Sorry, no practical experience.
But it sounds like it should be ok, in theory, from the figures you give. Assume that you're transmitting pretty much constantly (which is probably reasonable, given the number of airliners with TCAS that'll be interogating you if you fly anywhere even vaguely busy). That gives you a total consumption of 480mA. Round up to 500mA, and your 7Ah battery should, in theory at least, be able to keep it running for 14 hours. Even given that the battery will loose its capacity over time, and there'll be other imperfections in the system that will reduce this, it should still last longer than your bladder, as long as you ensure the battery is charged prior to flight.
My uneducated opinion is to go for it - and give it a nice long test-flight outside controlled airspace before you use it anywhere you actually need it, just to make sure.
FFF
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