Small off-grid system in Hawaii

[inetdog]

One of the things that you will see discussed here is how to get the most out of your generator with the least fuel and lowest run time.
If your generator is not the inverter output type, which allows the engine speed to be reduced without affecting the output voltage or frequency, then you want to minimize the amount of time the generator is running with a low load.
Your battery bank and inverter will help do this. To make sure that your batteries get to full charge, especially when your panels are not able to completely replace the energy used each day, you need to keep the batteries on charge for longer than the time your panels are producing useful power.
The general consensus is that the way to bring in the generator for charging is to use the generator for a few hours first thing in the morning to do most or all of the bulk charging, and then turn off the generator and let your panels and CC take on the job of finishing the charge.

[jflorey2]

We'll be starting out with just our generator for the first month, and then moving towards building a battery bank for that. Solar was the last part of my thought process because we are approaching our energy needs primarily through our generator, and then finding more efficient ways to complement that (diverting low power needs to battery/avoiding nighttime use), so solar would be to help us maintain our battery bank, and not our primary energy source. Please advise if you have thoughts or disagreements with that approach . . . .

I think that's a very reasonable approach. It gives you fairly reliable power and allows you to take good care of a battery bank when you are starting out. The solar you will add later can then be used to reduce generator run time; if you get bulk taken care of in the early morning (i.e start before sunrise) you can then get the best efficiency out of your generator and leave the end of absorb/float for solar.

If you need more reliability, then a second generator is a pretty good investment. That way one can be in town getting rebuilt when it dies while the second carries your loads. The EU2000i is especially nice for this since it's so portable.

The true thing is that math will save the day in the end, huh? Just need to pin down all the variables and calculate it out.

Realizing that will put you ahead of most people trying to get started with off-grid living. Good luck and let us know how it goes.

[mia.da]

Hello everyone! Many spreadsheets later...

Up top, I'm very enamored of Midnite Solar's Kid. Obviously their Classics are incredibly nice, but the ability to stack Kids will be helpful to me in starting out small and increasing the system later. And, hey, MPPT.

And yes, (math saves the day) I'm looking at a 24v or 48v system. I like that it means I can have my battery bank in series, no parallel strings, and meet daily Wh needs. Wiring is better. No, I'm not an electrical engineer, but yes, I understand voltage drop, and that amps & voltage are inversely proportionate when you want to deliver the same amount of power, resulting cable size, etc.

Overall I'm aiming for that sweet spot for a good entry point, but don't want to corner myself in from future expansion. Pricing looks to be around $3000 for the system I'm planning (I'll probably throw on another $500 buffer for random nuts & bolts along the way) and I'll be able to purchase items in steps, but still have functionality along the way- first the generator & headlamps stage, then a battery bank maintained by generator, then solar panels & charge controller, then nicer/larger inverter at a future time.

Re: jflorey2 & generator reliability- the EU2000i is well suited to pairing, we'd probably look at picking up a second one at some point! Another good thing is if we're in a dire pinch before we do that, our friends nearby have portable generators as well, for now.

A challenge in Hawaii is always availability and shipping cost, which trickles down on way or another.

Batteries- Trojans/etc are higher cost here. And funny enough, almost everyone I've come across just goes to Costco for the GC2's? I know they're not as high quality as other brands, but for my first time around, it wouldn't be a bad set to try out on, will it? Easier replacements/readily obtainable stock/reliable source. My ideal would be T-105's or L-16's. Weighing it out. A friend out here has had his bank of GC2's going for 8 years now, but I don't know his specifics.

I found a Steca fridge in stock out here (5.8 cu ft, aiming to purchase 8-10 months from now) that also can run on 24 volt, and is more efficient than a not-available-out-here Sundanzer of the same size (140wh/day for Steca with average residential use at 35°C/95°F, our location will normally be between 50°-85°F, so could expect better). It's rather neat- digital controls, can be programmed as a fridge or freezer. Planning ahead.

[Logan005]

Sounds like a well though out plan. hope to see some future pic's of wiring and battery bank. maybe a pic of your vista. are the GC2's sealed? or FLA?

[Mike90250]

Hello everyone! Many spreadsheets later...

Up top, I'm very enamored of Midnite Solar's Kid. Obviously their Classics are incredibly nice, but the ability to stack Kids will be helpful to me in starting out small ....

Stacking kids is the same as paralleling any controller. each controller has to have it's own PV array, and the outputs go to the battery bank.

[mia.da]

Logan- GC2's are FLA, 208ah. $85 here. T-105's are closer to $200.

Mike- Oh, duh! That's true. I must have been more enamored with Midnite's approachability/marketing- one part art deco, two parts 70's magazine print ads!
I guess that you can sync the Kid via cable (must be like other cc's), but I must say I haven't surveyed the field for all the possible charge controllers that would be good for me. More research.

[inetdog]

Stacking kids is the same as paralleling any controller. each controller has to have it's own PV array, and the outputs go to the battery bank.

In theory two MPPT CCs could exchange information for the MPPT algorithm, which would let them share the same array too. But I have not seen that feature advertised yet.

I take that back. I have now. From the Midnite manual for The Kid:

Can be input paralleled for a true 60 Amp single controller

Twin Mode: is true paralleling where the inputs and outputs are paralleled. You are allowed only two KIDS in Twin mode. This is a Master/Slave configuration. The Master Twin tells the second Kid what to do.

Sync Mode is where the outputs are paralleled, but each input has its own PV array. Twin mode only works when two kids are connected. Sync Mode: When any one of the KIDs change state, Absorb, Time, Float or Equalize it sends a signal downstream to the next one to follow and change state. Then the second one sends the same message downstream and so on until it finally comes back around the communications circle and all units are in the new state. There is no limit to how many controllers can be connected in Sync mode. Both Sync and Twin mode are MidNite Solar exclusive methods of applying multiple controllers.

The sync cable is actually a serial data/networking cable, so it can enable anything that the firmware was written for.

[zed]

My shopping list to the OP?

Allow say...US$15k

1 x Sunny Island controller
1 x Sunny Boy TL grid tie inverter
4 x AGM 200 AH batteries in 48V string

8 x 200w 24v solar panels...(.add more later if the Sunny Boy is big enough)

Then get one of the new Samsung Fridges with inverter compressor technology (40 watts on full sing)

problem solved and scaleble

[mia.da]

Just a little update

We are now two months into our adventure, and we just graduated from the headlamps-and-solar-lights stage into the generator stage! We drove our brand new Honda EU2000i home today.

Looking back on these few weeks, I must say that roughin' it is... rough! (Short list: mold, rain, more mold, getting water, lack of regular showers/hygiene, timing perishable foods, isolation/learning how to be out in the sticks), and really, I think any of the difficulty is in the transition itself, because it gets easier every day. It is completely worth it. I also, ha, won't look at modern convenience and infrastructure the same way again! It's been a fascinating process whittling down to the bare essentials, and I'm thankful to experience this before building our own infrastructure back up with newer eyes.

Soon we'll have a bathhouse and water catchment set up... Next up in electricity land will be a battery bank!

[Logan005]

sounds like you are off to a good start, learning to live with less electricity is very hard, but worth it in the end especially if you only need a 500lbs battery as opposed to a 1200lbs battery.

[jflorey2]

Just a little update

We are now two months into our adventure, and we just graduated from the headlamps-and-solar-lights stage into the generator stage! We drove our brand new Honda EU2000i home today.

Looking back on these few weeks, I must say that roughin' it is... rough! (Short list: mold, rain, more mold, getting water, lack of regular showers/hygiene, timing perishable foods, isolation/learning how to be out in the sticks), and really, I think any of the difficulty is in the transition itself, because it gets easier every day. It is completely worth it. I also, ha, won't look at modern convenience and infrastructure the same way again! It's been a fascinating process whittling down to the bare essentials, and I'm thankful to experience this before building our own infrastructure back up with newer eyes.

Soon we'll have a bathhouse and water catchment set up... Next up in electricity land will be a battery bank!

Good to hear it's going well. In a few months, you'll be the one giving advice to the people here who buy a $500 solar kit and decide to "go off the grid."