Where Do You Start for a Lithium Battery and Coach Electrical Upgrade?

SSTraveler

2014 LTV Unity Murphy Bed
When starting the process to expand your boondocking/off grid capabilities the biggest decision points are what size Inverter and how much battery capacity do you need. To define these, the first question you must answer is, Do I want to run the air conditioner? Because the air conditioner uses the most amps of any appliance in your coach. The answer to this question pretty much defines how much battery capacity and what size Inverter you need to run everything in your coach.

If the answer is Yes, I want to be able to run the air conditioner off my batteries, then the next question that must be answered is, How long do I want to run the air conditioner with the batteries? The answer to this question pretty much defines how much battery capacity (watts/amp hours) you need. A good rule of thumb to use is that it takes about 1700 watts or 170 amp hours (ah) to run the air conditioner for 1 hour off Lithium batteries. Additionally, a 3000w Inverter is required to run the air conditioner, but you must add an EasyStart/SoftStart to the air conditioner to dampen the high spike in amps that the compressor draws when it starts.

If the answer is No, then you need to decide if you want to be able to run the Microwave, since it's the next largest amp user. Go through the same process described above. Bottom line if you fail to define what appliances/items in your coach or that you bring with you (i.e. CPAP machines, portable ice maker/refrigerator/freezer, etc.) that needs to be able to run off the batteries, you may find it very costly and labor intensive to go back and upsize the wiring and to replace your new Inverter with another larger one, or try and find a way to add more batteries in an already very space limited small motorhome. Start with the End in Mind!

Here is a great video by James of FitRV that talks in more detail about the process.

 

SSTraveler

2014 LTV Unity Murphy Bed
It appears based on some recent Forum installations and looking at lithium battery options of other RV Manufacturers (like the Freedom EGen and Li3 ( Xantrex/Lithonics) and Volta), that 600ah Lithium battery capacity is seemingly the sweet spot. I have seen on this Forum that people who have gone with 400ah have lamented that they should have gone with 600ah, while others just added more batteries to go to 600ah. But how much is really right for you! The vast majority of Lithium battery upgrades signal the fact that people want to be able to run the air conditioner. Once people realize it is totally possible to run the air conditioner off the batteries, they or their significant other or both want that ability. Even for people receiving the 2020 and 2021 Leisure's, which have the 2000w Xantrex Inverter/80a battery charger and 30a Sterling, they quickly realize that simply being able to run everything in the coach except the air conditioner is not acceptable. As with anything, people always want more! So, defining your needs and understanding how you are going to use your Leisure is critically important in making any changes, regardless of the age of your coach.

So let's break down what to expect. I'm going to reference running the air conditioner (AC) as the umbrella term for an AC with an EasyStart/SoftStart installed, no solar contribution (we'll discuss more on this later), and to cover the entire coach operations from batteries (assuming all propane powered appliances [3 way Refrigerator, Water Heater, cooking top, etc.] are be running off propane). Today (2020 and 2021), Leisure's come standard with lead acid AGM batteries. These will not run the AC, but are adequate for very short microwave operations. So if one wants to run the AC from batteries you must replace lead acid batteries (Flooded Wet Cell or AGM) with Lithium batteries. The simple reason for this is that lead acid batteries drop in voltage very quickly under load and it's not good to run lead acid batteries below 50% State of Charge (SOC) and AGMs can go as low as 75% SOC, so many higher amp drawing appliances either won't work or stop operating very quickly on lead acid batteries. Lithium batteries on the other hand don't do this and you can safely run them down to something like 10% SOC. So let's layout what you can expect from the various capacity choices. I've gotten this information from posts, but it would be interesting to hear specific numbers from others experiences.

Lithium Battery Capacity Approximate AC Run Time (time will vary depending Thermostat setting and outside temperatures)
200 ah 45 minutes - 1 hour
300 ah 1.75 - 2.25 hours
400 ah 2.25 - 3.5 hours
500 ah 3 - 4.25 hours
600 ah 3.5 - 5 hours
800 ah 4.75 - 7 hours
900 ah 5.5 - 9 hours

So what's right for you?
 
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woundedpig

2018 Unity MB
While you're doing your analysis of why folks might want/need hundreds of AH of lithium batteries, perhaps you can comment on the charging quandary that will arise if 300-500 amps hours or more of daily recharging is required following 2-3 hours of AC use. And is it a good idea to minimize assumptions of battery depletion from other sources, like compressor fridges, induction cooktops, CPAP machines, fans, recharging of phones, operating the TV, etc?
Even if the roof is covered with solar panels (assume an optimum 600 watts of panels), it will not be possible to reliably capture that amount of energy to restore battery charge during a typical solar day assuming the coach is stationary and in full sun at an opportune latitude and ambient temperature.
Will people need to run the generator to recharge the lithium bank? If so, why not run the generator for 1-3 hours to have the coach cooled?
Some folks who have large lithium banks are forced to run their generators or break camp and move daily in order to utilize alternator charging. However, even with a 60 amp DC/DC charger available to protect the alternator, the net current available to the house bank may only be 45-50 AH due to cable losses, and other coach loads, especially a fridge running on 12V. The 30 amp DC/DC charger now standard on LTV coaches is too small to charge a large lithium bank and I wonder how well the unit charges even the stock AGM batteries. Replenishing a house bank depleted by 300-500 AH or more could take many hours of driving.

A 2nd alternator could charge the bank faster, but at higher additional cost, complexity, and effects on fuel economy.
Would folks who predominantly or exclusively camp with access to shore power need such large lithium banks?

This calculus is made all the more difficult by the power hungry rooftop AC's used by LTV. There are much quieter, more energy efficient AC's out there, like mini splits used in Europe, but typically not used on Class C's in the US.

Seems like the initial question should be how folks use their coaches, where they travel, and how they camp - then go on to discussions of electrical upgrade analyses. We are talking about what are huge potential expenditures for most of us.

I upgraded the electrical system in our Unity predominantly to be able to fun the microwave and other small appliances safely, and to rewire all plugs to work off the inverter if needed. 300 AH lithium is actually overkill for this, but it is what we have, along with a 2000 watt Magnum inverter.
 

msmolow

2019 Unity CB / 2018 Chas
Seems like the initial question should be how folks use their coaches, where they travel, and how they camp - then go on to discussions of electrical upgrade analyses.
Great comment, WP. I upgraded to a 3KW inverter because in the morning I need the microwave to defrost the bagel and then the toaster oven and Tassimo coffee maker. At peak, I'm drawing 2800 watts for four minutes so a 2KW inverter wouldn't work for me. The tradeoff is the higher internal power draw of the 3KW vs 2KW inverter. I could use each appliance is sequence and get away with a 2KW inverter, but I'd be cutting it close at peak, and I don't want to deal with resetting a breaker or blown fuse if I screw up the morning's energy management.

On sunny days my 400 watts of solar keeps up nicely. In the evening I'll sometimes watch 2-3 hours of TV or movies then turn the inverter off.

I still use the FLA batteries that came with my 2019/2018 Unity and it works for me. I tend to drive long hours between campsites so the Victron 30 amp dc-dc charger can keep up, even on cloudy driving days. As you said, my three way fridge sucks 10-12 amps when driving so the dc-dc charger needs hours to work its magic. I do occasionally use the generator if, for example, I'm using the toaster oven or Highpoint convection for more than five minutes or I get to a campground with less than fully charged batteries.

This past week it got down to 5 degrees F. here in Northeast Pennsylvania., so for now the cost of a heated lithium battery for my usage is not warranted. In storage I keep the coach batteries charged with solar and disconnect the chassis battery by the accelerator.
 
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woundedpig

2018 Unity MB
in the morning I need the microwave to defrost the bagel and then the toaster oven and Tassimo coffee maker. ......
You sound like us, though we just do things sequentially. We need our hit of bacon in the morning from the microwave. Then the coffee cups get warmed in the MW. Then two cups of cappucino with frothed milk via a compact Breville Bambino machine. I'm forgetting something from our generally hedonistic practices.
We did not get a larger Magnum because of the significantly higher static draw when on, but our battery bank could have handled it of course.
We have 600 watts of high efficiency Renogy ridgid panels. We had never intended to try to run th AC off batteries.
 

Vantastic.pa

Active member
I am actually able to run my ac off if my 2000w inverter with an easy start installed. I just upgraded to 400ah from 300ah and have one more battery coming for a total of 500ah which for me us over kill but I got a good deal so I had to. I personally have the ac but only really use it when I plug in at someone's house which is not very often. I haven't been in extremely high temps yet that I felt the need to turn it on I mainly use fans and open window for air flow but I am eager to see how long I can run the ac with all my new power. I do see that a low battery light will flash on my controller a little while after running off batteries then when I turn it off it is fine again. I believe it is anticipating how much power I am using. I could be wrong for that reason or because I am drawing so close to the 2000w limit of my inverter
 

SSTraveler

2014 LTV Unity Murphy Bed
I currently have AGM batteries and you can safely use them down to 25%. So I have been thinking there was no real advantage to going with say an equivalent amount of Lithium batteries. This video does a great job of explaining the differences between AGM and Lithium batteries, http://rotory.com/video/lithiumvagm.mp4.

When looking at the amount of amps you may need, remember all amps are not equal. Appliances/equipment in your coach either runs of 120v alternating current (ac) [shore/generator/inverted power] or directly off the batteries which is 12v direct current (dc). This is important to understand because you have to convert the amps used at 120v alternating current (ac) to amps at 12v direct current (dc), to understand your true battery use/capacity needs. Having appliances/equipment (Dometic 3 way absorption refrigerator, cooktop, water heater, furnace) that runs off of Propane can be an advantage since those things only use 12vdc battery power to keep the propane solenoid open (0.75a) and to power the ignition of the item. A good rule of thumb is that for every 10 amps per hour (ah) required at 120vac [shore/generator/inverted power] you need about 110 amps at 12vdc from your batteries. So you can see why only being able to use about 100ah (50% SOC) out of 200ah Lead Acid batteries doesn't go very far!

Since I have replaced a number of my appliances , never use propane, and need to support 2-CPAP machines for sleeping, I would have to increase my amp hour need assumptions from what I previously described. Have a compressor refrigerator that uses on average 2a (12vdc). I use my 2 way Suburban Water Heater on electric which draws 12a (120vac) when the heating element is on. I replaced my propane cooktop with an dual element induction cooktop, which can use up to 15a (120vac) when using both elements. I use a cube heater rather than the propane furnace at night, and it can use up to 14 amps (120vac) if I have it on full, but I typically only use it at about it's half setting. During the day after it gets above 40 degrees, I use the heat pump of the roof top Dometic air conditioner/heat pump, which uses up to 15a (120vac). The CPAP machines use 120vac or 12vdc and use up to 7a each. So you need to fully understand how you use your coach and account for the big draw items that your batteries will be need to support if you plan to not use shore power hookups.

In planning for a big upgrade I never start with how much things cost. I believe that limits you design the optimal system/solution you are looking for. As an engineer I like to define/design the best elements for a project and consider the cost at the end. I'd rather understand what the best approach is for me and then decide if that's what I'm willing to pay for. This is how I selected my Leisure, sure there were less expensive Sprinter motorhome options, but I thought the Leisure Unity was the best. I would encourage you not to limit your options by making cost the driver, because you might end up still spending a lot of money to be dissatisfied. I personally would rather pay a little extra to get the Best, than be frustrated because I settled for less. The reason I haven't upgraded to Lithium yet was because I didn't think their were good options for larger battery capacity needs in small spaces, batteries with internal heaters, and several other technical reasons that I feel I have resolved in my mind since I have experience been helping others on their battery/electrical upgrades, particularly those who hacpve selected Lithionics batteries. But I'm still studying battery options and will discuss later.

I guess when I started this thread it was to help other who were looking to do a big battery/electrical upgrade over the winter down time, but I find that I am making a case for myself to consider an upgrade. So I'll make this thread part of my process of thinking through the needs and options as well! I would like to be able to run my air conditioner on batteries, since this is the maximum amp (120vac) using appliances in our coaches, but do I really need to based on how I use my Unity. I do want to understand the options from just upgrading enough to continue to use my coach just the way it is (standard 600w inverter) or just upgrading to add use of the microwave or upgrading to be ableto run the entire coach including the air conditioner off batteries. I haven't decided just how much more capability I really need. So whoever is interested, come along, there are still lots of elements to cover, including how to keep the Lithium batteries charged!
 
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hilld

Well-known member
Can you reduce the AC need (load) by adding insulation behind the wall panels and perhaps have window covers that are insulated?
 

msmolow

2019 Unity CB / 2018 Chas
So I'll turn this thread into my process of thinking through the needs and options myself! I would like
You might consider starting a new thread. It will get buried in this one.
 

SSTraveler

2014 LTV Unity Murphy Bed
Can you reduce the AC need (load) by adding insulation behind the wall panels and perhaps have window covers that are insulated?
Absolutely, I use Reflectix on every window and skylight. I put Reflectix on every exterior wall space (lined every cabinet, wardrobe, behind drawers, on the wall under the Murphy bed window) I could to reduce infiltrating hot/cold. I also have 2 insulated cab curtains, a long one attached to the short one that came with my Leisure and then one that closes off the cab that hangs below the over cab cabinets. I also replaced all my window shades, except the ones with MCD shades, with blackout insulated shades. The one at the Door i replaced with a long shade that i can pull down and completely cover the door. All these things help significantly to reduce the heat and cold infiltrating in, thus reducing the cycling time of Air conditioner/heat pump/Furnace!
 

blue

2011 LTV Unity CB
SSTraveler - you said, "In planning for a big upgrade I never start with how much things cost." Contrary to that, I looked at the cost of lithium battery technology and decided that I was not interested. I wouldn't mind more battery Ah, but not at huge cost. On the other hand, my son-in-law has a business where he deploys remote monitors using solar and battery systems. He uses Trojan FLA batteries https://www.trojanbattery.com/pdf/datasheets/L16EAC_Trojan_Data_Sheets.pdf that cost about a tenth of Lithionics batteries, but weigh a lot more. His applications are not restricted by the weight of the Trojans. I would consider pulling out my generator and going with FLAs. Not for you though -- I remember that you have an aversion to FLAs.
 

lvuman

Active member
I think this is really an excellent thread! With so many different setups and models plus everyone having their own unique priorities, it's a great place to discuss the "hows and whys" of the individuals that have modified their rigs and give the undecided a broader understanding of the process. There are no wrong answers and I for one, appreciate everyone's input.

In our particular situation, we wanted to be self-contained with some extended ability. It's rare that we ever use the AC but, when we do, it is usually for a short duration like cooling off the cabin before going to bed or keeping our two pups cool while we are out to dinner or shopping. I really don't like using the generator if possible. It's stinky and noisy for us and certainly for our neighbors. I think we have about 50 hours total on it but, it's still a security for charging my batteries so deleting it is not an option for me personally. SSTraveler is correct, 600ah seems to be a sweet spot for us with our 650W of solar. I really like the freedom it gives us.

We've found having a large battery bank is fun even if you're one who predominantly camps with access to shore power. As an example, we like to camp in the desert for one night a week in the winter. It's good for the rig and excellent for us! It's really nice to pull into any spot anywhere and use all the battery storage we need without any thought to conserving amps knowing when we get back home, and our rig is tucked away at storage, our solar will top off our two Lithionics batteries to 100% SOC in a day or two without having to plug into shore power. Last night was one of those nights. We wanted to view the Jupiter/Saturn conjunction. We were really decadent! We left our frig on battery for 14 hours, lit Christmas lights outside, and on a small tree inside, turned on a cozy 120v lamp most of the evening, ran the furnace, watched satellite TV to midnight, took 2 long showers, and charged our computers. Our batteries were down to 66% SOC this morning. Our Renogy 50A DC-DC charger and solar array charged the batteries to 79% during the hour drive back to storage. Oh, and another thing, our 2015 MB electrical panel is now wired with every circuit on the inverter panel. We no longer need to find an inverted outlet to charge our phones, run the generator to microwave a snack or to watch a TV program. The convenience is awesome.

During the summer, we camp along the coast in California without any shore power. With our 50 gallons of water (25-gallon aux tank), we can go a week easily before dumping tanks and refilling our water supply but we still had to be really careful with our energy usage. Sometimes we would drive to a non-public location and run our generator to charge our two, 6-volt, Allstate batteries when we had a day or two of rain or fog. This next summer will be wonderfully different. We will still use our propane for the furnace, cooktop, and heating water as we usually do but with a little energy management, we will easily be able to occasionally use the microwave and the AC when needed without the generator.

I agree with SSTraveler. Every time we use our motorhome, I'm so pleased we didn't scrimp on the installation. Although an LTV is a relatively costly purchase, we're really pleased we went with LTV instead of the brand "X" we were originally considering. We also believe the installation was a compliment to the coach we did purchase. It's a personal choice but just another perspective.
 

DiverBob

2018 Unity TB
I agree with SSTraveler on her method of designing her systems. When I first got my LTV in the spring of 2018 we used it as delivered for the summer learning about what it was like to have a motor Home and what kind of camping we wanted to do. It taught us the limitations that the RV had for us to get the full enjoyment out of the experience. We realized that we didn’t like the noisy generator, we wanted to be able to run the microwave off the batteries, my wife didn’t want to think about power, and her CPAP machine was a overnight power hog. Based on those requirements I went about designing an electrical system that would meet those requirements.
Overall I believe I obtained that goal despite a few ‘detours’ along the way (my long thread on this group on my electrical and solar installations talks about the decisions and reasons behind them, primarily to document a process and hopefully the next person can avoid some of the issues I encountered). Luckily I have a pretty extensive electrical background and really enjoy the design and build process, even when things don’t go exactly right. The main thing is to not keep going down a path once you discover issues, be ready to check and adjust. This facebook group is great for advice and inspiration when I needed it, lots of people here who have built up some great systems.
In my design process I figure out what the goal is, then look for equipment that can get me to that goal. Lastly I look at price to ensure I can afford to do it. Luckily I have a very understanding wife who indulges me but also likes the conveniences these changes provide that make traveling more fun.
 

Klipstr

2018 Wonder FTB
It becomes interesting when needs and wants collide! I am a technologist by training and experience so like to have the latest greatest whenever possible. Fortunately, my dad taught me the value of money early! Money in has to exceed money out at all times.

I've been kicking around a number of upgrades to our rig including conversion to a compressor fridge, upgrading the inverter to support that and replacing my FLA with Lithium of some sort. I keep running into the fact that I don't really "need" any of those things. We've spent more than 200 nights in our rig since we bought in including a three month trip to AK. Never had a problem with energy consumption and we had plenty of cloudy rainy days on that trip. 400W of solar and 235AH of storage. All the normal things as folks have documented. And we think we're happy!

I "want" the challenge of doing the project! I would prefer to do the project on someone else's rig with someone else's money. That would make me as happy as if I did it for myself.

These threads that SS started in the past couple of days have forced the collision of my needs and wants. Thanks!!!

I'm heading to Show Low on Christmas day and will probably crawl all over my coach deciding where the dang new Lithionics are going to fit and start thinking about wiring, etc., to accomplish the task. The good news is that will distract me from all the woodworking I've been doing. Oh, and when I had my rig at our local repair shop fixing the stupid Truma I asked them about installing the new fridge for me. $250. I think I'll go that route. I'm not lazy or afraid of work but $250? Really? Electrical: I like the challenge. Mechanical: depends, but pulling out the fridge, based on all I've read, doesn't appeal.

I wonder what would happen if I ever just sat down and read a book?
 

Danarbor

2017/2018 Unity Twin Bed
I "want" the challenge of doing the project! I would prefer to do the project on someone else's rig with someone else's money. That would make me as happy as if I did it for myself.

Hmmm, Michigan in the winter or a trip to Arizona to meet Klipstr and make him happy by letting him help me upgrade the electrical in my 2017/2018 UTB with my money??? That is certainly worth pondering. :cool:
 

SSTraveler

2014 LTV Unity Murphy Bed
Great! Now that we've covered the information one needs to really get an understanding of their battery capacity needs, based on how they use their Leisure. Let's look at the next big component, the Inverter. I agree with DiverBob, I like to define the various components/functions I need for a project and then see what is available on the market. I forgot to add earlier, that before you start any electrical project, you really need your coaches wiring diagrams. They are very easy to get , just send Leisure's Willie Neufeld, WNeufeld@tripleerv.com, an email with your VIN#, email address, and phone number. Requesting him to send me, via email, the PDF versions of your Leisure's 120vAC and 12vDC electrical systems wiring diagrams. Then follow it with a call to him (877-992-9906 ask the operator to connect you to him) and leave a message on his voice-mail of what your email requests. He will very promptly send a single or multiple emails transmitting your electrical system wiring diagrams. Here is a thread, https://sprinter-source.com/forums/index.php?threads/92289/, that has some diagrams on it already that may match your Leisure. If you do get wiring diagrams please consider posting them on this thread, it may just help someone else.

Now let's consider how our coaches work on batteries (12vdc) and shore/generator/inverted power. Our coaches are equipped with a power distribution panel/box (120vac breaker/12vdc fuse box) and an inverter. Here is a simple chart (not intended to show every detail) that shows the simple power distribution on a 2014 Leisure. Different model years have differences on power distribution panel/box model and model/size Inverter/Charger, so this is why having the wiring diagram for your model/year/floorplan is important. But conceptually the functions are the same. If you look at post #27 here, https://sprinter-source.com/forums/index.php?threads/91673/page-2, you'll see a lot more detail on the panel differences and wiring. I'm going to get to that and everything on the chart thru later posts, but for this post I want to focus on power distribution.

As you can see power comes from 3 sources; batteries, shore/generator or solar (if equipped) power. The batteries support everything in the coach that runs off 12vdc, which the batteries supply. It either feeds those things directly or thru the 12vdc fuse box side of the power distribution panel/box. The batteries also supply the Inverter which converts the 12vdc battery voltage/direct current (dc) to 120vac (120 volt alternating current, same power as your house uses for household appliances or high amp draw equipment like air conditioner, microwave, hair dryer, washingmachine/dryer, stove/oven, etc.). In my 2014, I only have a 600w (6a) Inverter, so it can only supply about 6 amps, which Leisure connected 2 outlets to this Inverter. So I can only use it to supply low amp simple things like tv, satellite, phone chargers, small LED lights, a curling iron, etc. or I will trip the breaker on the inverter. The inverter is also wired into one breaker on my 120vac power distribution panel/ breaker box so when on shore/generator power those 2 outlets are powered (but still limited to 6a, even though the wiring can support 15a) that way instead of having to always use batteries to supply those 2 outlets. This capability of the inverter is called pass-through. The inverter uses the battery power to supply the 2 outlets or it passes-through the shore/generator power to the outlets. This is a very desirable feature for any inverter. My inverter doesn't have a battery charger (charges the batteries when on shore/generator power) with it so we'll cover battery charging later in a subsequent post.

The solar power also charges the batteries, which are supplying the coach. So if your solar system is supplying 10a (12vdc) and the coach/house is using 10a then your batteries stay at 100% charged. We'll discuss battery charging and solar input later on in this thread. But keep the potential solar system on the back burner.

Now the 120vac breaker panel side of the power distribution panel/box is connected to the Automatic Transfer Switch (ATS) which is supplied by 120vac from either Shore power hookups or from the generator. The ATS senses which 120vac power supply is available and sends it to the 120vac side of the breaker box. My power distribution panel/box is a WFCO 8955, which also includes a battery charger and a converter that converts 120vac to 12vdc, so when I'm hooked up to shore power or using the generator, my house/coach batteries get charged and the coach gets supplied with 12vdc so the batteries don't have to. I think Leisure switched to a WFCO 8930/50 in 2016, which doesn't have these extra features, rather they went with an inverter that has a battery charger (that charges the house batteries by pass-through power from shore/generator) and rely on just the batteries to supply all 12vdc to the coach.

So in looking at the 120vac side of the power distribution panel/breaker box, you need to decide what functions, or all of them, you want to be able to run off batteries. Because you need that information to determine what size pass-through style Inverter you need. You'll want an inverter that has a battery charging function as well, but we'll look at that part of it later. I just want to focus on figuring out what size Inverter you need. So here's about how the sizing goes. Everything in your entire coach runs off of a 30a 120vac power supply, so that means you'll need at least a 3000w Inverter to run those same things off your batteries. And remember when running the 120vac side of the house things off batteries, you are also still supplying all the 12vdc items from your batteries. So now you are running absolutely everything in your coach off batteries, including the air conditioner. This distinction is important because that's what you need to remember when determining how much battery capacity you think you need. Remember to consider the difference between 120vac amps and 12vdc amps (10a 120vac = about 110a of 12vdc power) for battery capacity needs! If you want to just run most everything, including the microwave but not the Air-conditioning, then you'll need at least a 2000w inverter. If you just want to supply the outlets up to their 15a rating, water heater, entertainment systems, etc. Then you'll need a 1500w inverter. If you only want some of your outlets supplied up to 12a, and entertainment systems then a 1200w inverter is fine. And then if you want a couple of 10a max outlets a 1000w inverter is fine. You can use this understanding of the power distribution to start thinking what size Inverter you want. If you know you want at least 2000w of capabilities and aren't sure if you want to add the air conditioner operation to the batteries, then my advice is to select a 3000w Inverter, because there is only a couple hundred dollars difference between the two. Selecting a 3000w Inverter gives you the ability to expand your system to add the air conditioner later. I like to choose components that give me future options if I am undecided on some things. But based on the experiences that others have shared, it seems most decide that more is better! The same with batteries, size your wires with the possibility of adding more, but we'll get into that more later. If I've missed something on power distribution please chime in.
 

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DiverBob

2018 Unity TB
To add on to what SSTraveler has stated, choosing a inverter size should be based on what you want to power in your RV. But remember that the bigger the inverter the more power it uses even just sitting there with nothing plugged in. This power drain may seem small but over the course of a day it adds up.
 

SSTraveler

2014 LTV Unity Murphy Bed
Good point what is the amp charge to keep the inverter on, 1-3 amps depending on inversion amount.
 

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