Configuring generator to not directly carry house loads

Discussion about OutBack Inverters in Off Grid Applications

Moderators: OutBack, OutBack Moderator Team

Post Reply
rpbancroft
Forum Member
Posts: 22
Joined: Mon Oct 29, 2018 10:41 am
My RE system: VFXR3524A inverter, FlexMax 80 charge controller, Mate3s

Configuring generator to not directly carry house loads

Post by rpbancroft » Wed Nov 14, 2018 2:08 pm

Hey there,

Is it possible to configure an Outback system's connected generator to only directly charge the batteries and ignore house loads? I would prefer to use my generator only on the batteries, and to have house loads pull from the batteries at all times. I'm not using an inverter generator (open frame instead). This re-config would solve the following problems I'm having:

1) loads in the house running "rough" while powered by the generator (lights flicker slightly constantly [especially ones on dimmer switches], uninterruptible power supply constantly clicks if on [probably due to rough power], and a few others); this is probably due to the type of generator I'm using, but, if the system pulled only from the batteries, this shouldn't be an issue I believe; I think the charge controller or inverter (not sure which governs it) would ensure the power reaching the batteries from the generator is safe for them.
2) the battery charge + house loads over-taxing the generator, the generator drops the load, tries to charge the batteries first and takes on house loads after, finds too much between the two, drops the load again, repeat until I turn off a heavy load. I can partially control this by reducing the permitted amps the inverter allows the generator to supply to the system (set at 18 amps right now), but big surges (1200W cooktop element, fridge/freezer compressor, hot water heater) still cause it to hit its max and drop the load if any charge is being supplied to the batteries.
3) if it worked this way, I could start running heavy loads (like heaters) at any time, or leave them running. The generator would just be like a supplier of power to the batteries, and nothing in the house would even know a generator is running.

Basically, I want the generator to be responsible for charging the batteries, and nothing else. I'm hoping to cap it at 50% of its capacity (1800W), and let it just take on battery duty when needed.

Is this possible, either directly or through a series of related configs?

As an aside, I realize now that, according to Outback's inverter documentation, my generator is undersized. They recommend you get a generator with a running wattage roughly double your inverter's maximum wattage (in our case, 3500W). Ours is a 3600W generator. I didn't realize that I would need it so very much (got it as more of a backup) since we're an all-electric house with apparently vastly insufficient battery storage (1500W of heaters will put our AGM battery array from 100% to 60% in about 3 - 3.5 hours). The easy answer would of course be to get a bigger generator, but I can't afford that right now. I hope this reconfig is possible... it seems simple conceptually, but perhaps there are system-design limitations to something like this?

Thanks so much for any thoughts!

~Ryan

User avatar
Jorge Guzman
Strategic Platforms
Posts: 248
Joined: Thu May 29, 2014 9:44 am
My RE system: VFXR3524A, FM80, MATE3. 3x 260W REC. 4x Trojan L16 FLA 370Ah.
Location: Arlington, WA

Re: Configuring generator to not directly carry house loads

Post by Jorge Guzman » Wed Nov 14, 2018 2:12 pm

This is not possible with the OutBack Inverter/chargers.

A work around would be to install an additional OB Inverter/Charger solely for battery charging and if paired with a MATE3 you can program the auto start function.
Jorge Guzman
Sr. Strategic Platforms Analyst


Watch easy to follow video tutorials:
https://www.youtube.com/c/wattschool

Mike Curran
Forum Emperor
Posts: 1523
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 repl'd MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied, no longer AC- coupled

Outback Skybox - Barn roof: (2019)
- 14 (2x7) Talesun 275W (DC array input to SB charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input from 14 Talesun 275W, Enphase M215 modules

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: Configuring generator to not directly carry house loads

Post by Mike Curran » Wed Nov 14, 2018 2:20 pm

Jorge - Wouldn't mini-grid mode be sort of a "let's meet in the middle" solution? Ryan would have to use AGS to start his generator so that it's on when mini-grid resorts to the grid to charge the batteries. Unfortunately his loads would then see the noisy generator AC output, but maybe this is better than nothing...

What am I missing? - Mike
Screenshot_20181114-171414.jpg
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

rpbancroft
Forum Member
Posts: 22
Joined: Mon Oct 29, 2018 10:41 am
My RE system: VFXR3524A inverter, FlexMax 80 charge controller, Mate3s

Re: Configuring generator to not directly carry house loads

Post by rpbancroft » Wed Nov 14, 2018 2:27 pm

Thanks so much for the reply, Jorge!

Ahh, okay, that's unfortunate. Is there a technical reason why that's not possible? Is there any chance it'll be made available in future firmware or system updates, or with future hardware?

Does this "rough" load cause any problems for house electronics? Are the loads being conditioned at all by the Outback equipment, or is this direct generator power (basically is the inverter/charger acting only as a passthrough)?

Intrigued by Mike's idea, too... I don't know a much about mini-grid mode. Even if "rough" power were still being supplied to internal devices, would the total load be strictly capped at a configurable amount?

~Ryan

User avatar
Jorge Guzman
Strategic Platforms
Posts: 248
Joined: Thu May 29, 2014 9:44 am
My RE system: VFXR3524A, FM80, MATE3. 3x 260W REC. 4x Trojan L16 FLA 370Ah.
Location: Arlington, WA

Re: Configuring generator to not directly carry house loads

Post by Jorge Guzman » Wed Nov 14, 2018 2:36 pm

Hi Ryan,

That is due to the internal transfer switch. Here is a video explaining this: https://youtu.be/ssMhDa6tdu4
Mini-grid will also connect/disconnect in the same manner plus it will need the "grid" or generator to be present all the time for it to work.

Another thing you can look at is a DC generator which AGS is compatible with as well. You will just loose the 3-stage charging which is preferred for battery longevity.
Jorge Guzman
Sr. Strategic Platforms Analyst


Watch easy to follow video tutorials:
https://www.youtube.com/c/wattschool

sodamo
Forum Czar
Posts: 775
Joined: Mon Apr 03, 2006 1:55 am
My RE system: Totally off grid - Hamakua side, Big Island, Hi

36 Trina 280 & 16 Phono 250 in 48 volt array (fixed) 14080w
Radians GG8048/GS4048 w GSLCs
4 FM 80 charge controllers
Hub 10.3
FNDC w/3 shunts
Mate 3s
OpticsRE - MMKL - Ninole Hi
12 SimpliPhi 3.8
14Kw Kohler 14RESA Propane

Charging Only
2FX3048T
Hub
FNDC. - shared shunt feeds from Radian FNDC
Mate 3s
10Kw MEP 803a Military gen

Honda EU7000i

Davis VantagePro2 Wx Station
On line at: https://www.wunderground.com/dashboard/pws/KHININOL2
Location: Ninole, Hi

Re: Configuring generator to not directly carry house loads

Post by sodamo » Wed Nov 14, 2018 11:05 pm

Ryan, thanks for bringing this up as I have similiar thoughts. My primary generator does not produce good power. Charges just fine, but several of the household loads do not like it, washing maching, microwave oven, garage door openers to name a few. So I wanted to do as you suggest. Thank you Jorge for explaining why it isnÔÇÖt possible. Problem is only this generator, but my backups are undersized to fully support both charging and max household loads.
So my goal, when budget permits is to replace my FX3048ÔÇÖs, installed in 2007 and no longer available once they start failing. Most likely I will replace with FXR3048 FlexPower Four. I will repurpose the current FXs, Hub, and Mate3 to a dedicated charging station powered by this generator and configure AGS to prioritze as backup. At some point IÔÇÖll be looking how to wire, hopefully Jorge or some OB tech will be helpful.
David
Please visit http://vacation.ninolehawaii.com

jbakker
Forum Guru
Posts: 217
Joined: Fri Feb 23, 2018 5:47 am
My RE system: 2 VFX3648 Inverters 2 FM60 150VDC Charge Controllers Mate3 3.4 KW of panels 15kw JC Onan NG Generator made in 1975 I love that generator almost as much as my wife.
7 banks of 14 cells each from a 2017 Chevy Volt. Parallel for the AMP Hour. 7 Chinese made BMS systems.
Location: Goderich Ontario Canada

Re: Configuring generator to not directly carry house loads

Post by jbakker » Thu Nov 15, 2018 4:41 am

Hello Ryan

One way would be to have your generator power a good sized 24 volt battery charger. Use the generator for just that charger. No connection to the inverters at all. I have seen this done at a few places that had access big 48 volt forklift chargers. Finding a good sized charger for cheap may be a issue.
Good Luck with the system.

rpbancroft
Forum Member
Posts: 22
Joined: Mon Oct 29, 2018 10:41 am
My RE system: VFXR3524A inverter, FlexMax 80 charge controller, Mate3s

Re: Configuring generator to not directly carry house loads

Post by rpbancroft » Thu Nov 15, 2018 2:19 pm

Jorge, thanks for the resource! I'll check it out when I get a chance. Do you by chance have a video or concise written resource describing the three-stage charging process? Just trying to soak up all I can about these systems. I poked around for DC generators or battery chargers, as jbakker suggested. I assume a battery charger would also skip that benefit? Sounds like anything that bypasses the system would?

Sodamo, thank you so much for commenting! It seems like you have a lot more experience exploring and managing Outback systems; posting your plans helps me see what's possible, and also introduces me to new ideas. What is a FlexPower Four? I get an image of four charge controllers running in parallel... also, if I'm interpreting correctly, it sounds like you'd be implementing Jorge's suggestion of running a separate system, independent from house loads, to direct-charge the batteries. If you need to replace or upgrade your existing hardware, but it's still functional, that sounds like a great way to achieve this goal. I didn't wire the system, so I'd be super curious to see how that would be speced out, as well. I wonder if Outback has a wiring chart similar to the fold-out I received along with the inverter/charge controller/etc. system that explains how all of the internal wiring is lined out? That would be really helpful.

Jbakker, thanks for the suggestion! I apologize for the inevitable ignorance the following question will reveal, but I hope this question makes some sense at least. My system is 24V (at least as measured from panels to charge controller), but the batteries measure around 12V (according to the DC electronics in the house). Would a 24V battery charge always be appropriate for any battery bank (or at least for the AGM one we have), or is that determined by the voltage at which the overall system is configured? For example, if we had a 48V Outback system, would the type of battery charger we need be different? Or does it even matter, since I'd be bypassing the rest of the system anyway?

As a follow up idea on this, does anyone know if it's possible to throttle, so to speak, how much house load or battery charge an incoming AC source provides? That might be an alternative way to achieve at least some of the original goal(s). For example, if I have my system set to cap at 18 amps, can I only allow, say, 3 of those amps to hit the batteries at any given time (and they'd of course throttle down as the charge controller requires once the battery charge is almost capped out), and have the remaining 15 available to house loads? This would give me the flexibility to keep on high-surge electronics (like the fridge/freezer) when the batteries are low right after connecting the generator to the system.

Thanks!

~Ryan

SandyP
Forum Guru
Posts: 369
Joined: Tue Jun 21, 2011 4:44 am
My RE system: 8 x 190W 24V Suntech panels (4 strings of 2) July 2011
4 x 325W 24V Suntech panels (2 strings of 2) added Sept2018
Mate2
Outback FM60 MPPT (max output lowered to 55amps)
12 x 2V Hoppecke GEL 660 Ah C100 - 24V System
Outback VFX3024 Inverter/Charger
Victron BMV-602s
Honda 5.5kW Genset
Location: Victoria, Australia

Re: Configuring generator to not directly carry house loads

Post by SandyP » Thu Nov 15, 2018 9:15 pm

rpbancroft wrote:....As a follow up idea on this, does anyone know if it's possible to throttle, so to speak, how much house load or battery charge an incoming AC source provides?...
Yes, you can set a limit as to how much power (AC amps) the inverter draws from the generator and, in addition, also limit how many AC amps coming from the generator can be used for charging.

jbakker
Forum Guru
Posts: 217
Joined: Fri Feb 23, 2018 5:47 am
My RE system: 2 VFX3648 Inverters 2 FM60 150VDC Charge Controllers Mate3 3.4 KW of panels 15kw JC Onan NG Generator made in 1975 I love that generator almost as much as my wife.
7 banks of 14 cells each from a 2017 Chevy Volt. Parallel for the AMP Hour. 7 Chinese made BMS systems.
Location: Goderich Ontario Canada

Re: Configuring generator to not directly carry house loads

Post by jbakker » Fri Nov 16, 2018 4:49 am

Hello Ryan
I believe that when you are measuring the battery voltage you are getting a reading of each battery.
Since you have a 24 volt battery bank I assume that you are using 12 volt batteries connected in series to get your 24 volt battery bank. How many 12 volt batteries do you have?
Most of the time a person would use 6 volt batteries to make a 24 volt battery bank or 48 volt.
So 4 6 volt batteries would give you 24 volts or 8 of them would give you 48 volts.
You can also have an 8 6 volt batteries and connect them up as a 24 volt bank. You would be wiring up the bank as a parallel/series combination. Not recommended as itÔÇÖs hard to get all the batteries balanced even.
When you go to a bigger battery bank say a 48 volt 800 to 1200 Ah unit the battery is made up of 2 volt cells 12 of them for a 24 volt bank and 24 for a 48 volt bank.
We have several large traction battery charges here at work in 24 volt DC and 48 Volt DC.
The smallest 24 volt charger we have can put out 100 AMPs and it runs off 240 Volts AC. The bigger units can put out 175 amps DC. They run off 480 volt 3 phase. So you can find the smaller 24 volt chargers out there. Issue is it will bring your 3500 watt generator to its knees.
All our chargers here at work do the 3 stage charging like the inverters do.
So to solve your problems you can do a few things.
Install second 24 volt inverter that is just connected to your generator and use it for charging up the battery only. If in the future you get a bigger generator and wire the extra unit into your system.
Would give you extra capacity for loads and for charging, and give you the option for 240 volt if you ever need that as well.
Upgrade your system to a 48 volt setup. This is more efficient then a 24 volt system. Your closer to 120 volts eh. Smaller wire size as well. Will cost you for the upgrade.
Search for bigger generator.
I like the Onan generators. Can find them used if you look around. Come in gasoline versions, NG or propane versions, even diesel. Most are 1800 RMP. Say you can find a 6000 watt of 7.5 KW unit, you can pull the full 7.5 kw from that unit all day and it wonÔÇÖt complain. Try that with a big box store bought generator.

Good luck hope the advice helps and its just my 2 cents worth eh ´üè

Post Reply