Charge from generator while keeping load on Pure Sine inverters

[shanemgrey]

I am building a 48 volt battery with 560ah and would like to keep the power to the house clean and stable all the time.

But there currently isn't enough solar to keep up with demand if we have a few days of rain. So we use a natural gas powered generator. This generator works fine for most loads in the house when it's passed through. But some things like the microwave don't like it. And it's probably not great for other things even if they stay running.

I'd like to avoid running the house on the generator, and keep it fed from the inverters 24/7 instead. But I can't use the inverters to charge the batteries while also providing power. They have to pass the generator power through so they can switch to charge mode.

What would I need to purchase so I can use the generator to charge the batteries without involving the existing inverters?

The generator produces 7000 watt max continuous with a 30amp 240 volt split phase output as well as a couple 20amp 120 volt. Ideally I could run it at about 5000 watts over the 30amp connection. But it seems very hard to find any chargers that can take split phase power.

Can anyone point me to what I would need to make this happen? Or reasons I should do something else?

 

[Supervstech]

I am building a 48 volt battery with 560ah and would like to keep the power to the house clean and stable all the time.

But there currently isn't enough solar to keep up with demand if we have a few days of rain. So we use a natural gas powered generator. This generator works fine for most loads in the house when it's passed through. But some things like the microwave don't like it. And it's probably not great for other things even if they stay running.

I'd like to avoid running the house on the generator, and keep it fed from the inverters 24/7 instead. But I can't use the inverters to charge the batteries while also providing power. They have to pass the generator power through so they can switch to charge mode.

What would I need to purchase so I can use the generator to charge the batteries without involving the existing inverters?

The generator produces 7000 watt max continuous with a 30amp 240 volt split phase output as well as a couple 20amp 120 volt. Ideally I could run it at about 5000 watts over the 30amp connection. But it seems very hard to find any chargers that can take split phase power.

Can anyone point me to what I would need to make this happen? Or reasons I should do something else?

I wonder if a full bridge rectifier would work, and send 240v ripple to the charge controller...

 

[Roswell Bob]

I am building a 48 volt battery with 560ah and would like to keep the power to the house clean and stable all the time.

But there currently isn't enough solar to keep up with demand if we have a few days of rain. So we use a natural gas powered generator. This generator works fine for most loads in the house when it's passed through. But some things like the microwave don't like it. And it's probably not great for other things even if they stay running.

I'd like to avoid running the house on the generator, and keep it fed from the inverters 24/7 instead. But I can't use the inverters to charge the batteries while also providing power. They have to pass the generator power through so they can switch to charge mode.

What would I need to purchase so I can use the generator to charge the batteries without involving the existing inverters?

The generator produces 7000 watt max continuous with a 30amp 240 volt split phase output as well as a couple 20amp 120 volt. Ideally I could run it at about 5000 watts over the 30amp connection. But it seems very hard to find any chargers that can take split phase power.

Can anyone point me to what I would need to make this happen? Or reasons I should do something else?

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I would tend to load the generator close to 7000w. Whatever charger you use - you want something with PFC. PFC will pull nice sine waves off of generator. Your generator will like this. Without PFC you have to use a generator oversized 2x. I have one of these units on order.

 

[Roswell Bob]

I wonder if a full bridge rectifier would work, and send 240v ripple to the charge controller...

This would work but it would need a large smoothing capacitor at the output of the bridge to reduce ripple voltage. Charge controller loops are generally very slow so that you end up with some ripple voltage on the bus. A little bit of ripple voltage on the bus will produce a lot of ripple current on the battery. Some say this is not good, but I have my own ideas. This arrangement also pulls large, narrow pulses of current out of the generator that are rich in harmonics so the rms currents are very high. You need to oversize the generator to overcome the high rms currents.

 

[MichaelK]

I have a Schneider XW+6848, and generator input and inverter out work seamlessly with each other.

 

[shanemgrey]

I have a Schneider XW+6848, and generator input and inverter out work seamlessly with each other.

I have two MPP Solar LV6548 systems which I intend to connect for split phase 240. They can only invert or charge, not both at once.

 

[shanemgrey]

I'm currently considering just buying another 4000 to 6000 watt 48 volt inverter charger and dedicating it to the purpose of charging from the generator. But since I don't need pure sine output that a high quality inverter isn't necessary. I'm thinking there must be some good straight charger options out there, but haven't found anything other than a few sketchy options on alibaba.

I'd like to learn of options that users here have experience with instead of risking another $500 on some unknown vendor for a charger, or $1200 on a quality inverter/charger.

 

[Steve_S]

A Regular NON-PureSine Generator works BUT they are Mod-Sine and any Pure Sine Inverter taking it in as Mod-Sine passes that along, they do NOT correct for Sine Wave types. Inverter Generators ARE Pure-Sine and that passes through the Inverter/Charger to house & to battery charger.

My 9kw Gasser Industrial Genset can & will charge my 30kwh bank & pass through BUT the effects are Noticeable especially on motors (fridge/freezer/AC Compresor motors) and even fine electronics. Mod Sine will also vary in frequency depending on Loads and can float from 55-66 Hz frequency and even worse if Overly Loaded. Many Pure sine Inverter/chargers will LIMIT such deviance & cutoff.

My 4kw Inverter Genset stays exactly at 60hz, regardless of load, nothing ever fails to start and as such is "Clean Power In & Out".
GIGO Applies, Garbage In = Garbage Out.

Have a Look @ Champion Inverter Generators, which are reasonably priced and work great, I've been using Champion for industrial & residential use for over 2 decades with no issues... But I am a Maintenance Freak so oil changes etc On Schedule and only use Synthetic 0W-30 Oil !

 

[RCinFLA]

I have two MPP Solar LV6548 systems which I intend to connect for split phase 240. They can only invert or charge, not both at once.

That is a limitation of many of the cheap HF inverter/chargers.

They have a limitation in battery to HV DC converter. They actually switch modes from a forward DC to DC converter to supply AC output or switch to a buck DC to DC converter when charging battery from AC input. They cannot quickly switch modes so when there is AC input applied they only allow AC pass through to AC output and charging of battery.

Also because the HV DC to AC PWM sinewave H-bridge chopper is used to rectify AC input for charger, they may not allow supplement to AC output from PV input power when AC input is applied. PV input can only be used for battery charging when AC input is present.

Some HF inverters, like SolArk can do load shaving. They have much greater HV DC capacitor storage allowing them to make the mode switching. A low frequency inverter/charger is a better choice for supplementing AC input. Make sure you select an inverter/charger that has load shaving capability. Low freq inverter/chargers are better for attaching an external generator than HF inverter/chargers. LF inverters have very good AC input power factor load on generator for battery charging. Some HF hybrid inverter just use simple rectifiers to convert AC input to HV DC giving them poor AC input power factor for charging.

For synchronous constant RPM generators, engine RPM governor stability is the most important performance factor. RPM instability translates to frequency output instability. Hybrid inverter/chargers AC input phase tracking is slow tracking so if generator vary in their frequency output too quickly the inverter/charger will release from, or refuse to connect to generator.

A synchronous generator with electronic RPM governor controlling a stepper motor driven throttle are usually better for RPM stability. Inverter-generators have good frequency stability but limited surge load capability, especially if run in ECO mode where they reduce RPM at lighter loads. They take some time to rev up RPM when a heavier load is applied. During this RPM rev up time the sinewave output peaks are clipped in voltage.

 

[12VoltInstalls]

wonder

like to avoid running the house on the generator,

@Supervstech im including you because you might know about this foolishness. I haven’t researched it yet but laying in bed watching the pre-dawn light brighten at 4:30 last week I had an idea. Bear with me…

I thought of a horizontal shaft gas motor driving either a rewired automotive alternator rectified 48VDC to directly charge a lithium battery bank. I’d have to externally regulate with a safety overvoltage shutdown as that has the potential for crazy 20VDC+ if something went wrong. Like the the regulator failing or a sudden failed/bad connection (I’ve seen both).
This would not be huge- maybe 25A @ 48V nominal- but (in my case) would probably be more than enough to not need grid supplements this coming winter with LiFePo to run my heat; the constant low-amp draw and/or cloudy days isn’t favorably accepted by lead acid.

In my mind that’s a low-buck not-manufactured-generator approach to charging LiFePo. The only problem is finding a decent 100% duty 48VDC rectifier and voltage controller at a commodity level. There’s these though.

I don’t need 48V right now- and I can do 12V fine- but my thought was when I buy property I’ll want 48V for the shop.

Any thoughts?

 

[littleharbor2]

That is a limitation of many of the cheap HF inverter/chargers.

Seems to me any inverter/charger only works one way at a time. My Trace SW4024 turns from an inverter to a charger when connected to a generator. Thing is when connected to a generator the generator powers the loads with its ac power and the inverter takes whatever power is available after powering the loads and converts the ac into dc to charge the batteries. Am I missing something here?

 

[Steve_S]

I use a Samlex EVO Inverter/Charger with Dual AC Inputs (1 for grid, 1 for genset), and comes with built ATS Handling for both ends and can be programmed for priorities, related to incoming & outgoing power.
This is a Pure Sine, Low Frequency which only "sips" 8W when no load is present and Eco/Powersave Modes is OFF.
BUT this is also a $2300 USD Inverter/Charger and it is what you pay for.

 

[shanemgrey]

It seems pretty easy to find cheap 12v chargers at reasonably high amps. It's easy to find hybrid inverter/chargers at 48 volts with reasonably high amps. But it's hard to find cheap 48 volt chargers at reasonably high amps. Golf cart chargers seem to be good except they seem to all require 3-phase at the higher wattages.

I don't have grid power here. All I have is a tri-fuel champion generator (non-inverter) which is being fed natural gas directly from a well. It's likely that the gas is not up to distribution quality standards and thus has a lower energy density. But it's free due to the well being 100 feet away.

An inverter generator would be nice and I'm aware they exist. But they are much more expensive for the amount of wattage needed to power the household, and it's hard to find them already setup for natural gas. I imagine I could find one that would do everything if I went into the "home backup power" lines by Generac and the like. But then I'm looking at $8000 installed. That's about as much as the rest of the entire system with PV, Batteries, and Inverter.

All I need right now is something that can take dirty 240 split phase at around 4000 to 6000 watts and turn it into a charge current for my 48 volt 280ah banks. It seems like a single simple device should exist to do this perfectly, and a price that's lower than inverter/chargers designed to produce pure sine output.

I understand that there are many ways to accomplish getting power to a house. But each have their disadvantages and situational challenges.

An inverter generator would fix the issues with devices wanting better quality sine waves. But they are expensive, tend to be lower wattage, and are hard to find to run on natural gas.

A hybrid inverter charger like the MPP LVX6048 would do everything I'm asking, and more, for more money. This might be the route I go, but I don't need the AC output, or the solar charge controller that it offers. So it's wasted money.

All I think I want (recognizing again that there are a lot of ways to get to the same results), is a charger that can take 240 split phase power and output a 48 volt charge current around 100 amps, with a high voltage cutoff.

Victron sells the Skylla-TG Charger for 48 volt charging, but it's expensive of course, and only outputs 25 or 50 amps. If I can buy a MPP LVX6048 for about $1500 which can do double the amps and all the other hybrid stuff, why can't I buy something cheaper that just does the charging without the (presumably more expensive) need for pure sine AC output?

Sorry for the long post. But it seems like such a simple thing that I'm confused why there are so many work arounds instead of just a "48 volt 100 amp charger with 240 split phase input"

 

[12VoltInstalls]

I'm confused why there are so many work arounds instead of just a "48 volt 100 amp charger with 240 split phase input"

Maybe lower your expectations a bit. 24V?
I think there’s way more stuff to do what you want at the 24V level. I think MPPSolar has 24V stackables for transformerless 120/120 split.

 

[shanemgrey]

I already have 2 LV6548 systems and a 16s BMS. I want to stick with 48 volt for the lower overall cost per watt. And at this point changing over the rest of the system to 24 volts just for the sake of being able to find a cheaper 24 volt charger seems counter to my goals.

I agree that 24 volt stuff seems more common, and 12 volt even more so. But I'm just surprised that it's possible to get All-in-one systems at 48 volts for pretty cheap, yet I can't find a cheap "charger only" at the same volt/amp output. Maybe it's just not that much harder to build an inverter/charger compared to a charger alone, so the market just fills the dual purpose models and ignores the single purpose.

So far no one has posted a link to a 48 volt 100 amp charger that runs on 240 split phase. Nor has anyone suggested a better alternative. So I'm guessing I'll be buying an inverter charger in the near future.

I'd like to offer a little more explanation why I think this is the best possible setup for my situation rather than the alternatives that have been suggested.

First, everything I have is off grid. The grid is at least 2 miles away. But the household is a "modern suburban" style house with normal household appliances like a washer, water pumps, computers, fish tanks, window AC, and so on. The heating appliances are all natural gas. But the house still occasionally needs 60 amps all at once.

When running from the inverter, this is no problem. Everything runs great. But the 7000 watt portable generator struggles with the peak loads and sometimes dies after browning out the household. The microwave can't be run on the generator (presumably because it's not pure sine), and the EV that I plan to charge here also gets very picky about the waveform, frequency, and so on. It is not recommended to charge the EV on non-inverter generators.

So the simple solution is to always power the household and the EV charger with the inverters. But like everywhere else on earth, the sunlight reaching the panels is intermittent here. And the battery bank is not oversized enough to charge an EV very much when there is no power coming in.

So the simple solution is to have some other source of power on demand, like a generator. But to avoid the problems that pass-through causes, it's necessary for the generator to be providing DC 48 charging power instead of AC. This allows the inverters to continue working as if they have infinite battery to draw from. And they never have to switch to charge/pass-through mode.

If I could have bought a natural gas generator that outputs 48 volt dc charging level power, that would have been perfect. But there's no mass market option for that like there is for 240 volt split phase output. The simplest, if not most power efficient, solution is to put a charger between the generator and the battery.

The dedicated generator powered charger allows the battery to be a buffer and intermediary for the power, letting the inverters provide pure-sine power to the household all the time.

If I know I need to charge the EV a lot, and the sun isn't out, I don't have to cycle the batteries all the way down and back up several times. I can just start the generator and the EV won't even know about it. I could set the EV to pull just the wattage required to keep the battery state roughly the same while being "charged" by generator. So it saves charge cycles.

It's fun that off-grid power still has so many options to fit different situations. In a lot of ways it seems like too much choice. Yet somehow there are still "holes" in the market for some things like this.

 

[12VoltInstalls]

But the house still occasionally needs 60 amps all at once.

When running from the inverter, this is no problem. Everything runs great. But the 7000 watt portable generator struggles with the peak loads and sometimes dies after browning out the household.

That’s because it’s max is 30A per leg.

 

[shanemgrey]

That’s because it’s max is 30A per leg.

That makes sense. I didn't mean to suggest it shouldn't die when overloaded. I just meant to point out that it can't handle the "normal" loads, while the inverters can.

 

[Hillbilly_4ge]

A Regular NON-PureSine Generator works BUT they are Mod-Sine and any Pure Sine Inverter taking it in as Mod-Sine passes that along, they do NOT correct for Sine Wave types. Inverter Generators ARE Pure-Sine and that passes through the Inverter/Charger to house & to battery charger.

My 9kw Gasser Industrial Genset can & will charge my 30kwh bank & pass through BUT the effects are Noticeable especially on motors (fridge/freezer/AC Compresor motors) and even fine electronics. Mod Sine will also vary in frequency depending on Loads and can float from 55-66 Hz frequency and even worse if Overly Loaded. Many Pure sine Inverter/chargers will LIMIT such deviance & cutoff.

My 4kw Inverter Genset stays exactly at 60hz, regardless of load, nothing ever fails to start and as such is "Clean Power In & Out".
GIGO Applies, Garbage In = Garbage Out.

Have a Look @ Champion Inverter Generators, which are reasonably priced and work great, I've been using Champion for industrial & residential use for over 2 decades with no issues... But I am a Maintenance Freak so oil changes etc On Schedule and only use Synthetic 0W-30 Oil !

Its crazy you wrote this so long ago and it just solved my queries here in 2023. Thank ya