Setting up a solar system for a truck camper

bigtexnick

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Hello everyone. I am new to solar and have taken on a project that I have several questions about and cannot seem to figure out (even with internet help). So I've decided to ask the question by telling you all what I want to eventually have and getting a recommendation for a solar setup. So, I am building a truck camper; a small to medium size (solo size) camper. I will be putting a solar system on it in order to power the basic components. I cannot figure out, however, how many panels and batteries I will need or what size charge controller and size of inverter I should be using. Honestly, I've tried to look at so many videos that I am totally and completely lost as to how to calculate all this stuff. I just get lost after listing out all the appliances and loads.

Here are all the appliances/loads I currently intend to use in the camper:

*small fridge
*small oven
*laptop 1
*laptop 2
wifi booster
inverter
*phone charger
water pump 1 (for minimal sink usage)
water pump 2 (for minimal sink usage)
exhaust fan
basic lights
*night fan

I put asterisks (*) next to the appliances that I currently have and have the energy label --- with watts/volts/amps info --- saved to my computer and can provide, if asked. If need be, I can modify this list of appliances and use a shorter list. However, these are all the things I envision using fairly regularly on my truck camper trips. BTW, I will not be living out of the camper; it will be strictly used a handful of times during the year, from anywhere from 1 night to 14 nights (give or take a few nights).

I am not terribly constrained in terms of budget spending, but would like to keep it as reasonable as possible. Also, I know that the LifePO4 batteries are very expensive and I am well aware of this, as these are the ones I want. I will have a limitation on how many solar panels I can put on my roof. Based on my current calculations, my roof will be right about 8ft x 7ft (and the entire roof will be dedicated to solar, nothing else will be on the roof). If I have to expend this area to put more solar panels on top due to system requirements, I can do this - but I would really like to avoid having to do so; but I may only be able to expand to as much as 8ft x 9ft, realistically speaking). Also, I would like to hook up my solar system to my truck alternator to provide "drive time" charging.

I am asking for recommendations on: the number of batteries needed, the number of solar panels required, the size of the charge controller, and size of the inverter.

If there are any questions, let me know as I will be checking this thread continuously.
 

bigtexnick

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FYI. The small fridge I have is a "dorm room" style, roughly a 3ft x 3ft size. I plan on using this continuously during trips.
 

MrNatural22

🌞SW sunshine =⚡️⚡️lit up thru the darkness✌️
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I started with a dorm style fridge in my cargo conversion trailer but mobile use was hard on it and it eventually failed. Plus the inverter had to be on continuously.
Now I have switched and am using this massimo (alpicool) 12/24v compressor fridge continuously now for 7 months with no problems. It is a 54qt model and holds as much as the dorm fridge but operates very efficiently on 12v. Draws 45w 3a from my 100ah LiFePo when cycling. 45w 1.5a when I run from a 24v LiFePo I also have.
I have 1 327w sunpower pv on the roof mounted flat. Easily keeps my LiFePo charged and during the day the fridge is powered solely by the pv. ⚡⚡
These sell at Costco for under $300 most of the time. If you have deep pockets you could buy Dometic brand at more than
2-3x the cost 🙄 but these Alpicool built fridges with LG compressors are very dependable and will cool to 0deg f if you prefer. I keep mine at 32deg with no issues.

21C87608-44A3-4399-8115-DA9D22E45BE9.jpeg038DBD81-87F5-4618-A8C0-DC203CB7A6BE.jpeg
 
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chrisski

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Really need to do an energy audit to be precise with an energy audit.

With the energy audit, look at the plugs and figure out how many watts it draws, and number of hours to the tenths of an hour you want to use. That gets you a few devices, but there's so much more in this audit than just what plugs in the wall so you need to measure amps for those. You can get an ammeter that reads DC amps and clip around the battery wire. Simply turn things on, one at a time and write down how many amps you use and then multiply by the number of hours you expect to use it.

Now there will be a few things left that have "Hidden plugs" like a hard wired fridge. I have my inverter hooked to the battery and the inverter provides a number of watts drawn, and I was shocked to see 300 watts pulled. At night I run the fridge off propane and in the day, I run it off excess solar production after the batteries are charged.

After you have all your watt hours add them up, and this is how much power you go through in a day. I want 1200 watt hours. I also want to be able to go one day without power, so I need 2400 watt hours stored. I have lead acid batteries, and if I discharge these below 50%, they can't be recharged many more times, so I needed at least 4800 watt hours of batteries. I ended up getting four tall golf cart batteries which store 5300 wh.

Before getting solar, you can upgrade certain things. For me I just finished swapping out three incandescent bulbs in my RV to LEDs, which should have cost about $40 in bulbs, but of course cost me $200 because I bought wrong parts and broke a lamp doing it. Those incandescent bulbs were what we had used as night lighting in our RV when plugged into shore power, but they drew about 4 amps when plugged in or 48 wh. I was also shocked to see that all other lights in my RV were were LEDs and they drew next to no power.

I also avoid turning my inverter on when not needed, because it will pull at least 12 watts an hour with no load.

The big draw I saw you mention is the oven, if it is electric. For me, I would not want to run a toaster oven off my 12 volt system, but may feel comfortable with 24 volts 400 ah of lithium batteries, but not lead acid batteries.

Solar power can cost anywhere from 10 to 40 times the cost of a gas generator. The higher number is for things that draw a lot of power like electric ovens and air conditioning. Can also be done at two to four times the cost of a generator if all you're doing is charging USB devices, powering a few LEDs, and a couple other low draw items.
 

beanbaggs

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This post has a good example of an energy audit in the first picture of the spreadsheet. If you can do math in excel or Google sheets, you should be able to put one of these together relatively easily.
Somewhere near the power plug on your devices, you should be able to find the power draw in Watts (W) or Amps (A). Power is measured in Watts which is simply Volts x Amps (V x A = W). In the spreadsheet from the post, he uses Watts x hours (Wh = W x h)to get the amount of energy consumed from the battery over the course of one hour. Multiply that by 24h in a day and then by the number of days you want to run without any power generation and you will get your battery bank size in Wh. Divide by nominal voltage (LFP: 12.8v) to get total Ah of the battery bank that you need.

For solar generation, you typically want to meet a days demand of energy plus some wiggle room for cloudy days. I live in WA, I have 8 x 100W panels mounted flat on top of my van. In winter, each panel generates on average 75Wh/day for a total of 600wh, which isn't much for an array of that size. However, it keeps the fridge and heater running non stop all through winter. I also have 600ah of lithium, and alternator charging (Sterling Pro Alt C 210A) just in case, so I can go several days without sunshine.

If you plan on having your inverter running all the time to power the dorm fridge, that's going to draw close to 600Wh/day just in idle mode, van plus another 600Wh/day running the fridge so I would highly recommend getting a 12v fridge which will be more efficient and probably only take ~400Wh/day, depending on the size.

What kind of oven do you have?
 

MrNatural22

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This what my 12v compressor fridge uses in wh
921BD463-F66F-4A32-98B2-7747819953E1.jpeg

So 16 wh x 24hrs = 384wh
On my 1200wh LiFePo fully charged,
1200wh / 384Wh= 3.125 days if drawn down 100%
So my 12v fridge will run 24/7 for 3 days if there is no solar available. If any becomes solar available reserve power would increase accordingly. Using a 12v compressor fridge would make much better use of your battery and your inverter could be turned on only as needed. But electric ovens are major power vampires. Leds and small fans use very little.
✌️
 
Last edited:

bigtexnick

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Nov 24, 2020
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This what my 12v compressor fridge uses in wh
View attachment 28610

So 16 wh x 24hrs = 384wh
On my 1200wh LiFePo fully charged,
1200wh / 384Wh= 3.125 days if drawn down 100%
So my 12v fridge will run 24/7 for 3 days if there is no solar available. If any becomes solar available reserve power would increase accordingly. Using a 12v compressor fridge would make much better use of your battery and your inverter could be turned on only as needed. But electric ovens are major power vampires. Leds and small fans use very little.
✌️
I guess I'm just really stupid, because I legit have no idea what you just said. All I saw was a bunch of Chinese and then, boom, you can run a small fridge for 3 on your battery. Do you mean a battery like this one? ====> https://www.amazon.com/LiFePO4-Volt...t=&hvlocphy=9027261&hvtargid=pla-571575372143

Would you mind venturing an answer to my original question: assume all of the listed electrical loads, at reasonable use rates, what would I need in terms of solar panels, batteries, charge controller size, and inverter size?
 

bigtexnick

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Joined
Nov 24, 2020
Messages
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This post has a good example of an energy audit in the first picture of the spreadsheet. If you can do math in excel or Google sheets, you should be able to put one of these together relatively easily.
Somewhere near the power plug on your devices, you should be able to find the power draw in Watts (W) or Amps (A). Power is measured in Watts which is simply Volts x Amps (V x A = W). In the spreadsheet from the post, he uses Watts x hours (Wh = W x h)to get the amount of energy consumed from the battery over the course of one hour. Multiply that by 24h in a day and then by the number of days you want to run without any power generation and you will get your battery bank size in Wh. Divide by nominal voltage (LFP: 12.8v) to get total Ah of the battery bank that you need.

For solar generation, you typically want to meet a days demand of energy plus some wiggle room for cloudy days. I live in WA, I have 8 x 100W panels mounted flat on top of my van. In winter, each panel generates on average 75Wh/day for a total of 600wh, which isn't much for an array of that size. However, it keeps the fridge and heater running non stop all through winter. I also have 600ah of lithium, and alternator charging (Sterling Pro Alt C 210A) just in case, so I can go several days without sunshine.

If you plan on having your inverter running all the time to power the dorm fridge, that's going to draw close to 600Wh/day just in idle mode, van plus another 600Wh/day running the fridge so I would highly recommend getting a 12v fridge which will be more efficient and probably only take ~400Wh/day, depending on the size.

What kind of oven do you have?
Ok, so I need to get a 12v fridge. Got it.

BTW, as stated, I honestly do not understand any of the audit math. I am truly confused. I just get it. In your link, the person arrives at requiring "1300 wh/day." I don't know what that means. In a vaccum, I don't understand "1300 wh/day." It's like saying, "I need 45 billion googleebits." I don't get what 45 billion googleebits means, just like I don't get what 1300 wh/day means.
 

bigtexnick

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Messages
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Really need to do an energy audit to be precise with an energy audit.

With the energy audit, look at the plugs and figure out how many watts it draws, and number of hours to the tenths of an hour you want to use. That gets you a few devices, but there's so much more in this audit than just what plugs in the wall so you need to measure amps for those. You can get an ammeter that reads DC amps and clip around the battery wire. Simply turn things on, one at a time and write down how many amps you use and then multiply by the number of hours you expect to use it.

Now there will be a few things left that have "Hidden plugs" like a hard wired fridge. I have my inverter hooked to the battery and the inverter provides a number of watts drawn, and I was shocked to see 300 watts pulled. At night I run the fridge off propane and in the day, I run it off excess solar production after the batteries are charged.

After you have all your watt hours add them up, and this is how much power you go through in a day. I want 1200 watt hours. I also want to be able to go one day without power, so I need 2400 watt hours stored. I have lead acid batteries, and if I discharge these below 50%, they can't be recharged many more times, so I needed at least 4800 watt hours of batteries. I ended up getting four tall golf cart batteries which store 5300 wh.

Before getting solar, you can upgrade certain things. For me I just finished swapping out three incandescent bulbs in my RV to LEDs, which should have cost about $40 in bulbs, but of course cost me $200 because I bought wrong parts and broke a lamp doing it. Those incandescent bulbs were what we had used as night lighting in our RV when plugged into shore power, but they drew about 4 amps when plugged in or 48 wh. I was also shocked to see that all other lights in my RV were were LEDs and they drew next to no power.

I also avoid turning my inverter on when not needed, because it will pull at least 12 watts an hour with no load.

The big draw I saw you mention is the oven, if it is electric. For me, I would not want to run a toaster oven off my 12 volt system, but may feel comfortable with 24 volts 400 ah of lithium batteries, but not lead acid batteries.

Solar power can cost anywhere from 10 to 40 times the cost of a gas generator. The higher number is for things that draw a lot of power like electric ovens and air conditioning. Can also be done at two to four times the cost of a generator if all you're doing is charging USB devices, powering a few LEDs, and a couple other low draw items.

Ok, suppose I got a 12v fridge instead of the one I have, and also ditched the oven. So now my question is: how many solar panels do I need to purchase? How many batteries do I need to purchase? What size charge controller do I need to purchase? And what size inverter do I need to purchase?
 

bigtexnick

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I started with a dorm style fridge in my cargo conversion trailer but mobile use was hard on it and it eventually failed. Plus the inverter had to be on continuously.
Now I have switched and am using this massimo (alpicool) 12/24v compressor fridge continuously now for 7 months with no problems. It is a 54qt model and holds as much as the dorm fridge but operates very efficiently on 12v. Draws 45w 3a from my 100ah LiFePo when cycling. 45w 1.5a when I run from a 24v LiFePo I also have.
I have 1 327w sunpower pv on the roof mounted flat. Easily keeps my LiFePo charged and during the day the fridge is powered solely by the pv. ⚡⚡
These sell at Costco for under $300 most of the time. If you have deep pockets you could buy Dometic brand at more than
2-3x the cost 🙄 but these Alpicool built fridges with LG compressors are very dependable and will cool to 0deg f if you prefer. I keep mine at 32deg with no issues.

View attachment 28604View attachment 28605
Thank you for the suggestion. Looks like from what you and everyone say, I will be forgetting the idea of using my small dorm fridge and opting to get a 12v fridge.
 

Hedges

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Ok, so I need to get a 12v fridge. Got it.

BTW, as stated, I honestly do not understand any of the audit math. I am truly confused. I just get it. In your link, the person arrives at requiring "1300 wh/day." I don't know what that means. In a vaccum, I don't understand "1300 wh/day." It's like saying, "I need 45 billion googleebits." I don't get what 45 billion googleebits means, just like I don't get what 1300 wh/day means.
1 volt x 1 amp x 24 hours = 24 watt-hours per day (24 Wh/day)

120V x 10A x 6 hours run time = 7200 Wh/day.

Output of PV panels is trickier. It depends on which way the panel is pointed, what season, and where you are located.
In my area I assume 5 hours effective sun, on average. Might be 7 hours in summer, 2 hours in winter. Although the day is long than that, the sun isn't always at the best place in the sky for my panels on fixed mounts.
Also, panels don't produce what the label says after warming up in the sun.

A 100W panel might produce 80W.
5 hours effective sun x 80W = 400 Wh/day.

7200 / 400 = 18, 100W PV panels needed to power a load of 120V x 10A = 1200W that runs 6 hours per day.

Something similar for battery capacity to last through the night. And, we don't completely discharge batteries, want some charge remaining to avoid causing damage.
 

chrisski

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Messages
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Ok, suppose I got a 12v fridge instead of the one I have, and also ditched the oven. So now my question is: how many solar panels do I need to purchase? How many batteries do I need to purchase? What size charge controller do I need to purchase? And what size inverter do I need to purchase?
Have you watched any of the siteowner’s videos, Will Prowes? Also, there’s some good basic systems in the DIY Solar Blueprints tab up top.

Honestly don’t want to answer those questions. TOo many what ifs, a few that will lead to batteries draining prematurely (too small of a battery bank, Not enough panels, or both). Also, there’s a real risk of fire when building this if some procedures are not followed. Also, I watched a good video of ten inverters, all that perform far under their claimed specs, and two that had flames when plugged in.

We’ll work with you to learn how to build it, but you’ll still have to do some math yourself.
 

Critter350

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Messages
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I agree with the advice given above, but perhaps if I relate my experience it will help.
I have a ‘small truck camper’ too, 2007 Toyota hilux. I run a 50L Engel fridge, water pump, few LED lights, charge 4-6 USB devices a day and a small battery charger for 18650 cells (opus brand, draws up to 3A at 12V). very occasionally I charge my laptop from small can inverter.
this all runs from a single 100Ah FLA house battery, that runs down to ~12.15V overnight. I can charge the house battery from alternator, but run the breaker open. A 200W Flexi panel stuck flat on the roof (typical max yield 150W) and victron 100/20 controller has the battery back in float by lunch time.
I plan on building a 280Ah LiFePO4 pack, that I believe will give my 5-7 days power with a tarp over the solar panel. Fully depleted would take 2-3 days of solar to charge, but I can also close the breaker and go for a drive to bulk charge from the alternator too.
Sounds like your loads are similar (assuming you swap out the fridge), so hope this helps.
 

bigtexnick

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I agree with the advice given above, but perhaps if I relate my experience it will help.
I have a ‘small truck camper’ too, 2007 Toyota hilux. I run a 50L Engel fridge, water pump, few LED lights, charge 4-6 USB devices a day and a small battery charger for 18650 cells (opus brand, draws up to 3A at 12V). very occasionally I charge my laptop from small can inverter.
this all runs from a single 100Ah FLA house battery, that runs down to ~12.15V overnight. I can charge the house battery from alternator, but run the breaker open. A 200W Flexi panel stuck flat on the roof (typical max yield 150W) and victron 100/20 controller has the battery back in float by lunch time.
I plan on building a 280Ah LiFePO4 pack, that I believe will give my 5-7 days power with a tarp over the solar panel. Fully depleted would take 2-3 days of solar to charge, but I can also close the breaker and go for a drive to bulk charge from the alternator too.
Sounds like your loads are similar (assuming you swap out the fridge), so hope this helps.
Thank you for this response. This is the kind of thing I was looking for (basically a similar sample of loads and then get a sample solar setup from there).

What is a "FLA house battery"? Is it similar in power/specs to this one: https://www.amazon.com/LiFePO4-Volt...t=&hvlocphy=9027261&hvtargid=pla-571575372143 ???

So you only have one 200W solar panel? That seems, well, fairly lacking in solar capacity (I'm not being critical, it's just that, as admitted, I honestly wouldn't know any better). Based on my camper build setup and roof space, I had guessed that I would need multiple panels with something along the lines of 600-800 watts, in total. Am I overestimating with this? BTW, I have gotten a lot of my information from watching a lot of boondocking RV channels on YouTube because originally I had planned on purchasing a travel trailer (with more roof space than my truck camper).

Yes, it looks like I will have to get me a 12V fridge -- which will not be a problem. I will just have to decide which model, the size, and proper "fit" in the camper.

Also, are you able to run your fridge all the time and, also, can you take on more loads while the fridge is "plugged in"? This is what I want to do -- you know, basic stuff, like running minimal lights, charging a laptop (not constantly having a laptop plugged in, but charging it long enough to run it on its own for a while)??
 

MrNatural22

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FLA house battery is a flooded lead acid battery such as a cars starting battery, standard wally world deep cycle or golf cart deep cycle.

I am using one single 96 cell 327 watt sunpower solar panel that fits well on my small trailer roof along with a 100ah LiFePo battery thru a 40a EPever Mppt charge controller. 1500w pure sine inverter if needed.

To answer your question it handles running my 54qt 12v fridge 24/7 at 33deg with a couple led lights on when needed while charging my phone or laptop and listening to the radio with no problems.
During a good sunny AZ day everything is basically running on the solar power and after dark or inclement days the battery does its thing.
Usually fully charged by noon the next day after running all night.
LifePo is a higher cost battery but recharges faster and can be used down to 20% state of charge.
The battery in your link is a Battle born LIFePo and is a great battery but $$, there are many other good performance tested available for less cost.
 

bigtexnick

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FLA house battery is a flooded lead acid battery such as a cars starting battery, standard wally world deep cycle or golf cart deep cycle.

I am using one single 96 cell 327 watt sunpower solar panel that fits well on my small trailer roof along with a 100ah LiFePo battery thru a 40a EPever Mppt charge controller. 1500w pure sine inverter if needed.

To answer your question it handles running my 54qt 12v fridge 24/7 at 33deg with a couple led lights on when needed while charging my phone or laptop and listening to the radio with no problems.
During a good sunny AZ day everything is basically running on the solar power and after dark or inclement days the battery does its thing.
Usually fully charged by noon the next day after running all night.
LifePo is a higher cost battery but recharges faster and can be used down to 20% state of charge.
The battery in your link is a Battle born LIFePo and is a great battery but $$, there are many other good performance tested available for less cost.
Thank you for that response. That is very helpful.

A couple of questions. First, you said you have a specific inverter "if needed." I thought you had to have the inverter on all the time, with various loads plugged into it, in order to be drawing from the system? Again, I guess I'm confused. Is your fridge plugged into the inverter? Or is your fridge plugged directly your battery?

Also, another question: suppose that --- in addition to your fridge, LED lights, and charging phones/laptop --- you added an exhaust fan, two water pumps, and a night fan. What would have to be added to your current system in order to power all of these items (assuming reasonable use)?
 

bigtexnick

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Also, another question for you, MrNatural22: at your current usage for the system and components you described, how many of those mysterious "watt hours" do you use in a single day?
 

bigtexnick

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.... Fully depleted would take 2-3 days of solar to charge, but I can also close the breaker and go for a drive to bulk charge from the alternator too.
....
Could you provide the components necessary for hooking up your system to your vehicle's alternator/battery? I would like to add this to my system, but totally clueless how this would work.
 

MrNatural22

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The inverter is there solely for any need for 120v AC (coffee pot, power tool, etc or anything that requires 120v ) Inverter is only on when needed and gives me the option for 120ac availability. It draws 500ma when is stand by mode which isn't bad but still a n unneeded draw if not needed.

The fridge runs on 12v as are led lights, 1 water pump, small fan various usb and 12v sockets for charging items.so inverter not required. Fan is used only when needed (small 12v table fan do not have exhaust fan such as a fantastic fan type roof vent) as my 1 H20 pump.

Watt hour use will always vary with usage. Example my fridge runs about 4 5 minute cycles per hour at 45w so it runs 20 minutes per hour which is 1/3 of an hour. 45wh divided by 3 is 15watt hours per hour. 15wh X 24hrs = 360wh per day total use for fridge. My battery has appx 1000wh's capacity. 1000wh battery capacity divided by 16wh per hour = 62.5 hours. That would be down to 100% depth of discharge.

That's only what my fridge use would be so you would calculate each accessories requirements the same and total for your personal requirements.
I am not as technically knowledgeable as many of the other members here but that is my basic understanding of figuring you power needs.
I also have an ali coulomb meter on the system which is VERY helpful displaying your power usage in and out of your battery and give a reasonable display of remaining capacity.
 

Critter350

Solar Enthusiast
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, I have gotten a lot of my information from watching a lot of boondocking RV channels on YouTube
A lot of people run loads through inverters. I’ve deliberately stuck to 12V everywhere (except charging my laptop, where the can inverter was half the price of an Apple 12V charger).
All of my load runs easily through the Victron 100/20, and probably maxes out at 12-15A. Yes, the fridge runs constantly when we are away, longest trip so far is 3.5 weeks.
The best way to answer your other questions is to do a proper load survey as suggested earlier in the thread. But if you are running similar equipment to me, my experience may help.
 
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