Cabin in the mountains with 12 kW Kohler Generator. Need to add batteries and get off-grid. I need feedback on my plan

[Old_Skewler]

Hello everyone,

I have a hunting cabin upstate NY currently powered by a Kohler 12kW Propane generator. I am trying to make this cabin more of a residence, so power becomes a critical item and propane gas is getting costly. I would like to make this cabin more off-grid.

My peak load is about 2,500 Watts with 4.5 kWh/Day energy usage. I could fine tune these numbers. For instance, my chest freezer converted to fridge is using more power than anticipated, so I may need to get a different brand.

The genset is 240 split phase and wired to a distribution panel: the cabin is 120V but the generator produces 240V.

My plan is to add a string of (4) 12V Lead-Acid batteries, 50AH or 100AH. I also plan to add (4) 450W solar panels.

According to NREL PVWatts Calculator, for my location and azimuth and 900W panels, I would get the following:
- 4.20 kWh / m2 / day Solar Radiation
- 1,039 kWh Annual production

A coworker, crazy scientist electrician but very knowledgeable has offered me an old stock inverter, Alpha Solaris 3500XP. Specs attached to this post. According to him, this was state-of-art inverter back in 2006 and it features a battery rack, MPPT charger for the lead-acid, 3500W inverter and 48V input. And it also has a relay for the generator to run, I believe, when batteries go below a setpoint. I have posted another thread asking for feedback on this inverter and whether I should consider it.

As of now, I would like to get feedback on the overall plan and possibly answers to some of my lingering questions:

1. Which lead-acid battery type is the safest: gel or AGM? Safety is a concern, since I will likely keep them in the unfinished basement/garage.
2. Which lead-acid battery is recommended for this setup? I do plan to use the cabin during the NY winter and I am open to heating pads.
3. Which alternative inverter solution should I consider for this setup, assuming the Alpha Solaris is a no go?
4. How does the energy balance work if I start with 48V 50AH instead of 48V 100AH?

Thanks in advance for any feedback.

 

[Daddy Tanuki]

TLDR: inverter OK (with caveats), batteries first timer go with AGM or LiFePo4 might or might not need heating pad depending upon battery type and location of battery box. Solar: 900 watts will be too small period. 1800 watts may or may not keep you happy. Your genset is probably 240 split phase, not 3 phase, most 3 phase is 208 from leg to neutral or leg to leg, split phase is 120 leg to neutral and 240 leg to leg.

first time working with batteries here are some issues you will run into.

flooded lead acid: if you do not have you charging parameters correct you will destroy them in a couple of months, so if this is a remote cabin that you only go to occasionally better off to start with AGM. (I have no experience with gel so no comments about them.)
as long as you can place them somewhere where it stays above freezing and your solar controller can be set to the batteries parameters expect 3-5 years use per set. I know some folks that tell of 10 years on them, heck I got 9 good years and limped on the 10th in my camper, but at my cabin I only got 3 and some change, and that was with experience from the camper.

when you jump up to a large AGM battery pack that is cycled daily getting them truly fully charged daily is difficult as they need a long absorb time= large PV solar array.

speaking of temps, if you have room under the house (sub basement or what not) then that's the perfect place for your batteries as a couple of feet below grade and the temperature really levels out. if not be prepared to make a box that is heavily insulated to trap heat in the winter. do that and you might not even need heating pads of any sort. I built a insulated power shed that held batteries, solar controllers and inverter and it rarely got below 4 or 5° C (40°F) even when it was -15°C (5°F) outside. biggest problem was I made it too large, if I had halved the size it would have stayed even warmer.

If you feel like experimenting a little bit LiFePo4 is the way to go at the moment when you balance out long term cost, longevity (cycle life) and power output. They will however need a heater pad and an insulated box as they are so efficient that they do not self heat at all. (plenty of plans, diagrams and mad scientist dreams floating on this here forum, so plenty of info, just need to do some sifting with the search button to find it.

inverter will work fine with these conditions:
Must have....a detailed installation manual that covers all adjustable settings? (need this to fine adjust battery charging portions).
Will 3500 watts be sufficient? (if free then this is a moot point you can live with a lot of things if its free. )

you will need more panels regardless. right now at this moment I am sitting at 3600' elevation it is early summer and we have cloud cover. with 4000 watts of PV currently installed (waiting to install next 4K of PV) It is an overcast day and I am getting about 20 amps of charge which is not quiet enough to offset what my split pack a/c, small chest freezer and small fridge are using. when the overcast is not here I see up to 50 amps of charge at the 54.4 setpoint for my lithiums. when its overcast like it is today...well you get what you get.

Regards, and best of luck!

Ken

 

[Old_Skewler]

Ken, first of all, thank you for the thorough reply. As expected, I have some follow up questions or comments:

TLDR: inverter OK (with caveats),

Could you explain what are the caveats? And btw, this inverter would NOT be a gift but I would have to pay for it. My colleague started the conversation at $1,500. I think around $1,000 could be fair, for a device that has been sitting for almost 10 years.

Also, we would test the inverter prior to closing a deal and I believe he would support the installation if I take this inverter from him. That has some value, as he is an electrical engineer and have been toying with this stuff for years now. Right now he is ordering a pack of small 12V batteries off Ebay to test and confirm the functionality of the inverter.

Solar: 900 watts will be too small period. 1800 watts may or may not keep you happy.

Understood and highly considering (4) panels instead of (2).

Your genset is probably 240 split phase

That is it, I'll correct my initial post to avoid further confusion.

speaking of temps, if you have room under the house (sub basement or what not) then that's the perfect place for your batteries as a couple of feet below grade and the temperature really levels out.

I am considering having the setup under the house but my only concern with the installation inside the house is fire hazard. Also, the Alpha Solaris has a NEMA 3R rainproof enclosure and pad mounting, so I am considering a concrete pad outside and keeping this stuff away from the cabin. I understand the batteries would need special care in the winter.

I need to better research and make a decision here. And to be honest, the cabin is not accessible when snowing, so I do stay here in cold days but not the coldest days of the winter.

If you feel like experimenting a little bit LiFePo4

Apparently the Solaris does not support Lithium and also Lithium seems to be a more risky than LeadAcid in terms of fire hazard. I understand the life-cycle analysis tilt the scale towards Lithium batteries but I cannot afford them at this time. I am trying to get a low cost system going to offset the propane operational cost.

inverter will work fine with these conditions:
Must have....a detailed installation manual that covers all adjustable settings? (need this to fine adjust battery charging portions).

I have the full installation and operator's manual for this inverter. And if I go with it, the electrical engineer would be overseeing and supporting the programming. For instance, he already located a Windows XP machine to run the Alpha monitoring program. Apparently the Solaris software only runs on Windows XP.

 

[Hedges]

Once you're talking about spending $1000+, there are various options.
Here's a hybrid (generator/PV/battery) for $800; I don't have any experience with it myself.

Amazon.com

Determine what you're going to power, when, how long (energy audit)
Enough PV can run loads during the day if inverter can put out the AC power needed.
Any motors need surge current 5x what nameplate shows. Inverter should be able to supply that for seconds, not just milliseconds.
Batteries need to supply night time power. Depth of cycling will relate to lifespan.

Maybe you will run generator for a short time to power heavy loads. If you have a battery that can take high charge current (LiFePO4 can recharge 50% in one hour, if at 25 degrees C), that can happen at the same time. But PV is so cheap, best to use that as much as possible.

Amortized over 10 years (or time to wear out),
$0.50/kWh using generator
$0.05/kWh PV & inverter

$0.50/kWh AGM battery
$0.25/kWh quality FLA
$0.50/kWh big-name commercial LiFePO4 (or other lithium chemistry)
$0.05/kWh DIY LiFePO4
$0.??/kWh various off-brand or recycled lithium batteries

This doesn't mean DIY LiFePO4 battery is the only feasible option. If you avoid using much power from battery, only small loads at night, it is OK to have smaller battery at higher price per kWh. AGM is simple and maintenance free. Quality FLA works, but needs care and feeding.
If you install 2x the PV you need, multiple orientations of panels so flat production during the day, power loads when sun is available, then you can get by with a small battery.


"upstate NY"

"According to NREL PVWatts Calculator, for my location and azimuth and 900W panels, I would get the following:
- 4.20 kWh / m2 / day Solar Radiation
- 1,039 kWh Annual production"

That's fine for grid-tie net metering (grid is infinite capacity battery) but you need to consider winter PV production and consumption. PV may work for a few loads, but you'll need fuel of some sort for heat.

Does that generator have water cooling? It is large, likely waste heat production is much greater than cabin heating needs. Consider insulated storage tank and hot water loop. "Combined Heat and Power"

 

[Daddy Tanuki]

Ken, first of all, thank you for the thorough reply. As expected, I have some follow up questions or comments:


Could you explain what are the caveats? And btw, this inverter would NOT be a gift but I would have to pay for it. My colleague started the conversation at $1,500. I think around $1,000 could be fair, for a device that has been sitting for almost 10 years.

Also, we would test the inverter prior to closing a deal and I believe he would support the installation if I take this inverter from him. That has some value, as he is an electrical engineer and have been toying with this stuff for years now. Right now he is ordering a pack of small 12V batteries off Ebay to test and confirm the functionality of the inverter.


Understood and highly considering (4) panels instead of (2).



That is it, I'll correct my initial post to avoid further confusion.


I am considering having the setup under the house but my only concern with the installation inside the house is fire hazard. Also, the Alpha Solaris has a NEMA 3R rainproof enclosure and pad mounting, so I am considering a concrete pad outside and keeping this stuff away from the cabin. I understand the batteries would need special care in the winter.

I need to better research and make a decision here. And to be honest, the cabin is not accessible when snowing, so I do stay here in cold days but not the coldest days of the winter.



Apparently the Solaris does not support Lithium and also Lithium seems to be a more risky than LeadAcid in terms of fire hazard. I understand the life-cycle analysis tilt the scale towards Lithium batteries but I cannot afford them at this time. I am trying to get a low cost system going to offset the propane operational cost.



I have the full installation and operator's manual for this inverter. And if I go with it, the electrical engineer would be overseeing and supporting the programming. For instance, he already located a Windows XP machine to run the Alpha monitoring program. Apparently the Solaris software only runs on Windows XP.

Sorry I aught to be a author the way I post.

the caveats were:

being used you need a manual to figure it out, a lot of folks lose stuff like this after they stop playing with/using. at that age finding one online might be dicy.

need this to set inverter to match battery used, regardless of chemistry

@ 3500 watts is this enough?

last was price... 1500 is too much. you can buy a brand new 4kw or 4.4kw Magnum 4048 50 amp service in 120, or 4448 30 amp service in split phase 240. Both new with warranty and the ability to charge any type of battery for about 1700.00 from Northern Arizona Wind and solar. Plus its a proven low frequency design that will have quite a bit more oomph for starting hard loads than the solaris which if I am not mistaken is a high frequency design..

LF inverters have huge honking transformers that allows them to use less fragile electronics to work trade off is in cost, and thy us a wee bit more power at idle.

HF inverters have small transformers and FET running in the MHtz range to make the power. big difference in reliability and surge current.

Plus being brand new, you can still get all of the accessories for it.

now if your friends used unit that is ten years old and totally out of warranty and the chances of you getting any of its expansion accessories is slim wants to sell it for like 500 then that's a reasonable price for a fairly middle of the road unit. which is what any HF unit is.

and as far as lithium goes, LiFePo4 is the most stable (at this time) of lithium's and does not explode or catch on fire, that is a different chemistry, yes its lithium but its like saying regular compared to premium compared to AVGAS. they are all gas, but totally different. there are even videos of idiots purposely overcharging the LiFePo4 cells and even when they totally ballooned up all it did was pop the release vent and vent electrolyte. the only LiFePo4 cells I have seen "explode" was a video on youtube where fellow purposely overcharged them to almost venting and then struck it with a pick axe. it did not explode, but did catch on fire.

so its totally different from laptop/vape gear/cellphone batteries... different chemistry. and different from electric cars, some of which do use the LiFePo4 chemistry but they are charge/discharging at very high C rates that you would never see in home solar use.

regardless you will need a bigger bank then 100 a/h at 48 volts, as thats not quite enough to even run a fridge all night.

R

Ken

 

[Bossrox]

I wouldn't sink that kinda $$$ on an inverter that old. It may work fine initially but old inverters are likely to have near dried up capacitors that will likely fail before too long. I'd look at a 6kw growatt with a built in 5kw charger. I've seen them as low as $1200 & they have a 5 year warranty, 10 if you register it. Flooded lead/acids in a confined space could cause dangerous build up of hydrogen gas & an explosion hazard so agm is the way to go there. I have my batts in an outside heavy insulated cabinet with thermostatically controlled heating pads under them like the kind you'd use for seed germination. They don't draw a heavy load & in a well insulated container will keep them nice & toasty. I'm in a small cabin 144 sq/ft here with another 200 sq/ft shed & keeping them air conditioned comfortably along with everything else, I'm averaging 3-4kw continuous power needed during the day, about 1/4 that overnite & it's just keeping up with the demand with 36 300 watt panels & enough to bring a 48v 1300 a/hr battery bank back up from the overnite draw but even with that I still need a few hours a day of grid power. Ultimately I'll need 48 panels & double my battery bank to be set well enough to go off grid. Just giving you an idea what my real life experience is to compare with your scenario.

 

[Old_Skewler]

Once you're talking about spending $1000+, there are various options.
Here's a hybrid (generator/PV/battery) for $800; I don't have any experience with it myself.

Amazon.com

Very true, the market is saturated with inverters and panels... but the problem is finding out what is worth considering. A lot of non-reputable products out there as well.

Determine what you're going to power, when, how long (energy audit)
Enough PV can run loads during the day if inverter can put out the AC power needed.
Any motors need surge current 5x what nameplate shows. Inverter should be able to supply that for seconds, not just milliseconds.
Batteries need to supply night time power. Depth of cycling will relate to lifespan.

I have done this work, although the numbers need to be fine tuned.

Maybe you will run generator for a short time to power heavy loads. If you have a battery that can take high charge current (LiFePO4 can recharge 50% in one hour, if at 25 degrees C), that can happen at the same time. But PV is so cheap, best to use that as much as possible.

This is my plan. I do intend to still run the Generator when needed.

Does that generator have water cooling? It is large, likely waste heat production is much greater than cabin heating needs. Consider insulated storage tank and hot water loop. "Combined Heat and Power"

I know CHP very well as this was the bulk of my engineering work up to few years ago. I do not see the necessity or the applicability of it for this little cabin project. I am trying to keep this simple, small and doable. right now my biggest issue is having an off-grid electrical system to provide power to some vital equipment.

 

[Old_Skewler]

need this to set inverter to match battery used, regardless of chemistry

@ 3500 watts is this enough?

The solaris seems to handle only lead-acid batteries. or at least this is what their list under the specs.

3500 Watts right now would make my life very comfortable. Yes, it is enough. For now

last was price... 1500 is too much. you can buy a brand new 4kw or 4.4kw Magnum 4048 50 amp service in 120, or 4448 30 amp service in split phase 240. Both new with warranty and the ability to charge any type of battery for about 1700.00 from Northern Arizona Wind and solar. Plus its a proven low frequency design that will have quite a bit more oomph for starting hard loads than the solaris which if I am not mistaken is a high frequency design..

now if your friends used unit that is ten years old and totally out of warranty and the chances of you getting any of its expansion accessories is slim wants to sell it for like 500 then that's a reasonable price for a fairly middle of the road unit. which is what any HF unit is.

Thank you for the feedback. I will bring this to the negotiation table. And nope, I also don't know if the Solaris is HF or LF. To be honest, I am not sure what that means either and I am not sure if I need to know much more than what you already explained.

regardless you will need a bigger bank then 100 a/h at 48 volts, as thats not quite enough to even run a fridge all night.

I am surprised to hear that. Could you explain why you think 48V 100Ah cannot run a 5 cubic feet chest freezer converted to a fridge?

 

[Old_Skewler]

I wouldn't sink that kinda $$$ on an inverter that old. It may work fine initially but old inverters are likely to have near dried up capacitors that will likely fail before too long.

Thank you for the feedback. Very good to know where the market is.

I'd look at a 6kw growatt with a built in 5kw charger. I've seen them as low as $1200 & they have a 5 year warranty, 10 if you register it.

Do you have any actual experience with these inverters or this manufacturer? And which product would you recommend for my application?

Flooded lead/acids in a confined space could cause dangerous build up of hydrogen gas & an explosion hazard so agm is the way to go there. I have my batts in an outside heavy insulated cabinet with thermostatically controlled heating pads under them like the kind you'd use for seed germination. They don't draw a heavy load & in a well insulated container will keep them nice & toasty.

Thanks for the feedback. I was considering either AGM or Gel for this application.

Just giving you an idea what my real life experience is to compare with your scenario.

And I appreciate you sharing your real experiences. Thank you.

 

[Hedges]

Very true, the market is saturated with inverters and panels... but the problem is finding out what is worth considering. A lot of non-reputable products out there as well.

Yup. The higher end stuff includes Outback, Midnight, SMA, Trace, Schneider, Victron, maybe others I've missed.

I am surprised to hear that. Could you explain why you think 48V 100Ah cannot run a 5 cubic feet chest freezer converted to a fridge?

Start by determining idle draw of the inverter. See what fraction of battery would be drained overnight. Vs. what DoD you want to cycle.
Maybe no reason to operate either freezer/fridge or inverter at night. Refrigerator with top freezer would be best, store cold as H2O or H2O + NaCl phase change, cheaper than Pb or Li.

I have 48V 405 Ah and 4 fridges, not sure what else. When I left yard lights and rope lights and other things on, hit 70% DoD at 3:00 AM. With the extras off, should last until dawn. All older less efficient equipment. My bank of four inverters should draw 100W no-load, maybe I can get half to sleep for 62W. But I presently would consume 1200 Wh at night.

 

[Old_Skewler]

you can buy a brand new 4kw or 4.4kw Magnum 4048 50 amp service in 120, or 4448 30 amp service in split phase 240. Both new with warranty and the ability to charge any type of battery for about 1700.00 from Northern Arizona Wind and solar.

Ken,

Could you expand a bit on the relationship of my existing split-phase generator and the inverter type I should be considering in order to work properly with my generator?

I am a little lost on what specs the inverter needs to have because the generator is 240V service in split phase.

As a bonus, could you also clarify the correct language I should be using when talking about my setup. I feel like I understand what is going on but I do not have the correct language to describe it.

For instance, I suspect my generator is 240V and it does not care what happens down the line.
And I also suspect that my service (electrical panel) is splitting the 240V from the generator into 120V, thru a physical splitting of the wires.

Is this correct?

 

[Hedges]

Generator would have to have L1, L2 Neutral for 120/240V split-phase. If it just had 2-wire 240V you couldn't get a reliable 120V from it.

Inverter/charger should similarly be 120/240V split phase, with L1, L2, Neutral input and output.

 

[Daddy Tanuki]

100 amp hours equates to 50 amp hours at 50% depth of discharge, or 50% state of charge. (I get these two terms mixed up a lot), but basically one is amount remaining and one is amount used. regardless at 50% they are equal. dropping below 50% = short battery life for non lithium batteries. happy percentage cycle wise for AGM, gel, and FLA are use up to 30% of total capacity over night recharge next day while powering everything via the panels. occasionally dip to 50% on bad days. this will give you maximum service life from the batteries. so with a 100 amp hour pack you have 50 usable.

as to why is 100 Amp hours (50 useable) not enough?

well i run a energy efficient Fridge and freezer, (both smaller units) and an air injection pump for the septic tank that run 24/7 regardless of if we are here at the cabin or not. These together use about 140a/h of usable battery capacity for a given time frame from when the solar harvest drops (currently summer season 1730ish to 0700 when it resumes, depending upon season) and much lower in the winter as they are in an unheated entrance (but less solar) and much higher in the summer as it will hit about 90 on a daily basis (still cooler than in the city). If I run the A/C split pack then that will jump to 220ish a/h per night and the need to recharge that amount + power all appliance's in the day. hence I run a 400 a/h bank but I am using lithium so using 50% of my capacity is not an issue. in the past for the same load with AGM's I had to have a 600 a/h bank to stay in the use 30% range.

@Hedges is correct, in regards to the gen set. If your gen set is 120/240 split phase then it will work with any inverter/charger.

An inverter charger that is 120/240 split phase would be better though as it can use the full capacity of the genset to charge batteries while it is powering house at same time. you will of course need to set whatever unit you get to use xx amount of incoming for charge vs xx amount to power house while you are charging. this is regardless of genset or inverter style.

If you need 3500 watts to run the hotel load and your genset is a 12kw unit that leaves 8500 for battery charging. (thats a lot BTW) I would run the gen set for about an hour to fast charge the batteries to about 80% and let the solar take over after that.

everybody has their opinion of what is 1st tier when it comes to products in this industry. I am not tied to any one brand and my system I chose to use different makers for different items depending upon their reputation over all, not just in the states, or Europe, Australia etc.

Magnum, Outback, SMA, Trace, Schneider, Victron all make great inverters, but in my opinion their solar charge controllers are OK...

Morningstar, Midnight solar both make tier one solar controllers but their inverters are OK (once again my opinion.)

a lot of it is which brand you can feel comfortable with as well. but I would not spend money on any brand that does not have one of the above names on it even if its only a widget thats an interconnect of some sort. they all have a reputation to uphold as tier one/two entities.

In a nutshell your Kohler is a 12kw 240 split phase genset it puts out 5-6kw per leg in 120 or a total of 12kw at 240. normally you see one of these run into a panel and split for home use, with maybe one or two lines of 240 used to power a heat pu0mp or a well pump. It can be used to power either a 240 split phase inverter and you divy up where the power goes in the inverter via settings, or it could power a single phase 120 inverter with one line and the other line could be wired through a separate transfer switch to power the house while the inverter is charging. options are available either route you take. but at 1500 used... I would be buggin NAWS for either a MS4048, or a MS 4448 pae a 200.00 difference is minor for a warranty and a brand new unit. The difference is how you want to wire it. that's new with a warranty and the ability to send out for repairs if you boff it up somehow. (oh and get lightening arresters for whatever you buy.... ask me how I know. Midnite solar is the place for those by the way.

 

[Daddy Tanuki]

to clarify this statement: " if you need 3500 watts to run the hotel load and your genset is a 12kw unit that leaves 8500 for battery charging. (thats a lot BTW) I would run the gen set for about an hour to fast charge the batteries to about 80% and let the solar take over after that."

Lead acid batteries as well as AGM and gel will charge quickly up to about 80-90% and after that they are slow as the amperage tapers off as they approach full, so bulk charge with the genset and once the amps starts to taper off shut the genset down and let solar take over. Oh and having a big genset like that is a boon when you are charging as you can charge and power house completely at the same time. not so good if you just want a little power though.

I have three gensets depending upon what I am doing. a 10kw denyo that is 3 phase for powering the shop (welders, compressors, lift etc.) and a 240 split phase 5.5kw makita I use to boost charge the battery pack. its not large enough to boost charge and power house, so I set my inverter charger to accept 30% for charging and the balance to the hotel load. I also have a little 1.6 kw suitcase denyo for the camper that we use to boost charge if the solar on the camper cannot keep up with use.

R

Ken

 

[Daddy Tanuki]

I wouldn't sink that kinda $$$ on an inverter that old. It may work fine initially but old inverters are likely to have near dried up capacitors that will likely fail before too long. I'd look at a 6kw growatt with a built in 5kw charger. I've seen them as low as $1200 & they have a 5 year warranty, 10 if you register it. Flooded lead/acids in a confined space could cause dangerous build up of hydrogen gas & an explosion hazard so agm is the way to go there. I have my batts in an outside heavy insulated cabinet with thermostatically controlled heating pads under them like the kind you'd use for seed germination. They don't draw a heavy load & in a well insulated container will keep them nice & toasty. I'm in a small cabin 144 sq/ft here with another 200 sq/ft shed & keeping them air conditioned comfortably along with everything else, I'm averaging 3-4kw continuous power needed during the day, about 1/4 that overnite & it's just keeping up with the demand with 36 300 watt panels & enough to bring a 48v 1300 a/hr battery bank back up from the overnite draw but even with that I still need a few hours a day of grid power. Ultimately I'll need 48 panels & double my battery bank to be set well enough to go off grid. Just giving you an idea what my real life experience is to compare with your scenario.

Wow and I thought my wife and kids ran through power! I don't think I use that much at the sticks and bricks, let alone my cabin

 

[Old_Skewler]

Generator would have to have L1, L2 Neutral for 120/240V split-phase.

My existing generator is as described above. I have opened the service panel in the cabin and clearly (3) wires come from the generator and the loads (breakers) are split between the hot legs and neutral. So yes, the Generator has a L1, L2, Neutral coming to the electrical service panel.

Inverter/charger should similarly be 120/240V split phase, with L1, L2, Neutral input and output.

And this is the part I am struggling with. Could you kindly elaborate why does the inverter need to be 120/240V split phase, to match the generator? I am really trying to understand how this works but this element of the equation is not clear to me.

TIA!

 

[Old_Skewler]

@Hedges is correct, in regards to the gen set. If your gen set is 120/240 split phase then it will work with any inverter/charger.

An inverter charger that is 120/240 split phase would be better though as it can use the full capacity of the genset to charge batteries while it is powering house at same time. you will of course need to set whatever unit you get to use xx amount of incoming for charge vs xx amount to power house while you are charging. this is regardless of genset or inverter style.

Ken, what is the "unit" in the sentence above? Which one of the devices would need to be "set to use xx amount of incoming for charge vs xx amount to power house while you are charging."?

And how is this "setting of the device" done? Is this a software programming?

Could you please expand on what you mean?

TIA!

 

[Old_Skewler]

Oh and having a big genset like that is a boon when you are charging as you can charge and power house completely at the same time. not so good if you just want a little power though.

Welcome to my life! Regardless of what I need to power (the 1/2HP water pump OR the 50W tablet) I always have to run this 14kW Generator - just found out that it is actually 14kW when using propane instead of 12kW.

Very wasteful, as you point out. And at $3.5/Gal of propane, it gets costly.

My plan is to level and buffer these loads out with the addition of a BESS and Solar PV.

 

[Hedges]

My existing generator is as described above. I have opened the service panel in the cabin and clearly (3) wires come from the generator and the loads (breakers) are split between the hot legs and neutral. So yes, the Generator has a L1, L2, Neutral coming to the electrical service panel.


And this is the part I am struggling with. Could you kindly elaborate why does the inverter need to be 120/240V split phase, to match the generator? I am really trying to understand how this works but this element of the equation is not clear to me.

TIA!

It doesn't. If you connect a 120V inverter (e.g. one Sunny Island), it can take half the generator output, about 6kW, and feed to loads plus charge battery (depending on how high a charge current you set according to battery capacity.)

If you connect a 120/240V inverter (e.g. two Sunny Island wired in series), it can take all the generator capacity, about 12kW. A smaller inverter might accept less input (but you could run other loads direct off generator.)

If you added a 120/240V transformer, you could feed all 12kW into a 120V inverter (e.g. two Sunny Islands wired in parallel, or a single large inverter.)

Your goal would be to run generator at its most efficient load, or to run heavy loads from the generator while charging as much as possible into the battery. You might use a separate charger (e.g. if you had a forklift battery, could use a large forklift charger), but have a battery shunt so Sunny Island knows how much has gone into the battery (if you use Sunny Island; it is supposed to be very good at managing lead-acid batteries for long life.)

 

[Old_Skewler]

If you connect a 120/240V inverter (e.g. two Sunny Island wired in series), it can take all the generator capacity, about 12kW. A smaller inverter might accept less input (but you could run other loads direct off generator.)

If you added a 120/240V transformer, you could feed all 12kW into a 120V inverter (e.g. two Sunny Islands wired in parallel, or a single large inverter.)

Got it! Thank you for clarifying, understood.