Battery present hardware trigger?

Hi all, I've been having an interesting issue with my 2010 Macbook Pro (out of warranty). A few days ago, I found that the system no longer recognized that the battery existed, and further digging in System Information revealed this:

Battery Information:

Charge Information:

Charge Remaining (mAh): 0

Fully Charged: No

Charging: No

Full Charge Capacity (mAh): 0

Health Information:

Cycle Count: 0

Battery Installed: No

Amperage (mA): 0

Voltage (mV): 0

The system will not boot and will shut down immediately if unplugged. I'm out of warranty, but had the battery replaced today. Still no luck. I have reset the SMC and tried cleaning the contacts to no avail. Further hardware tests say that there is likely nothing wrong with the logic board, and here's the interesting bit. If I unplug the system while it's booting up, the system will boot and run off the battery just fine, though the System Information and menu bar icon still say that there is no battery, and obviously won't show me my current charge. If I put it to sleep while it is running like this, it shuts down and won't turn back on until it's plugged in again.

Given that this is the case, the system can clearly charge and draw power from the battery, but it doesn't know the battery is present. Do you know of any sort of hardware triggers that relay this information to the system?