I don't want to hear that generator anymore!!

ramloui · September 2012

Hello all! This site is so informative and everyone is so knowledgeable!

I've purchased a fishing cabin this past year and the former owner had 6 car batteries that he would use to run the water pump and to power a few 12V lights. He would use the generator to recharge the batteries.

Well that generator is driving me nuts, especially in the morning when I make coffe and use the toaster!!!!! Plus, obviously, the batteries are always dead!

So my big project this winter will be to get together all of the components required to power my cabin.

Here are my needs and the loads I came up with:
- 12V water pump... say 2 hours at 8 amps = 192Wh
- coffee maker (label says 1200 watts) for 1 hour a day: 1200Wh
- toaster (label says 1000W) for 20 minutes a day: 333Wh
- 10 lights total (3-4 running at the same time for approx 4 hours per day): 4 x 15W x 4 = 240Wh
- occasional power tool like a circular saw: say 1800W x total of 15 minutes per day = 450Wh
- recharge the trolling motor battery: No clue. I've been told that I would be better off recharging this with a generator rather than with the solar system.

The cabin is used only in the summer, 4-7 days at a time, 2-3 weeks between each use. From above, total daily load is 2415Wh plus whatever would be required for the trolling motor battery. Does everyone agree with this number?

Figuring things out for a 12V system, the battery bank needs to be 2415Wh / 12V = 201 Ah x 50% DOD x 5 days = 2010 Ah... Wow!!! Is this reasonable?
Should I up things to 24V? That would still be 1005 Ah bank capacity...

I have a lot more questions on the rest of the system but I think I need to figure this out correctly before I go any further. Thanks for all of your input!!!

Louis R.
49.2,-69.6

Cariboocoot · September 2012

Re: I don't want to hear that generator anymore!!

Oh no, Louis; that's not what you want to do.

The first thing you want to do is get rid of the electric coffee maker & toaster. Much cheaper to use propane to heat things with than to buy enough solar electric to do the job.

By your own calculations a 1005 Amp hour @ 24 Volt battery bank. That is big. Really big. That needs about a 3kW array ($2 per kW if you are lucky) and two charge controllers! Where are you going to put it all?

Now remove the electric heating devices and see what you get.

You're better off using the noisy generator to run the power saw on occasion. Or even getting a quieter generator (the inverter-generators are much quieter than conventional type).

The trolling battery could be recharged from its own dedicated solar panel/charger controller depending on when you use it (fish in the morning, charge during the day).

ramloui · September 2012

Re: I don't want to hear that generator anymore!!

All right!
So if I take out the coffee maker and toaster loads, that's 1533Wh, then I'm left with 882Wh. At 12V, 50% DOD and 5 days autonomy then I would be looking at a battery bank reserve of 735Ah, right?

Now, taking this a little further, to get 735Ah, I would need 4 6V batteries each at 370Ah, wired as 2 strings of 2 batteries. Again, please chime in if my calculations are wrong...

Ok! What's next? Sizing the PV array? I've read that I should have approximately the same amount of watts as I have Amp.hours bank, which would be 735 total watts. I assume that my location has something to do with this. Also the fact that I can afford the battery bank to be recharged over a period of 3-4 weeks until I'm back at the cabin...

Thanks for everyone's help!

Louis R.
49.2,-69.6

westbranch · September 2012

Re: I don't want to hear that generator anymore!!

I would compare cost of going to 24v and using golf cart batteries at about 225Ahr rating against 12 v.

One example:http://www.trojanbattery.com/Products/T-1056V.aspx

ps loads always grow...

inetdog · September 2012

Re: I don't want to hear that generator anymore!!

ramloui wrote: »

Also the fact that I can afford the battery bank to be recharged over a period of 3-4 weeks until I'm back at the cabin...

Not quite. That woud be fine if only the batteries (either AGM or FLA) did not suffer from a phenomenon called sulfation, in which the battery permanently loses capacity if it spends too long a time at less than full charge. If you can get it back up to 80% within one or maybe two days, you will be in relatively good shape. But taking a week or more to get from 50% charge back up to 80% charge will cause loss of battery capacity.

Cariboocoot · September 2012

Re: I don't want to hear that generator anymore!!

ramloui wrote: »

All right!
So if I take out the coffee maker and toaster loads, that's 1533Wh, then I'm left with 882Wh. At 12V, 50% DOD and 5 days autonomy then I would be looking at a battery bank reserve of 735Ah, right?

Now, taking this a little further, to get 735Ah, I would need 4 6V batteries each at 370Ah, wired as 2 strings of 2 batteries. Again, please chime in if my calculations are wrong...

Ok! What's next? Sizing the PV array? I've read that I should have approximately the same amount of watts as I have Amp.hours bank, which would be 735 total watts. I assume that my location has something to do with this. Also the fact that I can afford the battery bank to be recharged over a period of 3-4 weeks until I'm back at the cabin...

Thanks for everyone's help!

Louis R.

882 Watt hours / 12 Volts is roughly 74 Amp hours. But you need to factor in DC to AC conversion and the inverter consumption (which inverter will make a significant difference in this; if you can use the Morningstar 300 it will go to standby and draw very little power and only uses 6 Watts running but is limited to 300 Watts output). This should be a number around 120. Multiply by at least 2 and preferably 4 (50% DOD or 25% DOD). Never mind five days autonomy. If you try for that you will again be spending big $ on batteries and panels that sit and do nothing most of the time. Using 25% DOD gives you two days autonomy by allowing you to pull down to 50% on the second day. Third day, start the generator.

Do not fall for the "the battery bank will recharge while I'm gone" scheme. Technically it is possible, but the batteries die an early death. When panels were expensive and batteries cheap you could do this and buy new batteries every couple of years. Now it's the other way 'round, so it makes sense to try to keep the batteries as long as possible.

So what you've potentially got here is a need for 120 Amp hours * 4 or 480 Amp hours @ 12 Volts. With care you could trim that down to a 450 Amp hour bank: two parallel strings of the inexpensive golf cart type batteries. Especially if you can use the MS 300. We are now talking bargain power!

What's more, you are now looking at a lot fewer panels: 45 Amps peak charging current @ 12 VDC / 0.77 = 700 Watt array. This is with an MPPT charge controller. You would probably need more with the PWM type because it only passes current; it has no ability to down-convert higher array Voltage to current. Still, you've just saved a lot on not having to power the coffee maker and toaster.

Anyone who told you the array Watts should be the same as the battery Amp hours forgot about the Voltage: I sure couldn't charge my 232 Amp hour bank from 232 Watts; it's 24 Volt. Curiously, it has a 700 Watt array.

BB. · September 2012

Re: I don't want to hear that generator anymore!!

Louis,

A seasonal cabin is difficult to justify a full off-grid solar power system... At 9+ months a year occupation, the power costs you somewhere around $1-$2+ per kWH... When you only use it for 4 months a year, the costs just about double (i.e., the solar power system cannot give you any useful power for ~8 months of the year--so wasted investment).

A battery (or battery+solar) that provides enough 120 VAC for lights+radio+computer+cell phone+water pumping+etc.) using 2-4 6 volt golf cart batteries for a 220-440 AH @ 12 volt system probably is a good starting point for a "paper design".

And you can review how useful such a system would be for you. And add a Honda eu2000i 1,600 watt (or possibly eu1000i 900 watt if your AC loads are "kept small") as they are pretty quiet (use a 50-100 foot extension cord behind some plywood or in a depression--and you probably will not even hear it). And you will get anywhere around 4-9+ hours per gallon of fuel.

Use the generator for heavy loads and bumping up the charge for the battery bank (20-40 amp @ 12 volt charger would work well on the eu2000i).

If you have the the occasional need for heavy loads (power tools, electric saws, etc.), you can always use a "cheap" 3.5 to 5kW genset to power those (and as emergency backup).

The MorningStar 300 watt TSW 12 volt AC inverter (600 watts for ~10 minutes) is about perfect for lower power systems (it also has a remote on/off input and a "search mode" to cut back on DC power usage when nothing is turned on). You could always use a 1kW MSW inverter for the occasional power tool/pump usage--if needed.

I really like to suggest a smaller TSW inverter for "critical" loads (computer, cell charger, CFL/LED lightning, etc. About 80% of the AC loads out there will work OK on MSW, and about 10% will fail (small things like wall mount transformers, battery/cell chargers, small computers/DVD player supplies, etc. tend to overheat on MSW inverters).

The problem--it is not always "obvious" which type of device will work OK on MSW vs those that will fail/have a short life. Given that your cabin is in the "middle of nowhere" (it appears), the added reliability for TSW inverter powered devices makes the extra costs of TSW a "not bad" investment.

-Bill

icarus · September 2012

Re: I don't want to hear that generator anymore!!

Mimic my system, get rid of the coffe maker (coleman makes a really nice stove top drip coffee maker) make toast on the stove, (I use a little propane catalytic heater to make toast!). My 400 watts of PV provides an nice 5-800 WH of power per day, into 450 ah of battery gives several days before we get to 70%. Then use a Honda eu 1000 or 2000 coupled with a good iota or xantrex charger.

The Rogue controller works gat on a system this size, and the Shursine 300 is perfect.

Not cheap in the net, but PV has never been cheaper, and while it won't "save" you money, you should get many yers of service. We are in year 5 wi th the batteries, and I expect 5 more.

Tony

Coach Dad · October 2012

Re: I don't want to hear that generator anymore!!

Ramloui
- I know what you mean regarding the generator driving you crazy. I ran my cabin on a generator for 7 years before going solar. I was using about 6 gallons of gas per weekend. Using today’s price it comes to about $100.00 per month in gas alone. The cost of running a generator adds up quick. So make sure you factor your gas costs in when setting a budget for your solar project.
- I didn’t see a TV or Laptop on your load list. Is that an oversight?
- I suggest you get a Kill-A-Watt meter and actually measure how much power your coffee maker uses. My coffee maker uses 860 Watts, and it brews a 12 cup pot of coffee in 15 min. So that is about 215 watts [Watt*Hours or WH... -BB] of total power usage. I tried the Coleman propane coffee maker and found it took about 45 minutes to brew a 10 cup pot of coffee. So I went back to the electric.
- I don’t use a toaster at the cabin, but my home toaster makes toast in just a few minutes. Where did you get 20 min.? Again… use the Kill-A-Watt meter to get a real number.
- Your fishing cabin is a Summer time usage cabin. You have long sunny days with plenty of power. So Forget the 5 days of autonomy. Use 2 days (at the most). The 5 day rule is intended for the full time off grid resident.
- Solar panels are cheaper today than ever before. So I suggest that you buy more PV and less Battery. More PV will charge your battery bank faster. Having more PV will even give you some usable power on rainy days. Just make sure your battery bank can handle your load.
- If needed, use your generator to bulk charge your batteries before going home and let the PV do the absorb charge when the sun comes out.

BB. · October 2012

Re: I don't want to hear that generator anymore!!

Agree with Coach Dad...

Once your system exceeds a certain size and support the 900 watts or so, peak, of your coffee maker--The short time that they run can be easily supported by the solar power system (in many cases).

Having accurate numbers with the kill-a-watt meter helps a lot with planning.

-Bill

icarus · October 2012

Re: I don't want to hear that generator anymore!!

This,, is a pretty good alternative,,http://www.amazon.ca/Coleman-5008C700-Camping-Coffee-Maker/dp/B001K7IDVU/ref=sr_1_1?ie=UTF8&qid=1349198227&sr=8-1

Running an electric coffee maker would nearly double my daily averge,

Tony

Blackcherry04 · October 2012

Re: I don't want to hear that generator anymore!!

I am a major Coffee Drinker, 3-4 pots a day running 18/7. I take a Bunn regular coffee maker and put a switch on the main submersed heating element ( 900 W ) and that leaves the tank blanket element to heat the water and the hot plate the pot sits on. It pulls 70 watts to keep the Coffee hot and to keep the next pot of water hot in the tank. When you pour in a pot of cold water it takes 3-4 hours to heat the water for the next pot, but the low watt consumption is worth it. If you are ever in a hurry for the next pot you can switch on the 900 watt element. When you turn the pot heater to off the water tank heater pulls 30 watts.

It's the price I pay for something to keep me going.

ChrisOlson · October 2012

Re: I don't want to hear that generator anymore!!

Cariboocoot wrote: »

The first thing you want to do is get rid of the electric coffee maker & toaster. Much cheaper to use propane to heat things with than to buy enough solar electric to do the job.
.

I disagree somewhat on this for off-grid appliances. Our off-grid home is totally electric, including 240 volt range with a high-efficiency induction cooktop (over double the energy efficiency of propane cooking), 240 volt electric water heating (>90% energy efficient), even 240 volt electric clothes dryer. Propane is a fossil fuel and I'm in the business of reducing or eliminating my use of fossil fuels. With an electric appliance you have the option of running it on RE, or fossil fuel (thru the generator). With a propane appliance you limit your options to only using the fossil fuel to power it. And while propane is touted as "clean", in reality it's not. The environmental impact of getting the stuff into your fuel tank makes it anything but "green" or "clean".

Things like the induction range aren't that bad. The litz coils in the cooktop draw 2.5 kW for the big ones and 1.6 kW for the little ones. But that's only while the cooking vessel is heating up. As soon as the cooking vessel gets up to proper cooking temp (which is VERY fast with induction cooking), the power requirement drops to usually only 500-600 watts to maintain the proper cooking temperature.

The same holds true for things like electric coffee makers. It only draws 800-1,000 watts during brew. But once that's done the hot plate cycles on and off to maintain the temperature of the coffee, so it draws 0 - 250 or 300 watts intermittent. You can run most coffee makers with a cheap 1,000 watt WalMart inverter and a deep cycle boat battery with no problem at all.

So I never discourage people who want to use electric appliances for off-grid situations. They work well. They are efficient, the energy source does not pollute the environment, and it is very doable and practical. Sure, you still resort to fossil fuel to power it if Mother Nature doesn't cooperate and supply enough RE. But for us, 95% of the time, we can run all our electric appliances on solar and wind power.

Most of these electric appliances (like a toaster for instance) are only short term heavy draw - usually just for a few minutes to make a couple pieces of toast. The thing won't even use 300 watt-hours in a typical day, probably. If you use that toaster every day, it only takes an extra 80 watt solar panel to provide the energy for it, long term, and reduce your carbon footprint by reducing your use of fossil fuels.

That's my .02 cents on it.
--
Chris

Cariboocoot · October 2012

Re: I don't want to hear that generator anymore!!

Yes, but Chris your system isn't exactly small-scale.

2manytoyz · October 2012

Re: I don't want to hear that generator anymore!!

If it were me, I'd probably go with a hybrid setup. Use a battery bank to run the lights, and other small loads. Use solar to recharge the batteries. For the heavy loads, I'd rely on a Honda or Yamaha inverter style quiet series generator. I can't hear our generator from inside the camper.

Doesn't take long to make toast, brew coffee, or run a saw. When your done, turn the generator off. I do agree about using propane to heat rather than electric.

I have used Alt-Power to make coffee, here are my numbers: http://www.2manytoyz.com/coffee.html Take note that my coffee pot doesn't have or need a hot plate.

The generator gives you another source of power when the weather doesn't cooperate!

ramloui · October 2012

Re: I don't want to hear that generator anymore!!

Thanks for the great input eveyone!!
I went out today and bought the Coleman coffee maker, the one you put on the gas stove. I will give it a try this weekend as it is, sadly, time for one last trip to the cabin and close it down for the winter.

Next question is about the PV panels: anything that is 150W or so and above puts out 28-35V. Can I use this on a 12 V system? Is that what the MPPT charge regulator is for? Or do I need to stick with the lower voltage panels? If I'm going to have 4 x 6V batteries, should I just wire them all in series and setup a 24V system? If so, then what do I do with the lights? Step the voltage down to 12V or set up to run them off an inverter at 120V?

Thanks for your patience with me!!

Cariboocoot · October 2012

Re: I don't want to hear that generator anymore!!

ramloui wrote: »

Thanks for the great input eveyone!!
I went out today and bought the Coleman coffee maker, the one you put on the gas stove. I will give it a try this weekend as it is, sadly, time for one last trip to the cabin and close it down for the winter.

Next question is about the PV panels: anything that is 150W or so and above puts out 28-35V. Can I use this on a 12 V system? Is that what the MPPT charge regulator is for? Or do I need to stick with the lower voltage panels? If I'm going to have 4 x 6V batteries, should I just wire them all in series and setup a 24V system? If so, then what do I do with the lights? Step the voltage down to 12V or set up to run them off an inverter at 120V?

Thanks for your patience with me!!

Louis R.

You can use the high or 'odd' Voltage panels on a 12 Volt system with an MPPT type controller; it will down-convert the Voltage into higher charge current. You can use them with the PWM type controller, but you will lose a portion of the power due to its inability to do this (it only passes the panel current; Voltage is pulled down to battery level). Be advised a 24 Volt system needs an array Vmp around 35 to properly charge.

Ideally the 24 Volt system will be ever-so-slightly more efficient. But you can run two parallel battery strings for 12 Volt without much trouble. This is one of those times to carefully consider your future expansion needs; you don't want to buy a 12 Volt inverter now, then toss it and buy a 24 Volt one later.

If you go with 24 Volts for the inverter you can run a DC to DC converter to get 12 VDC, depending on the power needs. Like this: http://www.solar-electric.com/12to24or24to.html

BB. · October 2012

Re: I don't want to hear that generator anymore!!

For coffee/hot liquids... Use a good thermos to keep them warm (pour boiling water into the thermos before filling with hot drink/soup/etc.). Will save a bunch more power over a "keep warm" heater.

ramloui wrote: »

Next question is about the PV panels: anything that is 150W or so and above puts out 28-35V. Can I use this on a 12 V system? Is that what the MPPT charge regulator is for? Or do I need to stick with the lower voltage panels?

Pretty much, yep. The farther you get from Vmp~17.5 volts/12 volt battery bank ratio (35/24; 70/48), the more power you will lose with a PWM controller and the more sense a MPPT controller will make.

More or less, a Vmp~35 array on a 12 volt battery bank with PWM controller will cost you about 1/2 of the solar panel's rated wattage.

If I'm going to have 4 x 6V batteries, should I just wire them all in series and setup a 24V system? If so, then what do I do with the lights? Step the voltage down to 12V or set up to run them off an inverter at 120V?

You can... A lot depends on your loads. For a smaller system/AC inverter, a 12 volt bank may make more sense (use the very nice MorningStar 300 watt/600 watt ten minute TSW 12 VDC inverter with low power options) is hard to beat.

If you go with a larger system, then going higher bank voltage usually makes sense...

As a starting point, less than 1,200 watts/100 amp DC, a 12 volt system is usually OK.

For 1,200 to 2,400 watt system, a 24 volt system is usually a better bet.

Over 2,400 watt, 48 volt starts making a lot of sense.

Remember that charge controllers are based on amp output... So a 60 amps system can handle:

60 amps * 14.5 volts * 1/0.77 panel+controller derating = 1,230 watt array on 12 volt battery bank
60 amps * 29 volts * 1/0.77 panel+controller derating = 2,260 watt array on a 24 volt battery bank
60 amps * 58 volts * 1/0.77 panel+controller derating = 4,519 watt array on a 48 volt battery bank

So the same controller can "manage" a larger array on a higher voltage battery bank...

It all goes back to loads (and size of solar array too).

-Bill

Blackcherry04 · October 2012

Re: I don't want to hear that generator anymore!!

BB. wrote: »

For coffee/hot liquids... Use a good thermos to keep them warm (pour boiling water into the thermos before filling with hot drink/soup/etc.). Will save a bunch more power over a "keep warm" heater.

Of course you have to boil the water first, what you save depends on what you use to heat it. I have several, " Air Pot " with a pump gismo on it, Carafes both Glass and Stainless Steel, Pre warming them does help them, I find them lacking after a hour or so. Like I said, it's a price I am willing to pay.

ChrisOlson · October 2012

Re: I don't want to hear that generator anymore!!

Cariboocoot wrote: »

Yes, but Chris your system isn't exactly small-scale.

Well, darn it anyway. I'd do it anyway for a fishing cabin

We got kind of the same sort of deal with our 5th wheel RV. We go to Canada fishing with it and live off-grid in it for up to a week sometimes. We run an electric coffee maker every day - but we make the coffee with it and put it in our thermos's. Plus my wife takes her hair dryer (1,800 watts), we use the microwave quite a bit (not sure how many watts - I think about 1,000), we use the toaster to make toast for breakfast (about 1,000 watts), we run the vacuum cleaner to vacuum the carpets in the camper, and my wife even has these crock pots that she'll put some food in so it's ready and hot for us to eat when we get back from fishing. I think her little crock pots are maybe 200-300 watts or so.

And we run it all with a MSW AIMS 3,000 watt inverter/charger, two Interstate SRM-4D batteries, two Group 29 125 ah batteries, and two 123 watt Sharp solar panels on the camper roof helping out. We've lived pretty comfy with that setup for five days of fishing sometimes. The batteries get gradually depleted because the solar panel can't keep up with everything. But when we get home I plug the inverter/charger into our home system and charge them batteries back up, then let the solar panels maintain them until we go again.

It works good. So, I dunno. If it works for an RV, why won't it work for a fishing cabin? Just sayin'. I even made a movie about that setup in our camper once because I told folks about it and they couldn't comprehend it:
http://www.youtube.com/watch?v=aEMghPY9UGs&feature=share&list=UUdQyT7lod1HabPrN6HAyCXg

So my fishing cabin has all the stuff the OP wanted in his - only difference is, mine's on wheels.
--
Chris

Cariboocoot · October 2012

Re: I don't want to hear that generator anymore!!

Well if you've got the 'kick' to handle the draw (3kW inverter & enough battery capacity) it will work. Even with an AIMS inverter.

(MSW has no trouble handling resistive loads at all.) I'm going to guess you've got something other than 246 Watts of solar for recharging. Nothing like Bulking with a gen while running the heavy loads to save on the PV expense.

But when designing an off-grid system the first rule is to reduce the electric consumption as much as possible because it costs a lot to produce. It's even worse if you live in Canada instead of just fishing there.

In theory my system here would not meet the energy demands:
700 Watts * 5 hours * 0.52 = 1820 Watt hours, yet the daily consumption is about 1000 Watt hours more. 232 Amp hours of 24 Volt @ 25% DOD = 1392 Watt hours.
How do we do it? 82% (as opposed to 77% 'typical') panel efficiency from higher elevation, and very careful load shifting (lately I've been running power tools midday without any problem). The batteries are mainly to keep things running over night.
The generators are there for when things go wrong (like the recent weather). :roll:

icarus · October 2012

Re: I don't want to hear that generator anymore!!

It all depends on wht your priorities are. So much of my lifestyle envolved from being off grid for decades (some full time, some part time). We went from kerosene lamps (an Aladan lamp was a big step forward) to hauling water in bucketsin the winter, and everything had to be hand hauled in.

My life style evolved from that (we did use a genny at night for a couple of hours, but in the winter the lister diesel often wouldn't start!) to a simple reading light, to multiple lights, to now, we have 24/7 AC , pumped water year round, Internet etc. on balance, I since everything has been an evolution, we still stick to the basics, and keep every thing pretty simple. Coffee with the Coleman, into a stainless carafe preheated with water usually from the wood stove, ( and then I cover the carafe with a fleece toque (hat for the Americans!) and it stays hot till well after noon). Then I use an good insulated travel cup.

Toast is done on a modified catalytic heater run off a 16 oz bottle that I refill from a 100# tank. Lasts about 4 months. We don't micro wave, nor do we have a Tv,, but the computer/iPad ISP draw is now rivaling that what we might have if we had a tv. As my sig suggests, our little sstem works quite well, and is pretty well balanced. I have run the genny a total of 3 hours in the last 6 weeks, only because I didn't think the sun was going to come out after several day,, and it did.

If I had one thing to do over again, I would go with a conventional fridge, a couple more PV and a larger inverter to cut the propane cost. When I built the place thaqat wasn't a realistic option. Nowadays, with PV cost so cheap, fridges so efficient, (and cheap) when this one fails I might convert. At current course and speed, our daily consumption is up to ~800 WH/day, some days pushing 1.2 KWHs if I have lots of sun and want to charge all the drill batteries and laptops. We use 100#s of propane every 8 weeks, and perhaps a gallon of gasoline per month (not counting the shop, or vehicle/boat fuel)

So a fishing cabin, used part time could surely mimic my system. That said, add in a few other items, and the system gets bigger. One post talked about his coffee taking "only" 300 WH/day. For me, that is 1/3 my total. A toaster, might be another 1/4. It is all in the details, and what compromises you are willing to make.

Tony

ChrisOlson · October 2012

Re: I don't want to hear that generator anymore!!

Cariboocoot wrote: »

Well if you've got the 'kick' to handle the draw (3kW inverter & enough battery capacity) it will work. Even with an AIMS inverter. (MSW has no trouble handling resistive loads at all.) I'm going to guess you've got something other than 246 Watts of solar for recharging. Nothing like Bulking with a gen while running the heavy loads to save on the PV expense.

Yes, the solar panels can't bring the batteries back from the dead by themselves after a five day fishing trip. We have to either take the camper someplace where we can plug it into shore power, or bring it home and plug it in to our home system to recover the batteries.

But for an off-grid cabin that's where I see one of those little EU2000 Honda generators coming in really handy. On the last day of your stay at the cabin, fire the thing up and recover the batteries, then let the solar panels do their work maintaining them while you're gone. I really think it would work, and I actually think the OP could run all the stuff he wanted to run because there was some figures that were well over what some of those appliances actually draw for power.

Years ago, when we first built our off-grid home, yes we indeed did learn to reduce power consumption. It took us a lot of years to get to where we are today. And today I don't believe in conserving power when you live off-grid - I believe in making more of it

Also - I agree your system could not run the "want list" long term. But I think you are in a different situation permanently living off-grid, where the fishing cabin is part time like our RV. You are concerned about maintaining your batteries long term, or you have to run the generator. For these part-time off-grid deals like our RV, we abuse the batteries and pull them well below 50% SOC during a fishing trip. They're down to like 11.2 - 11.3 volts at rest when we finally pack up and head home. But we can afford to do that to the batteries because we don't cycle them every day like a full time off-grid home does.
--
Chris

ChrisOlson · October 2012

Re: I don't want to hear that generator anymore!!

icarus wrote: »

It all depends on wht your priorities are. So much of my lifestyle envolved from being off grid for decades (some full time, some part time). We went from kerosene lamps (an Aladan lamp was a big step forward) to hauling water in bucketsin the winter, and everything had to be hand hauled in

Yes indeed, Tony, this is so true. When we started out all we had was a generator, two boat batteries, and a small 2,000 watt inverter that I bought at Farm & Fleet. And we got by just fine. We had a 12 volt system that served us well for over 7 years. I don't know what our power consumption was when we had our 12 volt system - I would guess 4-5 kWh/day. But when I look back at that, I do not miss having to get up at 3:00 AM when it's 20 below zero to start a stiff gas charger because the inverter is singing it's low battery song and the blower on the wood furnace is about to quit. The attached photo was our standby generator for quite some time.

Attachment not found.
--
Chris

icarus · October 2012

Re: I don't want to hear that generator anymore!!

chris,

No wonder your genny wouldn't start. That is a Techumsa (sp?) engine isn't it? I have never seen a Techumsa that ever would start reliably!

It seems like you have it dialed.

Tony

ChrisOlson · October 2012

Re: I don't want to hear that generator anymore!!

It was a Tecumseh 6hp snowblower engine on there. With a Delco 10SI alternator with the regulator grounded so it would put out full power. I used to start that thing and let it idle at about 2,200 rpm just about every evening in the winter to keep our batteries up so we could run more stuff in the house. It was not automatic start, but it was auto-shutdown - the tank held 1 quart of gas and it would auto-shutdown after two hours because it was out of gas

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Chris

ramloui · October 2012

Re: I don't want to hear that generator anymore!!

I love to read this and the good arguments in either direction!!!

Here is where I think I'm going to take my system:
- Since life has been good to me, I want to indulge a bit in overdesigning this system,
- The battery bank will be 2 strings of 4 6V batteries for 24V,
- Morningstar TriStar 60 MPPT
- Magnum inverter/charge MS2024 with MPP panel. I want PSW to be able to plug in my drill battery charge...
- Lights will be 120V. Mights as well with the above inverter, plus 120V supplies are more easily procured
- Enough PV panel watts to recharge the batteries at the proper rate. Can someone help come up with this number?

I know this is much more than I need now for my stated loads but, as someone has said, they have a tendancy to grow over time. Plus I would very much enjoy being able to plug in whatever appliance I want once in a while. If that is not enough, then I can turn on the generator while I'm away fishing and not around to hear it!

Other than the money involved, if you see anything stupid in the above, I'd like to know about it. I would very much like this project of mine to be succesfull the first time I turn it on.

Thanks for all your feedback!

Coach Dad · October 2012

Re: I don't want to hear that generator anymore!!

I like your plan and your thinking process… :cool:

You didn’t say what size batteries you are going to use…
But the rule of thumb for calculating how much PV you need to charge your battery is 5% to 13% rate of charge with 10% being a healthy nominal rate of charge.
The calculation goes like this: Battery AH * Charge Voltage * (1/.77 de-rating) * Rate charge = PV wattage needed
For Example if you have a 610AH 24 volt battery bank and you want 10% charge rate
610 AH * 28.6 volts * 1/.77 * (0.10 Rate charge) = 2266 PV watts
610 AH * 28.6 volts * 1/.77 * (0.05 Rate charge) = 1133 PV watts
610 AH * 28.6 volts * 1/.77 * (0.13 Rate charge) = 2945 PV watts
Since you are using it mainly in the summer on a part time bases I would suggest the lower end (but then again the PV are cheap these days).

Since you are going down the nice system road,,, you should consider the Magnum 4024PAE inverter which gives you 240V split phase so you can eventually run a 240V well pump… I’ve got mine wired to a standard house circuit breaker box with branch circuits for the well pump and lights.

Finally: You mentioned that you are going to the cabin this weekend to close up for the winter… I suggest you stop at Home Depot and pick up a kill-a-watt meter to take with you… Measure all of your usage and write it down… You will have all the numbers with you to play with during the winter.

Endurance · October 2012

Re: I don't want to hear that generator anymore!!

Sounds like a nice setup. I am wondering about the charge controller choice. I was thinking that an Outback FM60 or FM80 or even a Midnite Classic 150 charge controller might give you a whole lot more controller for a little more money. Perhaps someone with more experience can tell us if that's true.

Cariboocoot · October 2012

Re: I don't want to hear that generator anymore!!

icarus wrote: »

chris,

No wonder your genny wouldn't start. That is a Techumsa (sp?) engine isn't it? I have never seen a Techumsa that ever would start reliably!

It seems like you have it dialed.

Tony

Me neither!
Probably the worst engines ever made.

Cariboocoot · October 2012

Re: I don't want to hear that generator anymore!!

Endurance wrote: »

Sounds like a nice setup. I am wondering about the charge controller choice. I was thinking that an Outback FM60 or FM80 or even a Midnite Classic 150 charge controller might give you a whole lot more controller for a little more money. Perhaps someone with more experience can tell us if that's true.

Yes: the MidNite is the best controller going right now. The Outback has slipped to #2. Morningstar charges extra for the meter, so you could buy the MidNite lite version for $500 if you can live without the neat display (which can be added later). The TriStar 60 MPPT and the Classic lite 150 are the same price. The Classic is better in my opinion. The FM60 at $517 with display is the best bargain.

Morningstar TriStar 60 MPPT http://www.solar-electric.com/motr60ampmps.html
MidNite Classic Lite 150 http://www.solar-electric.com/misoclli150m.html
Outback FM60 http://www.solar-electric.com/oupofl60mpso.html

I don't want to hear that generator anymore!!

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