Off The Grid Video

dexter12353 · November 2017

https://www.youtube.com/watch?v=3kLVedPEMkg

Hey guys, New to the forum!

I have read a lot of great stuff on here and has really helped me to build my setup.

I'm not really one for typing novels, so check out the video.

Any tips or anything like that would be greatly appreciated!

Thanks!

Ralph Day · November 2017

That's some really nice setup Dexter.
My only concern is the exposed buses on the DC side of things, especially below the inverter/charger. If anyone happens to brush a tool or a metal coat zipper between them you have a catastrophe waiting to happen with all that battery amp hours. Maybe some industrial shrink wrapping, like is done for boats out of season? Some coroplast taped over them? Something, please.

Do you really need that big a diesel generator? I had a 10kw when off grid, but i had to stuff dump loads on it when it ran to charge batteries. Does your inverter work in a generator support mode like Schnieder products (OUtback too I suppose)? What's the likelihood of needing full loads and full generator loads at the same time? Probably not a likely scenario, maybe 7-10kw would suffice.

Anyway, good looking work.

Ralph

dexter12353 · November 2017

That has so far been pretty much the only concern anyone has had with they system. My original intent was to assemble the system, then disassemble to polish the bus bars to remove any scratches and whatnot, then coat them in clear polyethylene - you can get it in spray-on form. Unfortunately I built this system in summer and the demand to get it up and running for air conditioning did not really allow for me to take it all back apart in order to do said coating and additionally I had not until this last weekend finished the bussing on the second rack.

When I work on anything around the inverter, I disconnect the batteries from the negative bar (Far left of left rack - potential between any tools and rack is zero so not really too dangerous) and then proceed to work on the system.

Inverter does not offer generator support.

In the process of considering a diesel generator, which is not yet complete until I actually order it, I was thinking the inverter output is 12kva, with a battery charger pulling up to 6 kva. In an attempt to avoid having to upgrade the generator at a later time, I figured go for the worst scenario.

Our well was just drilled about 1600 ft from the location of this shipping container, (The well is drilled 530ft deep and from the top of the well to the top of the hill where the water will be used is about 120 ft). I plan to run power down the hill and use the diversion output of the outback CC's to run the pump when excess power is available. I also plan to setup the well pump to run whenever the generator is running. I'm sure the first thought is "HOLY COW 1600 FT?!?"...I plan to step up 240 to 480v single phase, run down the hill with 1AWG Aluminum, then step down to 240v Single phase 50 amp service (12KVA - Matching max cont. output of inverter). The step up will allow for a significantly smaller conductor size and now I don't need to build a whole new solar setup for just the well pump.

I am an electrical trainee, and where I work we do a lot of commercial/industrial feeds...Typically when we order material we go overkill and my boss who is a great family friend really wants to help out with our goal of being off the grid. He is open to excess material going into this project - Thats how I eneded up with two matching 120/240 - 240/480 Transformers. Just gotta be patient and save material one piece at a time.

Thoughts?

Estragon · November 2017

Diesels have traditionally liked to be run at ~75% load, not just to be fuel efficient, but also to prevent wet stacking and crankcase dilution. That said, I see semis running at idle for long periods. Don't know if something in the design of those engines gets around these potential problems. I'm pretty sure PO of my sailboat used to run the 35hp diesel to charge 200ah house batteries for hours at a time while anchored. I had to replace it because of scored cylinder a couple of years ago. It was old, but in a sailboat pretty low hours for its age, which leads me to think the issues are real in at least some diesels.

My inverters have limits for charging and total current draws when on generator, which I adjust according to which one (honda eu2000i, or 4kw diesel) I'm charging with. You really shouldn't need to way oversize the genny for "worst case".

dexter12353 · November 2017

I'm certainly going to need to re-evaluate this when I know what the actual load that I will have to run the well - They put the pump in on Tuesday this week....the draw for the Battery Charger (120A@48v) is 5760 watts (24 amps at 240v) in a perfect world. That would be Let's go hypothetical and assume the well is drawing about 20A at 240v which is not an unreasonable figure based on the circumstances - We will most likely need a booster pump at some point too, so that can be a calculated load.

~6KW for battery Charger
4.8KW for Well pump (Estimate)

10,800/18000 = .6 = 60%

That's 60% generator load

Add a few other misc loads that are typically on (15% of 18kw is 2700w so that doesn't bring quite all the way up to 75% load...)

But either way we are close to that 75% mark you suggest.

What if I need to run the air compressor and plasma cutter - That uses the full 50 amps@240v my inverter has available. If the generator is running I dont really want to have to shut it down to do work in the shop.

If we were to go with a 10kw genset, then we would in theory (Because actual well load is not yet known) be exceeding power capability of that genset.....I want the generator to auto-start and I do not intend to be there babysitting the draw of the battery carger at 3 in the morning when the batteries might go dead.

It leaves some cushion for future expansion....Buy right the first time so you don't have to buy twice?

Note: Battery charger shown in video does allow for output percentage adjustment.

Thoughts?

mike95490 · November 2017

Look into the Generator Support feature on some of the better inverters. My 6 year old XW-6048 does it well. You program in the generator capacity, and your battery charge rate. When it senses the approach of the limits of the generator, it throttles back battery charging. If Generator continues to increase, it switches from battery charging, to inverting, to share the load of the generator. Set up right, it's seamless. When loads release, battery charging resumes.
Some folks say outback works / or not, others say XW works (Me) / some say not.

Estragon · November 2017

My Outbacks will dial back charging to supply increasing loads, but AFAIK, won't draw from the bank if loads > generator limit. A generator support feature might work well for OPs situation.

Just to put it out there though, off-grid means trade-offs. Sometimes the trade-off is money, but sometimes throwing money at the problem hides a bigger issue. On-grid, you turn on a load and it usually works. Someone else handles management of loads, peaking vs baseload capacity, etc. Off-grid, you're the manager.

For example, you say the pump load is 20a@240v. Is that LRA (to start pumping) or running amps (to keep running)? You mentioned needing a booster pump. Is this to boost pressure from a cistern? If so, filling the cistern is best done when the sun shines, not at 3am when AGS kicks in to charge a depleted bank.

Likewise, a compressor typically has a large startup surge load, and a much smaller running load. Inverters will handle a surge of ~ 2x rated output, but a generator probably won't. This means you need to get both start and running requirements for these kinds of load to size things properly, and a generator support feature like @mike95490 described may be nearly essential.

Off The Grid Video

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