Cabin solar setup with Auto start generator as backup

[tym90]

Hello all, new to the forums, but have been tinkering with solar for about 5 years now.

A little backstory.
I recently acquired a small cabin up in the mountains in Montana. It's around 2 miles from any electric access and currently it's being powered by only a generator. I'd like to add solar, and have an auto-start generator to maintain the batteries "hassle-free". The cabin will mainly be used to let friends and family come up and enjoy some time in the mountains and I'd personally like it to be as simple for them as possible and not have to mess with any kind of generator when they arrive.

I'm in the process of building a shop behind the cabin that will have a ~3k watt solar array on it and likely 2x Trophy Batteries 48v304E-2 for 30kwh of available power.
Shop will likely house the main panel and the cabin will be on a sub panel. I know there are hybrid inverters out there all the way from the low range of the 5k growatts for $800 all the way up to the solark 15ks for $7k+ that have an AGS option on them. I guess what I really want to know is what experience do any of y'all personally have with a setup like this and what hybrid inverter/generator combo do you run/like? I'm not opposed to spending money on a more expensive inverter if it's worth it for the application, but if a cheaper option will do what I need it to do I'll go that route.

If I could use the current generator on the property that would be a huge plus, it's a pretty expensive Perkins diesel generator with a 100gallon fuel tank and a little Dynagen ES52 Auto Start Generator Controller.
Perkins Generator

Only other question would be how are these typically wired in to the system? I've done a few decent sized off grid systems but nothing with a second power tie in alongside the solar.

Appreciate any help and any advice on products y'all are familiar with and like for this kind of application!

 

[DIYrich]

Most off-grid inverters can 2 wire control a generator. Growatt is good price. Schneider and Outback are worth the premium price if you are there 24/7. You don't need the added features of grid tied inverters.

There is an AC input for the generator, and a 2 wire control connection. Make sure the inverter has either: 1) 3 wire connection so you can select open or close to run generator; or 2) the right 2 wire connection for the Dynagen (assuming the dynagen can accept 2 wire inout).

BTW, "dry contact" is the two wire start on the growatt. Growatt is 240v, so you will need an auto transformer for split phase 120/240.

Generator will need its own lime to the inverter. Plan for that when laying wire between buildings, if generator is not by the inverter.

 

[SamDeleted]

You can also get a separate box to start the generator based on battery voltage , not sure on models , will do some research if you are interested...

I think victron smart shunts can do this also ,

 

[tym90]

Most off-grid inverters can 2 wire control a generator. Growatt is good price. Schneider and Outback are worth the premium price if you are there 24/7. You don't need the added features of grid tied inverters.

There is an AC input for the generator, and a 2 wire control connection. Make sure the inverter has either: 1) 3 wire connection so you can select open or close to run generator; or 2) the right 2 wire connection for the Dynagen (assuming the dynagen can accept 2 wire inout).

BTW, "dry contact" is the two wire start on the growatt. Growatt is 240v, so you will need an auto transformer for split phase 120/240.

Generator will need its own lime to the inverter. Plan for that when laying wire between buildings, if generator is not by the inverter.

Awesome, appreciate this info. I’ll check out the Schneider and outback. Generator , inverter, and batteries are all going to be in a “power” room in the shop so wiring should be fairly easy. So sounds like you just treat the generator as “shore power” when wiring it to the inverter, correct? Thanks again for the info.

 

[tym90]

You can also get a separate box to start the generator based on battery voltage , not sure on models , will do some research if you are interested...

I think victron smart shunts can do this also ,

Personally don’t want something to start on battery voltage given I’ll be running LiFePO4. Would rather something that reads SOC of the battery farm to trigger the generator.

 

[DIYrich]

So sounds like you just treat the generator as “shore power” when wiring it to the inverter, correct? Thanks again for the info.

yes.

 

[tym90]

yes.

Great, I was making this much more complicated than it really is in my head. Hahaha. Appreciate the help!

 

[SamDeleted]

Personally don’t want something to start on battery voltage given I’ll be running LiFePO4. Would rather something that reads SOC of the battery farm to trigger the generator.

Yes I understand, I know the victron bmv-712 can trigger a relay based on SOC

 

[MichaelK]

Design your system properly, and you won't ever have to depend on the generator at all. I had a very scary experience once with one of my generators, and would absolutely never allow one to start when I was not physically present.

Since you are building the shop and I assume will be using a lot of power tools, you need a quality sine-wave inverter. I'd forget the Sol-Ark completely, and go with a Schneider XW Pro instead. Side by side testing has demonstrated that a single XW6848 can outperform a single 12k Sol-Ark.

Since panels though are so cheap right now, I'd recommend going with 4000-5000W of panels instead of just 3000W. Will there be a well-pump? If yes, you'll be very happy with an XW6848.

 

[Madcodger]

Design your system properly, and you won't ever have to depend on the generator at all.

Oh, come on... EVER? It's a remote cabin in Montana. That either means the OP would need a bunch of elves clearing snow and ice off the panels, and/or one heck of a giant battery bank, and/or they just winterized the place to the point it doesn't even need electricity. If panels are near freezing temps as it starts to snow, that snow is much more likely to stick, and form ice. And if they get an actual ice storm and a few days of clouds? Even worse. It can take days for that ice to shed, even at a 60 degree tilt.

Inverter-chargers have generator start relays for a reason - there's a need. Could something bad happen? Sure. There are stories of appliances causing fires somewhere in the world, every day, but that doesn't mean we just stay home and babysit them. There are literally millions of auto-start generators in use all around the world, many of them at remote, uninhabited locations. If installed and maintained properly, they're an important and safe part of the infrastructure of those locations.

To the OP: It's hard to beat Victron. Rock solid reliable, proven in harsh marine and remote, off-grid environments. Several inverter-chargers to choose from, depending on your needs. Dexter at Current Connected very active here with an excellent reputation. I moan about Victron's lack of UL certs for the US market, but if that's not essential, I don't think their equipment can be beat.

 

[50ShadesOfDirt]

What are your fuel and storage options in that area? Is it easier to get diesel fuel or propane (in large quantities) in at various times during easy/hard seasons?

The diesel 1800rpm gens are great, and you absolutely have a backup power source that won't stop (except for maintenance) ... but diesel fuel is messy and heavy, and unless you really figure out the storage and usage patterns of it, it's going to get messier. A homesteader can handle it, but guests probably won't be good at it. You might be able to get a service to refill/maintain the system, but that could get iffy at times.

Propane, if you can get it in that area, can be stored in big site tanks (500 gallons or larger), and plumbed to the (propane) gen. I use an automatic start westinghouse wgen9500df ... it starts with a remote fob. There is no fuel-handling at all, when plumbed into propane, and a local propane supplier would just keep the site tank full.

Instead of training your guests to work the diesel and refuel/maintain it, I'd tend to keep that as the supreme backup power source for "everything else has crapped out" (and sooner or later, everything else will crap out, at the worst possible time). Instead, use the remote fob start gen to refill battery-banks when solar isn't filling them. Guests can look at a panel inside the house to see the SOC ... if low, remote start the propane gen. If battery-bank runs dead, remote start the gen, and everything automatically comes back to life.

wgen's are roughly $1000, and they last about 2000 or so hours. Get two, and one can backup the other, while the other is undergoing some scheduled maintenance. This is what we do. If one dies a horrible death (after a few thousand hours), we feed it's parts into another one, so we actually recycle generators.

The xantrex/magnum/victron (tier-1) inverters would also match up well with a "guest scenario", whereas the AIO inverters might be a tad "iffy" unless you had two (where one can carry the entire load for the other) and you had someone (a homesteader) who could sort out issues with, and recover from, a failure of one of them. This forum abounds with AIO support stories that makes me think a tier-1 would be better for guests ...

Hope this helps ...

 

[MichaelK]

Oh, come on... EVER? It's a remote cabin in Montana. That either means the OP would need a bunch of elves clearing snow and ice off the panels, and/or one heck of a giant battery bank, and/or they just winterized the place to the point it doesn't even need electricity.

Well, I had a generator for my own system. After several years of just sitting there doing nothing, the piston rusted in the cylinder. I finally forced it free by unscrewing the spark plug and spraying the inside of the cylinder with WD-40.

In the six years of operation of my new system, I've never HAD to start the generator to charge my batteries. Now I simply start up the generator every few months to make sure it can still run.

I now use the generator for welding projects only. I don't want to abuse my inverters that way.

 

[Horsefly]

Our cabin was built in 1974 wired completely for 120VAC, but with only a generator available. In 2017 we put in solar, and like @MichaelK the generator never is required any more. My brother likes to run it, so at least once per year it does get run for a few minutes. Otherwise, I think it might freeze up like Michael's.

Our system is currently pretty much all Schneider, but if I were doing it again I would certainly go with Victron instead. Schneider stuff is definitely rock-solid, but Schneider has a history of not being very DIY-friendly. They also routinely declare things end-of-life after a relatively short number of years. Victron is just as dependable and well-made, but has tons of forward-thinking DIY friendly features like Bluetooth connectivity, VenusOS, CerboGX, etc.

 

[Madcodger]

If you do go with a generator, please remember to run it periodically (once per month would likely do it but we try to so it once each week). Allowing an engine to sit for months (years!) on end, probably with fuel, and then thinking it should just fire right up and run fine is a bit into fantasyland. You'd think people would know that, and yet that doesn't seem to always be the case.

 

[jimf909]

Re: diesel v. propane? The OP has a 100 gallon diesel tank. I assume this is connected to the gen set and there's no need to refill except when the diesel delivery truck comes at the start of the season with winter treated diesel. If not, a basic fuel transfer system will be as simple as turning on a switch to transfer the fuel. 100 gallons of diesel easily fuels my Perkins/Marathon genset through a winter at 48+ degrees latitude (although I have 200 gallons of storage). Propane would be a good consideration if he OP didn't already have a generator portion of this system has been well designed for a few dozen winters.

Re: AGS is even easier than watching the SOC and hitting the keyfob: AGS will just run the gen as needed, no need to give it any thought. A good AGS system will also account for quiet hours, etc. Just alert the guests that the gen may start on its own and it's nothing to worry about.

Re: not running a genset? Days are short and sometimes cloudy up here and it's hard to have enough solar to not run the generator. Granted, more solar is always better but some situations require a generator as part of the mix.

Re: allowing a genset to sit? A decent AGS will exercise the generator at least once a month or more frequently to ensure that it's ready to run when it's needed.

 

[jimf909]

Re: Can you use the existing Perkins genset? Probably. How many hours are on it and has it been maintained? Is it clean, i.e. no oil leaks, injectors not leaking, etc. If you're not skilled in maintaining a diesel, find a local diesel mechanic (hopefully you'll find one through recommendations) to visit the site and provide an evaluation of the motor.

These diesels are operating 24/7 unattended in ag, forest and industrial settings around the planet. A cabin setup is childsplay.

Keep air and oil filters on-hand, maybe a solenoid and relay or two and change the oil every 500 hours or as recommended in the manual. If you don't have the manual get one online. Ensure that the diesel is treated for cold weather. It will either be treated by your delivery company or you'll need to treat it with an additive. These diesels can run for 10s of thousands hours with simple care and feeding.

Get your engine serial number. Consider using the Perkins Myengine app so you have details of your motor handy. It's not the end-all but it's handy to have.

https://www.perkins.com/en_GB/campaigns/myengine.html

Connect with your local Perkins distributor for parts and support. I chat with Joe at NW Power Systems in Boise and he's darn helpful if you have the engine serial number and ask straightforward questions.

Perkins distributor locator | Perkins

distributorlocator.perkins.com

Re: How are they wired to the system? I have 6 AWG (overkill) running from the genset to the AC input on my inverters and wires running from the AGS on my Cerbo GX to the genset auto start module (Deep Sea in my case).

As always, there are many ways to skin this cat. Ha! Don't be surprised if you see the Perkins diesel associated with CAT, CAT bought Perkins awhile back.

 

[jimf909]

OP, as you keep digging in to this you'll want to understand if your generator is a 4,6,10 or 12 wire generator. This relates to how the stator wires are connected and provides for a number of different output configurations ranging from 480 to 120 volts and three to single phase.

See pages 6-9 in this manual for the range of outputs a 12 wire generator can provide:

https://www.marathongenerators.com/generators/docs/manuals/SB504.pdf

A high level overview:

https://ps.buckeyepowersales.com/wp-content/uploads/2021/06/BPS_113_Generator_101_Part4.pdf

You may not have to change a thing but knowing that alternative outputs are available may be helpful based on how you design your system.

p.s. consider asking a mod to move this from Tiny Homes to Off-Grid.