I have a feeling I need to RMA my mobo but I'd rather avoid it if possible. About once a week I come in and find my computer off (when I left it on). When I press the power the fans spin for about a second and the lights come on but then immediately die. When I replace the CMOS battery this issue is remedied but I better have another on hand because a week (or three) later it dies again and needs to be replaced. Is this a bad Mobo? It's an MSI P6N.

Have you bothered to check the voltage on the batteries you are replacing? I'm guessing the battery has nothing to do with your problem. The battery serves to keep the BIOS settings WHEN the computer is shutdown. If the computer was running and shutdown by itself, it wasn't due to the battery. Possible causes could be overheating, Weak PSU, Power interruption. Check the logs.

What it may be are bad capacitors on the motherboard. I have had this problem with two different motherboards, both being Dell's. Look at the following link. It may at the least rule them out. http://www.badcaps.net/

IF the battery is actually drained then either something is connected wrong, or the MBoard MAY abe defective. I don't know if this is even possible but check the Clr CMOS jumper to be sure it is in the RUN position. Should be pins 1&2. Check your manual. Also check the case to MBoard wiring to verify it is connected properly. Finally, IF a voltage check on one of the used batteries show LOW voltage I suggest you pull the MBoard out of the case and check for shorts to ground on the back of the case. The most common cause of this is a metal standoff in the wrong position. Have also seen an errant screw end up between the case and board. This will usually result in the system not running. I am guessing that IF the short was in just the right spot it might show the symptoms you describe. Check the residual voltage in a used battery first.

I've done quite a bit with computers but I haven't a clue as to how to check the voltage of a used battery. Is it as simple as using a voltmeter on it? And if so, what voltage is ideal? The voltage stipulated on the battery itself? I don't think it's a short given that the first time this happened I completely rebuilt the computer but I'll check again. I know it isn't the batteries themselves I'm just wondering why I can't boot when they die and why they completely die so quickly. Everything else on the board works perfectly. I would think the system would be effected in other ways. Thank you all for the suggestions. I'll see what I can discover.

The MBoard should boot without any battery in place. The battery simply allows the BIOS to save custom settings. The Default sttings are on the ROM chip. If that chip is defective I don't think the computer would start at all. As for checking the battery voltage just use a volt meter and yes, the voltage should be what is stamped on the battery. Did you check the Clr CMOS jumper to verify it is in the run position?

There is a button rather than a jumper to clear the CMOS on this board. Without a fresh battery on the board, it will not boot. I've heard that some Mobos don't boot without a good CMOS battery but I can't even POST without a new one. I'll check the voltage out on the most recent dead battery.