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Old 04-26-2017, 03:55 PM   #1
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Solar/Inverter/Generator Help

Hey everyone.We are about to hit the wiring stage and we could use some help. We are looking for a system that runs off of solar and batteries, but also would like to have a backup generator that auto kicks on when needed. We are thinking about using an AC so this is where the generator comes into play.

We are looking at an 800w solar array which will give us a 5% overhead without the AC obviously. Renogy has some nice inverters with generator connections but do they auto switch the generator on?

Is there a way to wire the AC directly to a generator so that it auto start when it senses we hit the power button?

Thank you
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Old 04-26-2017, 04:11 PM   #2
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Most RVs simply have a remote control panel for the generator so you don't have to go outside to start your geny. A lot of automatic stuff can cause a lot of problems.
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Old 04-26-2017, 04:12 PM   #3
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A panel is fine if we were there to work it but with pets we can't leave them without some sort of auto situation. I was thinking all the windows open would be ok but in days like today they aren't helping because there's no breeze at all.
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Old 04-26-2017, 09:54 PM   #4
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Is it a push button start? Even if it's a key you could bypass it with a start/stop switch.
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Old 04-26-2017, 11:22 PM   #5
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I'm sure you can do that. It's common technology because there are lots of industrial compressors that start all by themselves. It could just as easily be actuated by a thermostat.
I just don't trust tech that much.
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Old 04-27-2017, 06:24 AM   #6
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I'm not sure about your question but you might look into something like the Magnum Energy ME-AGS-S Auto Generator Start. It is very configurable and includes the ability to start the generator based on voltage or temperature (and more).
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Old 04-27-2017, 08:20 AM   #7
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Some of the inverter/chargers out there also have a genset start signal you can connect to the generator.

See:
https://www.amazon.com/Power-PICOGLF...TQ8KNBR44KPXHD
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Old 04-27-2017, 08:24 AM   #8
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800 watts! Sweeet! I have 500 watts and four golf cart size batts and when the sun shines I can run a small Wally World AC for hours with little drain. I would think 800 watts and six batteries would give you ample overhead to run 8k BTU AC if you were modestly frugal. I can plug in when I have access and plan to charge from engine alternator on cloudy days while driving. No generator here. I have a short (6 window) bus. If I had the real estate I'd put another 250 watt panel up top.

Best of luck!

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Old 04-27-2017, 09:22 AM   #9
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Quote:
Originally Posted by Sasquatters View Post
A panel is fine if we were there to work it but with pets we can't leave them without some sort of auto situation. I was thinking all the windows open would be ok but in days like today they aren't helping because there's no breeze at all.
Have you looked at these? Maxxair - MAXXFAN Deluxe All-In-One RV Vent, Shield & Fan | Airxcel

It wouldn't replace your AC but on days like yesterday when you just need to get air moving it should work. The higher end model 7500k has a thermostat that can be set at a certain temp and then it will automaticly open the rain shield and turn the fan on.
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Old 04-27-2017, 11:20 AM   #10
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Rossfree,
You say you have 500W of PV panels and four golfcart batteries. If my calculations are correct, this means you're charging them at only about a 6 or 7 percent rate. You may want to get some more panels to ensure your batteries are not deficit-charged (i.e. not fully charged each day). If you charge batteries to only 95% each day, after a while they will be seriously under-charged with the attendant risk of plate sulfation, FLA batteries such as golfcart can be charged at between 5 and 13 percent rate, and I would recommend trying to achieve the higher end of that range simply because most bus and RV roofs are not configured as well as a typical home PV installation. FYI I have a tad over 2kW of panels to charge eight golfcart batteries, and they will do so at about 13% charge rate, just where I want it.

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Old 04-27-2017, 08:17 PM   #11
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Hi John

Not to hijack the thread but can you point me to your information source? I have had no trouble charging my batteries daily. I never discharge them more than about 30% between charges and I programmed my MPPT controller to charge at a higher voltage and current for a preset time before dropping to a maintenance charge. I haven't messed with the numbers in a while so I can't give specifics. But it has been working awesome! Haven't plugged in to shore power but a couple of times in the past year. Been plugging in power tools, using the AC, vacuum cleaner and a freezer modded to work as a fridge. I use a high end battery monitor to keep track of current in and current out. I water the batteries monthly and they usually take several cups of water to fill... another indication they are receiving a good charge.

Anyway... happy guy. Hope to be on the road in five weeks. Year and a half into the conversion.

Regards!

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Old 04-27-2017, 11:57 PM   #12
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500W of panels charges 450aH of 12V batteries at about a 6% charge rate. That's uncomfortably close to the minimum recommended 5% rate to keep your FLA batteries alive. The solar experts on the NAWS forum, especially Bill ("BB"), use the following calculation to determine optimum charge rates: Garage solar system size requirements? €” northernarizona-windandsun (Don't forget the 0.77 derating for typical PV and CC inefficiencies.) If you are seemingly charging your batteries OK with your present PV array, you should check each battery's electrolyte specific gravity with a trustworthy hydrometer after a full charge: it should be between 1.260 and 1.265 at about 75 to 80 degrees F battery temperature. I would not want to see you inadvertently kill your batteries after a year or two because of gradual deficit charging.

Just be aware that aH in/out SOC monitors can accumulate significant errors over time, so don't assume they are always accurate! SmartGauge has some interesting things to say about this subject.

Because PV is still cheap, usually well less than a dollar a watt for grid-tie panels, you could buy several hundred more watts of PV to ensure full charging even under less than ideal conditions. More is good!

John
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Old 04-30-2017, 06:47 PM   #13
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Thanks for the replies everyone. We don't want to install a fan because of having to cut a hole in the roof. Scary. That inverter looks good. Our friend went with a Renogy one. How does that work? Does it kick on when it senses that the batteries are at a certain percentage?
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Old 04-30-2017, 09:39 PM   #14
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Thanks for your input John. I read through your link. Not convinced that C-rates are as important as some think. We'll see. I have no doubt that I am reaching full charge daily. I have multiple indicators including a pure sine inverter that shuts down when the battery voltage reaches 15 volts. Annoying really.

Like I mentioned before, my charge controller allows me to set voltages and times to charge my bank. I lean to the side of overcharging and have a set schedule to water the batteries monthly. With 48 volt panels in parallel I am charging from dawn to dusk. On a nice day my batteries are at full charge from 15% drain by 11am.

I appreciate your input. If I had the real estate I would definitely put a third panel up but alas with my fan there isn't room. I would enjoy the overhead though.

I will test with a hydrometer as you suggested. Never done that. Nice to get a base line.

Anyway time will tell.

Thanks again!

Ross
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Old 04-30-2017, 09:48 PM   #15
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Hi Sasquat!

Go for the hole. The fan is a must have anyway. You will want to air out the bus from time to time. You can seal it up just fine. There is a goop you can purchase on Amazon that takes a while to cure. It oozes into all the cracks and crevices and seals things up nice.

I am a fan of MPPT and high voltage (36 - 48v) panels. Get one you can program your own settings. You will likely want to do that in the future. They come preprogrammed and seem to lean to the side of caution not knowing what you might connect it to.

Best of luck!

Ross
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Old 04-30-2017, 09:49 PM   #16
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We aren't covering or removing any windows so there will be plenty of air flow.
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Old 05-01-2017, 06:45 AM   #17
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Just how I felt!

I have a six window bus. Only two windows blocked... the shower and fridge. Love it!

Happy trails!

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