DallasSteve wrote:
Drew: When you say 12 hours average does that consider only drawing the battery to about half charged? I've read that you should not go below half charge on the ordinary RV batteries.
Yes, I was thinking you ought to avoid discharging much below half. Bear in mind that my estimate was only a rough, ballpark estimate, an order of magnitude number rather than a precise "expect exactly half a day" number. I was really more trying to suggest how one might go about making these sorts of useful but imprecise estimates quickly; having an idea of how to figure energy consumption vs. battery capacity is quite a useful skill for many things, not just fridges.
Eight hours is probably a better general estimate than 12 hours, based on the valid points (and presumably firsthand experience) mentioned by other posters. I'm not sure I can think of many situations where 12 hours of fridge operation would be sufficient but altogether insufficient; so it seems to me for practical planning purposes either estimate is close enough. You can get an afternoon or an overnight, but not both. One battery might be (barely) adequate with a residential for travel between campsites with hookups, but nowhere near sufficient for any real boondocking or dry camping.