how long will it run for on a 5 amp battery pack
Batteries are not rated in amps, but in amp-hours. Assuming that is 5 amp-hour 15w/12v 1.25 amp 5 amp?hour / 1.25 amp 4 hour
Commonly the amp-hr rating of a battery is at a 20hr discharge rate ( 0.25A or 3W for a 12V, 5Ah battery) and capacity tends to be less at a higher discharge rate. Also it is bad for a rechargeable battery to completely discharge it, so 2 or 3 hours might be realistic.
basic physics states that current power divided by voltage and in this case that equals a figure of 1.25. In essence the tv will drain 1.25 amps from the battery pack each hour so will last 4 hours
