Is 600w enough

[Blkbird]

I plan on putting 600w of solar panels on the roof of a small camper. The Panels will be able to tilt so I can get as much power as I can. My main use is to run a 5000 BTU AC tha draws 450w in the summer and a 500w space heater in the winter & a few little items like phones, tablets and led lights. I plane on buying one or two Battle Born Batteries. Heres my question, If I run the AC during the heat of day will the 600w keep the battery(s) charged up for the evening to charge the little stuff.

Dean

 

[Zil]

It is very difficult to have air conditioning with such a small battery. It is worse with heating.

 

[Hedges]

Panels rated 600W STC will produce peak of about 450W to 500W most days while they are aimed directly at the sun.
Throughout the day, assuming 5 hours effective sun (due to being off-angle most of the time), you can expect up to 2500 Wh.
During winter it will be less.
So during the summer you can get about 5 hours run-time of the A/C. The battery will cycle, charging while A/C is off and discharging while it is on.

Can you put up considerably more PV wattage, maybe double for 1200W? It isn't a lot of area. I'm considering four 300W panels just over the cab and hood of my pickup. Use a relay to enable a load (either A/C or water heating) when battery is fully charged, and avoid drawing down the battery to operate the heavy load. Then a small battery can be used, just provides starting current surge and runs lights at night. Batteries cost much more than PV panels. I do this for a larger system with A/C at my house.

 

[chrisski]

Here is a video of a guy who has 600 or 750 watts of panel on his roof and ran his A/C. Basically, not a good idea. The AC drew twice as many amps as the solar power was putting back in the batteries. He has a 25’ RV, so a small camper could have less power draw for A/C

https://www.youtube.com/results?search_query=rv+with+tito+air+conditioner

If you read the comments, others give suggestions to tell how to make it happen.

I hear split 110 VAC A/Cs use less watts and are much quieter than the roof mounted units. Putting solar capable A/C in my RV is at least a couple upgrades down the road. THe first would be a 24 VDC rating.

 

[DThames]

Can you set up your camper and run your AC unit while the camper is at your house, connected to house AC? If you can, you can get a power meter and see what power it uses throughout the day. I have a little 6000BTU unit. It will run about 570watts when the compressor is running. In a small space, the compressor should only run part of the time. If you have a feel for total power use during a hot day, you can get a better feel for your battery situation.

I would shoot for 4, 300 watt panels so to have enough power at any sunny moment to run the AC while charging the battery. If a cloud passes, you will be pulling from the battery. When the sun is back out, you want to quickly get the battery back to 100%.

 

[ianganderton]

I plan on putting 600w of solar panels on the roof of a small camper. The Panels will be able to tilt so I can get as much power as I can. My main use is to run a 5000 BTU AC tha draws 450w in the summer and a 500w space heater in the winter & a few little items like phones, tablets and led lights. I plane on buying one or two Battle Born Batteries. Heres my question, If I run the AC during the heat of day will the 600w keep the battery(s) charged up for the evening to charge the little stuff.

Dean

Where about are you?

 

[Deleted member 1888]

One thing that the makers of the AC and heater will never tell you is the start up surge. The AC may say its a 450w but that is after the AC has cooled down the room and is just maintaining it. The real draw will be closer to 1500w when you turn it on and wile it is cooling the room that is the surge. The same with the heater or any appliance that heats or cools. I have a 700w microwave that surges to 1200w when it turn on, I also have a 500w cook top that surges to 1500w. My freezer that is a 100w surges to 1100w when it first starts and cools down. With a surge that is the start up it will then drop after some time closer to what the manufacture claims it runs at.

So it is safe to assume you AC with hit 1500w surge and the heater will hit 1500w, for however long it take to heat or cool the room. So plane on needing a 3000-4000w inverter and it would be better to use a 24v not a 12v for that kind of draw. So 600w will not keep up with all that you need 1200 or better and a battery bank to match.

 

[chrisski]

One thing that the makers of the AC and heater will never tell you is the start up surge. The real draw will be closer to 1500w when you turn it on and wile it is cooling the room that is the surge. The same with the heater or any appliance that heats or cools.

There's soft starts to cut down on the surge. An added $350 but may allow you to do it with less than the 1500 watts you mention. At least in what I'm looking at building someday.

How long do you say that surge lasts? A Couple of seconds? I imagine the A/C surge is the couple of seconds I hear it hum as it turns on.

 

[Deleted member 1888]

There's soft starts to cut down on the surge. An added $350 but may allow you to do it with less than the 1500 watts you mention. At least in what I'm looking at building someday.

How long do you say that surge lasts? A Couple of seconds? I imagine the A/C surge is the couple of seconds I hear it hum as it turns on.

I don't know how long it was I just know that at the end of the day it was 3kwh VS when I left them plugged up and they pulled 2kwh for the day. Some days now I even see them pulling 1-8kwh for the entire day, so they stay plugged at all times.

 

[Hedges]

An A/C with 450W rating should never draw more than 450W except for a fraction of a second starting surge. That typically lasts 35 ms to 1/4 second. If a generator or inverter can't supply enough current, then it could last seconds or never start, and something trips or overheats.

Air compressors or refrigeration units can have a problem if power is briefly interrupted then restored. Single phase induction motors don't produce much torque from a standstill. Compressors should have an unloader that releases pressure on output of the pump, and A/C units should wait for refrigerant pressure to bleed off.

I took current measurements for a small window A/C unit. Label specs are 4.1A, 440W, 5000 Btu/h, 11.0 Btu/h W
Scope measurements (says "V" but is really "I" or amps from current probe) show 21.5A peak for < 10 cycles, 1/6 seconds.
After that it drops to 3.14A (and kind of an ugly waveform, not a nice sine wave.)
Compare those peak currents to 4.1A RMS, not 4.1A peak. So compare to 5.8 peak.
Starting current surge is about 4 times label, and running current is about 1/2 of label.

This A/C unit was sitting indoors, not working hard. If it ran a while and was trying to dump heat outside on a 100+ degree day, operating pressures would be higher and it would draw more current.

 

[chrisski]

What made the sine wave so sloppy? Is it not a pure sine wave inverter or does the amperage draw also effect the sine wave?

 

[Hedges]

What made the sine wave so sloppy? Is it not a pure sine wave inverter or does the amperage draw also effect the sine wave?

This was running off the grid. My PV system is separate, feeding grid in parallel with GT inverters.
I think it is just the current draw from the A/C.
The current probe is good for 100A so isn't saturated.
I also captured current from an oil-filled radiator and that was a sine wave.
I would have thought that inductive or motor loads would just draw current out of phase, but apparently not.
No indication this is an inverter drive A/C, just an induction motor.

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[DThames]

One thing that the makers of the AC and heater will never tell you is the start up surge. The AC may say its a 450w but that is after the AC has cooled down the room and is just maintaining it. The real draw will be closer to 1500w when you turn it on and wile it is cooling the room that is the surge. The same with the heater or any appliance that heats or cools. I have a 700w microwave that surges to 1200w when it turn on, I also have a 500w cook top that surges to 1500w. My freezer that is a 100w surges to 1100w when it first starts and cools down. With a surge that is the start up it will then drop after some time closer to what the manufacture claims it runs at.

So it is safe to assume you AC with hit 1500w surge and the heater will hit 1500w, for however long it take to heat or cool the room. So plane on needing a 3000-4000w inverter and it would be better to use a 24v not a 12v for that kind of draw. So 600w will not keep up with all that you need 1200 or better and a battery bank to match.

My new little 6000 BTU AC unit does not appear to have a surge

This was running off the grid. My PV system is separate, feeding grid in parallel with GT inverters.
I think it is just the current draw from the A/C.
The current probe is good for 100A so isn't saturated.
I also captured current from an oil-filled radiator and that was a sine wave.
I would have thought that inductive or motor loads would just draw current out of phase, but apparently not.
No indication this is an inverter drive A/C, just an induction motor.

5,000 BTU Window Air Conditioner - LW5016 | LG USA

Discover the 5,000 BTU Window Air Conditioner that features 5,000 BTU and 150 Sq. Ft of Estimated Cooling Area. Shop LW5016 from LG USA.

www.lg.com

Talking about that waveform, I wonder if there is a "run" capacitor in the circuit. A single phase motor's secondary winding with a capacitor are phase shifted by design.

 

[tazmann]

to give you an idea I have a 5000 btu window unit that I tried to see if it would keep camper cool on hot day direct sun, it wouldn't. anyway had 400 watts flat on roof and 400 watts on ground facing sun, compressor did not cycle stayed on for a few hours , good bright sun (not like now with all the smoke in the sky) Ran about even with the solar output. I don't remember the exact temps that day but it was over 100 degrees . On days like that my 15000 btu roof air keeps the inside around 80-82 degrees but it is drawing 1700 watts

 

[Snubber]

to give you an idea I have a 5000 btu window unit that I tried to see if it would keep camper cool on hot day direct sun, it wouldn't. anyway had 400 watts flat on roof and 400 watts on ground facing sun, compressor did not cycle stayed on for a few hours , good bright sun (not like now with all the smoke in the sky) Ran about even with the solar output. I don't remember the exact temps that day but it was over 100 degrees . On days like that my 15000 btu roof air keeps the inside around 80-82 degrees but it is drawing 1700

 

[Snubber]

Well , 100+ is not uncommon where this is. ?