Quote:
Originally Posted by Gordalder
All good advise from everyone, and some technical information, so I learned a few more things from this post. I do have a temperature sensor, so I will know the lowest temperature. I don’t believe the fridge is connected to inverted power (one question I didn’t get an answer for), so using the batteries will not be an option.
Again, thanks everyone for the responses.
|
In your original post, you mentioned running the fridge on propane. That means you have an RV fridge that is NOT residential. It does not use a compressor. It uses absorption (evaporation) for cooling.
https://www.heartlandrvs.com/why-hea...u-need-to-know
Those would not typically be run through an inverter. They'd be connected to the converter's 120 circuits directly and to propane. If you don't have 120 volts, the expectation is that you'll run on propane.
But you COULD install an inverter as an accessory and run the fridge from that (and have it for other purposes on a typical basis). A 2KW inverter is inexpensive, but you'll also need some serious wire to connect it to your battery. The wire might be #0 AWG...somewhere around the diameter of a pencil or more...the inverter will specify wire size over a given distance from the battery bank.
So, again, you could do it. When running, however, your fridge is likely to consume upwards of 30 amps at 12 volts. The 120-volts watts and amps draw should be on a data panel on the fridge (probably buried on the back of the cabinet) and available in the owner's manual. Google the model number, and the specs will be available online. Once you have the amps rating at 120 volts, multiply that by 10 to get the rating at 12 volts. That's what you'll pull from the battery.
Next comes the duty cycle. How much of the time does it run vs. how much of the time the cooling unit is shut off. Depending on the duty cycle, you could drain your batteries pretty quickly, because your batteries were not sized to run a fridge. On the other hand, this situation does not really replicate running a residential fridge full time.
Let's assume your fridge, full of food already at the proper temp and with the door never opened, will run 25% of the time. And, let's say 35 amps/hour X 1/4 of 8 hours (2 hours), your fridge may suck 70 amps from the battery bank (plus inefficiencies in the inverter and parasitic losses to things like the CO/Propane detector). Let's say 75 Amp Hours total as an estimate.
It won't be continuous draw, so your battery will get to rest, and the battery bank's capacity won't be as limited as some have suggested based on continuous draw. But back to the (overly-simplified) "50% rule of thumb", if you don't have a battery bank with a combined amp-hour capacity of 150 or more, you may over-drain the batteries. A 200 amp-hour capacity might leave a bit of cushion. The good news is that most 4 x 6 volt battery banks have a far larger capacity.
My previous answer--pretty far back now--covers most of this.
All that said, I think your ice tests will give you confidence to just shut it down for the ferry ride and fire up the propane as soon as you make landfall...and all will be well. Enjoy your trip.
P.S. some of the dire predictions of the limits of batteries are not born out in reality. I routinely pull about 35 AH out of my single group 24 12 volt battery in cold weather every night. It starts with 80 AH as the maximum possible...probably more like 70. I know the drains on the battery from simple math. This battery is going on its 5th season, and it routinely gives up 15 AH through an inverter to run an electric blanket for 30 minutes, and it runs the furnace (5 amps at 12 volts) on a roughly 50% duty cycle for at least 8 hours a night (20 AH). That doesn't count parasitic losses, water pump, hot water heater and propane fridge ignition, and limited use of the lights. I just tested the battery (in storage) and it's good to go for another season. I've run this same battery for a 5 day trip (4 nights) without my solar array. It just not that complicated.
Linear Mode
