That is a completely different situation. You were issued a piece of equipment by the department you work for. You didn't go out and buy one to listen to the scanner and jump arrests randomly. I have zero problems with your situation and would honestly be surprised if responders in an area such as your were not issued one.
To the OP, please don't take this the wrong way, I'm not trying to be rude but you're opening yourself to huge liabilty. FFEMT and I don't see eye to eye, at all, but he brings up a very valid point about maintenance records. Also, you may potentially run into trouble if a Good Samaritan law came into play. Yes you are technically a good samaritan however you pay for medical direction which a good lawyer could use against you. Depending on the verbiage in your state's GS law it may not apply to you.
Also, I'd be suspicious of the functionality of an AED purchased for $110 when they generally are well over 1k...has it been tested/inspected? Is it actually operational? Do you have a defibrillation test brick? Our monitors defib function is tested at least once a month if not more. For a while they were testing it every morning in front of us when the checked it out to us.
Again, don't take this as a personal attack, I applaud your desire to help others however you need to get with a lawyer and make sure you're safe from a liability standpoint if you use it. Helping others is not worth putting you and your family's livelihood at risk. we come first, before any patient, no matter what the circumstances.