Off-grid system review

[Sunking]

Your so full of it, you'd need a 10ft ladder to smell clean air.

Well thank you partner, I appreciate it. Back at you.

[Cult of Dionysus]

The advice of experienced people here is to strive for a single series string, or two if absolutely necessary. I believe there are sources on the net that say 3 string maximum. I am only a newbie, but I know which direction I would go.

One example of a battery that would give you a single string is the Rolls S-1660, which is 1284 Ah - exactly what you stated. 2v each, you would need 24 of them.

How do these compare to the 12 4KS25PS noted by Sunking? Seem to have comparable storage, but the 4KS25PS cost a lot more... $10k vs $14k mainland prices.

[Sunking]

How do these compare to the 12 4KS25PS noted by Sunking? Seem to have comparable storage, but the 4KS25PS cost a lot more... $10k vs $14k mainland prices.

The difference is in construction and warranty. Rolls has 3 class series of 3000, 4000, and 5000. 3000 being the low end, and 5000 being the high end. The s-1660 is a 4000 series.



Read The Warranty of the 3, Pays yours Money, and take your chances.

Another great less expensive option is Trojan. The Trojan Smart Carbon Technology is Trojans answer to Aquion AHI batteries. Made to operate as PSOC. Difference is Trojan is 1/3 the price, has a great reputation, Been around for decades and will be around tomorrow, and a hell of a lot better warranty than Aquion.

IND23-4V
IND27-2V
IND29 -4V
L16RE-2V

The IND or industrial grade are warranted 36/96, and RE or Renewable Energy are 24/60. Trojan being a US made product should be less expensive than Rolls.

You can hate me later after I stink up the place.

[Cult of Dionysus]

Thanks.

[inetdog]

Thanks, appreciate that.

Last question, then I'm out of your hair, what did I do wrong to calculate the Amps of the panels? Per this website (sorry, a competitor), the LG300 panel produces 9 amps. Don't I just then multiply that by the # of panels? Then divide the battery banks Ah by the panels' amps to determine the C rate?

http://www.wholesalesolar.com/produc.../LG300N1C.html

If and only if you connect the panels in parallel do you add the amperage from each panel (i.e. multiply by number of panels.)
If you put them in series, you multiply the panel voltage by the number of panels in a single string instead.
But the wattage into an MPPT controller will be exactly the same either way, with minor variations in practice from wire losses and changes in the CC efficiency with input voltage.


If you are using a PWM CC, then you would be using low voltage panels and would have no choice but to put them in parallel.

[Sunking]

Energy is measured in watt hours, not amp hours. Amp Hours is meaningless baby jigger jabber without a voltage associated with it. To design you determine how many Watt Hours you need in a day. Say 13,333 watt hours or 13.33 Kwh. Battery systems with MPPT are 66% percent efficient, so you would need to generate 20,000 watt hours per day. So how many watts of panels does that take. Well we know 20,000 watt hours, and say we have a 5 Sun Hour day. All we do is factor out the time element. Watt = Watt Hours / Hours. So 20,000 wh / 5 h = 4000 watts. Amps has nothing to do with anything until we determine battery voltage.

Next is what size charge controller with MPPT

4000 watts / 12 volts = 333 amps. That does not work because the largest charge controller is 80 amps. So real dang fast we think: That is why I asked why 2 controllers.

4000 watts / 48 volts = 83 amps. Holly cow that will work with an 80 amp controller. All you need is 1 controller. But still has nothing to do with Amp Hours = Amps x Hours. Midnite Solar Classic 150 is a 91 amp controller and can handle 5000 watts input on a 48 volt battery. You don't need two of them. I just saved you $800.

If we use 13.33 Kwh a day we are looking at a 65 Kwh battery. What Amp Hour Capacity is that? Well it is 65,000 Kwh / 48 volt battery = 1354 Amp Hours. Amp Hours is the very last thing you worry about until you know what system voltage and watt hour capacity has been determined.

So we now have a 1354 AH battery being charged with 83 amps. What is the C-Rate? C = 1354 AH and Amps = 83 amps right? 1354 AH / 83 Amps = 16.3 Hours or C/16.3

Continue with our regularly scheduled program " Hating SK and Finding Your Sense of Humor".

[SunEagle]

Thanks, appreciate it.

The simplest way of determining the charging amps is by dividing the total panel wattage by the battery voltage. So a 4500 watt panel array using an MPPT charge controller for a 48v battery bank would get you 4500w / 48v = 93.75A. That amp level is then divided into the battery AH to get your C/x rate.

[Cult of Dionysus]

Thanks, appreciate it.

Maybe the 6-CS-25PS might be something for me? Would need 8 of them, which would get me 820 Ah and 39.36 kWh of total capacity, of which 19.68 kWh would be usable (assuming 50% DoD). Single string.

With the 15 LG300 Mono panels (4.5 kW), the C rate would be a hair under 9. These panels would generate about 15 kW per day, assuming 5 hours of sun and a 66% efficiency. That is about how much juice I plan to use per day. Though I could imagine there being some additional inefficiencies....

A small Honda EU3000 could augment/backup the system for peak loads and when the deletion hits a certain level....

Am I on the right track now?

[Sunking]

Maybe the 6-CS-25PS might be something for me? Would need 8 of them, which would get me 820 Ah and 39.36 kWh of total capacity, of which 19.68 kWh would be usable (assuming 50% DoD). Single string.

You can go as low as 80% DOD in a pinch. The thing with batteries when you look Discharge vs Cycle Life you are looking at accelerated lab test in a controlled environment under computer control with as many as 5 to 10 cycles in a day. Fact is all batteries have a Calender Life whether you use them or not. When the warranty ends is when the Calendar life Ends.

So when you look at those cycle vc DOD charts first look at the warranty. Example 24/60 is 5 years or roughly 2000 cycles. Now look at the chart and find where the DOD meets 2000 cycles. That will tell you how far you can go, but I did not tell you that.

With the 15 LG300 Mono panels (4.5 kW), the C rate would be a hair under 9. These panels would generate about 15 kW per day, assuming 5 hours of sun and a 66% efficiency. That is about how much juice I plan to use per day. Though I could imagine there being some additional inefficiencies....

Am I on the right track now?

You are on the right track, but your 5 Sun Hours may or may not be true. Off grid systems are designed on the worse case months. True Hawaii has good Insolation and varies widely from Island to Island, and varies quite a bit from one part of an Island say dry side, to the Tropic side with frequent cloud cover. That is where you have to be careful and not make assumptions. 1 of 3 things happen when you do that and 2 of them are BAD.

As I took a quick look of the 5 main Islands December numbers come is at 3.5 to 5 Sun Hours. Only Kahului came in with 5 Sun Hours. The other 4 came in at 3.5 to 3.9. So you need to make sure, not guess or assume.

[Cult of Dionysus]

http://www.focussolar.de/Maps/RegionalMaps/America/Hawaii%20Big%20Island

On the coast in the northwest, right in the blood orange.

[Mike90250]

We won’t use more than 4 kWhs at night, if that much (one load of dishes, tv, lights, fridge/freezer).

So, you can save power, by load shifting. Run that dishwasher in the sunny afternoon with power right from the PV's and skip the +50% battery loss. If your dishwasher consumes 1.5KWh cycle, that will need about 2.5Kwh of harvest to recharge batteries. (if you run it at night), or just 1.5kwh if run while the panels are putting out juice. Timing is everything in off-grid.

[Cult of Dionysus]

So my GC's solar contractor has proposed the following system to me, based on a 12-15 kWh daily use assumption.

24 Suniva OPT270-60-4-1BO panels (6.480 kW)(3 in series, 4 in parallel)
24 Rolls 2V S-1660 batteries (1284 Ah)
1 Outback FP2 system with 2 FX3048T inverters, MATE2, HUB10, RTS, Midnite surge protector
2 Outback Extreme charge controllers (1 for each 12 panels)
1 Honda EU3000iS

This system would have a C rate of about 9.5.

I took a look at the Life Cycle charts for both battery options (24 S-1660s as above and 8 6-CS-25Ps paired with a 4.5 kW panel system). And if we assume 2000 cycles for each, then the S-1660s would be able to deliver about 256 Ahs per cycle (at 20% DOD). Meanwhile, the 6-CS-25Ps would be able to deliver 656 Ahs per cycle (at 80% DOD). If this is correct, then the 6-CS-25Ps would last twice as long as the S-1660s as I would only need to charge the battery bank once every two days (assuming 15 kWh daily use), while the S-1660s would need to be re-charged daily. And I've been told that the 6-CS-25P option would be $1,500 cheaper.

ScreenShot475.jpg ScreenShot476.jpg

Question: How often are batteries moved around during maintenance, if at all? Either set would be readily accessible from the front and top, so unless they need to be moved, the 300 pound batteries should not cause any additional inconvenience.

The FP2 system was recommended as it is a sealed system, which will protect the inverter and charge controllers from dust (which is an issue at the site). The solar contractor is certified on Outback equipment, so he favors it.

[donald]

based on a 12-15 kWh daily use assumption.

What are you doing to use that much power in Hawaii? Arc welding hobby?

One thought on using the Honda as an autostart generator is that both the LP and the auto start are a hack. Who is going to fix it when it breaks? Even though you may never use the generator, I suggest you answer the repair question before picking a brand.

One possibility is to have the generator installed by the good local generator guy. It's only an on/off interface to the charge controller (plus electrical). There's not going to be any value in calling your solar sub when the engine won't start.

I still think the Honda may be the way to go, especially with your big and expensive battery system. If you bought the Generac for off grid you would have a controller that would do monthly testing, which is an advantage. But the hardware is not as well designed and made as the Honda. With the generac and similar you would typically have a service contract and the unit would report monthly to the installer with who you would have a service contract.

You seem to be spending money to insure trouble free electrical service. Part of that equation is service.

[Amy@altE]

Personally, I'd go with the 6-CS-25Ps, but not at 80% DoD. Still plan on a lower DoD, and you'll get an even better life out of them.

I'd also upgrade to the Mate3 instead of Mate2. Your installer can order the FP2 from Outback with the upgraded Mate, or just switch it out himself if he already has the FP2 in stock. MUCH more user friendly and has remote monitoring capabilities with their new OpticsRE capability.

[Sunking]

http://www.focussolar.de/Maps/Region...20Big%20Island

On the coast in the northwest, right in the blood orange.

You need to find a better map as that says you get 2 Sun Hours.