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kittysmitty
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# Posted: 16 Aug 2024 03:57pm
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Just though I would throw this out there. Remote off grid cabin. Used maybe 3 days a month except deer season. Today my batteries are on float at 10:30 am. I have 1500 watts of panels. So all afternoon, I'm not using/making any power. Any ideas how this extra power could be used? I have internet and are using smart plugs that I can turn off and on remotely. Any thoughts or ideas? Thanks
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Tim_Ohio
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# Posted: 16 Aug 2024 05:10pm
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It's too bad it doesn't have some monetary value. If it did, you could put it away in a fund to help pay for the replacement panel and batteries in the future.
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Brettny
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# Posted: 16 Aug 2024 06:40pm
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Its extra until theres a cloudy day. Lol
If your in a humid environment and your inverter allows you could run a dehumidifier. That's really the only semi lasting thing I could think of that would have a benefit in a day or two when your there next.
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FishHog
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# Posted: 16 Aug 2024 08:47pm
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Portable ice maker and more cold beer or drinks
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ICC
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# Posted: 17 Aug 2024 12:03am
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Why worry about it? Life is simpler with fewer worries.
If an off-grid system is sized to be truly usable without needing to watch every watt while the place is being used, there will be "waste" when it is unoccupied. Just a fact of life as far as I am concerned. Both my cabin and my home "waste" a lot of available solar kWh's a year. It has not been a big deal to me because everything works so well when I want to use power. It did take me a few years to chill out and ignore the "waste".
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ICC
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# Posted: 17 Aug 2024 03:05am
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About 20 years ago many early off gridfers really worried about power waste because panels cost so darn much.
Some tried using extra DC power directly to heat water. Resistance heaters are voltage specific and pv panel voltage wanders all over with sun intensity. So that was hard to do effectively. Heating with AC power through an inverter works better. But then you need a control system to shut off the AC heater when there is no longer DC power to "waste".
Pumping water with a variable DC voltage pump like a Grundfoss solar pump can be useful. Those are not cheap pumps though.
Excess solar power could be used to pump water to a higher elevation storage area; pond or tanks. Then when power is needed it is piped down to a turbine generator. Requires a big investment to make it operational.
I could never come up with much that was simple, or inexpensive as well as being truly useful.
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paulz
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# Posted: 17 Aug 2024 11:33am
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Quoting: ICC voltage pump like a Grundfoss solar pump can be useful. Those are not cheap pumps though.
Hmm, interesting thought Izzy. About the only useful thing I can think of once the bank is full and I’m not here. Right now I have to fill my tank about once a week or two, using a 220v dedicated gas generator feeding the well pump. Problem is it’s 100ft down the hill and another 50 down the well. Be nice to have the tank always topped up with solar power, even just a 1/4” hose, if there were a DC pump that would do that. And worth the trouble…
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travellerw
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# Posted: 17 Aug 2024 05:31pm - Edited by: travellerw
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My plan is to pump water out of a self drilled well into a holding tank. Then use that water to water my lawn and garden on a timer.
Another option.... I can turn my mini-split on and off at anytime. So I can keep the space at a constant temp and reduce wear on inside items from drastic temp swings.
Water heating is another option. Although its still kind of a waste to have just a big tank of water hot when no one is there.
In the winter you could use the extra power to keep you batteries warm. Warm batteries are happy batteries and perform much better.
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gcrank1
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# Posted: 17 Aug 2024 08:55pm
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Imo, it isn't 'wasted' elec any more than the full tilt potential of my home grid power is 'wasted' if Im not using it all.
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Brettny
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# Posted: 18 Aug 2024 11:52am
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Quoting: travellerw Another option.... I can turn my mini-split on and off at anytime. So I can keep the space at a constant temp and reduce wear on inside items from drastic temp swings
Do you have a DC powered mini split? I was seriously considering the DC solar hybrid 12kbtu EG4 unit. This would have it's own pannels so I would basicly set it and let it take care of its self when the sun allowed. Indoor humidity and musty smells can be a problem.
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ICC
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# Posted: 18 Aug 2024 12:48pm
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I have not given this question of what to do with excess solar power once the batteries are full for 15 years or so. The main problem I could not find a solution to is a fail-safe control system. How to turn on the secondary use and turn it off when there no longer was any excess solar. Even allowing for maybe a maximum draw down of , say 5% of the primary battery before shutting off the secondary use.
Solve that without any expenditure that would likely never pay for itself.
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travellerw
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# Posted: 18 Aug 2024 03:14pm - Edited by: travellerw
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Quoting: ICC I have not given this question of what to do with excess solar power once the batteries are full for 15 years or so. The main problem I could not find a solution to is a fail-safe control system. How to turn on the secondary use and turn it off when there no longer was any excess solar. Even allowing for maybe a maximum draw down of , say 5% of the primary battery before shutting off the secondary use. Solve that without any expenditure that would likely never pay for itself.
I built my system with a Victron BMV-700. I'm not including this as an expense since I wouldn't build a system without it.
The BMV-700 has a relay connection that you can trigger with pretty much ANY condition. That relay could be used to trigger just about anything. Of course it can't be used to trigger any heavy loads, but you could use it to trigger another big relay to trigger anything heavy. Zero cost.
The above would be the easiest way to do it. However, another option if you have Victron controllers would be to use an arduino connected to the ve.direct port. Ve.direct is an open protocol that sends data clear text via standard serial connection. It gives ALL details about the controller (solar input, battery level, charge stage (bulk, absorption or float), ect,ect). You could easily use that data to have the arduino trigger anything. The total cost for the arduino and an external relay board might be $20.
This is one of the big reasons I'm such a Victron fan. Everything is open and well documented allowing integration or customization.
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travellerw
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# Posted: 18 Aug 2024 03:29pm
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Quoting: Brettny Do you have a DC powered mini split? I was seriously considering the DC solar hybrid 12kbtu EG4 unit. This would have it's own pannels so I would basicly set it and let it take care of its self when the sun allowed. Indoor humidity and musty smells can be a problem.
No, my mini split is an AC unit that runs off my inverter. I have multiple ways to trigger it to turn on. However since I send all my data to the cloud the easiest is to just use the cloud to control it since the mini-split is also connected to the same cloud. I use Arduino cloud and its pretty flexible. Right now I'm just manually controlling it, but it would be super easy to put a condition in like.
- Turn on once battery is %100. Continue to run until battery is 95% SOC or 2 hours before sundown
P.S. my mini-split is one of the Chinese units that is basically an unbranded Midea. It uses all the same control sequences as the Midea and is well documented in the maker community.
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paulz
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# Posted: 18 Aug 2024 03:53pm
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Did a brief bit off researching my solar water pump pipe dream I mentioned earlier. Turns out there are many solar powered well pumps on the market, I guess many live stock troughs are filled that way.
Also some of these setups don’t require batteries, in fact maybe not even a controller! I know nothing about this, but the pump motors must be brushless not to burn up under marginal power.
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ICC
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# Posted: 18 Aug 2024 04:39pm - Edited by: ICC
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@travellerw... For many years, decades I have "tinkered" with electronics including Raspberry Pi and Arduino and other things lost to the more distant past. My issue with the "home grown" sort of thing is that the vast majority of people around me get a glazed over look if they have deal with many of my "toys".
In recent years my realization that I am 12 years past my life expectancy in the year I was born. I've been trying to make what I leave behind uncomplicated if I can. Okay, that is just my attitude. Not applicable to everyone. I still have lots of doo-dads I designed, modified, repurposes, but I know some are destined for the trash if they develop problems or nedd a reprogramming.
However, I do find it interesting to know that there are advances that I have not followed and it would be easier today to automate some use of excess solar. But I am more "chill" about not actually using available excess as I was at one time. Maybe I'll live longer if I don't sweat all the small stuff like I used to. 
@paulz. The solar powered pumps that could lift the water the 150 feet you mentioned likely cost more than you and many others would find economical. I'm not saying the idea is bad, it does work. The ranch has three solar pumps. Requiring a pump depth of 400 feet made them pricey, but the cattle needed the water.
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paulz
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# Posted: 18 Aug 2024 06:52pm
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This one says 230ft lift. Don’t see about battery or controller but that I can deal with.
Starting to sound like a maybe. If my dedicated well shack 220v genny or well pump die might be an option.
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gcrank1
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# Posted: 18 Aug 2024 07:43pm
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I was slow on the uptake.....
EXTRA power, we should all be SO lucky! lol
Iz, just the other day my wife said," I need to know how 'your' electric system works". Guess when my heart stopped last Jan got her athinkin. Fortunately for me I have it about as simple and basic as can be; still, a short document/diagram would be invaluable for her or anyone she would call upon.
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travellerw
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# Posted: 18 Aug 2024 09:48pm
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Quoting: ICC In recent years my realization that I am 12 years past my life expectancy in the year I was born. I've been trying to make what I leave behind uncomplicated if I can. Okay, that is just my attitude. Not applicable to everyone. I still have lots of doo-dads I designed, modified, repurposes, but I know some are destined for the trash if they develop problems or nedd a reprogramming.
That is what makes the BMV solution so good. There is no programming or extra doo dads. Its completely built into the Victron device with good documentation.
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