12v (DC to DC charger) suggestions

There are many threads on PC on the subject of inverters and also excellent videos on YouTube
Here is one.

If you’re going to the trouble, stick to a 1000w pure sign wave inverter like a Xantrex Prowatt 1000
Also do not skimp on the wire gauge and install breaker

 

Regardless of what else you do, you likely will NEED a generator.......unless your power needs are REALLY small and your overnight stays are few.

Can you arrange it so that the Prius supplies all of your power needs ?
Yes maybe. But it likely will be a giant pain in the backside and may cost a bunch too.

YMMV

 

Have you worked out your desired power budget yet?

Starting with that, then it's just a matter of looking at options for how to meet it.

 

100 Ah tells us your energy budget (around 1300 watt hours). But your power budget (straight watts) also matters. What gear are you intending to run, using that energy at what rate?

 

Details are important.

Given ONLY what you put in that last post, I don't think you really need ANYTHING extra to supply the power.

And if the purpose of the fridge is only convenience to keep drinks and food cool........a good cooler and a bag of ice should be sufficient.

It now sounds like your "plan" is WAY overkill.

 

For a fridge you need to know more than one number. My 28-liter one has a label with a 6.5 amp draw at 12 volts, working out to about 80 watts. But that's the power it draws while it's running. That is one number you need to know. Your supply circuit has to be able to provide that when needed.

A key thing with a fridge is that the only time you see it run continuously is when you first turn it on and it is coming down to temperature. Once it gets there, it cycles on and off. It then has an average power draw that reflects its running power draw times the fraction of the time that it runs. That is the figure (times ten hours) that you need to cover with your stored energy capacity. Ideally, that initial long run that pulls the fridge down to temperature can be in the house (if it's a dual-voltage fridge) or in the car in READY, so you aren't spending your stored energy budget on that.

Depending on who made your fridge, it might come with graphs sort of like these. (These are for an Engel MT27F.)



You'll notice there are three graphs, for three different surrounding temperatures. In all three, the temperature inside the fridge is eventually being held around 4 or 5 ℃, but at the higher surrounding temps it takes longer to get there, and it runs for more of the time in order to stay there. In this example, at 25 ℃ surrounding, it only needs to run about a quarter of the time, corresponding to about 20 'average' watts. At 45 ℃ surrounding, it is running more like four fifths of the time, so closer to 65 average watts.

If the thing will be inside your car, then the "surrounding" temperature really means the temperature inside the car, which can be a lot higher than outdoors if the car is unattended in the sun.

You can see some funny notation when you're looking at fridge specs. For example, in the graphs above, you can see the average current draw summarized as "1.46 Ah/Hr" under the middle graph. An "amp hour per hour" is just an amp, a "watt hour per hour" is just a watt, but the fridge folks like to spell it that weird way to remind you that it's the average holding-temperature figure, and not the rated amp or watt figure for when it actually runs.

You'll also notice those summary Ah/Hr or Wh/Hr figures work out to even lower power than we guessed by just multiplying rated running power by the fractional run time. Multiplying amps by 12 to get watts, we see (for that Engel) about 8 watts (or "Wh/Hr") in 25 ℃ surrounding, 18 watts at 35 ℃ surrounding, 27 watts at 45 ℃. That's because, once down to temperature, the compressor isn't just running less of the time, but also at a lower pressure.

So you can see that, if you had a similar fridge, you would need to give it a supply with about 6.5 amp (~ 80 watt) capacity, but you would also expect it to be drawing only around 30 watts steady-state, even in a fairly hot car. For ten hours of that, you would need 300 watt hours of capacity.

When you add your laptop charger, that's an extra 120 watts, but only for as long as it takes to charge the laptop battery. Probably the easiest way to figure that energy budget is to look for a watt-hour spec on your laptop battery. That's how much energy you'd need to put a full charge on it from empty (if batteries were perfect. They're not, so multiply it by about 1.5).

All the fridge discussion above pretty much assumes a compressor, refrigerant-cycle fridge. Some less expensive options just use a thermoelectric cooler, and are a lot less efficient. One of those probably will be drawing 45 or 50 watts or so, and drawing it pretty much continuously.

 

Laptop at 120 watts for 3 hours sounds like quite a lot for a charge, 360 watt hours. Even using the "overstate by 1.5 to account for charging losses", that would be a 240 watt hour battery in that laptop.

That would be a big battery. If you were flying on an airplane, for example, the normal limit of 100 watt hours is supposed to "allow for nearly all types of lithium batteries used by the average person in their electronic devices." You would need the airline's approval to bring on board anything between 100 and 160 watt hours, which would be considered to cover "larger after-market extended-life laptop computer batteries and some larger batteries used in professional audio/visual equipment."

Now, if you weren't thinking only to leave the laptop charging there, but to actively use it in the car while powered by the adapter, then I could see you using 120 watts for three hours of use, if it's a high-end laptop and you're pushing it hard.

 

The holy grail of Prius backup power.
1000w inverter and two of these in parallel
https://www.costco.com/lion-energy-safari-ut1300-2-pack.product.100663833.html

only $1400 plus inverter!

Features:

• 12.8V, 105Ah, 1344Wh
• Can be Used in either Series or Parallel Configuration
• 150A Continuous Draw, 100A Charge
• Lithium Iron Phosphate Battery Chemistry for Long Life and Reliable Energy Storage
• 3,500 Full Depth of Discharge Lifecycles