XW6048 for whole house battery backup

dBeaudBeau Posts: 24Registered Users
I'm looking for some advise on how to build a hybrid battery/generator backup system for my on-grid home. The goal is to coast through small (2 hours or less) grid outages on battery power with minimal disruption but to also use a generator to handle the longer outages. I'd like the system to be quiet, fuel efficient, and as automated as is reasonably possible.

At first glance, the XW6048 seems to be just the ticket. I am sure that some of it's cost is due to also being able to support a PV array. While I am not planning for this as part of the initial project I do want to plan for it. I have 400sq of prime unshaded (though nearly flat) roof space and another 350sq of partially shaded in the morning and again in the late afternoon roof space that I'd like to press into service at a later date. Right now, the primary goal is just backup power.

I'm thinking that the first phase will be to separate my breaker panel (200amp service) into loads that I want backed up, and those I dont. I currently have many loads that would would never make sense even on a generator. These include two zones of (rarely used) baseboard heat, oven, clothes dryer, pool pump, etc. I suspect that what remains could all be fed from a 60amp sub-panel.

My current panel (30+ circuits) is monitored by 3 Brueltech 1240's. They give me 21 channels of monitoring so I have a pretty good idea of my loads. For any five minute period my total load rarely goes over 7kw and typical is far lower than that with an average under 30kwh/day. With the big loads out of the way, I would think the XW6048 would be just fine.

Assuming the XW6048 is the way to go, the remaining questions have to do with the size and technology for both the generator and the battery bank. My (simple minded) analysis here is that I would need a minimum of 8-10kwh of capacity to get two hours of runtime assuming a 2kw average load for those 2 hours and a target of 50% discharge.

My only experience with battery banks so far is with a large UPS in a data center where I hang out. It uses a two banks of 40 UB121000's and is designed to dump them all 80 in under an hour. So for my little project, it would seem that 8 would be able to handle my load and then some. Of course, Liebert doesnt expect that this system will be cycled continuously over the course of an extended outage. I'd guess they are making battery life trade offs that I dont understand. Regardless, they do expect the batteries to last 5 years in their intended role as a stand-by power source.

In my hypothetical system, two hours into an outage my batteries are down to 50% then the XW6048 tells the generator to kick in and charge the batteries to 80%. Assuming 80% efficiency for the charge, this would be about 3kw for an hour, or a bit more than half what a 6kw generator could produce and would still leave enough head room for the 2kw (average) load. Another assumption I'm making here is that the remainder of the batteries would still available to the inverter to handle any surge or short term increase in the load while charging.

I'm sure I've missed many details here, but if I am even close, it would seem that a 6kw generator and 8kwh of battery would give me somewhere around a 50% duty cycle (1 hour on 1 hour off) on the generator. While all that sounds great, I'd like to understand better the limits and factors that affect the generator's duty cycle.

So my questions to the experts are: 1) how far off are my estimates? 2) would this line of thinking work with FLA batteries? 3) Does the XW6048 "clean up" the generator output or pass it through directly? and related, 4) would I need to use an "expensive" inverter based generator for any reason other than noise control? 5) When grid power is available will I notice the load associated with keeping the batteries topped off. 6) What have I missed?

Thanks in advance for playing along.
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Comments

  • mike95490mike95490 Posts: 6,290Solar Expert ✭✭✭✭
    Re: XW6048 for whole house battery backup

    the XW6048 has no solar provisions, other than it can run off a battery that is charged from PV panels, via a Charge Controller.

    It does not alter the input AC power, but does have "generator support" so if you are using the genset to run some loads, and charge via it's internal 240VAC charger, and you have a large surge, like a well pump engage, the inverter will "assist" the generator to keep the voltage stable.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • ChrisOlsonChrisOlson Posts: 1,807Banned
    Re: XW6048 for whole house battery backup
    dBeau wrote: »
    At first glance, the XW6048 seems to be just the ticket. I am sure that some of it's cost is due to also being able to support a PV array.

    The cost of the XW-series is due to it being 120/240 split phase, integral, without stacking inverters. And it is pretty much the "Cadillac" of residential battery-based inverters. It has three power inputs - DC from your battery bank, grid input, and gen input. It has no provision to directly support a PV array.

    When on gen power it's internal transfer switch switches all loads to to the gen input. It monitors the gen input voltage and frequency and if it goes out of range (such as a heavy surge load lugging the generator down) it will disconnect gen input and momentarily switch the load back to battery to meet the heavy surge load, then bring the generator back online to meet the continuous load. The XW6048 has roughly 2x the surge capacity of most 6 kW generators.

    Most of the description of your proposed system seems reasonable.

    For the generator, if you want one that is VERY quiet and fuel efficient, I can highly recommend the Generac EcoGen. It is designed for off-grid use and therefore comes configured for 120 volt output. For 240 split phase you have to purchase a field installable 240 kit on it. But if you intend to use it only to take over the inverter loads and charge batteries when the bank gets sacked, I think it would be the perfect unit. It has a low rpm (2900) engine and makes about as much noise as a central AC unit running. It's two-wire start system will work nicely with the Xantrex generator control.

    That all being said, the only real flaw in your plan is that it would be much cheaper to simply install a standby generator for two hour outages and forget the battery backup inverter. The only reason I would use the inverter is if you have loads that have to stay lit when the utility power fails, as the XW6048 will seamlessly switch over to battery power without the lights even flickering. It will take 10 seconds or better to bring a standby generator online. But from a cost standpoint, the standby generator makes more sense.

    If you plan to add a PV array and/or wind power, then the big Xantrex starts to make more sense.
    --
    Chris
  • techntrektechntrek Posts: 1,355Solar Expert ✭✭✭
    Re: XW6048 for whole house battery backup

    I have most of my 120 volt circuits on a separate panel, attached to a UPS (the few remaining 120 volt circuits are things like attic lights). When we are home and awake the continuous load is usually around 1500 watts, and it is less than 500 watts during sleep/away periods. This includes 2 fridges, 1 freezer, a whole-house air circulation unit, the blower on 1 of my 2 heating/cooling systems, TVs, lights, things charging, etc. I have a 22 kw battery bank and under normal loading - no conservation measures - it will last up to 17 hours.

    Bottom line, I don't think you need 10 kw of battery to last you 2 hours. I also agree with the suggestion that just for 2 hour outages you should stick with an automatic genset and put small UPSs on things like DVRs to carry over until the genset takes over. If you anticipate longer outages then a hybrid battery + genset system makes sense to improve efficiency since gensets run most efficiently near full load. This is the reason I added a battery + genset to my house, since we are on the edge of the distribution system and often get outages (neighbors have stories of being w/o power for 2 weeks after an ice storm...).
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • dBeaudBeau Posts: 24Registered Users
    Re: XW6048 for whole house battery backup
    ChrisOlson wrote: »
    For the generator, if you want one that is VERY quiet and fuel efficient, I can highly recommend the Generac EcoGen. It is designed for off-grid use and therefore comes configured for 120 volt output. For 240 split phase you have to purchase a field installable 240 kit on it. But if you intend to use it only to take over the inverter loads and charge batteries when the bank gets sacked, I think it would be the perfect unit. It has a low rpm (2900) engine and makes about as much noise as a central AC unit running. It's two-wire start system will work nicely with the Xantrex generator control.

    From the specs I was able to find, the EcoGen seems about right. Until you pointed it out I'd been considering the Honda EU6500is with a propane conversion. The EcoGen specs have it even quieter than the honda but fuel efficiency seems about the same. I do know that the honda will play nice with my home automation (computers, UPB light switches, etc). But heard some stories about other generacs not doing so well. With the honda, I'm still trying to figure out if it's remote start will play nice with the XW6048's generator control.
    ChrisOlson wrote: »
    That all being said, the only real flaw in your plan is that it would be much cheaper to simply install a standby generator for two hour outages and forget the battery backup inverter. The only reason I would use the inverter is if you have loads that have to stay lit when the utility power fails, as the XW6048 will seamlessly switch over to battery power without the lights even flickering. It will take 10 seconds or better to bring a standby generator online. But from a cost standpoint, the standby generator makes more sense.

    I'd love to say that cost is no object, but I cant. On the other hand, I am willing to spend a bit to eliminate the annoyance of short outages. I dont really expect to use the generator much at all as most of the outages are well under two hours. I just want to keep everything running without interruption. I'm already running about 3kwh of UPS battery and have been tempted to get a couple more small units. Instead, it looks like $10k (plus my labor) will get me a nice generator, inverter, and battery bank that will not only take care of the short outages but protect me from the kind of mess the northeast is dealing with right now (family and co-workers still have no power). From what I've seen with my collection of UPS, I'd expect that one large inverter will be more efficient than many small ones. My large 1000va unit uses 35 x 12v @ 5ah batteries at cost of $500 for replacement batteries alone! I'd rather not replace those batteries again.
    ChrisOlson wrote: »
    If you plan to add a PV array and/or wind power, then the big Xantrex starts to make more sense.

    With the right kind of planning I figure I can add 4kw of PV to the system for the price of a charge controller and the panels. I have a bit more usable roof space but due to shading issues, I suspect I'd have to go with micro-inverters to make the most of it. I'm pretty comfortable with the XW6048 as the heart of the system. It's all the details around the edges that have my head spinning.
  • Dave AngeliniDave Angelini Posts: 2,142Solar Expert ✭✭✭✭
    Re: XW6048 for whole house battery backup

    Your thinking sounds reasonable. Most of my offgrid clients can afford the best and I certainly do not want to spend anymore time than I have to with equipment. Plug and play! Look at the XW-80 CC also! Really simple installation.
    "we go where power lines don't" Sierra Mountains near Mariposa CA
     http://members.sti.net/offgridsolar/
    E-mail offgridsolar@sti.net

  • techntrektechntrek Posts: 1,355Solar Expert ✭✭✭
    Re: XW6048 for whole house battery backup

    A downside to the Generac Eco is it can't idle down under a light load, where the Honda can. I have a Generac, but if I had to do it all over again I would have the Honda instead.

    No reason to replace your UPS batteries with another set of gel-cells. I bought my first UPS (see my signature) specficially to replace its batteries with standard flooded lead acids. Way more watts for the buck. Downside is the float voltage isn't optimal, but I compensate by manually charging occasionally. Larger APCs can be programmed to up their float voltage but I'm not sure about the smaller ones like yours.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • dBeaudBeau Posts: 24Registered Users
    Re: XW6048 for whole house battery backup
    techntrek wrote: »
    A downside to the Generac Eco is it can't idle down under a light load, where the Honda can. I have a Generac, but if I had to do it all over again I would have the Honda instead.

    I'd think with the generator control of the XW6048, the EcoGen would only be running when the batteries need charging. But yeah, I guess if you wanted to top them off, the honda would be better.

    I am curious about the output of the EcoGen... how clean is it compared to that of the honda?

    techntrek wrote: »
    No reason to replace your UPS batteries with another set of gel-cells. I bought my first UPS (see my signature) specficially to replace its batteries with standard flooded lead acids. Way more watts for the buck. Downside is the float voltage isn't optimal, but I compensate by manually charging occasionally. Larger APCs can be programmed to up their float voltage but I'm not sure about the smaller ones like yours.

    When replacing those batteries I spent a bit of time trying to determine if the charger in the UPS could do the job. I never really got there but was willing to try. In the end, $500 was as cheap as I could go for the 2100AH. The problem came down to the 60v input. Ten golf cart batteries would have doubled the price and I couldnt find a large enough 12v for under $100/ea either.
  • ChrisOlsonChrisOlson Posts: 1,807Banned
    Re: XW6048 for whole house battery backup
    dBeau wrote: »
    I am curious about the output of the EcoGen... how clean is it compared to that of the honda?

    I guess HDTV's are supposed to be real sensitive? We have a big Toshiba HDTV and have never noticed any problems with it when the gen is running.

    The EcoGen has an electronic governor, and every time I check it with the inverter Control Module panels, the output is dead on 60 Hz and 121 volts per leg (we have the 240 split phase kit on ours).

    I have a friend about 30 miles away that has a Honda EU6500is and he has never gotten it to work with his Outback inverters for auto-start. It is not set up for remote one or two wire start (option not even available from Honda - all they have a remote wireless thing) and he always claims he's going to hack in to the controls on the generator to see if he can make it work, but never has. Our EcoGen is DEFINITELY quieter than the Honda. The EcoGen makes about as much noise as a residential central AC unit running when you're standing right by it.

    As far as the EcoThrottle on the Honda? It's totally useless for off-grid use. A properly set up off-grid system does not use the gen to "top off" batteries, and start and run the gen at partial loads. For off-grid you set up your inverters so when they bring the gen online, they warm it up for about 10 seconds, then take it to full load.
    --
    Chris
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: XW6048 for whole house battery backup
    ChrisOlson wrote: »
    As far as the EcoThrottle on the Honda? It's totally useless for off-grid use. A properly set up off-grid system does not use the gen to "top off" batteries, and start and run the gen at partial loads. For off-grid you set up your inverters so when they bring the gen online, they warm it up for about 10 seconds, then take it to full load.
    --
    Chris

    I disagree. I've logged thousands of hours on Hondas running off-grid using the eco-throttle. It works fine and saves gas. Loads are not constant, nor is charging. And sometimes the sun doesn't co-operate at all and you have to use the gen to do the whole charging process. Better to do that on eco-throttle than to waste the gas used by a fixed RPM gen.

    BTW you bring the little Hondas "on line" by pulling the rope and plugging them in; there is no auto gen start possible for these small units.
  • BB.BB. Posts: 24,523Super Moderators admin
    Re: XW6048 for whole house battery backup

    Many of the smaller gensets with electric start are not setup for autostart--So, you do get between a rock and a hard spot (small genset with manual start--rope or electric; vs a 7-10 kW minimum genset really setup for autostart/run/stop).

    If you can charge your battery bank with ~50% or more of generator loading (large enough charger, large enough battery bank to take the current), then a larger genset would probably still be fairly fuel efficient.

    If you have a small battery bank and AC charger, then the smaller/manual gensets are going to be much more fuel efficient.

    Typically, the rule of thumb is ~5% to 13% of battery bank AH capacity is the recommended current--Although, you can go upwards of 25% current--but you should have a remote battery temperature sensor to prevent overheating (also, you will not be able to charge very long at 25% rate of charge before the battery hits the programmed absorb voltage and starts to naturally current limit).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ChrisOlsonChrisOlson Posts: 1,807Banned
    Re: XW6048 for whole house battery backup
    I disagree. I've logged thousands of hours on Hondas running off-grid using the eco-throttle. It works fine and saves gas.

    I think that's a misconception. It's a nice marketing thing on Honda's part. But I'm a mechanical engineer by trade, and a good portion of my career was spent working for Cummins-Onan.

    The facts are, you can't get power from nothing. Reducing the speed of the engine will lengthen its life due to the reciprocating and rotating assemblies completing less cycles to do the same work. But at the same time it does not improve mechanical efficiency, nor improve volumetric or thermal efficiency of the combustion chamber. With any internal combustion engine you have to realize an increase in one of the above to realize the same output with less BTU (or calorific) input.

    The basic horsepower and torque curve of a reciprocating engine, measured on a dynamometer, vs Brake Specific Fuel Consumption does not change at lower rpm vs higher rpm at the same mechanical, volumetric and thermal efficiency. Honda can not change the fact that 1.0 horsepower-hour = .7457 kWh, and horsepower on the dyno = torque x rpm / 5252.

    This is due to various basic laws of thermodynamics, physics and mechanical engineering. And no amount of marketing on Honda's part is going to change them. Oh sure - a lot of people believe it because it sounds so logical. But hundreds of thousands of hours dyno testing engines has shown me that a 1,800 rpm 4 pole 60 Hz genset is not inherently more efficient than a 3,600 rpm 2 pole 60 Hz set, at the same output, just because it runs at half the speed, using the same engine. At least not unless you can tweak a few of the basic Laws of How Things Work.
    --
    Chris

    Edit: There is only one exception - and that is if the genset is running with no load on it, at basically zero percent efficiency. Then a unit that is idling is going to use less fuel than a unit running at governed rpm. But even that difference that is not very much.
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: XW6048 for whole house battery backup

    I'm fairly well experienced with mechanical things myself. A few decades of experience in fact.
    I use the Hondas; the eco-throttle works as claimed. Everyone else who actually has and uses them will say the same thing. Not a theory, not a misconception; functional fact.

    I don't think you understand how inverter-generators work.
  • SevenSeven Posts: 292Solar Expert ✭✭✭✭✭✭
    Re: XW6048 for whole house battery backup

    I will add that an engine consumes more fuel at 3600 rpm compared to 1200 due to the simple fact that the cylinder fires more times. Rpm designates a minute of run time. Actual efficiency in this case is based on run time on a specific amount of fuel. It doesn't take into account actual power output.

    You guys are both correct.
  • RCinFLARCinFLA Posts: 1,280Solar Expert
    Re: XW6048 for whole house battery backup

    What you are looking at is very similar to my setup.

    For the XW6048 240vac split phase you need a 240vac split phase generator feed.

    As to generator, it should be sized to cover you peak load plus some extra to charge batteries.

    I have two generators I use. One is a rather loud 15kW Generac that I use during days of outage (after hurricane) to run by electric water heater and house A/C. I run it for about 2 hours in morning and about 2 hours in evening to top of the batteries and heat up water.

    I have enough battery capacity to run the central A/C totally from battery power during the night hours. It totals about 200 to 240 AH's of battery capacity during the night.

    I also have a Yamaha EF3000i inverter generator. It is my super quiet 'trickle charger' that I can run more often as it is very quite (actually lower SPL then by outside A/C unit). I have 120vac to 240vac split phase isolation transformer to convert the 120vac only output from the Yamaha generator.

    For two hours of outage you should be able to ride on battery power only, which I do often. I have my breakers setup as a couple of small transfer switches to keep the high current 240vac appliances off the normal UPS backup (which covers all the house). I can manual switch in the 240vac appliances, along with some manual load management when needed. This is not usually needed for a two hour outage. If the outage is long enough to need the high current 240vac appliances then it also time to pull out the generators. I have autostart capability but almost never use it.
  • ChrisOlsonChrisOlson Posts: 1,807Banned
    Re: XW6048 for whole house battery backup
    Seven wrote: »
    I will add that an engine consumes more fuel at 3600 rpm compared to 1200 due to the simple fact that the cylinder fires more times.

    There are too many other factors such as cam/valve timing events, and efficiency of the combustion chamber that affect fuel efficiency more than the number of combustion cycles with throttled spark ignition engines. Spark ignition engines are least thermally efficient at idle speed, and reach peak thermal efficiency at the mean piston speed that maintains constant gas expansion pressure during the power stroke.
    I don't think you understand how inverter-generators work.

    It could be a mistake to assume such a thing.

    But I digress - apparently generators are kind of like religion. You either believe in the Great Honda or you're going to heck.
    --
    Chris
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: XW6048 for whole house battery backup
    ChrisOlson wrote: »
    There are too many other factors such as cam/valve timing events, and efficiency of the combustion chamber that affect fuel efficiency more than the number of combustion cycles with throttled spark ignition engines. Spark ignition engines are least thermally efficient at idle speed, and reach peak thermal efficiency at the mean piston speed that maintains constant gas expansion pressure during the power stroke.

    Absolutely true. And when you add in the factors involved in generating electricity you can get even wider differences in efficiency.

    It could be a mistake to assume such a thing.

    But I digress - apparently generators are kind of like religion. You either believe in the Great Honda or you're going to heck.
    --
    Chris

    Wrong again.
    Unless you have actual experience with an inverter-generator don't presume to know more about them than those who do.
    In a fixed load situation you would not find much difference between a fixed RPM and an I-G unit. But loads are rarely fixed. From having used both types of gen over many years I can tell you for an absolute fact that the fuel usage difference between loaded and unloaded on an I-G is vastly different than it is on a fixed RPM gen. The inverter-generators are more fuel efficient over-all, due mainly to the fact generators are usually not run at full load.

    BTW, I still have an old Onan that runs despite having a stripped spark plug on one cylinder. Those things are tanks! But it sucks up huge amounts of gas for the 3 kW it's capable of. The technology has improved greatly since then.
  • RCinFLARCinFLA Posts: 1,280Solar Expert
    Re: XW6048 for whole house battery backup

    The problem with the eco-control is when a large load hits it usually will cause the inverter to disconnect from generator. Turn on the microwave and inverter spits off the generator. This is because the sinewave peak get severely clipped as engine comes up to needed speed to make the required power. The inverter spits off the generator due to low input voltage.

    This can be mitigated by setting up load shaving parameters on the XW inverter. It works most of the time but the load shaving reaction time is not that fast and sometimes it still spits off the generator.

    Running without eco-control pretty much eliminates the problem if the max input amperage on inverter is setup correctly. This setting is one of the mutated software definitions on XW (IMHO) and is called max input breaker size. This setting has a designed in 120% factor that you need to fudge this into the setting for desired generator maximum amperage load.
  • ChrisOlsonChrisOlson Posts: 1,807Banned
    Re: XW6048 for whole house battery backup
    The inverter-generators are more fuel efficient over-all, due mainly to the fact generators are usually not run at full load.

    They can be if they're tuned that way. But an inverter gen is nothing, basically, but an inverter strapped to a car alternator. The electrical and power efficiency (power in vs power out) will never match a conventional rotating field generator because you're going thru too many steps, first generating three phase AC, rectifying it to DC, then converting it back to AC output.

    You can compare a Yanmar YDG-series diesel with a Honda and the Yanmar will beat the pants off the comparable output Honda inverter gen across the board. In fact, the Yanmar will burn less fuel at 50% load than the inverter gen will burn at 25%.

    Don't get me wrong - inverter gens are all the latest craze because they generate super clean power, and are lightweight, quiet (at partial load) and popular because of their size and weight. But they are not the best thing since sliced bread in generators. They have their place, that's all.

    The OP here did not ask for a knock down drag out fight over who's favorite generator he should get. He asked which one will work the best for what he wants to do. And I recommend the EcoGen because I have personal experience with it. It's not as fuel efficient as a diesel, but it's quieter, has all the bells and whistles built-in to interact with inverter auto-starting, is reasonably priced, is sized perfectly for 6-8 kW inverter/chargers, and is sold by a company that has a huge network of professional dealers/installers who will come right to your place and repair it under warranty if need be. The Honda is not the unit for this job. It's a portable, not a true standby unit.
    --
    Chris
  • ChrisOlsonChrisOlson Posts: 1,807Banned
    Re: XW6048 for whole house battery backup
    RCinFLA wrote: »
    This can be mitigated by setting up load shaving parameters on the XW inverter. It works most of the time but the load shaving reaction time is not that fast and sometimes it still spits off the generator.

    Yes, but my SW's spit the EcoGen off too sometimes. If the master inverter starts the gen and it's pushing 220 amps into my bank, and then the well pump starts, it will sometimes spit the gen off because of low voltage when the gen lugs down because it doesn't have enough torque to meet the surge requirement.

    I can see, however, where that problem would be worse with a generator with the Eco Throttle because the engine is running well off it's peak torque curve when the heavy load hits.
    --
    Chris
  • RCinFLARCinFLA Posts: 1,280Solar Expert
    Re: XW6048 for whole house battery backup
    ChrisOlson wrote: »
    They can be if they're tuned that way. But an inverter gen is nothing, basically, but an inverter strapped to a car alternator. The electrical and power efficiency (power in vs power out) will never match a conventional rotating field generator because you're going thru too many steps, first generating three phase AC, rectifying it to DC, then converting it back to AC output.

    You can compare a Yanmar YDG-series diesel with a Honda and the Yanmar will beat the pants off the comparable output Honda inverter gen across the board. In fact, the Yanmar will burn less fuel at 50% load than the inverter gen will burn at 25%.

    Don't get me wrong - inverter gens are all the latest craze because they generate super clean power, and are lightweight, quiet (at partial load) and popular because of their size and weight. But they are not the best thing since sliced bread in generators. They have their place, that's all.

    The OP here did not ask for a knock down drag out fight over who's favorite generator he should get. He asked which one will work the best for what he wants to do. And I recommend the EcoGen because I have personal experience with it. It's not as fuel efficient as a diesel, but it's quieter, has all the bells and whistles built-in to interact with inverter auto-starting, is reasonably priced, is sized perfectly for 6-8 kW inverter/chargers, and is sold by a company that has a huge network of professional dealers/installers who will come right to your place and repair it under warranty if need be. The Honda is not the unit for this job. It's a portable, not a true standby unit.
    --
    Chris

    You are talking 'apples and oranges'.

    The larger the generator the better the kWH/gallon will be, but you have to be able to consume the greater power. The typical residence will average 500 to 1500 watts load over a day. To get the peak loads you have to use a much larger generator. You burn a lot of fuel just keeping the larger generator spinning and cooling itself.

    Diesel will outdo gasoline on kWH's/gallon by about 2 to 2.5 to 1. But small diesel's don't really exist. (unless you consider the China 'disposable' 3600 rpm 5kW diesel models)

    In my opinion, the best solution is a 12-15kW 1800 rpm diesel that you use to charge the batteries and run off the XW inverter. The batteries have to be large enough to take the maximum charge current capability of the XW so you can get a good load on the generator when it is running. Even with the efficiency losses in charging the batteries you end up consuming a lot less fuel then running the generator all the time for 1000 watt average load.
  • techntrektechntrek Posts: 1,355Solar Expert ✭✭✭
    Re: XW6048 for whole house battery backup
    ChrisOlson wrote: »
    They can be if they're tuned that way....

    ....and is sold by a company that has a huge network of professional dealers/installers who will come right to your place and repair it under warranty if need be.

    Unless you are always running a fixed load on the genset, such as a charger, the load will always be variable and for a home it will only be a few hundred watts over 50% of the time. Which is where the variable throttle comes into play. For my Generac, or the Eco, that means a huge waste of fuel.

    Yes Generac has a large network of dealers. In general they aren't reliable when the stuff hits the fan. I'm a regular on a Generac forum and it is the single biggest complaint of home owners around the country. It gets installed, it breaks, and nobody wants to deal with it. Most don't break, but when they do, good luck.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • ChrisOlsonChrisOlson Posts: 1,807Banned
    Re: XW6048 for whole house battery backup
    techntrek wrote: »
    Unless you are always running a fixed load on the genset, such as a charger, the load will always be variable

    From what I understood, that's what the OP said here - the gen would rarely be used because the inverter/battery system would handle most of the short outages. The gen only comes online if the outage is longer and is started by the inverter. It's a battery charging gen, in that case. Just like any other off-grid installation.

    Unless I misunderstood something.
    Yes Generac has a large network of dealers. In general they aren't reliable when the stuff hits the fan.

    The place I bought my Generac from is an electric motor rewinding shop and generator dealer/installer with certified Master Electricians on their staff. That's all they do. If I have a problem with that generator on Christmas Eve, one phone call to their emergency call number, and somebody will be there to fix it.

    I have little sympathy for people who buy a generator from Menards to save a buck, have a problem with it, then complain about it when Menards tells them, "Oh, you have to call Generac for that because we just sell 'em - we don't service 'em."

    Or let me put it this way - if Menards started selling cars, would you be stupid enough to buy one from them?
    --
    Chris

    Edit: I would like to add that I did have one warranty issue with my generator. It was within a month of when it was installed. It would start, run for a few seconds and shut down due to a no oil pressure error. I called my dealer late in the afternoon and told them about it and they asked if I needed it fixed right away or if they could schedule the service truck to come the next day. I told them to come the next day because I got my diesel Duke 80 backup generator to charge batteries. They came the next day, the technician diagnosed the problem as a failed oil pressure sender. They did not have the sender in stock for the EcoGen. So they had to order it from Generac. The sender came the next day, the tech came out and replaced it, and it has worked fine ever since. But it did take two days from the original call to get the genset up and running again.
  • dBeaudBeau Posts: 24Registered Users
    Re: XW6048 for whole house battery backup

    Wow... I didnt expect such a spirited discussion of generator technology, but I do appreciate it.

    I had been leaning heavily towards the EU6500is mostly because I know it puts out clean enough AC (I suspect the shape of the wave is more important than frequency) to keep my light switches working. That it's a portable unit had me thinking it would be more versatile. Though unless I get a truck, it's unlikely to ever leave my property. I was also unable to verify that it can be started easily by the XW6048's generator control.

    It would seem less of a hack to go with the EcoGen. It's going to be a bit more trouble to install, but considering the scope of my project, that really shouldnt figure in. I'd also expect it to require less maintenance. As for the cleanliness of the power I'll have to take my chances, but I cant help wondering if there would be a way to wire the XW to only feed the charger from the generator and always keep the house on the inverter (unless the grid is available).

    Does anyone have any thoughts on battery bank design for my project? A spirited discussion on this subject would be quite welcome. I'd like to keep that in the sub $2500 range. So three strings of UB121000 or two strings of T105? The key design points being the ability to discharge quickly enough to satisfy my peak loads on the inverter and to take a charge fast enough to minimize generator run time.

    I figure these two options are quite different. If I was suggesting a system like this for a friend, I'd probably push for minimizing maintenance. But that's only because most of my friends have not been infected by the DIY bug like I have. Personally, I wouldnt mind having to check the SG and add water every now and then. I am a bit concerned about the installation though. With FLA's (especially used the way I am planning) I'd have to have a ventilated cabinet to hold them and a cabinet to hold 16 would have to be a bit larger than one to hold 12.

    Of course any comments on Outback's GS8048 vs the XW6048 would also be helpful.
  • mike95490mike95490 Posts: 6,290Solar Expert ✭✭✭✭
    Re: XW6048 for whole house battery backup
    Does anyone have any thoughts on battery bank design for my project? A spirited discussion on this subject would be quite welcome. I'd like to keep that in the sub $2500 range. So three strings of UB121000 or two strings of T105? The key design points being the ability to discharge quickly enough to satisfy my peak loads on the inverter and to take a charge fast enough to minimize generator run time.

    Assuming this is at 48V ? What's the AH of the bank ? I've not memorized all the battery sizes/capacity.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • dBeaudBeau Posts: 24Registered Users
    Re: XW6048 for whole house battery backup
    mike90045 wrote: »
    Assuming this is at 48V ? What's the AH of the bank ? I've not memorized all the battery sizes/capacity.

    ...actually, that's part of the question ;) Yes, it will be a 48v bank. I'm thinking that with 30% of the bank's capacity to play with (discharge to 50%, charge to 80%) while the grid is down, a worst case-ish average of a 2kw load over the two hours I'd like to span between generator runs, I'd need a minimum of 12kwh or 250AH@48v (pardon my rounding). The other goals are that the generator run no more than 50% of the time and the total battery cost be under $2500.

    My understanding is that FLA batteries cannot be charged as quickly as AGM batteries so more might be needed to meet the goals. On the other hand, AGM batteries might meet the goals with fewer batteries but for the money would have less overall capacity. So in this case the charge rate and discharge rate and perhaps battery technology will play as much a roll in determining the bank size as load. But please feel free to question my assumptions and understandings. I'm just a newb trying to learn, and I learn best when others point out my mistakes.
  • RCinFLARCinFLA Posts: 1,280Solar Expert
    Re: XW6048 for whole house battery backup
    dBeau wrote: »
    t.
    I had been leaning heavily towards the EU6500is mostly because I know it puts out clean enough AC (I suspect the shape of the wave is more important than frequency) to keep my light switches working.

    Frequency stability is most important. Conventional generators speed control, if it becomes unstable at any load, will cause the syncronous inverter to release from generator. Many mechanical governor systems wobble a bit particularly at no load. This can prevent inverter from locking on and connecting.

    The EU6500is is good on absolute frequency and frequency stability.

    When a surge load flows through to generator it will adjust throttle to the new load. If it boggs down too much, loosing rpm, the inverter will release.

    In the case of inverter-generators, while in eco-mode., they have to increase their rpm to service a heavier load. It takes some amount of time to get the engine to the higher rpm. The input DC to the generator's inverter will slump in voltage causing a clipping of the tops of the sinewave AC output as engine comes up to needed rpm.

    For a EU6500is you would like to be able to consume 4000 watts for charging. For a 48 v battery system that would be 4000 x 0.92 for XW inverter efficiency or about 3700 watts into batteries. 3700w/52 vdc = 71 amps of battery charging capability. If that is 15% of battery AH for safe charging, then battery bank would be 475 AH.

    You have to also look at your load expectations and how long you want to go between charging. A 475 AH battery, utilizing 50% capacity, yields 238 AH available.

    (50vdc x 238 AH) x 0.92 efficiency yields about 11 kWH's available between charging.
  • mike95490mike95490 Posts: 6,290Solar Expert ✭✭✭✭
    Re: XW6048 for whole house battery backup

    Somewhere, I heard a "rule of thumb" [for 48V banks] of needing 100A of battery capacity, for each Kw of expected load, so a XW6048, should have 600ah of battery, to minimally meet it's 120hz peak expected load
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Posts: 24,523Super Moderators admin
    Re: XW6048 for whole house battery backup

    It also works out that the 12,000 watt surge rating of the XW 6048 is equal to a 600 AH 48 volt battery bank at C/2.5 (the typical recommended maximum surge current for a flooded cell battery bank):
    • 600 AH * 48 volts * 1/2.5 = 11,520 Watts
    It also sounds like that this magic number of 600 AH per 6 kW (at 48 volts) is also a good idea for the 6kW solar array charging the battery bank.

    Too small of battery bank, it sounds like the MPPT algorithm and the relatively slow responsive time of the MPPT charge controller can cause the battery bank to over voltage (>72 volts) as the charge controller does its sweeps (and/or reacts to clouds passing over, etc.).

    AGM's appear to have the ability to run less than 600 AH per 6 kW (48 volt) on discharging--But a smaller AGM bank does not appear to b able to "drink" the excess current once fully charged by a large 6kW solar array (based on my readings and guess work here).

    Is this a design issue of the MPPT Charge Controller (I believe these were Xantrex 60 amp MPPT) or is this the nature of the requirements (proper MPPT algorithm sweeps demanding a place to put the excess energy during sweeps)... I don't know.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RCinFLARCinFLA Posts: 1,280Solar Expert
    Re: XW6048 for whole house battery backup
    mike90045 wrote: »
    Somewhere, I heard a "rule of thumb" [for 48V banks] of needing 100A of battery capacity, for each Kw of expected load, so a XW6048, should have 600ah of battery, to minimally meet it's 120hz peak expected load

    That is for a solar PV push via a charge controller through battery node. You get ripple current on batteries as they provide the filtering for the constant DC from charge controller to 120 Hz pulsing DC into the inverter.

    Although, if you are going to use the full potential of a 6 kW inverter you need a big battery bank. Depends on what loads you want to support and for how long.
  • techntrektechntrek Posts: 1,355Solar Expert ✭✭✭
    Re: XW6048 for whole house battery backup
    dBeau wrote: »
    As for the cleanliness of the power I'll have to take my chances, but I cant help wondering if there would be a way to wire the XW to only feed the charger from the generator and always keep the house on the inverter (unless the grid is available).

    Absolutely, there is no reason you shouldn't/can't. Although if you have a large load(s) that you only want powered from the genset (well pump?) you'll need a separate panel just for those loads.

    You have an additional variable to add in when you are sizing your system. To get the best kw-per-gallon you want to load the genset above 50%. Preferably to 75% if your charger isn't power factor corrected, I would go to 90% if it is (assuming you aren't going to add other loads like a pump). So you want to be sure that your battery bank is able to accept a 5500 watt charge rate (the EcoGen is a 6kw genset). This may mean getting a slightly larger battery bank than your loads dictate, but that would just mean the battery will last longer since it will be more shallowly discharged.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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