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Old 02-10-2019, 11:59 AM   #43
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Running on batteries

This is an interesting thread to me because I'm doing the extreme end of what is feasible for battery-only power. The victim in this case is my 1978 GMC motorhome but I intend to do a slightly scaled down conversion to my 33' Airstream race car hauler (long story). I've installed 1860 watts of solar panels on the relatively small roof of the GMC, and I'm building a 18.4KWH Lithium battery for it using a chevy volt battery from a wreck. Not a project that anyone who isn't a little nuts would undertake, but it does demonstrate what is currently feasible and not all that expensive--ignoring a few thousand hours of labor. With the 4KW inverter I'm using I can run my Coleman Mach 15 AC unit with or without the easy start I added. Of course I'll run it with the easy start, but it's good to know I can. The motorhomehas a 5KW generator that I have no plans to remove, but I don't expect to need it often.

For my Airstream, I indend to add 620 watts of solar, 4KWH of battery and the 2500 watt inverter and charger that came out of my Moho. That suits the intended use well. The Airstream generator is two 2000 watt Yamaha inverter generators with a coupling cord to yeild 4K watts. This runs the AC unit nicely if loudly. The 2500 watt inverter is not enough for the AC even with a soft start.
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Old 02-10-2019, 01:00 PM   #44
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For a answer to all electrical / solar questions .
Gather the spec.s of what ever your working with --- and learn Ohms Law http://www.ohmslawcalculator.com/ohms-law-wheel
Then just do the math , its simple really .
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Old 02-10-2019, 01:50 PM   #45
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Originally Posted by JohnTF View Post
For a answer to all electrical / solar questions .
Gather the spec.s of what ever your working with --- and learn Ohms Law http://www.ohmslawcalculator.com/ohms-law-wheel
Then just do the math , its simple really .
Except that there's always Murphy's Law which can and will apply on it's own whim and accord. - Brad
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Old 02-10-2019, 04:01 PM   #46
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Lewster is the man

Lewster did our first-class job while we took a cruise to Cozumel. Kind of fun running the ac for short periods off the batteries. All my ac outlets can be live off the inverter just by selecting to do so. Bluetooth monitoring keeps you informed

He does great work and thinks of things do do right long before you can imagine them.

Note that an inexpensive cruise is likely cheaper than lodging and dining in Naples!

Pat
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Old 02-11-2019, 02:56 AM   #47
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Originally Posted by JohnTF View Post
For a answer to all electrical / solar questions .
Gather the spec.s of what ever your working with --- and learn Ohms Law http://www.ohmslawcalculator.com/ohms-law-wheel
Then just do the math , its simple really .

Sorry, but that's not true. Ohm law won't tell you much about AC reactive loads. It's also not useful for understanding how much load you can connect to a solar controller, what size wire to use, how to make reliable high-current connections, or how much of an overload equipment can manage, how far you can discharge a battery without shortening it's life, and how quickly and fully you should charge them. There's a lot more to know than simply calculating volts, amps, watts and resistance.
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Old 02-11-2019, 09:36 AM   #48
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OK , leave out the world " all " , but it is the most basic way for answering the question .
Ohms Law is not the only electrical law , but again it is , it is the first electrical law to answer the question the post asks .

Ponobill , at least your response indicates some knowledge , so is mostly just argumentative , with the knowledge your reply indicates , you should be able to perceive the point of my reply - add up the wanted power to be used with the power that is needed to be produced .
My point being , that with some basic knowledge , in this case Ohms Law & look at the spec.s , anyone / most anyone can get well underway to knowing what can & can not be done .

SuperTrooper , That is argumentative & [ well I was going to say just plain ignorant { but there is no technical statements what-so-ever } Murphy's Law is not any kind of technical law , it is a joke about common occurrences ] so is only argumentative .
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Old 02-11-2019, 10:34 PM   #49
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Micro-Air

We can now run our 15k roof air with one Honda 2000. This is after installing our Micro-Air Easy Start.

Works wonderful with the generator or hooked to an electrical service. Also provides start up protection if it detects something wrong on the electric supply voltage.

Another benefit is duty cycle soft start no huge amperage draw and less strain on the compressor. The bang on Bang off is eliminated. Lotís of information on line and with Youtube.
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Old 02-12-2019, 01:12 AM   #50
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I don't intend to be argumentative, it's simply that there's a lot more to consider in sizing batteries, panels, controllers and inverters. Here's an example from an article I wrote in my blog. A typical Coleman Mach8 heat pump draws 16 amps at 115VAC, or 1840 watts. Ignoring small inverter efficiency losses that means 76 amps at 24VDC. Starting current is around 60 amps at 115V, so 6900 watts or 290 amps at 24VDC.



You can encounter similar differences in starting current for any AC reactive load.



Here's a link to the article: https://www.ponostyle.com/solar-power-for-rvs/ There's also an article about wire size there. I haven't gotten around to writing more.
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Old 02-12-2019, 07:45 AM   #51
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In our 2015 23D International Serenity, we have the hybrid Magnum MSH3012 inverter charger so it will provide the surge power necessary from our 300 amp hour lithium battery to start out stock 13.5K BTU air conditioner using a Honda 2000 generator. There are also five 100 watt solar panels on the roof to help keep the battery charged when the sun is out. All the 120Vac outlets can be powered using the battery.
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Old 02-12-2019, 09:05 AM   #52
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Just to be clear, for models with two AC units, the requirement for running the AC without shore power is that you turn one off with the thermostat before starting the 2nd one?
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Old 02-12-2019, 09:49 AM   #53
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2 AC RVs are equipped / wired for 50amp. When not on shore power what is the power source? 50 amp is 2 times 50 or 12,000 watts, all at 120vAC; where 30 amps is 3600 watts max. 30 isn’t enough for 2 ACs running simultaneously.
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Old 02-12-2019, 02:07 PM   #54
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Specifically, I just want to make sure that running one AC at a time is simple and clear with the factory thermostat, rather than requiring special relays or alternate circuits to be able to power only one AC unit through the inverter.
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Old 02-12-2019, 03:36 PM   #55
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Specifically, I just want to make sure that running one AC at a time is simple and clear with the factory thermostat, rather than requiring special relays or alternate circuits to be able to power only one AC unit through the inverter.


It is simple and clean. You simply use the CCC2 interface to turn off the secondary air con. Do it all the time.

BTW - most people run a split panel - and only one side is powered by the 50A inverter circuit. In other words when not on shore power the other side of the panel never sees power - so you couldnít run the second AC even if you tried.
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Old 02-12-2019, 04:30 PM   #56
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It is simple and clean. You simply use the CCC2 interface to turn off the secondary air con. Do it all the time.

BTW - most people run a split panel - and only one side is powered by the 50A inverter circuit. In other words when not on shore power the other side of the panel never sees power - so you couldn’t run the second AC even if you tried.
Ah! So each AC unit is powered by one pole (are they still called "poles" in this situation)? That makes sense.

I did see one blog post that covered an upgrade like this, and they also split the breaker box. Other than for safety, though, I am not sure what appliances I'd want to limit to shore-only power. It seems as long as you were a little deliberate with consumption (i.e. turn off the AC when trying to run a clothes dryer or something), you wouldnt need to build in this limitation, no?

Hrmm. I suppose a single-throw, double-pole relay could be used to guarantee that inverter power could only go to one side of the pole or the other. That way one could split up big-draw items to help guarantee you wont draw too much for the inverter to handle. Kinda spit-balling, of course.
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