Help me select a PSU, please

IsuzuDrew · 05-08-2008, 11:31 AM

I'd like some opinions on the proper PSU to acquire. I've decided that I want to go with an inverter, only because I'd like to plug in additional devices aside from a carPC from time to time (music sampler, various battery chargers), so an extra outlet would be helpful.

What I would ideally like to get out of the carPC: music, videos, GPS, hands free phone, FM tuner, WiFi.

My donor laptop is a HP Pavilion DV1010US (Celeron M, Socket 478), sans screen, and I am planning on purchasing a Lilliput EBY701.

I considered a 400W and 700W inverter, both by Xantrex. I'm guessing that either of these would work with my setup, power-wise? The 400W is compatible with lighter receptacles, but the 700W has to be wired to the battery. I already have power running from the battery (8 AWG) for an amp I used to have. Are there pros/cons to using one method over the other? Ideally I'd like to be able to draw power without the car running but the ignition on.

Thanks for any suggestions (feel free to make other recommendations).

DarquePervert · 05-08-2008, 02:51 PM

http://www.mp3car.com/vbulletin/advf...iew&advfaqid=3
and
http://www.mp3car.com/vbulletin/advf...iew&advfaqid=6

IsuzuDrew · 05-08-2008, 03:32 PM

With all due respect, I read both of those before posting, so if you don't mind doing a little more hand-holding... will those posts answer my questions about whether an inverter will be on with the ignition on vs. starting the car? I found the part about DC-DC being more efficient for using when the car is off, but what about inverters?

Also, neither of those posts delve into the differences between hardwiring to the battery and just plugging into the cigarette lighter (at least that I could decipher).

We are noobs for a reason, you know

rijndael · 05-08-2008, 03:48 PM

just ignore darque...he doesnt like noobs...lol...j/k

your cig lighter is probably wired into your accessory line, so when you turn the key without starting your engine, it should start providing power to whatever is plugged into the cig lighter.

as far as having your inverter hardwired to the battery, is there a remote wire to turn it off and on, or is it just going to be on the whole time?
answer that, and you have your answer...

DarquePervert · 05-09-2008, 06:42 AM

I also don't like inverters for powering a PC.

They are not the best choice for a PC install for a lot of reasons. They're not good for a laptop for even more reasons.

If you're dead-set on using an inverter, you should wire it straight to the battery.
If the inverter has a remote lead, then wire that you can put a switch on that line and wire it to your 12v source (battery) and use the switch to power the inverter on/off.

If the inverter does not have a remote lead, you can use a relay with a switch to power the inverter on/off with the switch.

Honestly, I'd look into a DC-DC power supply.
An inverter converts DC from the car to AC for a home electrical outlet. The laptop's PSU will convert AC back to DC which the PC uses. It's an inefficient process that can create noise in your audio system and generates heat. It also introduces more connections and more potential points of failure in your setup.

A DC-DC power supply is far more efficient than an inverter for this purpose as it doesn't do the double-conversion.

IsuzuDrew · 05-09-2008, 07:23 AM

Thanks for the replies. A couple more questions and I will be closer to venturing out on my own.

1) What about those cigarette lighter laptop chargers that plug right into the laptop? Good idea or no?

2) Assuming I am wiring directly to the battery with either an inverter or a DC-DC, which would be the more efficient method for running power to them and the amp? A) Run a 2nd 8 gauge from the battery to the PSU and use the 1st for the amp, or B) Pull the existing 8 gauge, run a 4 gauge from the battery to a distribution block, then run an 8 to the PSU and an 8 to the amp? Is one more beneficial over the other?

Bugbyte · 05-09-2008, 08:07 AM

1. Yes, good idea.

2. One is not more beneficial than the other, but many distribution blocks are fused, which adds a level of protection that you should have inside the car. If the power supply wire between the PSU and the battery shorts somehow, because it is much larger gauge it can cause a fire before it burns through. If there is a fuse in the distro block, the fuse will blow and prevent the fire.

If you don't use a distro block and go with separate wires, just make sure you fuse both wires near the battery.

IsuzuDrew · 05-09-2008, 08:23 AM

Excellent, thank you. I think then that I will use the lighter plug charger to power the laptop and use the existing 8 gauge to go to the amp (it is already fused near the battery). Since I have two lighter outlets in the front of the truck, I'll wire the monitor to the 2nd. I'll hold off on an inverter for powering other devices for now, since the applications are not directly related to this project.