Raspberry Pi UPS

I've had an ongoing issue with my Raspberry Pi's corrupting the SD card if the power failed during a write cycle, at least that's my assumption. On occasion, after a power outage, I cannot access the Raspberry Pi and have to reboot it. By watching the terminal display, it often indicated a kernel panic and I know that I have to re-write the SD card. About 10% of the time I cannot and have to throw the SD card out.

Most often, it seems that the power outages last for a brief period of time. So I went looking for a short term backup solution. My first thought was to go with rechargeable batteries, and I may still follow this route, but for now I've settled upon standard alkaline batteries to provide my short term coverage.

I've come up with the following circuit to prevent power loss to my raspberry pi's. I use a 12VDC wall adapter together with 6x1.5VDC (AA) batteries. Both feed the 10-30VDC > 5VDC power supply through diodes. My reasoning is that as long as the wall adapter is working, it will supply the voltage & current to the power supply, since the battery diode is reverse biased. If I lose utility power, the wall adapter voltage drops to zero, and then the battery diode becomes forward biased and supplies the voltage and  current to the power supply.

I have sourced the power supplies & wall adapters from China. 6 cell AA battery holder from my local electronics store and using 1N4007 Diodes to provide the isolation.