[jdeas]

Has anyone used the Powerstream 12 DC UPS as a backup source?
http://www.powerstream.com/DC-UPS-1212.htm

The new AFS-5000 series does not have an internal battery but after looking at the suggested solutions, I wanted the option to increase the capacity to cover my 300XL to keep the GPS alive.

Doesn't hurt that the unit and a good 2AH SLA battery is under $75

 

[RV7Guy]

AFS

You can get the back up from AFS. They are pretty reasonably priced.

 

[Dynon]

A 2AH battery isn't going to be good for more than about 30 minutes of backup power when new, and will go down as it ages. Just something to consider with a backup of that size. Most EFIS backups are at least 50 Watt-Hours (4AH @ 12V). Add in a 300XL and you might be down to 15 minutes.