What size generator?

[sunshine_eggo]

I thought the victron multiplus did exactly that?

Only in PowerAssist mode, and it won't charge then. I didn't want to complicate things. It effectively acts like a grid-tie inverter in that mode - it syncs to the incoming AC and then boosts it.

 

[sunshine_eggo]

Cool. I'm supposing the the electronics in the charger are making sure that they don't exceed that, which makes sense now that I think on it since they have to control the current to the batteries in the process of charging them. Thanks for confirming.

Not in the way you think. Something to tuck into your skull: A 15A/120V wall outlet can provide 1800W of power, but when you plug a 13W bulb into it, you only get 13W out of it.

The charger is doing this:
1) if below X volts, send 18A.
2) if at X volts, reduce amps to hold X volts.
3) if Amps < cut off (full charge), stop charging.
4) If volts is below Y volts (some lower safety limit), stop charging.

Your scenario as a water tank example: You have a very large water tank. You are draining 60gpm from the bottom of the tank. You are adding 40gpm to the top of the tank. The 60gpm drain has no influence on the 40gpm input... until the tank is empty, and the drain exceed the fill. At some point, the low water sensor cuts off the drain.

I was not clear on that prior but I got the picture after reading up more. That bypass was the mode it operated in while charging from utility just was not known to me before hand. As soon as I started it though and noticed it refused to charge while in BSU priority mode but in USB it did and stayed in bypass I knew my previous assumptions were probably in error. Makes sense if the pathway through the electronics is shared.

Think of it this way: Charging is AC to DC. Inverting is DC to AC. the same circuitry handles the conversion, it just depends on which direction things are going.

 

[Checkthisout]

Only in PowerAssist mode, and it won't charge then. I didn't want to complicate things. It effectively acts like a grid-tie inverter in that mode - it syncs to the incoming AC and then boosts it.

Well yeah if it's fully loading the Gen with the house load then it can't also charge the Batts the idea being you can run a 2kw gen and run intermittent high draw stuff without overloading the generator or undercoating it when the high draw stuff is off and you want to resume battery charging.

 

[sunshine_eggo]

Yeah so it's not like other inverter chargers.

It is the same. It simply has an added feature. The statement still holds true. It can't invert and charge at the same time. If powerassist is activated, charging immediately stops.

This is a handy feature for an undersized generator when intermittent loads exceed generator capacity. Benefitted from it many times.

 

[Checkthisout]

It is the same. It simply has an added feature. The statement still holds true. It can't invert and charge at the same time. If powerassist is activated, charging immediately stops.

This is a handy feature for an undersized generator when intermittent loads exceed generator capacity. Benefitted from it many times.

?

Well yeah if it did then it would overload the Gen like the EG4.

 

[John Frum]

It is the same. It simply has an added feature. The statement still holds true. It can't invert and charge at the same time. If powerassist is activated, charging immediately stops.

This is a handy feature for an undersized generator when intermittent loads exceed generator capacity. Benefitted from it many times.

But can it bypass and invert at the same time?
I'm guessing that even though it can syncronize with the upstream source it doesn't, but I'm not sure.

 

[Checkthisout]

But can it bypass and invert at the same time?
I'm guessing that even though it could syncronize with the upstream source it doesn't, but I'm not sure.

Yes, it bypasses and inverts at the same time in assist mode.

This is what makes its different than other inverter chargers.

 

[photomankc]

Okay.

So for the time being I'm going to live with bypass mode and set charge current to 20A. That will leave me some room to operate most of my stuff as long as I'm aware of not doing two high current things together, which is fine as Im still building. I'll start hunting for a 30A to 35A charger to setup separate from the inverter. I already have a nice set of generator-only 20A outlets that I could use for that. With that charge current a 10KW setup would be a nice sweet-spot and with solar added in I think it would handle 15KW without much trouble too.

I appreciate the info, thanks!!

 

[sunshine_eggo]

But can it bypass and invert at the same time?
I'm guessing that even though it can syncronize with the upstream source it doesn't, but I'm not sure.

It does.

Dexter demo-ed zero export on 120VAC - basically a grid-tie inverter that won't backfeed with the appropriate sensor installed:

VICTRON 24V Multiplus II 2x120v Purchase Availability

It means that your AHJ must accept something besides UL listed equipment. You would need to write up the plans indicating the lack of UL listing and provide other justification for its use and get them approved. Your earlier post referred to ‘UL 1741’ The Multiplus II 120x2 is UL listed...

diysolarforum.com

 

[John Frum]

It does.

Dexter demo-ed zero export on 120VAC - basically a grid-tie inverter that won't backfeed with the appropriate sensor installed:

VICTRON 24V Multiplus II 2x120v Purchase Availability

It means that your AHJ must accept something besides UL listed equipment. You would need to write up the plans indicating the lack of UL listing and provide other justification for its use and get them approved. Your earlier post referred to ‘UL 1741’ The Multiplus II 120x2 is UL listed...

diysolarforum.com

Makes me suspect that is why only distributers are supposed to have full access to the configuration.

 

[sunshine_eggo]

Makes me suspect that is why only distributers are supposed to have full access to the configuration.

Yep. Victron only complies with certain grid standards, NONE of which include the U.S. grid, and a password is required to set or change the grid standard.

EDIT: "NONE" was "one" - so wrong.

 

[AstroBob]

I'm a little confused with this thread. The folks I know with very large 5th wheel RV's and other large TT's all seem to get by quite well with no more than <=4500 watt gennys when boondocking. (including PV, of course). With my own small (18ft) trailer, I run the 13K AC and micro with a 2200 honda. I have a rural property with a 750 sq ft cabin, and I can run the furnace and fridge and most everything else on a wen 3800 gen. I can't possibly imaging why a tiny house on a trailer would require such incredible amounts of energy to sustain them, even in a cold climate.

Perhaps a mobile military communications center or something. lol.

Isn't the entire point of a tiny house to be efficient?

Is not the "combi boiler" a gas powered unit?

So, where does the need for 5Kw power come in? Where are these massive loads coming from? I am curious.

 

[photomankc]

I'm a little confused with this thread. The folks I know with very large 5th wheel RV's and other large TT's all seem to get by quite well with no more than <=4500 watt gennys when boondocking. (including PV, of course). With my own small (18ft) trailer, I run the 13K AC and micro with a 2200 honda. I have a rural property with a 750 sq ft cabin, and I can run the furnace and fridge and most everything else on a wen 3800 gen. I can't possibly imaging why a tiny house on a trailer would require such incredible amounts of energy to sustain them, even in a cold climate.

Oh were it just the generator I'd have no issue at all. The 3000W covers most anything I really do beyond starting very large inductive loads. But when it's going to spend 4 to 6 hours with 1600W siphoned off then its a different story. I imagine once solar is in place that might not be as much of a concern so I grant that.

Isn't the entire point of a tiny house to be efficient?

Probably all manor of reasons people get whatever it is that's called a "tiny house" now. For myself we built the largest structure we could afford to dry in as a getaway cabin. It's not a garden shed and its not really a house. It kinda sits in the middle. For us efficiency is a distant 3rd or 4th. Main consideration was to have a system we could grow into and expand and that could handle most tasks without power management being top-of-mind. I also prefer these Chinese electronics to spend most of their lives working in the low end of their specs. Will be building this system like the cabin itself. A little bit at a time.

So, where does the need for 5Kw power come in? Where are these massive loads coming from? I am curious.

As above, for me its having lots of headroom if someone is showering with the pump running, the microwave is on, and my daughter is using the kettle for tea. Were it only ever going to be me there I'd live without a lot of that, but since it's wife and daughter, making sure for the most part power is not something to juggle I went oversized on the inverter.


Not really trying to refute you here either, just explaining where I'm coming from on my system.

 

[sunshine_eggo]

If I didn't have a Victron with powerassist, I'd be pissed with generator charging too. My generator can only output 15A per 120V leg, so I'm limited to < 1800W PERIOD.

PA has saved my bacon multiple times.

 

[AstroBob]

Oh were it just the generator I'd have no issue at all. The 3000W covers most anything I really do beyond starting very large inductive loads. But when it's going to spend 4 to 6 hours with 1600W siphoned off then its a different story. I imagine once solar is in place that might not be as much of a concern so I grant that.

Alrighty. I thought you said 5K watts, not 3, but maybe I wasn't paying attention. On my off toad trailer, I have 200watts solar, + 600 portable in needed, 206Ah LifePo4 + 2000 watt inverter if needed. Obviously, I don't run the 13K AC off the batts, and rarely the micro. Water heater and furnace are propane, as is the fridge.

The small genny is just to power the AC when needed, and to charge the batts when no solar, so maybe not all that dissimilar to the tiny house thing, I venture. - or maybe not.

Probably all manor of reasons people get whatever it is that's called a "tiny house" now. For myself we built the largest structure we could afford to dry in as a getaway cabin. It's not a garden shed and its not really a house. It kinda sits in the middle. For us efficiency is a distant 3rd or 4th. Main consideration was to have a system we could grow into and expand and that could handle most tasks without power management being top-of-mind. I also prefer these Chinese electronics to spend most of their lives working in the low end of their specs. Will be building this system like the cabin itself. A little bit at a time.

Yeah, I get it. I am no EE, just trying to compare your interesting project with a somewhat similar use case. It seems to me that with a "Tiny" house you have a huge advantage over any travel trailer or camper in that you can insulate to whatever specs you want. Travel trailers are mostly all very poorly insulated. I am just speculating but from what I know, good insulation isn't cost prohibitive, and can make a large difference in energy consumption. Sounds like low hanging fruit to me, anyways.

As above, for me its having lots of headroom if someone is showering with the pump running, the microwave is on, and my daughter is using the kettle for tea. Were it only ever going to be me there I'd live without a lot of that, but since it's wife and daughter, making sure for the most part power is not something to juggle I went oversized on the inverter.

Do you mean an RV style water pump, or this a pump part of the combi unit? My RV pump doesn't use much power. Hard to avoid the power drain from the micro, but I don't use mine much, so not a problem for me off grid. But it's understandable that you want to include that.
I do all of my cooking with propane, it sounds like you need/want electric. That's cool.

Not really trying to refute you here either, just explaining where I'm coming from on my system.

It really didn't sound like you were refuting my comments, I was just expressing my interest in your project. It sounds like fun to me.

 

[RCinFLA]

I believe Victron LF inverters do have user setting for maximum AC input current allowed. (load shaving)

Charging from AC input will be limited by charger parameter settings or maximum AC input allowed.

When AC output exceeds user set AC input limit, AC output will be supplemented by battery power through inverter. This is great for smaller generator operation.

AC output load has first priority on limited AC input power. As AC output load increases there will be less overhead AC input power available for battery charging. This is a smooth transition from charging battery to drawing from battery to support greater AC output loads.

The AC output load can exceed what generator or inverter is capable of individually by combining power from both sources.

There is a small response time in the order of 10-20 msecs for AC output surge loads before inverter/battery picks up any excessive AC output surge load current. This can cause generator to momentarily bog down from momentary surge current, causing a shift in its AC frequency output, which causes inverter to release from generator. As long as inverter can support AC output load, the inverter will not shut down for overload and the inverter will resync and reconnect to generator again after a 20 sec to minute gap.

 

[photomankc]

LOL... this adds a wrinkle. Kind of a both worlds thing:

https://a-ipower.com/products/gxs7101ird-remorte-dual-fuel-inverter-generator

My inlet is 240V capable. I COULD use a generator like that to get two branches of juice. Break the hots out and send one to the outlets and the external chargers. Then one to the inverter. That would leave the full 30A capacity of one leg for cabin loads via bypass and up to 19A to power the chargers. That means no consumption from battery during generator run time and plenty of juice even to likely start an AC while charging.

That assumes the charger on the 6500 can be disabled or can co-exist at lowest setting with the other charger/s.

So that leads to another question... are parallel chargers okay? One 30 or 35A is hard to find but two 18A would do the job assuming they can coexist.

 

[photomankc]

Alrighty. I thought you said 5K watts, not 3, but maybe I wasn't paying attention. On my off toad trailer, I have 200watts solar, + 600 portable in needed, 206Ah LifePo4 + 2000 watt inverter if needed. Obviously, I don't run the 13K AC off the batts, and rarely the micro. Water heater and furnace are propane, as is the fridge.

I'm not the OP and I think you are correct, he referenced a 5000W inverter and a recommendation he got for a 10KW generator.

Yeah, I get it. I am no EE, just trying to compare your interesting project with a somewhat similar use case. It seems to me that with a "Tiny" house you have a huge advantage over any travel trailer or camper in that you can insulate to whatever specs you want. Travel trailers are mostly all very poorly insulated. I am just speculating but from what I know, good insulation isn't cost prohibitive, and can make a large difference in energy consumption. Sounds like low hanging fruit to me, anyways.

I'm 2x4 walls and going to use a lot of rock-wool insulation. Still R13 or so but adds quiet. Way better than trailers but still not amazing. Heat will be propane though and cooling is really a very once-in-a-while thing. Not much fun to be outdoors near Arkansas in late June/July/August so I just stay away.

Do you mean an RV style water pump, or this a pump part of the combi unit? My RV pump doesn't use much power. Hard to avoid the power drain from the micro, but I don't use mine much, so not a problem for me off grid. But it's understandable that you want to include that.
I do all of my cooking with propane, it sounds like you need/want electric. That's cool.

Probably a 1/2HP shallow well pump and tank. I looked at continuous run pumps too but think I'd prefer the pump/tank. Electric for cooking is limited to microwave and kettle/coffee pot mostly. The kettle I kind of got attached to. Getting 1.5L of boiling water in very short time is really nice, and I don't have to break out the camp stove and pots. Microwave is nice because I bring leftovers to warm up most construction trips. Again, convenient to just pop in and eat vs cooking after swinging a hammer all day.

It really didn't sound like you were refuting my comments, I was just expressing my interest in your project. It sounds like fun to me.

It is fun. Having the lights on without a generator running for the first time was GREAT!

 

[sunshine_eggo]

I believe Victron LF inverters do have user setting for maximum AC input current allowed. (load shaving)

Yes. One needs:
USB-MK3 + VEConfig or Victronconnect
VE.bus smart dongle + victronconnect (can only change the AC input value but monitor all others)
External control panel that allows one to set AC input with a dial.

Charging from AC input will be limited by charger parameter settings or maximum AC input allowed.

Yep. First one hit establishes the limit.

When AC output exceeds user set AC input limit, AC output will be supplemented by battery power through inverter. This is great for smaller generator operation.

Yep, and the inverter is AGGRESSIVE in protecting AC input. It will initially supply DOUBLE the overage to prevent exceeding AC-in even momentarily. If load stabilizes, it dials back to 1.0X. This is a programmable value that defaults to 2.0.

AC output load has first priority on limited AC input power. As AC output load increases there will be less overhead AC input power available for battery charging. This is a smooth transition from charging battery to drawing from battery to support greater AC output loads.

Confirmed. Power loads with AC-in and charge with surplus up to AC input limit or charger output limit. It is smooth, but you hear it when it happens. She growls.

The AC output load can exceed what generator or inverter is capable of individually by combining power from both sources.

Confirmed. One has to size Victron AC output wires for the max AC-in + PowerAssist.

FWIW, If powerassist is not enabled, one can readily overload the generator regardless of the AC input setting.

There is a small response time in the order of 10-20 msecs for AC output surge loads before inverter/battery picks up any excessive AC output surge load current. This can cause generator to momentarily bog down from momentary surge current, causing a shift in its AC frequency output, which causes inverter to release from generator. As long as inverter can support AC output load, the inverter will not shut down for overload and the inverter will resync and reconnect to generator again after a 20 sec to minute gap.

I'm guessing that's the "growl" I hear...

 

[photomankc]

Yep, and the inverter is AGGRESSIVE in protecting AC input. It will initially supply DOUBLE the overage to prevent exceeding AC-in even momentarily. If load stabilizes, it dials back to 1.0X. This is a programmable value that defaults to 2.0.

Yeah that's awesome. The cheap-o's just slam the generator with the whole load then shrug their shoulders when it falls over.

 

[sunshine_eggo]

Yeah that's awesome. The cheap-o's just slam the generator with the whole load then shrug their shoulders when it falls over.

Exactly what the Victron does if PowerAssist is disabled... Learned that for myself.

 

[RCinFLA]

Inverter is 60Hz (or 50Hz) so control sensing is dealing with a sinewave that is 16 msecs long. This limits reaction time to about half to one cycle of AC depending where a sudden surge current hits in the sinewave cycle. Then there is a little time for inverter control to readjust PWM sequencing in inverter feedback control to the LF transformer drive to feed greater AC supply current to the AC output current.

This is why up to a couple of AC cycles of a sudden AC surge current, like a single phase motor starting up, may make it through inverter to generator. Usually, it is just a small bump in the road to the generator. Single phase motors take about 0.3 to 0.5 seconds to spin up so most of any starting surge beyond inverter AC input current limit will be covered by inverter/battery.

 

[12VoltInstalls]

If I was the OP I would omit supplying all that stuff and just say the thing is "solar ready" or some such nonsense.

If people want an offgrid teenyhome they should learn how to live offgrid. If they need a generator they can buy one.

folks I know with very large 5th wheel RV's and other large TT's all seem to get by quite well with no more than <=4500 watt gennys when boondocking. (including PV, of course). With my own small (18ft) trailer, I run the 13K AC and micro with a 2200 honda

cuz you know how to manage and not be dumb

 

[12VoltInstalls]

Having the lights on without a generator running for the first time was GREAT!

It weirded me out for a few years (and still does!) that I can do whatever I want without a grid connection (within limits but the limits aren’t a big deal). I have no generator either.

 

[Checkthisout]

It weirded me out for a few years (and still does!) that I can do whatever I want without a grid connection (within limits but the limits aren’t a big deal). I have no generator either.

I have a generator and it still weirds me out, especially when it's stormy and all power is out, trees are down and I get the recreational property and everything is normal as it is any other time. Internet works (cellular) . All lights on etc.