Boston Mangler said:
What about starting the rig every 8 hours or so and letting it run for a bit?
I will be with 4 or 5 other rigs that could "Jump" me if needed.
What do you think?
I think that would be a waste of fuel and add unnecessary pollution to the beautiful skies of Baja
If you let the fridge flatten the battery, you will just reduce the life of the battery. If it's a deep cycle, it won't eat into the life cycle as much. If it's a starting battery, you will do some pretty good damage to it by letting it run flat.
Scott, the ambient temp that you cited in your record - is that outside ambient air temp? If so, what time of day is the recorded run-time happening? Was the fridge on the whole time for each run time cited? What temp. were you maintaining inside the fridge, and what was the temp inside the truck cabin during the run time?
"Technically, if the fridge ran non-stop, you would reach an optima blue top depth of draw at 10.8 hours.
Engel 45l: Amp Draw: 2.5
Optima at 50% DOD: 27 amps
27/2.5= 10.8 hours"
When you say 27 amps, you mean amp-hour capacity, correct? The fridge doesn't run non-stop, it cycles on and off as conditions dictate to maintain the temperature setting via thermostat control, so I think the 10.8 hours could be potentially doubled or quadrupled or even more depending on variables such as ambient temps, contents of fridge, lid-opening frequency, humidity, etc.
BTW, I found my notes for that one little test I did at KOFA. This was during a pretty warm time of the year, and I did a little expiriment using some ice containers in my fridge to supplement the cooling and reduce run time. Keep in mind that I maintained a temperature a bit above what I normally run, which is 28-32 degrees F.
To quote myself:
" This past weekend, I went to the Kofa Nat'l Wildlife Refuge to train with Scott and Uwe for the adventure race. I tried an obvious trick with my fridge - I used two plastic containers of water totaling 3.5 gallons, and froze them before I left on the trip. I loaded them in the fridge with my food and drinks and left on Friday afternoon. I got to camp around 7 pm on Friday night. The truck stayed parked until Sunday around noon (about 41 hours). I adjusted the thermostat on the way to Kofa so that the fridge would maintain about 33° F (0.5° C). At camp on the first night, I adjusted it to about 36° F (2.2° C). Before retiring for the night, I turned it off. I was careless and did not record the overnight ambient air temperature in the cabin where the fridge is (in fact, I neglected to record actual cabin temps all weekend - my mind was preoccupied with other things). My guess is that overnight temps were in the low 60's F (mid teens C). When I checked the fridge temp. in the morning, it had only increased by 2 degrees. We left for the day's training, and I had to lock up the truck. I left the side vent windows cracked open for some air circulation. I adjusted the thermostat to the highest temperature setting to drain the battery as little as possible. I am sure the ambient temperature inside the cabin exceeded 100° F (38° C) during midday on both days, as outside temps were likely in the mid 90's F (mid 30's C). I checked the fridge on late Saturday afternoon when we returned, and it was at a cool 40.7° F (4.8° C). Not bad! I again turned it back down to a setting of about 36° F (2.2° C) for the rest of the evening. Once again, I turned it off before retiring. Sunday was a repeat of the previous day, except that we departed camp around noon. Before leaving, I pulled the negative connections from the battery and let it sit for about 15 minutes before taking a voltage reading with the MM. I recorded a voltage of 12.7 volts. Keep in mind that other than the fridge, I only used the battery for about 20 minutes of VHF radio operation, and maybe 10 minutes for a 5W halogen lamp.
Using this info, I can see an advantage to having a 60 liter fridge is the ability to put some nice big ice containers in there to reduce power consumption, and still have ample room for food and beverages. Of course, this ratio would diminish on a longer trip, but it is still pretty nice. Also, adding some insulation to the box for the time when it is sitting idle in the heat would certainly help as well. I noted that one of my ice containers (2.5 gallon), did not have a chance to freeze completely before I removed it from the freezer at home and left for the trip. The one gallon container did. If I was able to get the larger container to freeze solid, that would have helped even more. Using this preliminary data, I am speculating that I could use about 35-40% (24 liters) of the storage capacity for ice containers, and use the remaining (36 liters) for food and drink, and be able to park the vehicle for possibly 4 days without flattening the battery (or running out of food?). Beverages can always be added to the fridge as needed (but this will increase power consumption somewhat). And this also depends on the type of beverage and ambient dry storage temperatures. I will just have to expiriment more! "
Needless to say, That was over a year and half ago, and I haven't really done any more recorded testing.
