Help with Off Grid Situation

[BobCobb]

I just build an off the grid cabin and am currently using a Honda EU2000i to run it while I put together the funds to have a solar system installed.

I bought the Honda and the Honda Companion unit but found that using only one Honda will run my entire cabin (lights, fridge, freezer, tvs and computers, etc.) with no problems at all using some basic energy management. We generally run it from 10 to 15 hours a day (shutting them down at night while we sleep) and the only time I really hear it wind up is for a split second when the freezer or fridge kicks on or when we use the microwave.

What I would like to do is add a couple of batteries into the mix hoping that the 10-15 hours a day the generator is already running will keep them charged so we can have a couple of ceiling fans running at night and perhaps the occasional bathroom light for a minute at night when needed.

The 2 bedroom ceiling fans we have use 72 watts on high speed each and I assume less on lower speeds although the manufacturer doesn't share that info with us.

Can someone here help me with what components I would need to make this work and how it would need to be assembled?

Thanks so much.

[inetdog]

The 2 bedroom ceiling fans we have use 72 watts on high speed each and I assume less on lower speeds although the manufacturer doesn't share that info with us.

Loads which are on continuously add up to a lot more battery usage than lights that you turn on and off for short periods.
You can get ceiling fans that use a lot less power if that becomes a problem.
With a 100% efficient inverter running from a 12 volt battery, you will be looking at 12 amps continuous for two bedroom fans. Assuming 12 hours per day for the fans on with the generator not running, that means 144AH (amp-hours) per day for the two fans together. You would need a battery capacity of at least twice that and preferably five times that.
That is a lot of battery and could justify paying a few hundred dollars for more efficient fans.
You can get fans that use as little as 20watts on high and move air at efficiencies up to almost 400 cu. ft per minute per watt of energy. These tend to be long bladed (52" nominal size or larger) fans.

[BobCobb]

Thanks, inetdog.

Unfortunately, my wife loves these fans (decor of the house) so i know changing them is not an option. I need to find a solution that will work for the ones we have.

We calculate that we will need them 8-9 hours a day while the generator is off. The power for them will be supplied by the generator when it is running.

I am just looking for the best, most cost efficient solution to give us this nighttime power with the situation we have now.

Thanks.

[russ]

Living off grid is either -

1) A compromise and conservation of power at every point or

2) Very expensive

[BobCobb]

Living off grid is either -

1) A compromise and conservation of power at every point or

2) Very expensive

Really?

Gee, that is helpful.

While I appreciate you sharing the philosophy of off grid with me, that really doesn't address my question.

I understand compromise and conservation and we have done those things. I don't really think keeping 2 ceiling fans that make my wife happy will break the bank over a few watts each day.

I also believe that while you may live off the grid you can still enjoy a few things in life.

I can simply run the Honda over night and spend an extra 4 bucks a day and have all the power I want at night. In the scheme of things, 120 bucks a month isn't that much and our complete system will be installed by the end of the year anyway. I just felt like over the summer the 400 or so I would spend on gas could be applied toward batteries and whatever else was needed to be able to power 2 fans over night and be something I would still have and could use instead of blown on fuel for the generator.

Again, thanks for your insight but I would prefer a solution.

[russ]

Have fun listening to the generator!

[FloridaSun]

While I appreciate you sharing the philosophy of off grid with me, that really doesn't address my question.

Snot philosophy, tis fact

Originally Posted by russ
"Living off grid is either -

1) A compromise and conservation of power at every point or

2) Very expensive"

For your roughly 2Kwh a night (fans/lights stated) you may want you'll need a few thousand dollars worth of batteries, inverter and charger. That may not balance out in cost even considering the cost of fuel, oil changes and replacement cost of your overworked generator. It would be much quieter at night tho, set you up for eventual PV charging in the future, maybe even allow your genny a little down time during the day.... at the cost of cycling the batteries more and shorter life.
If you want the exact figures go to the off grid section of this forum and read the stickies. It's really not that difficult to work out the numbers.

[Sunking]

While I appreciate you sharing the philosophy of off grid with me, that really doesn't address my question.

Actually it does. On paper it is easy to do, but the paper is expensive. To provide you with 2 Kwh/day with battery, the battery cost alone are $2000 for a good 5 year battery. Enough of that here is what it will take to do what you want for as cheap as I can make it. It will take your generator roughly 3 hours to recharge the batteries replacing 2 Kwh.

8 Trojan T-105 Batteries. Wired in series for a 48 volt 225 AH set up. Unit cost $150, total $1200 and will last about 2 years.
IOTA DLS-48-20 Battery Charger. Cost $350
48 volt 1500 Watt TSW Inverter made by Aims. $430

That is what it will take to make the wife happy happy happy.

Happy shopping.

[BobCobb]

Thanks but I already have a solution and no, it doesn't cost thousands to do it.

I do appreciate the philosophy lesson, though.

[SunEagle]

Thanks but I already have a solution and no, it doesn't cost thousands to do it.

I do appreciate the philosophy lesson, though.

If your solution involves a generator then you are on the right track.

If your solution involves batteries then you are fooling yourself into thinking the system will not be expensive because you do not understand the limited life of the batteries. You are either under-sizing your battery system which will make them fail quickly or you are using lower quality batteries which will fail quickly. On top of that you probably selected inexpensive battery charging equipment and inverter.

The math that Sunking gave you is very accurate estimate of the cost and selection of a battery system that will work for your fans.

Maybe when the battery system you have selected fails you will convince your wife to change the type of fans she wants to use. Good luck.

[Sunking]

Thanks but I already have a solution and no, it doesn't cost thousands to do it.

I do appreciate the philosophy lesson, though.

Not philosophy. I am a 30+ year electrical engineer. Simple 5th grade physics, math, and economics. My way you run the generator 3 hours per day, and batteries will last 4 to 5 years using the least amount of fuel per day. How many hours do you run the generator per day?

[russ]

You already have a solution then what are you doing here?

Maybe your barber told you what to do - or there are always the DIY CD's