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Small Cabin Forum / Off-Grid Living / ac vs dc
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vidaliaman
Member
# Posted: 3 Oct 2014 10:23
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please educate me on the difference, what applications work better for ac and what applications work better for dc, please be as simple a possible, lol, i'm a green horn. i have read some post that say just keep it simple for just lights so use dc, help!!!

dave

MtnDon
Member
# Posted: 3 Oct 2014 10:40
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I believe the starting point is to determine/list what electric devices you want to run.

IMO, a few small lights in a small cabin work great on a DC system, especially if the lights are LED. A refrigerator designed for DC with a Danfoss compressor works well. Most other stuff; TV's, toaster, blender, internet, etc work best/easier on AC. Low cost modern higher efficiency household refrigerators work well on AC, but that should be pure sine wave AC.

vidaliaman
Member
# Posted: 3 Oct 2014 10:53
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so you would agree to run 4 or 5 LED lights in a 12 X 16 cabin close to a stream powered by a waterwheel and a battery bank it would be best and easiest to use DC?

Ruggles
Member
# Posted: 3 Oct 2014 11:02
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I have a 12X16 in colorado and run 12 volt dc. My "neighbors" on either side run 24 volt dc and 110 volt ac respectively. They both live up there year round while mine is a weekend cabin. 12 volt DC is the simplest and you can get almost anything short of air conditioning these days. I run 4 gel batteries charged from solar and do up to 5 lights, water pump, ceiling fan and various charging points for tools and phones etc. MtnDon is right though, it depends on what you want to run in your cabin. I don't use an inverter for anything but then again, I use an ice chest for refrigeration.

vidaliaman
Member
# Posted: 3 Oct 2014 13:42
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what you have ruggles is what i am looking for, tell be more about your gel batteries(brand and where to get them). i am looking to wire in 5 lights to start with 2 outlets, what do you run from your 4 gel batteries to the wiring at the cabin? and how do you connect to the cabin wiring? and lastly could a water wheel turning a low(200) rpm generator keep the 4 gel batteries charged for 3 day weekend?

cool stuff

bldginsp
Member
# Posted: 3 Oct 2014 13:51
Reply 


The advantage to running DC only is that you don't need to get an inverter, and you will use power more efficiently without one. The disadvantage to DC is that there are fewer appliances that run on DC, and some are expensive. DC lights are readily available and not expensive. DC hair dryers, radios, etc. are hard to find if at all.

If you run DC make sure all your wiring is done safely with proper DC circuit breakers etc.Reemember that at a lower voltage your appliances will use more amps, so be careful not to overload your wires. If you don't understand this, find someone who does to design a small, safe system for you.

Good luck!

vidaliaman
Member
# Posted: 3 Oct 2014 14:02
Reply 


should there be anything between the power source and the batteries?

Ruggles
Member
# Posted: 3 Oct 2014 14:05
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So my batteries are used from the UPS system of my company that I get for a bargain (recycler) price. Any good set of deep cycle batteries will work I think. I use a simple set of 3 15 watt solar panels (Harbor Freight) to recharge my batteries but I've never run out of juice on a 3-4 day weekend and then the batteries are charged the next time I show up, so I'm thinking as long as your water wheel system is charging, you're probably good although perhaps not optimum. I just use 12 guage wire from my battery bank (short runs) into a generic automobile fuse box and have 3 15 amps and one 30 amp fuse setup. I try to separate lights, pumps, outlets between the fuses. I've been building motorycycles since the late 60s so I just went at it like a bike, and it seems to work fine. Cheers.

MtnDon
Member
# Posted: 3 Oct 2014 14:54 - Edited by: MtnDon
Reply 


Quoting: vidaliaman
so you would agree to run 4 or 5 LED lights in a 12 X 16 cabin close to a stream powered by a waterwheel and a battery bank it would be best and easiest to use DC?


I would agree that if the electrical needs were limited to some 12 volt LED lights, then a 12 VDC battery system would work.

I would only agree on the water wheel power source if that was proven to be able to provide sufficient power to recharge the battery(s) quickly. Quickly as in the battery would never be below 100% charge for more than a day. That is because lead acid technology is not perfect and one of the deficiencies is they begin to sulfate if left discharged for days at a time. Of course the water generator has the advantage of being 24/7 whereas solar is 4 to 6 hours a day.

IMO, gel batteries are not the best choice. If they are free or nearly free that's one thing. If you pay $$ for batteries in a simple system good old FLA, flooded lead acid are hard to beat. Next best on the list would be AGM batteries. Disadvantage there is the price and the fact they are sealed. Sealed means you rely on voltage alone as the sp gr can not be measured.

bldginsp
Member
# Posted: 3 Oct 2014 15:40
Reply 


Vidalia- there needs to be a charge controller between the power source and the batteries, except for some small systems with only a few solar panels. The batteries must have the charge controlled or they will be damaged.

Don_P
Member
# Posted: 3 Oct 2014 16:52 - Edited by: Don_P
Reply 


You've mentioned creek and waterwheel several times... to get that part of the thought process moving, quantify a couple of things, how much flow does the creek have at low water, measure it in gallons per minute or cubic feet per second. What is the head, the drop, available.. or to put it another way, what is the diameter of the wheel? At one point you mentioned bicycle wheel.. they make small bicycle wheel generators, or used to.

vidaliaman
Member
# Posted: 4 Oct 2014 13:14 - Edited by: vidaliaman
Reply 


this water system is a culvert that empties out a pond, the water moves through it at white water speed which is constant year around, winter will not work because the northern michigan winters are so cold the wheel will gather ice, still this does not tell you all much so my experiment will be what rpms i can generate from this water source, wheel size vs pulley size. the lessons motor above, how many rpms is necessary for it to charge my battery bank efficiency? would i need 1800 rpms? what low rpm generator would you all endorse? even if i only can keep 4 LED lights going it would be a great learning experiment for me to gain more knowledge to improve off grid power down the road, thanks, all feedback is greatly appreciated.

one other thing, i wonder if one of those bicycle generators could charge one 12v battery because you could run 3 or 4 bicycle generators on one wheel

groingo
Member
# Posted: 4 Oct 2014 13:42 - Edited by: groingo
Reply 


How far is the culvert from your cabin... .need to account power drop over distance.
Also, check into sizing of your water wheel versus flow to get foot pounds of torque required to turn yourgenerator (torque is your best friend) basically the larger the wheel the better (more moving mass equals more torque potential) which will allow you more flexibility in pulley size to get the most generator r.p.m. for the least effort.

Bottom line, common sense and have fun doing it!

vidaliaman
Member
# Posted: 4 Oct 2014 14:08
Reply 


plan on building cabin right next to the stream, sill working on wheel idea may not use bicycle wheel, may build my own wheel. funny, i can build a cabin from scratch, wire a house from the electrical box through out and plumbing no prob, however i am ignorant when it comes to watts and amps and anything regarding alternative energy sources, however i am learning fast thanks to you all and this site

thanks again

Ruggles
Member
# Posted: 4 Oct 2014 17:32
Reply 


"...winter will not work because the northern michigan winters are so cold the wheel will gather ice..."
I grew up around Otsego and Ogemaw counties. Been in Colorado since the 80s. I ain't comin' back. hahahaha

vidaliaman
Member
# Posted: 4 Oct 2014 17:56
Reply 


ya i don't dare spend too much time out west i'd never come back either

ILFE
Member
# Posted: 5 Oct 2014 02:51
Reply 


Not sure if this will help you, vidaliaman. But, they are links I found a while back.

Link #1 - Determining Potential Power
Link #2 - Weir Gate

toyota_mdt_tech
Member
# Posted: 5 Oct 2014 21:13
Reply 


If it was me, I'd wire it fully for AC (typical) and then add 12V in areas where I might want all battery lights/accessories. In other words, a 12V supplemental system, but you could use it exclusively etc.

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