Battery PSU selection

[dpeterson3]

I posted a thread a while ago looking for a battery PSU. Now I need help selecting one. My main board is a Soyo SY-5EHM. The manual says to use a power supply with at least 200 watts. However, I am not using a lot of extra hardware. Here is what I am using
HDD- usb 2GB flash drive
Floppy drive for boot only
Ethernet card with WOL (though WOL can be ditched)
USB webcam
Audio card for MIC input (optional)
cooling fan
I don't want to have to get a 200 watt supply. Since I am not using a lot of extra hardware, would it be safe for me to use a 100-150 watt supply instead?

[DonRotolo]

Be careful underspecifying a power supply. Voltage sags can cause weird things to happen, undesirable things. HDDs consume a lot of power at spin-up, and a board can draw more power than nominal for a brief time at power up.

On the other hand, the manufacturer doesn't care if you need to spend more on an overspec power supply, their best interest is in making sure the system is rock-solid stable.

My 2 cents: 200 Watts it is. Remember, 200 is the max it can supply, not the nominal consumption.

[MrForbes]

what cpu are you using?

Do you have links to some of the PSUs you are considering?

[dpeterson3]

I am looking at these. They are cheap and if the specs are true, efficent.

http://www.mini-box.com/DC-DC

I am not using a real HDD. I am using a 2GB flash drive with Puppy Linux as an OS. There are no IDE devices attached. I am using a SY-5EHM as my main board
Link to board specs.
http://stason.org/TULARC/pc/motherbo...m-SY-5EHM.html

Link to manual
http://dl.owneriq.net/6/621f097a-73d...38daa2a9dc.pdf

[MrForbes]

no need for a 200w supply for that little computer...100 will probably work fine.I've run more powerful CPUs and all the other stuff in a normal desktop on a 145w supply.

You might want to look carefully at the low voltage cutout on the power supply, if there is one. Just to make sure how low the battery can get before it shuts down.

[dpeterson3]

Any suggestions on batteries. I was planning on using fisher price batteries until I realized they are only 9.5 Ah.

[MrForbes]

You need to figure out how much current it draws, and how long you want to run it, then look up the datasheets for some batteries and see what you really need. They have charts which show voltage as a function of time and current load.

Also consider how the thing is housed and how much abuse it will take, and how safe it needs to be. Might be able to get away with a low cost riding mower battery?