there are time when I want to leave the PC running overnight to synchronize files over the wireless network, etc. and of course the PC draws far too much power to run off the battery all night long.

I also have 15 amp, 13.8V AC/DC 'converter/power supply'. It is a device I picked up at Radio Shack that plugs into an AC outlet, and provides the above spec'd DC power via two terminals (Red/Black, +/-). I have managed to mount this device next to my car battery and routed the AC cord through the grill so that I can just pull out the cable and plug it in to my garage without even opening my hood.

I have successfully used this device in the past to power my CarPC by removing the terminals from the car battery and instead wiring them to this device. The 15 amps isn't enough to power headlights as well, so I have to be sure to turn them (and all other ancillary electrical devices in the car) off, but it is sufficient power for the CarPC itself.

I have however been hesitant to connect the terminals to between the Power Supply and the Car Battery because I don't know what would happen... Would the AC device actually charge the Battery? Would the battery's electricity somehow short out the AC device? If the AC device DID charge the Battery, what would happen when the Battery reached full capacity? Does anyone either know or at least have some educated input?
SolusCado is offline   Reply With Quote
Sponsored Links
Old 01-08-2007, 11:04 AM   #2
FLAC
evandude's CarPC Specs
 
evandude's Avatar
 
Join Date: Mar 2005
Location: Maine
Vehicle: 99 Jetta Wolfsburg
Posts: 937
My Photos: (0)
If you're worried about the car battery dying while your carPC is running from it, it seems to me it might make more sense to just buy a car battery charger. For not too much money you should be able to find one that is smart enough to switch between full charge and trickle mode so it automatically charges the battery properly all the time.

Car batteries are pretty rugged, and generally should charge and be just fine with a 13.8V supply hooked up. However, without actually trying it, it's difficult to say if your supply would be OK with it - if the battery was discharged a bit, it could try to draw a huge current from the power supply at first - the power supply voltage might just droop a bit under the load, or it might just shut off, or it might even damage it, depending on how the supply is designed.
__________________
But don't take it from me! here's a quote from a real, live newbie:
Quote: Originally Posted by Viscouse
I am learning buttloads just by searching on this forum. I've learned 2 big things so far: 1-it's been done before, and 2-if it hasn't, there is a way to do it.

eegeek.net
evandude is offline   Reply With Quote
Old 01-08-2007, 02:16 PM   #3
Newbie
 
Join Date: Oct 2006
Posts: 7
My Photos: (0)
I do actually have a car battery charger that is a pretty slick device, but its trickle charge is not enough to power my PC all night long, and in any case my DC-DC power supply/inverter/regulator (whatever the hell it is) monitors my battery power and shuts down the PC when it gets too low. So draining my battery isn't really a concern - it's not going to happen.

However, I DO want to be able to keep that PC on for as long as I want - by plugging in the vehicle. And since the power supply wasn't designed to be hooked up to a battery - it's just supposed to be a source of DC power for whatever bench work you may be doing - I'm not sure how it would interact with the battery in terms of drawing current. What stops the battery from just drawing as much power at the device outputs? Also, is there any likelihood that the battery itself would actually output power to the device?
SolusCado is offline   Reply With Quote
Old 01-09-2007, 08:08 AM   #4
Newbie
 
Join Date: Oct 2006
Posts: 7
My Photos: (0)
Well, I went ahead and connected the terminals to try it out - and nothing caught on fire, so that's good.

However, the PC left running still drained the battery. As noted previously, I have in the past successfully run the PC off JUST the power output from the Power Supply (though it was a different DC-DC regulator powering the PC then, one that produced fewer watts). I think I just need a more powerful power supply, and Radio Shack has a 25-amp version, so I think I will give it a shot next. Anyone want to buy a 15 amp 12V DC power supply?
SolusCado is offline   Reply With Quote
Old 01-09-2007, 11:55 AM   #5
Newbie
Ralphh85's CarPC Specs
 
Join Date: Dec 2006
Posts: 39
My Photos: (0)
a car battery charger would stop it from draining the battery.

it would realise the voltage was dropping and would up the power it was putting in, should keep the batter on 13.5 volts ish.


Ralph
Ralphh85 is offline   Reply With Quote
Sponsored Links
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Powering car from a 13.8V power supply ok? PURDooM Power Supplies 27 06-12-2006 11:56 AM
Timed relay: anyone cutting battery power permanently on shutdown with an Opus? azzurro General MP3Car Discussion 5 04-24-2006 03:16 AM
MPJA - MECI ASTEC DC-DC Converter Luc General Hardware Discussion 39 11-22-2004 09:31 PM
Can I put an extra battery in my Chevy? Mastiff Power Supplies 12 04-04-2003 02:19 PM
Here's an alternative power source.... A Boy and his Miata General Hardware Discussion 7 11-21-2000 11:44 AM


All times are GMT -5. The time now is 06:45 PM.


Sponsored Links
The MP3car.com Store

Powered by vBulletin® Version 3.6.8
Copyright ©2000 - 2008, Jelsoft Enterprises Ltd.
SEO by vBSEO 3.1.0
Copyright © 1999 - 2008 Mp3Car.com Inc.
Ad Management by RedTyger
Message Board Statistics