Inverter wiring for solar

[mikegascon1]

I am still at the thinking stage for solar. If I were to install a solar setup up, I would definitely want to install an inverter so my AC would work. How does that get wired in? To the power box under the shower? I assume they come with detailed instructions? I am not an electrical whiz bang and this is stumping me. I assume I am over thinking it and it is straight forward. Right?
Thanks

2007 3124
Vancouver, WA (close to Portland, OR)

[Bill]

Mike -

I am not an expert, but you will hear from the experts shortly.

The short answer is that the solar panels charge your batteries, and the batteries send DC power to the inverter. The inverter converts the DC power from the batteries to AC power, which is then used to power up the appliances and outlets. The air conditioner uses a rather enormous amount of power, so unless you have a LOT of batteries and a LOT of panels, running the AC may not be feasible.

As a quick benchmark, it is barely possible to run the air conditioner from a 2000 watt generator. Do you envision having well over 2000 watts of panels?

And now, over to the experts !!

Bill

[Wavery]

Originally Posted by Bill

Mike -

I am not an expert, but you will hear from the experts shortly.

The short answer is that the solar panels charge your batteries, and the batteries send DC power to the inverter. The inverter converts the DC power from the batteries to AC power, which is then used to power up the appliances and outlets. The air conditioner uses a rather enormous amount of power, so unless you have a LOT of batteries and a LOT of panels, running the AC may not be feasible.

As a quick benchmark, it is barely possible to run the air conditioner from a 2000 watt generator. Do you envision having well over 2000 watts of panels?

And now, over to the experts !!

Bill

Bill pretty well summed it all up. Running the AC from the inverter for more than 5-10 minutes a day is simply not feasible unless you cover every inch of the trailer with solar cells and spend $6K in lipo batteries..

Most of us that boondock run about 200W-400W of solar panels and 200-300AH of battery storage. Then we run a generator for the AC, microwave. A 2000-3000W (pure sine wave) inverter is practical on that size set-up for that 1st pot of coffee in the morning or running the microwave for 10 minutes or so.

[rickst29]

In general, the 12-VDC "12 volt" and "grounding" cables (between Inverter "input" and the battery terminals) need to be as short as possible, so that they do not consume power in wiring losses. If the Inverter is expected to run household appliances such as a coffee maker or microwave, those cables must also be very large. I use dual AWG 2/0 supply cables between my battery packs and my relatively big Inverter.

Although Solar power can contribute to the "12V" power draw on the batteries, the batteries themselves are the main source of power for an Inverter. The Solar system is wired to charge at the batteries (or their corresponding "bus" connectors, 12v and ground).

While the Solar system puts power into the battery bus terminals, the Inverter takes it away. The batteries themselves must provide any shortfall. If the Inverter is smaller than solar panels, or not being used for significant loads, then extra power remains to charge the batteries.
- - -
The most important questions, to ask you in return are: #1, how big are your batteries? and #2, what's the biggest appliance you hope to run?

[rich2468]

Originally Posted by mikegascon1

I am still at the thinking stage for solar. If I were to install a solar setup up, I would definitely want to install an inverter so my AC would work. How does that get wired in? To the power box under the shower? I assume they come with detailed instructions? I am not an electrical whiz bang and this is stumping me. I assume I am over thinking it and it is straight forward. Right?
Thanks

2007 3124
Vancouver, WA (close to Portland, OR)

(Adding some clarity to what's already been shared by others)

Hi Mike- to accomplish what you've stated you'd like to accomplish (the ability to run the A/C from battery power) using off-the-shelf materials starting with an "average/factory" build TrailManor, you'd need around 100 Amp Hour of battery energy per each hour of A/C use- so if buying Battle Born (or other popular Lithium brands), think of needing one battery for each hour of A/C use.

To safely convert the Direct Charge 12 volt electricity from those batteries to 12 volt A/C you'll need an inverter (likely in the 3000 Watt size, to be safe).

To replenish the charge of your battery bank, while running the A/C at about the same rate that the A/C (running via Inverter) is discharging it; you'll need around 1200 Watts of solar cells.

The above configuration should, hypothetically, run a TrailManor A/C under perfect conditions...but it's almost never going to be "perfect conditions".

Tree cover, cloud cover, solar panel orientation, etc. will all impact solar charging.

There are multiple ways to attack inefficiency/ uncertainty of solar changing, but the most obvious are-
1. Minimize load demand (buy a more efficient A/C)
2. Increase battery bank size
3. Examine practicalities of pursuing your TrailManor running A/C on battery power and minimize (or abandon) expectations

You may be able to buy or build a battery bank of sufficient capacity to mitigate some of the cost (of purchasing name brand Lithium batteries), but there are still significant hurdles to accomplish what you've stated.

The basic design of a TrailManor, which is awesome for tow-ability, is not easily conducive to the desired results of running a stock A/C on battery.


For a background: I am halfway to being able to do what you've stated. I can presently run my A/C from my battery bank and 600 Watt solar array and am in the process of adding 400 more Watts and doubling my Lithium battery bank, so that I can have additional capacity.
-The extremely tricky part is balancing the ability to do that with the practical aspects of the TrailManor and its usability.

To address one of your immediate questions, the 120 Volt out of the Inverter needs to be wired into the 120 power side of the TrailManor's power converter to power the 120 volt plugs and loads. An auto switch-over device is used to ensure that the Inverter never powers that 120 volt side of the TrailManor's power converter when the TrailManor is hooked up to shore power. Search YouTube for "TrailManor solar" to find Matt Carver's channel (the Critter and the Butterfly) for an explanation and video of his installation of solar and that automatically switch-over device.



Rich

[Bill]

Originally Posted by rich2468

To accomplish what you've stated you'd like to accomplish (the ability to run the A/C from battery power) ... To replenish the charge of your battery bank, while running the A/C at about the same rate that the A/C (running via Inverter) is discharging it; you'll need around 1200 Watts of solar cells.

Rich -

I'm not sure where the 1200 watt figure comes from. In 2007, I think TM was using a Coleman Mach 13,500 BTU air conditioner, which seems to require at least 1800 watts when running. Adding a true-sine inverter efficiency of 85% (admittedly a SWAG) ups the ante to around 2100 watts.

I think I found the YouTube channel you mentioned, but although it is titled Solar and A.C. Upgrades, I can't find anything about the air conditioner. Are we on the same page?

All your other points seem spot-on.

No matter what, it is a lot of power.

Bill

[rich2468]

Originally Posted by Bill

Rich -

I'm not sure where the 1200 watt figure comes from. In 2007, I think TM was using a Coleman Mach 13,500 BTU unit, which seems to require at least 1800 watts when running. Adding a true-sine inverter efficiency of 85% (admittedly a SWAG) ups the ante to around 2100 watts.

I think I found the YouTube channel you mentioned, but although it is titled Solar and A.C. Upgrades, I can't find anything about the air conditioner. Are we on the same page?

All your other points seem spot-on.

No matter what, it is a lot of power.

Bill

Hi Bill,
That's first hand experience.

When watching my battery monitor live as I turn on and cycle through my 2021 2922KB's stock Air Conditioning running through my Inverter I see the following:

1180 Watts with the AC on high, 1020 Watts with AC on low, 197 Watts fan high, 131 Watts fan low.

The reading I'm seeing is straight from my battery bank (so Inverter losses are accounted for).

Matt Carver (YouTube the Critter and the Butterfly) just covers his Lithium upgrade and adding the auto switch-over. His Inverter is not large enough to run an A/C. Mine is; I have a 3000 Watt pure sine wave inverter.

[Bill]

Originally Posted by Bill

I'm not sure where the 1200 watt figure comes from.

Originally Posted by rich2468

Hi Bill,
That's first hand experience.

Interesting. I can't imagine that TM has downsized the BTU capacity of the air-co, so perhaps they have found a more efficient unit for new builds. The online specs just say "Low profile roof air conditioner", which isn't much help.

Bill

[rich2468]

Originally Posted by Bill

Interesting. I can't imagine that TM has downsized the BTU capacity of the air-co, so perhaps they have found a more efficient unit for new builds. The online specs just say "Low profile roof air conditioner", which isn't much help.

Bill

I need to update my previous A/C load values reported.

I've realized that I had taken those in the evening, so it looks like my solar array was contributing to lower than expected numbers load numbers (despite it being well after 6 pm in March when I took those readings).

Here are my actual load numbers (today) with my breakers to the solar array switched off and 80 degrees Fahrenheit ambient temperature:

1350 Watts with the AC on high
1280 Watts with AC on low
187 Watts fan high
125 Watts fan low.

I do not see any major spikes to 1800 Watts through Victron Connect (when my A/C compressor kicks in) but am adding an A/C soft start as a proactive measure.

[rickst29]

Originally Posted by rich2468

(Adding some clarity to what's already been shared by others)

Hi Mike- to accomplish what you've stated you'd like to accomplish (the ability to run the A/C from battery power) using off-the-shelf materials starting with an "average/factory" build TrailManor, you'd need around 100 Amp Hour of battery energy per each hour of A/C use.

Rich

That 100Ah per hour figure seems a bit short, even for the new and MUCH more efficient TrailManor AC units, due to the "100Ah" battery pack BMS stopping discharge before 100Ah has actually been used. If we forget about lead-acid battery types and focus only on LFP, the following math will apply. (Lead acid batteries can't handle all the rotor-start current, and they can't be discharged as deep.) In this, which is mostly an addendum to your excellent post about your results with a new AC unit, I focus on the much worse situation with older models:

The average running watts of those older 13,500 BTU air conditioners is 1600-1800 watts while the compressor is running (depends on weather, and the condition of the AC compressor motor, and which model it actually is). The total capacity of each "100Ah" LFP battery, discharging from 100% full down to ZERO, would be around 1280 watt-hours, if such a battery could be discharged that far.

Discharging to 0% destroys LFP batteries. Their on-board "Battery Management Systems" will shut down before reaching zero, typically at only 10% left. But going that far down, on a frequent basis, would still hurt battery lifespan pretty badly. I don't go past about 20% left. I further reserve the first 100Ah of my batteries to run TM 12v loads and appliances (including a fridge) through the night and into mid-morning of the following day, when significant solar power again becomes available for recharging the batteries.

So, we have 80% maximum usable from 1280Ah nominal capacity, right around 1024 watt-hours per 100Ah. Conversion from 12.8-VDC to 120-VAC (in the inverter) consumes about 15% of that power, resulting in maybe about 850 watt-hours of 120-VAC power from each 100Ah of Lithium (LFP) battery. To run the older 13,500 BTU AC for one hour, with the compressor mostly "on", you would need around 1600 watt-hours. That's roughly 200Ah of LFP batteries, not just one.
- - -
In addition to the raw power consumed from the batteries, everything also needs to handle the extremely high extra "current load" which is required, for just a fraction of a second, to start the compressor motor. Each time the compressor turns "on" from an "off" State, the Coleman Mach 13,500 BTU compressor motor demands around 55 amps of current. (That's about 7000 watts). An Inverter smaller than "3500 continuous / 7000 peak" watts is unlikely to handle this "rotor start" loading, unless assisted by a high-quality "start-assist" device. With such a device handling "rotor start" peak loading, e.g. the 'SoftStartRV' (a load learning and really expensive one), you could get by with a somewhat smaller Inverter.

But not anything smaller than 3000/6000, because you'd be running at a high proportion of it's maximum continuous rated output. They're less efficient while being run that hard, and they burn out faster.

To feed a 3000/6000 Inverter, which will use more like 3500/7000 input watts at peak loading (because it is only around 85% efficient), you need "12VDC" wiring which provides a capability for more than 300 Amps. My own 2/0 wire pairs barely meet that requirement.

The costs add up, pretty fast. I know of only a 3 people who actually do this - JoeyCharismatic, Rich2468, and myself.