Need a sanity check - Small off-grid system for Yurt

jdzl · February 2013

Hi all - hopefully I'm not premature in reaching out to everyone, but the wife wants power - so I want power. :P

We are nearing completion (if you can ever be finished when self-building) a 450sqft Yurt in Northern California (way far north), as far as system goes here's what I'm thinking:

Average daily consumption: 1600wh (I'm estimating based on 2000wh)
... Largest load will be a 10-12 cubic/foot fridge
... 50-75 watts of LED lighting
... Laptop, LED TV, Stereo (smaller)

So nothing too crazy (I think)

System I'm envisioning:

Honda EU2000i Generator (Already have)
8 GC2 Batteries at 24V for 440AH battery bank
Mean Well PB-1000 Battery charger
1000 watt TBA solar panels on a mono pole mount (manual adjustment)
TBA 500-1000 watt pure sine inverter
TBA MPPT charge controller

What I'd like to do is:

Build battery box (insulated and outside since we're tight for space)
Buy / install the GC2 batteries
Buy / install the Mean Well charger
Buy / install the TBA inverter

Start using the system while I'm getting the rest of the system (pole mount, panels, charge controller) sorted out for the next 4-8 weeks

Can I do this without major detrimental effects on the batteries? Will I just be running the generator all the time anyway? How big is/are the wholes in my plan so far? (Before I start spending money :P)

Cheers!

Blackcherry04 · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

You shouldn't have a problem. I'd say 3-4 hours a day should charge your batteries if you don't run them down to far based on the loads you noted. You need to get some kind of a volt meter on them so you'll know where your at. Thats not the best way to tell their health, but it'll do. Pick a voltage, say 24.5 and start charging when it gets there and stop at say 28 Volts. Then every 4-5 days run a Full charge. Find out a routine and charge a couple hrs in the evening and a couple hrs in the morning. Meanwell has a great little TSW 1500 w inverter TN-1500-24 that has a 30 amp solar charger built in for $590.00 or so.

Eric L · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

It should basically work, but I have two suggestions to consider. One is to consider going with a smaller number (like 4) of a better quality battery like an L-16, which depending upon costs in your area might be cheaper than 8 golf cart batteries (this is true in my area, e.g.). L-16s have a longer service life.

L-16s are often a bit under 400 amp-hours (370 is common), but that may be o.k. if your use estimates are correct. 370 ah X 24 volts = 8800 watt hours, of which about half would be usable, giving you 4400 watt hours of usable capacity against your 1600 wh of daily use.

My second suggestion is to increase the panel to battery ratio a bit, either by downsizing the battery bank (e.g., with the four L-16s instead of 8 golf cart batts), or by increasing the array size, or both. A 1000 watt array, after accounting system inefficiencies, is only going to generate around 30 charging amps at 24 volts, which is just on the low end of being enough to charge a 440 amp-hour bank at that size. If you are also running household loads (likely, since you will have a fridge), then the batteries are getting even less current. Moreover, having a larger panel to battery ratio will give you better charging on cloudy days, and just makes the system work better.

With prices well under $1/watt, there is no reason right now to skimp on the pv panels, IMO.

vtmaps · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

jdzl wrote: »

Start using the system while I'm getting the rest of the system (pole mount, panels, charge controller) sorted out for the next 4-8 weeks

Can I do this without major detrimental effects on the batteries? Will I just be running the generator all the time anyway? How big is/are the wholes in my plan so far? (Before I start spending money :P)

One problem I see with your scheme is going to cost you a lot of money. You will lose out on most of the 30% federal tax credit on renewable energy systems.

The credits cover the batteries, inverter, conduit, cables, lightning arresters, panels, panel mounts, controller, battery monitor, and just about everything except your generator. If you commission the system without the panels it is NOT a renewable energy system. When you later add the panels you will get the credit on the panels, mounts, and controller, but you will have missed out on the credits for everything else.

--vtMaps

westbranch · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

It has been mentioned but no one has added it to the list, that is get a good battery monitor like one of these
http://www.solar-electric.com/nsearch.html?catalog=wind-sun&x=0&y=0&query=battery+monitor

BB. · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

Do you know how much sun you have in your area? (PV Watts around Oregon, Nevada, California sites closest in weather condition to where your home will be?)

Huge difference in sun near the coast (marine layer) vs the semi-deserts to the east of the mountain ranges.

-Bill

jdzl · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

vtmaps wrote: »

One problem I see with your scheme is going to cost you a lot of money. You will lose out on most of the 30% federal tax credit on renewable energy systems.

The credits cover the batteries, inverter, conduit, cables, lightning arresters, panels, panel mounts, controller, battery monitor, and just about everything except your generator. If you commission the system without the panels it is NOT a renewable energy system. When you later add the panels you will get the credit on the panels, mounts, and controller, but you will have missed out on the credits for everything else.

--vtMaps

Does anything have to be done to qualify for the credit? I had one local installer tell me that you only qualify if it's a permitted system? Not sure what that actually means - permitted by county? Is that true?

jdzl · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

Eric L wrote: »

It should basically work, but I have two suggestions to consider. One is to consider going with a smaller number (like 4) of a better quality battery like an L-16, which depending upon costs in your area might be cheaper than 8 golf cart batteries (this is true in my area, e.g.). L-16s have a longer service life.

L-16s are often a bit under 400 amp-hours (370 is common), but that may be o.k. if your use estimates are correct. 370 ah X 24 volts = 8800 watt hours, of which about half would be usable, giving you 4400 watt hours of usable capacity against your 1600 wh of daily use.

My second suggestion is to increase the panel to battery ratio a bit, either by downsizing the battery bank (e.g., with the four L-16s instead of 8 golf cart batts), or by increasing the array size, or both. A 1000 watt array, after accounting system inefficiencies, is only going to generate around 30 charging amps at 24 volts, which is just on the low end of being enough to charge a 440 amp-hour bank at that size. If you are also running household loads (likely, since you will have a fridge), then the batteries are getting even less current. Moreover, having a larger panel to battery ratio will give you better charging on cloudy days, and just makes the system work better.

With prices well under $1/watt, there is no reason right now to skimp on the pv panels, IMO.

Thanks for the info - I'm looking at L16 batteries now as 4 is definitely more attractive than 8 (wiring, battery box, etc) Are there any brands in particular that I should avoid / gravitate towards?

The only other thing I'm trying to sort out is what combination Inverter/Charger/Charge controller would suit my needs...

Photowhit · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

jdzl wrote: »

Does anything have to be done to qualify for the credit? I had one local installer tell me that you only qualify if it's a permitted system? Not sure what that actually means - permitted by county? Is that true?

This is an interesting question, likely need to speak with a tax professional, while I don't think it would have to be 'permitted' it does have a statement that implies installed to code (I can't recall exactly), It must be a residence, it can be a 2nd residence, but can't be a rental.

Here is the Summary page.

I was comfortable taking the credit for an installation in my cabin, which was my primary residence even before I had indoor, running water, I was living there though. I was living in a 2600 acre camping community, where people own their own lots, so it was easy enough to use the comfort stations.

I associate yurts with nomadic life styles and if you were not the lot/land owner I might hesitate.

newl · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

jdzl,

I would also suggest checking the power usage of the fridge during start up surges. You may find that your intended inverter size may be a bit too small. I have a small 80L fridge and my 600W inverter (surge to 1200) barely squeaks by with the surge time (it typically hits 950W or there about) even so much so that I had to wire up my old trusty 300W inverter yesterday to avoid the big one falling into overload protection.

vtmaps · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

jdzl wrote: »

Does anything have to be done to qualify for the credit? I had one local installer tell me that you only qualify if it's a permitted system? Not sure what that actually means - permitted by county? Is that true?

There all all sorts of state credits, for which you may or may not qualify. I know nothing about them. I was referring to the Federal Renewable Energy Tax credit. Read the IRS Form 5695. The renewable energy system does not even have to be at your principle residence.

One gray area that can trip you up is structures that are multi-purpose. For example: If you build a carport to mount your panels on, don't try to take the tax credit on the carport.

One more thing... the credit is non-refundable. That means you can only pay your taxes with it, but it can be carried over until (at least) 2016. For example: if your tax credit is $5,000 and your tax liability is $2,000, you pay the $2,000 with the credit and carry over $3,000 credit to the next tax year.

--vtMaps

PorkChopsMmm · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

It may have been mentioned here but plan for loads to expand dramatically. Will you heat water? Internet? Well pump? Etc? I have the same size battery bank but a little bit more solar panel (1400 watts) with a fridge, well pump, and some other items and it is hard to last 2 days without running the generator. I agree that you should get some more panels. If you *know* your loads will be and will stay small then you should be ok with another solar panel or two. My wife promised to use very little power... and then we moved in. She made the house a home and in that transition we needed to add more necessities. Just an FYI.

solar_dave · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

What is the largest consumer of power in a house!

The wife!

niel · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

solar_dave wrote: »

What is the largest consumer of power in a house!

The wife!

i'll 2nd that and add it applies to water and gas too.

Blackcherry04 · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

niel wrote: »

i'll 2nd that and add it applies to water and gas too.

and Toilet Paper. Anytime you building a new system it helps to have a stretchable wallet. Expected cost *2 = workable system. Looks like his Batteries have gone from $700 to $1,600 already.

jdzl · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

Luckily there is a spring on the property so no well or pump to run.

There are a few local suppliers or batteries, the GC2 are going from $90-130 and the L16 are $250-300. The ones I'm currently leaning towards are the Crown L16 430AH w/ 2yr warranty for $280 + core. At the other end of the spectrum would be the GC2 from Costco at $89.99 that's 225AH I believe. I'm torn since I've seen people say you should start with a cheap(er) battery bank your first time round in case you end up making some mistakes...

Also I'd like to go inverter/charger as it sounds like that would get me the most efficiency and smooth transition from battery to gen and back again. Picking an inverter seems straightforward enough, but not 100% on charger specs that would suit the EU2000i. Would something like the Outback GFX1424 be a good match?

Counterpoint to that would be, could I get the same seamless transfer using standalone charger, inverter and transfer switch? The PB-1000 seems to be well suited to the EU2000i and then I'd just need an inverter and transfer switch. Too many choices!

My main requirement at this point is well suited charger for generator and the ability to switch to charging without interrupting loads.

Thanks for all the info so far, it's been very helpful!

The wife is on board so far - we spent 3 months living in a Westfalia, so the yurt is palatial. We are using composting toilet (waterless), but I'll make sure to stock up on TP.

PorkChopsMmm · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

As someone who moved offgrid in the last year and already killed one batter bank -- I would recommend the GC2's. Reason is they are cheap and easy to replace if/when you need to. I learned on this forum (but didn't want to believe) that every new offgrid'er makes a mistake with their first battery bank. Since it is the most expensive part of the solar system (in the long run...) it makes sense to go with what is cheaper and easier to find.

My initial 8 x GC2's were damaged. I drove them down to Sam's and got new replacements the same day. They had ~40 batteries in stock. I think it would be hard to find that sort of warranty and ease of replacement with anything else.

Blackcherry04 · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

jdzl wrote: »

Luckily there is a spring on the property so no well or pump to run.

There are a few local suppliers or batteries, the GC2 are going from $90-130 and the L16 are $250-300. The ones I'm currently leaning towards are the Crown L16 430AH w/ 2yr warranty for $280 + core. At the other end of the spectrum would be the GC2 from Costco at $89.99 that's 225AH I believe. I'm torn since I've seen people say you should start with a cheap(er) battery bank your first time round in case you end up making some mistakes...

Also I'd like to go inverter/charger as it sounds like that would get me the most efficiency and smooth transition from battery to gen and back again. Picking an inverter seems straightforward enough, but not 100% on charger specs that would suit the EU2000i. Would something like the Outback GFX1424 be a good match?

Counterpoint to that would be, could I get the same seamless transfer using standalone charger, inverter and transfer switch? The PB-1000 seems to be well suited to the EU2000i and then I'd just need an inverter and transfer switch. Too many choices!

My main requirement at this point is well suited charger for generator and the ability to switch to charging without interrupting loads.

Thanks for all the info so far, it's been very helpful!

The wife is on board so far - we spent 3 months living in a Westfalia, so the yurt is palatial. We are using composting toilet (waterless), but I'll make sure to stock up on TP.

The batteries are a toss up, it's you choice. I either own or have control over 300, GC-2's in banks of 8 or 10 each. They work great and are hard beat for the price per amp hr. If you take care of them , you'll get 5 years.

I'v got a GFX 1312 on order for 3 weeks now and they had 9 in stock at OutBack when I ordered it, so I have not tested it yet, but if it works as advertised it will be a shoo in to use with the Honda EU 2000. I 'll post back as soon as I get it hooked up. Remember you have to buy a Mate $200 to adjust the GFX. My only concern is if the charger will put out the rated amps over time. If it over heats it'll shut down the charger. I ordered a Vented Case top to convert it into a vented model if it's a problem.

You do know you'll have to put a Relay on the GFX to create a Neutral to Ground Bond if you are using it in a Off Grid setup. Not a big deal, but thought you might want to know.

I hate to say this in advance, my gut feeling is there will be some kind of a glitch with the GFX working well with the Honda EU 2000. It's another $1,200 in the search for something perfect. The last 3 things I have tried have been less than satisfactory. The ECO throttle is picky on whats dumped on it, the inverter / chargers are not a soft start load with a ramp up and they drive it crazy and it'll surge and kick out. My hope is that there is enough latitude in the programing to allow voltage to be adjusted to point where it won't be a problem.

jdzl · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

So sounds like the GFX may not suit my needs completely...

So how viable would it be to use a PB-1000-24 charger (seems to work well with the EU2000i), and then a plain old 1000-1500w pure/true sine inverter? The part I get a little bit confused about is do I draw the load from the inverter even while the batteries are being charged, or should I transfer the load to the generator while charging (bypassing the inverter) and then transfer back after charging completed. The second option sounds more efficient - would a transfer switch be what I need to do that? (Transfers after 30 seconds etc) and are they quick enough to not drop the load going back and forth? (I don't want electronics to reset if possible)

Blackcherry04 · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

jdzl wrote: »

So sounds like the GFX may not suit my needs completely...

So how viable would it be to use a PB-1000-24 charger (seems to work well with the EU2000i), and then a plain old 1000-1500w pure/true sine inverter? The part I get a little bit confused about is do I draw the load from the inverter even while the batteries are being charged, or should I transfer the load to the generator while charging (bypassing the inverter) and then transfer back after charging completed. The second option sounds more efficient - would a transfer switch be what I need to do that? (Transfers after 30 seconds etc) and are they quick enough to not drop the load going back and forth? (I don't want electronics to reset if possible)

It depends on how you want to do it. Right now I use a stand alone charger with the batteries most of the time. I don't have a Meanwell PB -1000 so I can't tell you how good they work. The talk about them is not conclusive to me. You could set up a transfer switch of some kind with plugs where you changed back and forth to a Inverter. I think there is one at Northern Tool that is a cord Plug and Play. Your electronics should not reset with a internal transfer switch.

I tried to do the same thing with a Magnum MM1512 that we are talking about. It works, but you have to watch the charger close or it kills the generator, there is no power share or generator support.

To answer your question, you can run the Inverter off the batteries and charge at the same time.

Photowhit · February 2013

Re: Need a sanity check - Small off-grid system for Yurt

If you go with the Midnite classic Charge controller, sometime later this year they should introduce a shunt based module for it that will allow for accurate charging regaurdless of use or outside charging, as it will measure at the shunt just ahead of the battery.

Need a sanity check - Small off-grid system for Yurt

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