Propane/Gas Generator to use for charging solar battery bank?

Hello all,
this is my first post, so please be patient!

I looked through a bunch of threads that relate to my questions, but couldn't find enough info to make a decision.

I'm building a 1000 square foot off grid home in the Southern Gulf Islands in BC. It rarely drops bellow -5 here, and rarely hits +30.
I live alone and am fairly frugal with my power, so it's a small solar array.
12 335w panels and either 8 or 16 Surrette AGM Battery, 6V, 460 Ahr - 2.7kWh per battery, creating a 4KW system.

I'm looking for a generator to connect to the system to charge the batteries when they drop too low in the winter/high usage days.
the generator would only be for charging the batteries, not connected straight to the house. It would be wired to turn on when the batteries fell bellow 50%, so as far as I understand, any loads from the house would still be fine, as the batteries can supply power while being charged.

I know I need these features in the generator:
electric start
auto choke
2 wire system.
remote start capability

I'm curious how important folks think the following are:
auto primer (I'm hoping to use propane)
low oil sensor/shutdown
overheat sensor
overcrank arrest

Curious about using a 'portable' generator (which would allow me to take it offsite for work on other parts of the property etc)/vs 'home' generators.


I need something available in Canada.

I'm mostly interested in lived experience advice. Thanks!

Hi Meg! Welcome to Permies.

Folks around here love this kind of challenge. Stay tuned!

meg mayne wrote:Hello all,
this is my first post, so please be patient!

I looked through a bunch of threads that relate to my questions, but couldn't find enough info to make a decision.

I'm building a 1000 square foot off grid home in the Southern Gulf Islands in BC. It rarely drops bellow -5 here, and rarely hits +30.
I live alone and am fairly frugal with my power, so it's a small solar array.
12 335w panels and either 8 or 16 Surrette AGM Battery, 6V, 460 Ahr - 2.7kWh per battery, creating a 4KW system.

I'm looking for a generator to connect to the system to charge the batteries when they drop too low in the winter/high usage days.
the generator would only be for charging the batteries, not connected straight to the house. It would be wired to turn on when the batteries fell bellow 50%, so as far as I understand, any loads from the house would still be fine, as the batteries can supply power while being charged.

I know I need these features in the generator:
electric start
auto choke
2 wire system.
remote start capability

I'm curious how important folks think the following are:
auto primer (I'm hoping to use propane)
low oil sensor/shutdown
overheat sensor
overcrank arrest

Curious about using a 'portable' generator (which would allow me to take it offsite for work on other parts of the property etc)/vs 'home' generators.


I need something available in Canada.

I'm mostly interested in lived experience advice. Thanks!

hi meg welcome to permies.

Usually when you have a system like you described the generator runs the house using a transfer switch built into the inverter freeing up the inverter to charge batteries. Therefore you size the generator to charge batteries and run the house at the same time. You can do it with a smaller generator but you have to be mindful of your loads and it can take a lot of hours to charge the bank.
So there are options. Portable generators are usually cheaper but do not have two wire start capabilities. They might have a remote or a switch of some sort. Those can be modified to do two wire start voiding warranties and such. Many of them are not code compliant either in terms of propane shutoffs, safety enclosures etc. They are less expensive though.
Next comes the standby generators. I've been involved with the briggs, the generac, the winco and the koehler. They are all good with some pluses and minuses to all of them. Standby generators tend to have heavier duty longer life engines, oil filters, air filters so will last longer and are fully code compliant but they come with a price. I like the Kohler 8kw as a good compromise between size and price. Smaller then that and your run time is too long to charge batteries, too big and a lot of that capacity sits idle. Hope that starts the ball rolling.
Cheers,  David

Hi Meg;
Here is what I use  https://permies.com/wiki/98034
And here is how I converted it to Propane.  https://permies.com/t/96351
Here is how I wired in remote start and stop. https://permies.com/t/99015

We moved into our cabin with a 4 KW system with 8 Rolls Surrette 445 Amp-hours batteries in July. We've been using a portable Honda EU 2200i generator. It's a pull start and doesn't have have any remote options but has been effective and fuel efficient so far. In use it powers the house and the inverter charges the batteries with any excess power. Like David said, charging is slow going. I'll typically fire up the generator when our batteries get under 70%. After 4 hours or so it'll be around 85%.

We have a 12000 BTU mini-split system that the generator can run along with lights and still charge the battery bank but that's operating right at edge of it's load limit. It's proved invaluable during this recent freak Texas winter Armageddon and the occasional stretch of overcast days. If I had a larger bank I would get something slightly bigger though.      

A new place, exciting!

I'm not sure what your budget is, or how quickly you are going to have everything up and running, but if budget is somewhat important and you have the time, I might recommend starting with a modest portable generator, perhaps even one without all of the auto-start options, fully manual (okay, getting yourself an electric start model may be a good idea), and then you can be more informed about your specific needs in terms of buying a dedicated home generator with all of the features.

My thinking is that after living in the house for a bit of time you will be able to gauge how well your panels and batteries are meeting your power needs. You will better be able to answer the question of how frequently the generator is needed. Will you need it twice a year, once a month, 3x per week? If you are finding that you do not need to use the generator very often you can probably get away with a very simple system with a portable generator only. It will be cheaper, possibly simpler, easier to switch out in the future, and you will have a portable generator to use elsewhere as you suggested. When you notice the batteries getting low, or when it is convenient for you, you can start the generator and let it charge away. When it is done, switch it off. This is what I do. Though, an automatic system would be lovely....



Aaron mentioned the Honda EU generators. They are highly coveted machines! I've used them a lot in contexts outside of an off-grid home and have been very impressed. They are quiet and reliable, though much more expensive than other similarly sized generators. "Inverter generators" like the Honda EU series are especially good at throttling the engine up or down depending on the power demanded from it. This means that it is quieter and more fuel efficient. A typical, non-inverter, generator needs to be spinning at a certain speed in order to create proper AC power. So if you have a big generator and you only need a small amount of power from it, the engine will still be required to spin at full speed -- this equals unnecessary noise pollution and fuel burn. This also leads us to a discussion of battery charging and choosing generator size.

Often you can find generators available for resale, the trouble is getting them moved. Either Craigslist or generator maintenance people are good places to look.

My system is much larger so my personal experience isn't likely to be helpful. We have a 20v Koehler and a 48v diesel DC Shawnee.

Hello Meg
I already have in place a 48V system along the lines of what you are describing, with 15-300W panels, 8 Trojan L-16 batteries, and a Schneider XW+6848 inverter.  Take a look at the larger Magnum, Outback Radian, and Schneider inverters.  They are all designed to produce split-phase 120/240V AC, and all have a built-in generator charging circuit.  That is, along with the AC-out terminals that lead to your main electrical panel, there's also AC-in terminals that you can connect directly to a generator, usually 240V.  You simply wire the the appropriate generator fixture that looks like this on the wall next to the generator, then lead a four-prong electrical cord from the generator right to the wall.

The transfer switch is already built into the inverter, so all you need to do is start the generator, flip on the power, and the inverter will start accepting generator power to charge the batteries.  You'll need to go into the inverter's control menu, and specify the size of the generator, and what charging rate you want.  Then it's completely seamless.

Personally, I would suggest going with propane, though I myself am still using gasoline.  I would never, ever recommend auto-start with a gasoline generator, because I remember the day that I started the generator and noticed some funny motion underneath it.  The gas line from the tank to the carburetor had vibrated off, and gasoline was dribbling out of the tank onto the running engine.  Flipped the off switch just in time.  That was a valuable learning experience!

Unless you want to run a well-pump, or other really high-powered equipment, this Conext 4048 might be a good fit for you.
https://ressupply.com/inverters/schneider-electric-conext-sw4048-120240-invertercharger

Hi Meg,

I just saw your post here and I decided to reply. First, it is my first post in this forum as well and second I'm from ON using the solar energy in our off grid house.
I've got an 48V system using 8 of 445Ah Sourrette batteries charged by 2 Midnite Classic 200 and 2 PV arrays: 3.9Kw and 4Kw. I use a Magnum 4.4Kw inverter.
As all of us from Canada, in the winter the big challenge is the sun availability. Personally, so far this winter I'm experiencing an average of max 8h of sun per week plus snow covering the array regularly. As a result, the only option which I have was to charge the batteries by the use of generator.
I purchased an Westinghouse 7500DF, 7.5KW dual fuel(gas/propane) generator using it on propane. I'm running it usually every second or third day around 3 hours. I calculated the cost based on propane rate and came with around 1.8CAD/hour. It's quite an expensive solution plus don't forget that the oil needs to be changed at every 50-60hours. The generator is starting automatically based on battery voltage.

Hi Floyd! Great first post. Welcome aboard!

Wow! thanks everyone for your responses. What a wealth of knowledge and experience..

I should have mentioned that I will be using a Conext SW 4048 Inverter & Midnite Solar Contoller. The thought is to use it with a Conext AGS.
From what I've been told, with home generators it's usually best to aim for a generator that is double the wattage of your system, so in my case that would mean an 8kw gen.
As mentioned by a couple folks here, by the time you'r at that size in portable generators, they are very loud and running at full throttle all the time.
I think I'll get something that can be coupled, and start with one, maybe this one: https://www.championpowerequipment.com/product/100396-3400-watt-dual-fuel-inverter/ to see how well it can keep up, and buy a companion if needed. They run at just under 60 dba.
As John said, it would be nice to live in the house for a year or two and figure out what my needs really are before spending a big pile of cash on a generator.. This seems to allow for that.
Alternately I'd been looking at the honda 2200i companion option, but price wise it's way more.. I know they're great, I've used them on job sites, and the weight and quiet is amazing..
No auto start with either of these, but as I'll be ironing out kinks in the system, it might be good to physically go to the shed and check on batteries etc. at first.

I also found this one https://westinghouseoutdoorpower.com/products/wgen7500df-generator-dual-fuel which seems like a nice compromise of all the aspects I'm looking for. Quiet for the size and style, reasonable price, portable, powerful enough... but I seems to be completely unavailable to buy at the moment...

Thanks again for all the info and suggestions. super helpful!

Hi meg, sounds like you are well on your way. The schneider 4048 is a good solid machine. Waiting and seeing what your needs will be sounds like a very permie view of it. I would say if you go for the 3500 portableI dont think there is much advantage to the inverter generators. They shine when you are using it at a partial load and saving fuel. With a bank of l16 batteries when you do use your generator you will be using it pretty hard.
Have fun,  
Cheers, David

I have a question, why such a large generator when the load is really not that high, right pissed off with the high cost of power theses days. With most loads in my house are low, except a fridge and freezer, but with a few life style changes, I can get the load to be very low, LED lights ect. So can’t a battery pack sized to the load, and then inverters ect, but can’t a small generator do this or is it just better to last a 8000W generator to fast charge batteries.  Or why can’t the generator come on when battery life is low and slow charge them. I don’t want solar panels, just figured a few battery’s. Is this do able or not.
 At a reasonable cost. Especially when not being used there isn’t much cost to charge ect. Summer when lots light, bbq ect not much need for power. Just winter months, but mostly use a wood stove.

Stan Hudson wrote:I have a question, why such a large generator when the load is really not that high, right pissed off with the high cost of power theses days. With most loads in my house are low, except a fridge and freezer, but with a few life style changes, I can get the load to be very low, LED lights ect. So can’t a battery pack sized to the load, and then inverters ect, but can’t a small generator do this or is it just better to last a 8000W generator to fast charge batteries.  

One of the important issues is that the inverters tend to be fussy about the QUALITY of power being given to it.  The inverter is looking at the voltage, Hz, and waveform to decide if the generator is "qualified" to submit power to the inverter.

In my own personal experience, what I have actually seen is that my generator's power will not be accepted by the inverter at higher amperage levels, but will be at lower levels.  So, as the load in the generator becomes higher and higher, the generator has a harder time producing power as clean as at lower levels.  Interestingly, a second observation is the power gets cleaner as the generator warms up to it's proper operating temperature.  So, a charge level that's fine when warm, won't get qualified on the cold generator right at startup.

One real-world procedure that works well for me is starting the generator and making the initial charge setting just 10%.  Then after a few minutes, I ratchet the charge level up to about 45%.  It works.

Hi everybody, and meg mayne!

I found this string in the course of searching for discussions about the ability to use portable generators with Schneider's AGS. The jury's still out on that but I suspect it won't be possible. (I have a 4.5 kw array, 900 ah battery, Conext XW 5548. My Generac Ecogen 6 kw died last spring and we're considering replacing it with a portable generator because of the price difference.)

@meg mayne, I looked at that Westinghouse generator you linked to and saw that it didn't have one of the requirements the Schneider customer service person listed, which is that it needs to have a floating (not internally bonded) neutral, or else the inverter won't qualify the power. In my experience this is the requirement that disqualifies almost all of the portables. (That and THD, but some do exist with that under 3%.) If by chance you went with the Westinghouse, is it working for you?

Thanks for a great discussion.

Karin

I looked at that Westinghouse generator you linked to and saw that it didn't have one of the requirements the Schneider customer service person listed, which is that it needs to have a floating (not internally bonded) neutral, or else the inverter won't qualify the power. In my experience this is the requirement that disqualifies almost all of the portables

That is not as daunting as you think.  For many generators you simply pull off the generator enbell and locate the internal neutral to ground connection.  Most are a white wire and a green wire that is screwed onto a post bolt attached to the enbell frame.  Simply detach the white wire, leaving the green wire bolted to the frame.  It's that easy.

BTW, if you have the enbell off, you might want to make a voltage adjustment at the same time.  After the connections are changed, start up the generator and put a load on it.  Look for the voltage regulator, which will be a small black plastic crescent-moon shaped object about 2" across.  It will have a tiny little adjustment screw that you can adjust the voltage with.  Adjust it while under load to the exact voltage you want.  After getting your voltage just right, shut off the generator, and put the enbell back on.

Hi Karin,
A link to what Michael is talking about explaining it a bit more thoroughly:
https://generatorbible.com/blog/bonded-to-floating-neutral/

Michael, good stuff. I'm new to gennies having just inherited a portable. I understand the principles fully, but information on the field hacks is gold.