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Gone2TheCamp
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# Posted: 13 Nov 2018 10:28am
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So, I'm most of the way through building a 12x16 cabin. It will never have power, so I didn't really build electrical into it, but I did give it a lot of thought before building because the cabin started out as a small camper so I have an idea what I will and won't need for power as I've been going there for around 10 years.
My plan is:
All lighting will be 12v LED. All there will be is a ceiling fixture at each end with a pull-string, and a 3rd outside by the door.
As far as AC power needs, it will just be a small TV and a laptop, so I'm fine with just running an extension cord behind the couch or whatever...it's 12x16 afterall.
So...I have access to pretty much as many of those 12v AGM 7.2ah batteries as I want. They're changed out of UPS-type gear at preset intervals so I'd have no problem collecting a bunch of them.
They're not ideal, but they're free.
I have a small generator that I can fire up now and then to run the TV or laptop, and it has a 12v 8a battery charging port. So...I'm thinking I can use that to charge the battery bank while it's running to power the laptop/TV.
Grey area: I am waffling about running the lights on 12v, and the tv/laptop on the generator VERSUS running my 1500w invertor off the battery bank, and running the TV/laptop and the lights on AC.
It's not a big, complicated setup, but I have the batteries, a 1500w inverter, several 500w inverters, and the 1300w generator...so I have options, and I'd love input from those in the know so I can do it the best way right out of the gate.
So:
Lights on 12v and run the genny to power the TV and charge up the batteries?
Lights and TV on 1500w inverter and fire up the genny to charge the batteries when needed?
I figure I'll use WAY more power using the 12v bank to power an inverter to power AC lights as opposed to just running LED 12v bulbs....
It WOULD be nice to have the inverter and run the laptop to watch a movie in the evening without having to go outside and start the generator.
I dunno...toss me your ideas...
And when I say battery bank...I'm thinking likely six, eight, to, twelve...of the 7.2ah batteries. Again, I know they're likely the worst choice for something like this, but...free. How many of these would be needed to run a 1500w inverter for a few hours?
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darz5150
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# Posted: 13 Nov 2018 11:20am
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They have 12 volt TV/DVD combos. If you charge your laptop and top off your batteries when its convenient with the Genny. Then you can go straight off the batteries in the evening.
There are 12 volt ceiling fans available also.
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Gone2TheCamp
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# Posted: 13 Nov 2018 11:54am
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I don't think I'll need a ceiling fan....but maybe a small computer fan to push some air along the walls to help with moisture.
I usually bring the laptop when I'm alone...staring into the campfire is fun, but often it's nice to just sit inside and watch a movie or something in the evening after it's dark.
I might just experiment with the balance of batteries/inverter/genny, and see what works. I'm not smart enough to do the math...maybe 10 of those batteries would run the lights and AC requirements for 2 weekends before needing a charge. Possibly get a solar panel, let it top them up over the week, and then use them on the weekends....
Really not sure...
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jhp
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# Posted: 13 Nov 2018 11:58am - Edited by: jhp
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I think for starters, you'll want to get an idea of how much power your current inverter, TV, and laptop is consuming when they're all running, it might be more than you think. You might be able to figure this out if the power consumption is printed on the devices, or else you'll need to get something like a kill-a-watt meter to see for yourself what they draw.
A small investment in a latest-generation LED TV might cut the energy usage by 75% or more, just depends on what you have now. I think the 1500 watt inverter is overkill - again you can probably save a lot of power draw simply by getting a properly sized inverter. If you're only using up 100 watts, a 300-ish watt inverter might save you a lot of idle draw power. My 300 watt inverter draws about 5 watts at idle...I've seen much larger ones in the 1000 to 1500 watt draw nearly 50 watts without any load on them at all.
While free is great, I think you'll need a lot of the 7.4 AH batteries to make up a sufficient bank to get you through. 10 of those batteries in parallel would give you 74ah of reserve. At 12 volts that's 888 watt-hours of bank (12volts x 74ah.)
Keeping in mind you only want to draw them down to a max of 50% discharge that's 444 watt-hours. We'd need to know the power consumption of your TV, laptop, and inverter to figure out how long that is in hours.
My cabin setup and electrical needs are very similar to yours.
I run two 12 volt LED lights (7 watts each) and 99% of the time only use one as it lights up plenty of space for me. I mounted a 5" 100cfm 12 volt accessory fan in the ceiling to help move the air around, which is another 10 watts.
I like to watch a movie or two at night. My 300 watt inverter, 26" LED TV, and raspberry pi media player only draw about 40 watts when running.
So with everything running thats 64 watts consumed per hour. I have a single 100ah 12 volt battery that gives me 1200 watt hours total, or 600 watt hours at 50% discharge.
Figuring I only run the fan and lights intermittently my total power draw is about 60 watts per hour, or I can get about 10 total hours before I need to recharge the battery.
Most days I don't even use that much power so a single charge might last me two or three days. I pair this with an admittedly cheap and undersized 100 watt solar panel kit. It's always charged up when I get there and I have enough power to last me through a long weekend, more if it's anything sunnier than overcast or raining.
I'd say you're on the right track with the batteries, your load probably isn't enough to warrant running it all on AC off the inverter and generator.
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Gone2TheCamp
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# Posted: 13 Nov 2018 12:43pm
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Awesome...thanks!
With the TV, what I was actually thinking was use the 19" cheap-o LCD that the kids got me for Christmas the other year, and recycle my old playstation 3 as a time-killer and a movie player (via a usb-powered external hard drive).
Or, skip the TV and PS3 and just stick with the laptop.
I never measured but I picked up 11 or 12 500w inverters when Home Depot was selling them for $9 or something...one of those will run the laptop, but not the laptop and a light bulb. Now, that may also have been due to the too-small wires I was using between it and the car (20' away). Yeah...voltage drop..
I just found where Canadian tire has 60% off a Nova 100w kit..panel, wiring, controller... What you're describing is pretty much what I'm after; have the panel keep the batteries charged up during the week, run 2-3 low-draw light bulbs for 2 evenings, and that's about it.
I'm thinking too, that the best plan would be to just run the lights off the batteries, and then cross the laptop/TV bridge when I get to it. Also, to watch one movie, the laptop battery alone might be plenty...I just have this habit of always plugging in anything rechargeable if there's a way to plug it in...why run down a battery and get caught dead when you can keep it charged instead...? (Yes, memory, etc etc...haha)
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jhp
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# Posted: 13 Nov 2018 01:05pm
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For some other entertainment, I would recommend getting a cheap boombox that can run off of eight C-size batteries (12 volts) that you can also wire directly to the 12 volt battery. I have one that has AM/FM/CD/BlueTooth that was about $30 that draws about 5 watts. Mine pretty much runs from morning to night "for free" as the solar is usually charging well more than that.
The laptop could go either way - check out the power rating on the charger for an idea of what it takes to recharge the battery and figure it that way.
While you wouldn't think it would use that much, i know that Playstation type consoles can burn as much as 150-200 watts an hour. No problem for a grid or generator based system but pretty power hungry for battery/solar only.
If you can invest a little you can replace the PS3 with a Raspberry Pi or Roku type device paired with your USB hard drive and save a whole lot of power. Lot of options there for a media player from $30 to $100.
I think you'd probably be happy with your batteries and either a generator to boost them during the day or a cheap solar kit like I have. You just have to keep your power usage and overall expectations in line. You'll never run AC or a fridge or anything like that but if you get a little creative you can have some creature comforts for relatively little investment.
Check out a kill-a-watt meter or the knockoffs on Amazon, they're all under $25. That will really help you figure out your true power consumption and what will work for you.
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hamish
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# Posted: 13 Nov 2018 03:25pm
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At my camp I run 3 120V LED lights, 22" LCD, DVD player, radio and cordless tool battery charger all off an old Motomaster 175W inverter with no issues at all.
Battery power is from a 80AH deep cycle battery that usually stays fully charged from 160W of solar. Over this past deer season with 9 days at the camp i had to use the generator once for one hour to charge the battery on a bad solar day.
You dont need much!
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rayyy
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# Posted: 13 Nov 2018 05:13pm
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I gave up on the idea of running a 120 volt ac inverter off my 12 volt dc deep cycle batteries.I'd get an hour or two of running the TV but then the inverter would go into low voltage alarm.Instead,I use my eu2000i honda generator for all my 120 ac needs.I have all my light fixtures set up on the batteries using 12 volt dc LED light bulbs with E27 base.I also have several 12 volt dc cigarette lighter outlets wired up for use with my cell phone and tablet charging,12 volt fan and water pump and the controls on my propane refrigerator.I live off grid just as comfortable as anybody on the grid.
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rayyy
Member
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# Posted: 13 Nov 2018 05:17pm
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I gave up on the idea of running a 120 volt ac inverter off my 12 volt dc deep cycle batteries.I'd get an hour or two of running the TV but then the inverter would go into low voltage alarm.Instead,I use my eu2000i honda generator for all my 120 ac needs.I have all my light fixtures set up on the batteries using 12 volt dc LED light bulbs with E27 base.I also have several 12 volt dc cigarette lighter outlets wired up for use with my cell phone and tablet charging,12 volt fan and water pump and the controls on my propane refrigerator.I live off grid just as comfortable as anybody on the grid.
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darz5150
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# Posted: 13 Nov 2018 08:34pm - Edited by: darz5150
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Question. Any recommendations on the e27 base 12 volt bulbs. I just got a pair from amazon. Nice color/ brightness. But haven't had them long enough to know how long they will last.
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Gone2TheCamp
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# Posted: 14 Nov 2018 08:35am
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Funny. While figuring this lighting stuff out in my head, I went and read about what the bulb types and everything were.
Now, you both say you have E27 bulbs and bases, but the info I found says that E26 was North America and the E27 were used in Europe.
only 1mm difference, but they also said that the E27's likely wouldn't have the proper ratings or certifications for use in North America. If you're fine with that, so am I...but if something stupid were to happen, insurance found a way to deny a claim, etc etc... Just thought I'd mention it.
From EarthLED:
+++++++++++++++++++++++++++++++
The number following the E indicates the size in mm of the external thread screw. Thus a E26 has a 26 mm base diameter.
You may see low cost LED bulbs using an E27 base on eBay and Amazon from foreign suppliers. While these technically will work in E26 bases, this is usually a sure indication that the bulb was not strictly designed for the US market and this bulb may lack a proper North American, UL or ETL safety certification and therefore should be avoided.
++++++++++++++++++++++++++++++++
I'm curious if you guys went E27 on purpose, and if so, why? Or maybe you're across the pond....
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darz5150
Member
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# Posted: 14 Nov 2018 09:49am
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Actually the ones I got are e 26. But will fit standard fixtures.
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Gone2TheCamp
Member
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# Posted: 16 Nov 2018 08:54am
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Small update, I'm up to 12 of those 12v 7.2ah batteries now. They're taken out of gear we have that needs a battery backup, so most of them are about 1 year old, and have never actually been used, just sitting there on a 'maintainer'.
I have nothing to test them properly with, but they all power up a 500w inverter running a 100w light bulb. And, my home battery charger maintainer usually will charge a while and then say "Nope, this one's pooched." when I try to charge something that's toast. They all sat on the charger/maintainer for 2-3 hours, then it indicated green.
So, with that limited testing, I'm going with them all being good.
I also have to replace the battery in my car...last winter I had to charge it a couple times during 2 long cold snaps...but it's fine the rest of the year. So I'll add that battery to the 'array'.
It's not like I'm 500 miles from anywhere and will die if this plan fails, so I'll likely just hook everything up and see how it works and how it can be improved.
For paralleling these 12 batteries (they're 12v, the system will be 12v, etc) ...Any advantage to wiring them into 4 groups of 3, or 6 groups of 2, etc...? Or just run all the +'s and -'s to a common point? Obviously, there will be fuses as close to the +'s as possible, etc etc.
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creeky
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# Posted: 16 Nov 2018 12:23pm
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Running lead in parallel is a bad idea for someone who will die if his power goes out.
But for playing around and having some solar fun. Meh.
You might consider trying series connections for higher voltage.
The advantages of higher voltage are
* smaller wire (lower BOS cost)
* more solar on your solar controller = lower solar controller cost
* up to 6% more efficient inverter
* easier to "grow" the system (lower cost)
catch a theme here. more for less.
I would go 24 or 48v. I spent 5 years at 12v. Had no problems after I bought a decent inverter (sigh. miss that sweet tbs). But 48v brought be higher efficiency, easier install and lithium batteries. Huzzah.
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