Home Technology Lithium Ion Batteries for RVs

Boosted Electrons = Better Views

We’ve had a lot of requests for updates on our lithium battery system, but the truth is that it hasn’t been getting much of a workout.

We’ve spent the past several months focusing on being near family, and we haven’t had any opportunity to tackle the solar panel project or to do any boondocking.

Victron MultiPlus – The Postbox of Power

Instead of maximizing every electron in our battery bank, we have been hopping from pole-to-pole staying with friends and at RV parks, never really giving the batteries much chance to run down.


We have actually been making good use of the other core piece of our electrical system – our Victron MultiPlus 3000VA Inverter/Charger.

And the special features of this inverter coupled with our ample lithium battery capacity have actually given us a lot of flexibility beyond what a traditional RV setup would have been capable of, very literally improving our outlook on life.

Read on to learn how!

Converter vs Inverter vs Inverter/Charger

Every RV with a DC electrical system needs some way to power the DC system and charge the batteries when plugged into AC shore power.

The most common way this is done is via a component known as a “converter” which takes AC 120-volt input, and then converts it into DC 12-volt output.

The ancient 50-amp converter that came with our bus.

An “inverter” does the exact opposite task of a converter – taking DC power from the batteries and transforming that into AC power suitable for running appliances like TV’s and microwaves and computers when shore power is not available.

Inverters range in size from pocket sized devices which plug into a cigarette lighter jack and which can handle just enough wattage to run a laptop, on up to big boxes that need to be hardwired with hefty cables directly to the batteries, and which can generate enough AC power to run even the heaviest loads such as air conditioners or power tools.

Many hardwired inverters are actually inverter / chargers – replacing the need for a separate converter. If you have an inverter / charger in your RV’s electrical system, it will keep your batteries charged when you are parked and plugged in, and all your appliances running when you are disconnected.

A good inverter / charger is the heart of a quality mobile electrical system.

Sine, Sine, Tell Me – Do I Need Sine?

In addition to a range of sizes ranging from 50 watts to 5000 watts (and up!), inverters are offered as either “Pure Sine” or the often substantially cheaper “Modified Sine Wave” style.

This refers to the shape of the AC power output curve coming out of the inverter – a “pure sine” inverter produces a perfectly smooth sine wave that is likely a higher quality than the hard-wired power at any RV park.

On the other hand, the curve produced by a “modified sine wave” (MSW) inverter looks like stair steps, not smooth at all.

Most small electronics can’t tell the difference – and if all you care about is powering a laptop and some lightbulbs a MSW inverter is a fine choice. But motors (like fans and power tools) and compressors (air conditioning units, refrigerators) will often eventually burn up on a modified sine input. LED lights will very faintly flicker. Some battery chargers will fail over time. And perhaps most annoyingly, some sensitive electronics and radios will pick up a buzzing noise when using a MSW inverter.

In our Oliver trailer we built the system around a 1500 watt Xantrex Freedom 458 modified sine inverter / charger – and though we were mostly happy with it, in hindsight I wish we had gone pure sine – if only because our 24″ monitor buzzed faintly if we left it plugged in, even when it was turned off!

With the bus, there was no question – we knew that we wanted to invest in the best possible inverter that we could find. And that meant not only pure sine power, but the ability to boost it.

Are More Volts Better?

The Quattro has built in support for two AC inputs – shore power and a generator, avoiding the need for an external transfer switch.

24-volt components have an advantage in that they can carry twice as much power over the same size wiring as a 12-volt system, and thus 24-volt inverters tend to be available in more powerful sizes and require less massive (and expensive) battery interconnect cables.

Most RV’s however are built around a 12-volt system, but some buses (not ours) are designed around 24-volts.

Though the advantages of a 24 volt house battery bank and inverter / charger are tempting even in a 12-volt bus, we still decided against it. Since we were designing a power system from scratch, it makes sense to go with a house system that matches the chassis system so that it is easy to charge off the alternator while underway

If we had gone 24-volt, the ideal inverter / charger for us would have actually been the Victron Quattro 5000VA, but because of the size of the internal components required and lack of market demand Victron has indefinitely postponed bringing the 12-volt version of this awesome inverter/charger to production, and only the 24-volt model is available.

The Transformational Magic of Boosting

There are two commonly sized plugs used to connect an RV to shore power.

50-amp cords are huge and hefty.

Most larger RV’s use a hefty 50-amp cord that when connected to a four-wire split-phase (240V) source actually provides 100 amps (two 50-amp legs) of 120 volt power – up to 12,000 watts! This is enough power to run multiple roof air-conditioning units, charge the batteries, run the microwave, and more – all without risking blowing a fuse.

Smaller RV’s (especially those with just a single roof AC unit) usually have a 3-wire 30-amp shore power cord that can deliver a maximum of 3,600 watts. This is plenty for most needs, but turning on the AC, a microwave, and a hairdryer all at once still risks blowing the fuse on your incoming line. And with a powerful enough charger, even charging a depleted battery and running the AC at the same time risks overloading a 30A shore power circuit.

30-amp plug ends

Most RV parks offer 30A and 50A sites (and commonly charge more for 50A), but very few people (we love those who do!!!) have 30A RV plugs in their side yards.

If you are setting up camp in a friend’s yard, a typical home power plug and heavy duty extension cord can only deliver a maximum of 15 amps, and if you use an adaptor to plug in your 30A or 50A cord and then draw more than 1800 watts you will be blowing the fuse of the circuit you are plugged into.

It isn’t hard to do this – particularly since outside outlets are often sharing a 15 amp circuit with other home loads, such as exterior lights or the electric garage door opener.

A 100′ Heavy Duty 15-amp Extension Cord

A depleted battery and a powerful battery charger might actually be enough to blow a 15A shore power circuit even if no other RV loads are turned on.

Blowing fuses constantly is not a good way to get yourself invited back to camp in a friend’s side yard…

Fortunately, many higher end inverter / chargers have the ability to set a maximum shore power draw via a control panel or a dial. This way – as long as you remember to tell the inverter that you are on a 30A or 15A circuit, it will scale back and charge the battery slower – keeping you from using too much power and blowing a fuse.

But… What if even after the battery charger is dialed back to zero, you need 20 amps of power, and you are on a 15 amp circuit? Or 35 amps, and you are on a 30 amp circuit? What if you only need that surge of extra power for a minute or two, like the initial heavy surge current draw of an air-conditioning cycling on?

Victron’s basic control panel makes it easy to set a shore current limit.

Depending on the inverter you have and how it is configured – in this case you are back to blowing a fuse on the shore power circuit, having your inverter shut down and black-out RV loads, or having the inverter switch over to power all the AC loads only by the battery – draining it exceedingly rapidly and leaving you with a dead battery even though you may think you are plugged in and charging.

The few, the proud, the boosters…

An exceedingly few inverters support the ability to “boost” the incoming shore (or generator) power with battery power – for example, taking 15 amps of shore power and adding 5 amps of inverted power generated from the batteries to provide 20 amps overall.

This lets you use electricity as needed within your RV, without worrying about overwhelming a limited shore power connection or undersized generator. As long as your average usage remains below what your shore power input can provide, your batteries will not end up depleted.

This seems like an absolutely invaluable feature – but for some reason none of the primary US inverter manufacturers support boosting at all. The only alternative from the traditional RV inverter manufacturers is the long-discontinued and now legendary Xantrex / Trace SW4024 and SW2012. Those in the know hop on these when used models come up for sale on eBay.

To get boosting in a new inverter / charger – we had to turn to the European companies Victron and MasterVolt, both primarily only found targeting the marine market in the United States.

Our needs were substantial – since our bus has no dash air, we needed an inverter powerful enough to handle at least one of our roof air conditioning units off of battery or alternator power while underway without needing to constantly run a generator.

After a lot of research – we settled on the Victron MultiPlus 3000VA model, one of the most powerful and capable boosting 12-volt inverter / chargers we could find. The MasterVolt Mass Combi 12/4000-200 was a close second choice, and also has a stellar reputation.

Update: Magnum released the MSH3012M Hybrid Inverter, which has now been out for a couple of years – and has become a common similar booster to our Victron in the RV space.

Boosting Inverter = Smaller Generator

RV generators have traditionally been sized so that they can handle the absolute peak load that they might ever need to power – in particular, the surge current of multiple roof air conditioners turning on at once.

Onan HQD810 Hybrid Generator – A 7,500W generator that uses a paired inverter to boost to 10,000W.

You thus end up with 7,000W – 15,000W generators typically running at a fraction of their capacity, only rarely ever even approaching full power.

If you instead use a boosting inverter to handle spikes in demand, you can get by with a much smaller, cheaper, and more fuel efficient generator. It is a win all around, and the money you save by going with a smaller generator will likely more than cover the cost of a more capable inverter.

Cummins Onan has even embraced this design philosophy in their new flagship hybrid generators, bundling a matched inverter / charger right with the generator itself.

Victron MultiPlus Thoughts & Observations

Overall we have been really pleased with our MultiPlus inverter – but there have been a few disappointments and issues.

  • The Victron manual and spec sheet claim to support a shore current limit as low as 11 amps, and the control panel UI allows this. But only after noticing it not limiting as expected and contacting Victron did they confirm that the low limit had been raised to 15 amps. This makes it harder to share a shore power circuit that may also have other loads on it like exterior lights or a garage door.
  • The Victron inverter has a built in ground relay that automatically connects the Neutral output to the chassis if no external AC supply is available. Inverters that lack this feature will trip any GFCI outlet that they are plugged into. Since most exterior home 15A outlets are required by modern electrical code to have a GFCI, an inverter lacking this could end up severely limited when side-yard surfing. The classic SW2012 lacked this feature – I do not know about the new version.
  • The Victron control panel displays a wealth of information.

    The Victron is fabulously programmable via the “Blue Power Panel” remote control, and we can precisely set the charging profile to match our lithium batteries. But certain settings I wish were more configurable to better match our lithium battery setup. For example – the “DC Low Shutdown” can be set to any voltage, but the “DC Low Restart” must be at least 1.00 volts higher than the shutdown, and the Victron often needlessly flashes “low battery” any time the voltage is in this range. This is great for lead acid batteries, but lithiums drop so slightly over their range of use that I would prefer the ability to better customize this.

  • Victron’s newest (2012) models have added explicit support for talking directly with Victron’s own lithium batteries and battery management systems. I do not know if there is any way to integrate this in with a third-party lithium EMS, like the one we are using from Elite Power Systems. Our older inverter model is also not upgradeable.
  • I discovered a very weird bug with how the Victron Inverter and Blue Power Panel work together while installing the system, and actually thought that our inverter had died completely. In a nutshell – it is possible while connecting / disconnecting the battery power for the inverter to “crash” and get locked in a state that it will not wake up from – even toggling the hardwired power switch on the case does nothing. But – if you fully disconnect and reconnect the remote control panel (after leaving it disconnected for a full minute), everything resets and is fine again.

Using an Inverter to Improve Your Outlook on Life

The reason that so few companies have offered boosting is because so few people have really understood the benefits of it. So let me give a few examples from our past few months in Florida where being able to boost literally improved our views.

#1 – We spent the month of January staying on a friend’s absolutely beautiful patch of land in Kissimmee, with the only available source of power being a single outdoor outlet 50 yards away. By dialing our shore current limit down to 15 amps we were able to keep from blowing fuses, and thanks to boosting we were even able to run our electric heater on the coldest nights. In the morning the batteries would get charged, making up for the drain in the evening. Without our boosting inverter, we would have had to go without heat, or stay in a drab commercial RV park.

We love staying with friends whenever possible, and having a boosting inverter makes this vastly easier than it would be otherwise.

#2 – Just this week we have been staying at a commercial RV park on the water in Cedar Key, FL. Though we have a 30-amp outlet available, to reach it with our shore power cord we have to park the bus rear-end towards the water. But since we can get by with 15 amps thanks to boosting (and can even run the AC during the heat of the day!), we have been able to use a common heavy duty extension cord to allow us to plug in and park the bus nose in. (Sure we could carry around a huge and expensive 30A extension cord, but the bulk wouldn’t be worth the rare times that we’d actually be able to use it…)

Facing the other way, we would spend the day looking at a parking lot full of generic 5th wheels.

Tell me, which view would you rather have out your front window???

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55 Comments - Still Plenty of Room for Yours!

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  1. Hi Guys! Great article. We are getting ready to change out our old mastervolt charger in the boat, with a Victron Inverter/Charger. All things being equal, do you think the Quattro is worth the extra cash for the automatic transfer between shore and generator compared to the Multi Plus, or does the manual switch seem fine on the boat. I’m trying to think of a use case where I’d be running the gen then plug into power or visa versa. I’m assuming, the Multi Plus, if you are inverting, and the switch is on gen, when you turn on the gen it automatically switches to that power source? Same thing if you are inverting, and the switch is on shore power, and you plug into power? I’m looking for uninterrupted power between inverting and and a power source. Cheers, Shel

    • Hey Shel!

      The nice thing about the Quattro is that you can program different limits for shore and generator input, which is handy sometimes. And not having a second external transfer switch can make wiring a lot easier, depending on what is already in place. But if you already have a transfer switch, that might not be an issue.

      Also there is a difference in capabilities. The Quattro is 5000VA inverter and the MultiPlus peaks out at 3000VA, so if you want to run two large loads at once off battery the Quattro has a lot more headroom. Faster charging capability too.

      But both are awesome inverters – we have a MultiPlus in the bus, and a Quattro in the boat. Very happy with Victron gear overall.

      And nothing beats the geek points of the CCGX screen to visualize it all, even remotely.

      – Chris

  2. Guys, I am putting together nearly the same setup as you have, slightly smaller scale 400AH as I’m in a little Chinook Concourse (21′), but working out of it on computer all day with monitors. For the Victron Multiplus 3000, I plan on using two 2/0 cables for positive and negative. But I can not tell from the Victron install guide or manual (rather crappy, I must say) – what size ground cable from chassis to frame did you use? This is Step 7 in the Quick Install Guide, the cable marked as N.

    Thanks for any help you can give me,

    • ABYC would say it should be no smaller than one size smaller than your DC input wiring to the multiplus. I used 4/0 to the inverter, and 2 2AWGs for the inverter ground connection to my van chassis.

  3. Our Victron 3000W inverter is smoking with a burning electrical smell. Hi Folks, I believe we have the same Victron inverter outlined in this article. When you started off with this inverter did you ever notice a distinctive electrical burning smell? We returned our first Victron 3000W because it not only smelled while being used but also produced some noticeable smoke—after the first day. Now after our replacement install, the new Victron inverter is doing the same thing on the 2nd morning when running a 1500W water kettle. (We installed a smoke detector in the cabinet when the first inverter started acting up). This is frustrating to say the least 🙂 We were told a little ‘burning’ smell is normal, but smoking doesn’t seem normal at all. I also did not notice any warning lights, etc. from the inverter itself when the recent ‘smoking’ episode on the new inverter occurred. The Victron site seems to be lacking in troubleshooting info, so I thought I’d reach out. Any tips/experience here from you or your community?

      • @Don Rose, thanks for your reply. The cooling fan kicks on after about a minute running the 1500W water kettle or any other appliance in that wattage ballpark. The inverter is 3000W, so this load should be no problem. It’s installed in a interior storage closet in the bedroom. The closet has a door and is approx. 15L x 15W x 30H in. The inverter is upright and mounted to the back wall with 5 in. or more of space around all surfaces except the back. After seeing a lot of smoke coming from the closet (on the first day we used it! scary!!), we installed a smoke alarm in the closet. It now goes off every time we run a larger load but there are never any warning lights on the inverter itself (i.e. overload, high temperature, etc.). The smoke smells the same as the normal electrical smell when the inverter is running, only a lot stronger…no rubber smell. Our previous (also brand new) Victron 3000W inverter did the same thing, so we replaced it with this unit because our installer (an AM Solar certified tech) thought the last one was faulty. I would be surprised if smoke is a byproduct of normal operation, but this is our first inverter and first motorhome, so I can’t say for sure. Thanks for any replies from those more familiar with these issues.

  4. Guys,

    Needless to say your expérience is truly valuable.

    How long the charger is taking on 15A circuit bring back the battery bank from 20% to 100%. I know the last few bits of percentage takes longer, so let say from time to time back to 80% of their capacity?

    I would also like to know how long it would take from your alternator while running from one place to another.



    • The charge time all depends on what other loads are on the system. With a 15A shore power plug, if we have the water heater or any other large loads turned on there is only a little power left to dedicate to charging so it can take a very long time.

      But if we have everything else off, the charger can go at full speed on 15A.


      – Chris

  5. I’m looking at putting in a similar sort of system, using Victron equipment. I was wondering if there is some reason you chose a 12 volt system over 24? It would seem like 24 volts offer a number of advantages, especially when it comes to sizing the cables and MPPT controllers. I’m most likely looking at the 3kw Multiplus units because weight is an issue (Class C on a Sprinter chassis.) I can easily meet the 12v needs with a fairly small DC-DC converter.

  6. We really appreciate your articles and YouTube videos having learned much from them. Specifically to this article, I was wondering more about your settings for charging your lithium battery bank. I’ve been researching and talking to installers and manufactures about this issue. I have been told by one installer that Victron multiplus has a mandatory one hour constant voltage setting following “bulk” charging which, according to him, may result in shortening the lifetime of the batteries. My understanding is that ideally, a constant current up to the maximum charging voltage of 14.2v should be used then followed immediately by float. How have you set your multiplus?

    • There is no easy way (currently) with Victron to entirely skip an absorption phase unless you have a EMS system that can talk to the inverter. But when the batteries reach full, the charging current drops to nothing.

      When I checked in with our battery cell provider, they didn’t think it was a significant concern. More important is keeping the bulk voltage from being too high.

      – Chris

  7. Hey Guys, I just picked up the same model Victron unit as yours. Thanks for the awesome insight as I would not have known about this unit if it was not for your blog. Keep up the great work !!

    One quick question. Do you have a surge protector on your shore power line before it goes into the Multi Plus ? I have not seen anything mentioned about that in any of Victron’s data.

    Cheers, Mark from Ontario

  8. Hi Chris
    I have a victron 1600w multi has gone into overload overnight, nothing plugged in!!! Any tips?

    Phil, UK

  9. This was a fascinating article. I liked the technical detail and precise information! I had trouble understanding what that thing was in my RV – which you explained was a Converter. I am really glad I can remove it and replace with an Inverter-Converter which will be doing a better job, and providing Inverter functions as well. I never knew this existed until I read your article. Never knew about the concept of boosting type inverters either. This is more than just an article. It is a very valuable contribution to the Online RV knowledgebase. Many thanks for your generous time in writing about these technical challenges and solutions!!

  10. Hi Chris, I have the Magnum 3012 and it is quite flaky with GFICI outlets. Some of them trip instantly and some are just fine. I love having it, and can wire around it if need be, but it is annoying playing “Russian Roulette” with outlets.

    • A lot of inverters do have problems with GFCI outlets though – but I thought the Magnum was supposed to be better.

      The only time I had problems with our Victron MultiPlus with GFCI outlets was when there was indeed a ground fault inside our coach. Are you sure it is the Magnum having issues, and not the result of an actual problem?


      – Chris

      • Hi Chris, If it were a problem in the RV (A class C) then wiring around the Magnum would not clear up the problem. So I’m fairly confident that the Magnum is the issue. But why it works with some GFCI outlets (15 amp) at homes, and not with others is a conundrum. I even have one home where one GFCI outlet trips with the Magnum–but the other outlet does not.

        I can say that the tripping is essentially instantaneous when it does occur.

        It makes me glad I used “plug and play” for the Magnum rather than it being hard wired. I simply powered a 30 amp outlet from the inverter, and I plug in the shore power cord. So leaving the Magnum off line is a ten second job.

  11. Chris I am not good with written words (unlike your self) but Wow what a oasis of info! This next RV will be our third and I hope to have lithium house batteries of some kind on this one. Thanks Al Oakes

  12. We met a Burning Man at the Nomad gathering a few years ago, and ya’ll have been a big part of my inspiration to go house-free. I close tomorrow on a never-ending two-year remodel, and am purchasing a 2007 Sprinter to convert into a stealth RV. I wanted to thank you not only for the inspiration, but also the thoroughness of your research and online sharing. It will really help as I go forward with the conversion. I’ll *just* miss the Big Burn this year, but intend to make it out next year.

  13. “The Victron inverter has a built in ground relay that automatically connects the Neutral output to the chassis if no external AC supply is available. Inverters that lack this feature will trip any GFCI outlet that they are plugged into …. The classic SW2012 lacked this feature – I do not know about the new version.”

    Actually, there was a sine wave converter that had that same relay – either the SW2012 or the Magnum, I don’t remember – but it still tripped GFCI outlets. The problem was the relay was wired so it defaulted to bonding ground and neutral when the relay was de-energized, then broke the bond when it was energized by shore power.

    Unfortunately, relays are mechanical devices and they respond more slowly than a GFCI. It takes several milliseconds for the relay’s coil to overcome the mechanical inertia of the contacts and pull them apart. So when you plug into a GFCI outlet, enough time elapses to let the GFCI sense the ground fault and trip before the relay can react.

    If Victron wired their relay the way you describe, it will exhibit the same behavior. The fix is to make the relay default to NOT connecting the ground to neutral bond and let the inverter voltage energize the relay so it only bonds when the inverter is on. This way the bond doesn’t exist when you plug into shore power and the GFCI remains happy.

    • As I understand how the Victron works, they have inserted enough of a time delay to avoid any overlap that leads to a tripped GFCI.

      And it definitely works – we’ve spent plenty of time driveway surfing at the end of a long extension cord plugged into GFCI outlets.

      – Chris

  14. One of these days, I’m actually going to completely understand all this stuff. I thank you for keep trying to explain it all.

  15. Just a shout out of thanks for all of your info sharing. I enjoy both of yours zest for both living, and the way you dive into your various projects. Keep it up, and look forward to meeting you on the road…

  16. Would it be possible to use one of these hybrid units to run an array of solar panels as a grid tie system to lower the use of shore power, then when night comes, the unit goes back to relying on shore power?

    • This is precisely the sort of usage that Victron has been showing off on their website, and they have many white papers published on the topic. Check them out, and hopefully you’ll find something useful that matches your needs.

      – Chris

  17. The Magnum MSH3012M Hybrid boosting inverter/charger is finally released. Full details on the MagnumEnergy website. Pages 32-34 of the owner’s manual gives the details for load support.

    • This is great news! Have you had any hands on experience with this new model yet? Have they actually started shipping units to customers now?

      I just skimmed over the manual, and it looks very promising indeed.

      Thanks for keeping us updated!

      – Chris

  18. Aren’t solar grid-tie controllers doing essentially the same as those old boost inverters? I know they are costly though.

  19. I think this info is great for us RV now. what I would like to see is the Air conditioner manufacturer change the way their systems draw power at startup. I am in the fire protection business and we often install fire pumps which can draw 150-200 amps to push 2500+ gallons of water per minute through our piping systems. WHat we have seen is that at startup a standard across the line starter can draw upwards of 600-800 amps at full lock. this of course drops as the pump gets up to speed. one not necessarily new technology is to use Solid state soft start controllers.
    This Controller is a combined automatic and manual soild state reduced voltage soft start/stop Fire Pump Controller, used when the capacity of the power source does not permit full voltage starting of the motor. The starting inrush is reduced to 25-50% of normal starting current through the use of silicon controller rectifiers (SCR’s). The SCR’s control the applied voltage to the motor in a smooth, stepless manner, reducing the hydro-mechanical stress within the system piping. The acceleration rate is field adjustable between 0.5 – 10 seconds. When the motor reachs full speed, or after 10 seconds, a by-pass contactor closes, removing the solid state starter from operation. After a “minimum run” time of 10 minutes at full speed, and after all conditions that initiated the start return to normal, the by-pass contactor is opened and the controller reduces the applied voltage decelerating the Fire Pump motor to the “minimum speed” level (approximately 25% of full speed). The controller holds the motor at this “minimum speed” level for a period up to 60 seconds. When “minimum speed” period expires and no new starting conditions have occurred, the controller will decelerate the Fire Pump motor to a stop. If during the “deceleration” period or the “minmum speed” period a new starting condition occurs, the controller will immediately begin to re-accelerate the motor to full speed.
    This has helped in reducing the electrical supply from the city which then does not have to be a 600 am service that cost quite a bit more than a 200 amp service. if this type of controller where used in RV roof air conditioners the startup amps could drop possibly to a level that a smaller generator could handle such as a 2000 watt. perhaps this can be applied to a microwave. just my two cents I am a novice when it comes to electricity but this has been on the back of my mind for a while.

    • I know of several bus nuts who have installed mini-split air conditioning systems that use inverter technology to essentially eliminate the startup surge current. These AC units are also very efficient overall.

      But – I don’t know of anyone using this technology in roof-mount units, and it is hard to retrofit residential mini-splits into an RV.

  20. I really enjoyed this article on invertes. I have a question that has had varied answers. When do you use the inverter? I have been told it is only needed when no shore power and you run from batteries. I have also been told to leave it on all the time. I rarely boondock and since I use 50 AMP I am usually at campgrounds that supply it. A few times a year I am on 30 AMPS at rally sites and then I dial down and watch what I use so I don’t overload.
    If I used inverter all the time, would this be of benefit?

    • With our current set up, we leave ours on all the time. It does have a power overhead, which may be a concern for systems trying to optimize battery capacity. In our last RV, we did only use the inverter when we needed 110 power – as it did have enough of an overhead to impact our capacity, was loud in a small space and did cause the monitor to buzz (it was MSW).

      But now that we have a sizeable lithium ion battery bank – we find the advantages of having the inverter on all the time to be worthwhile. We don’t have to worry about if the campground power goes out, or if we have an unexpected surge we need to compensate for with our boosting or resetting AC powered clocks while underway. Ours is pretty quiet too, so we don’t hear it – eliminating another reason why turning off the inverter might make sense for some setups.

  21. Have a 3KW MSW inverter, took about 3 minutes to decide that it is for emergencies only. MCW can be heard outside when cooking! Tried a Xantrex 2000 and found out that the hook up diagram is to be taken with a large dose of salt, no mention of the units inability to take a load at start up. Worked as intended until the generator plug was plugged back in to allow AC while dry camping. Do not read anything with an ohm meter but it destroyed the Xantrex switching, charger still works. Am on the fence about another Xantrex unless there support has improved. I am a technician and a licensed electrician, perhaps the lack of factory support blind sided me.

    • Xantrex bought out the other major original inverter manufacturers Trace and Heart, and they have seemingly replaced the old solid designs with cheaper new models with a lot less focus on quality, durability, and repairability.

      I have heard a lot of stories from people being disappointed with Xantrex support.

      The old Heart and Trace teams have gone on to start new inverter companies – Outback And Magnum. They have much better reputations, but no boosting models – yet.

  22. Excellent article guys. I want to correct your impressions about the newer Freedom SW series. These do not support true supplemental load support the way the Trace SW series did, and they are completely unrelated (the Freedom units are descended from the old Heart product line; the SW2012 and SW4024 so prized by bus converters were descended from Trace). That’s because they can not synchronize power to the incoming waveform, a feature generally found only in grid-tie units.

    The way the new Freedom units implement “generator support” is by disconnecting the loads entirely from the incoming power and switching them to the inverter. At the same time, the battery charger is brought back on line and connected to the input power. This is the same as the “poor man’s load support” that I have advocated in the past (separate inverter and battery charger operated together).

    The net result is that the Freedom can still only support loads up to the maximum rating of the inverter, whereas the older SW Series products can support loads of the invterter’s maximum *plus* whatever incoming power is available. So a Freedom 3012 can support at most a 25-amp continuous load, even if the connected generator is itself capable of 30 amps. In fact, since the largest load-support value that can be set is 24 amps, the feature will not even activate with a generator this large.

    By contrast, a Trace SW2512 could support a load of 20 amps over and above the input source, so with a 30-amp generator you can run 50 amps of load, at least for as long as the batteries hold out.

    I do not consider the new Freedom products to be of any real benefit for supplementing either generator or shore power. It would help only in the very limited circumstance of a 15-amp shore circuit, wherein you could set the cut-in to 12 amps and expect to run up to 25 amps of load (at ~20% efficiency penalty) by using battery power.

    Victron, MasterVolt, or an older Trace SW Series are all better choices than the new Freedom product.

    BTW, the real reason this capability is not available in RV inverters has more to do with cost than customer education or understanding. In order to do this right, you need two hard-to-implement features: 1. Extremely precise synchronization of the output waveform to the input waveform and 2. “Anti-islanding” protection. This latter item needs to be certified by a testing lab, because failure means the possibility of electrocution to power linemen upstream of the inverter. I have a long technical discussion of what anti-islanding means, why it adds cost to the product, and why it is necessary for implementing true load support, but probably more than anyone wants to read in the comments.

    • Awesome info Sean, thanks.

      I am really disappointed to see Xantrex relaunch the SW line using the name / model number of the old Trace classic, but leaving off its signature feature. I stumbled across the product page and press release when I was adding links to the final draft of this post – I hadn’t taken the time to download the manual to confirm the details.

      I’m glad you are able to set the record straight – I will update the post with the details.

    • I just stumbled across a post on the RV.net forums from a former Trace engineer that is very exciting:

      “Actually we (ex Trace guys) are still here, just go by a different name now, Magnum. We do things the old Trace way, built in the good old USA with good old fashioned tech support that answers the phone!

      We are just releasing a new model MSH4024M (MagnaSine Hybrid 4k, 24v)that does everything the old Trace SW4024 did including true “load support” where the inverter is sync’d with the generator or grid power in order to start and run larger loads than the generator or grid can support but with a much better wave form. A 12v model will follow this fall MSH2812M.”

  23. “Most larger RV’s use a hefty 50-amp cord that when connected to a four-wire two-phase source actually provides 100 amps of 120 volt power – up to 12,000 watts! This is enough power to run multiple roof air-conditioning units, charge the batteries, run the microwave, and more – all without risking blowing a fuse.”

    They actually use single phase power. We only have single and three phase power in the US.

    I am impressed with the Victron systems. I find that marine electrical systems are far beyond RV systems in general.

    • Hi John – thanks for catching that!

      I meant “split-phase / dual-leg”, and referring to that as “two phase” is indeed technically incorrect.

      I’ve fixed the post to use the correct terminology.

  24. Hey Chris,

    Awesome series on the batteries and inverter, we just got back in the country and have been catching up on our internet time. We use the dial down feature on our Magnum inverter for the rare occasion when we actually plug our bus in. When we do it is usually some sort of jury rig like the one in your photo. Thanks for being the testers on this new battery system!


  25. Another cool post! Didn’t know about boosting!
    Totally agree that getting a pure-sine-wave inverter is worth it. We have a MSW in our motorhome and our convection/microwave has just crapped out for the 2nd time in 2 years…..I’m sure it’s the inverter since the machine audibly struggles everytime we run it boondocking. At some point we need to bite the bullet and upgrade.

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