Inverter/Chargers with “Power Assist”

We have a large 50amp 5th wheel that we live in full-time. There are occasions when we can only get a 30amp connection and unless we strictly manage our appliance and AC use, we need additional power above what the 30amp circuit can provide and honestly would prefer to not worry about what is/can run at a time and just live like we do on a 50amp connection.

The Victron MultiPlus and Magnum MSH series inverter/chargers have a “Power Assist” feature that supplements required AC power demand from the batteries when a shore power connection is insufficient. This isn’t a “boost” required for surge loads, it will use battery and shore power simultaneously when the shore power is insufficient for the load demand.

While researching and working on the design of our system I’d like to be able to determine which inverter/charger I’ll use early in the design phase but this feature doesn’t seem to be clearly identified for the Magnum like it is for the MultiPlus and I haven’t found other brands that advertise this feature.

Does anyone know of other brands and models with this feature?

We live in the US and right now I’m leaning towards a 24v DC - 120v AC system using 16 Lishen 275ah cells purchased through @Michael B Caro in an 2p8s configuration (I think that’s the right nomenclature). I live by the 2 is 1 and 1 is none philosophy so 48v is not an option.

On a purely price basis, the average $1285 price of the MultiPlus is attractive compared to the Magnum MSH4024M at $1640ish or the Magnum MSH4024RE at $1634ish.

On the feature side, the Magnum MSH4024RE looks attractive with it’s bigger inverter capacity at 4000w vs 3000w and generator support which would require a jump up the Victron Quatro to get generator support at twich the price of the MultiPlus.

One big advantage of the MultiPlus is that they are widely used by RV’ers so getting help is only a forum post away...

Would really like to know if there are other options in the same, or better, price range of $1200-$1600 that I should consider.

Note, quality and access to responsive technical support is a big factor over a cheap alternative.

Thanks!

This was informative to me. Victron was the only option I was aware of.

I'm a little confused by the "generator support". You can have AC input from grid or genny via a transfer switch. While the Quattro will accept 2 AC inputs, it WILL NOT USE 2 AC inputs at the same time in any scenario, nor do I expect will any other brand.

Power assist feature requires the inverter to essentially behave like a grid tie inverter thus matching the incoming AC voltage, frequency and phase and boosting it when necessary. With competing input AC, that would be impossible. The second AC input of the Quattro should be thought of as a built-in ATS that selects one of the AC-in. I don't remember which is selected when AC is detected on both.

Also important to keep 30A and 50A differences straight in your head. 50A is 120/240VAC split phase input. 30A is simple 120VAC input with the legs bridged together. You would need to design it around that restriction, and it would require at least one additional ATS. Easy to design it to work every time you plug into a 30A, but in that configuration, plugging the umbilical into a 50A would make for a very bad day.

Generator also influences it... 120VAC or 120/240VAC split phase output.

Things change fast... might want to consider this...

snoobler said:

Things change fast... might want to consider this...

New Victron Multiplus-II 12/3000/120-50 designed specifically for RVs with 30A/50A input flexibility available MARCH 2021

Just heard from a friend. Victron just had an educational session, and introduced the subject product. Key features: 12V inverter/charger (120A charging) Will accept 30A or 50A input and adjust accordingly. 30A input or in inverter-only mode will provide 120VAC to each leg. Power Assist...

diysolarforum.com

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Thanks for the feedback, I replied to the “new” version in the thread you created for it.

As for the Magnum, I’m not sure if it will automatically turn on the generator but it has separate input terminals for a generator and shore power and will use whichever one is active at the time. If for some reason they are both active I don’t know how it determines which one to use but as you surmised, I’m pretty sure it would only use one.

Every inverter/charger in the 3kw to 5kw range that I’ve looked at from the major brands have a built in ATS with battery backup on one leg and straight pass through on the other leg, so if running on inverter/battery power, unless you have a second inverter, the second leg goes dead.

In my case, I actually have an existing Xantrex Freedom 1200w for the residential Fridge and a few select outlets that I expect to be able to run the second leg to and in the event it goes dead when shore power (or possibly generator when/if we get one) it’s ATS will also kick it over to feed off the batteries. I’ll have to use a 24v to 12v converter to use it off the batteries though unless I change my mind and use a 12v system. Interestingly, the additional outlets all appear to be for the TV’s and associated entertainment devices.

The issue I’m basing my choice of 24v is the amp sizing requirements I’d have to use for the BMS, wires and fuses if I were to use a 12v system in the event that at least one of the 4 12v batteries in a 4p4s configuration died. With the assumption of 3 batteries feeding both inverters, taking into account a futue upgrade of the Xantrex inverter, I believe the BMS in a 12v configuration would have to be at least 200amps so I’d probably use 250amps for headroom and surges versus a required 100amp or 120-150amp for headroom based on 7000w with for surge (see below)

I pulled a screenshot of our Power Watchdog with the full potential power, other than surges, we would ever use at one time. I’ll install soft start devices on both AC’s to minimize their surge requirements.

Realized it is probably worthwhile to mention that I’m aware that until we get the second matching new inverter, we would still need to manage our simultaneous loads to not overpower the single inverter/charger a d our existing inverter.

I know the Outback Radians also have the 'power assist' feature. Spendy though.

I believe the “self consumption” function here is similar?

I’ll look in the Outback Radians and Schneider Context but wanted to note that Magnum has an RV model that can accept and passthrough 50 amps and assist up to 60 amps when on shore power or generator, but when there is no AC input it can only output 25 amps.

Model is MagnaSine Hybrid MSH3012RV and appears to sell for around $1800 for anyone interested.

Note that the MagnaSine does not support “stacking“ which I assume is equivalent to “Parallel” in Victron.

Maast said:

I know the Outback Radians also have the 'power assist' feature. Spendy though.

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I couldn’t find any references, including the product documentation, to it having any sort of power assist, but it does appear to be strictly designed for fixed sites like homes or business so it wouldn’t appear to be a good option for an RV.

Their site isn’t really all that informative though so let me know if you have a link that might provide more info.

JoeHam said:

I believe the “self consumption” function here is similar?

Schneider Electric 865-4024-21 Conext SW 3,400 Watts, 24VDC Inverter/Charger for Split-phase 120/240 VAC

The Schneider Electric SW model inverters do NOT support stacking. These inverters are only designed to operate independently. If you need stacking ability, take a look at the XW line of inverters. Please email us or give us a call if you have any questions.

www.solar-electric.com

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The Self Consumption is sort of the opposite, it can be configured to use power from your own PV array before using any grid or generator source.

”Power Assist” actually supplements available grid power from your batteries when the grid based power might be insufficient for your loads. This is pretty common in campgrounds that have 30amp power but you are trying to power a 50amp RV as is my case.

InMyImage said:

I couldn’t find any references, including the product documentation, to it having any sort of power assist, but it does appear to be strictly designed for fixed sites like homes or business so it wouldn’t appear to be a good option for an RV.

Their site isn’t really all that informative though so let me know if you have a link that might provide more info.

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They call it "grid support", page 36 and 37 of the manual. You're right though, the radians are big units. Their FX inverters are more aimed at the mobile/boating market and they mainly have the same programming so they might but I dont actually know for sure.

The Xantrex Freedom SW line has the power boost feature you're looking for. Xantrex Freedom SW 12v . I nearly bought one of these but went with the MultiPlus for easier integration with my other components. I wanted the option for those rare occasions when I have limited shore/generator power available and don't want to manage loads.

K8MEJ said:

The Xantrex Freedom SW line has the power boost feature you're looking for. Xantrex Freedom SW 12v . I nearly bought one of these but went with the MultiPlus for easier integration with my other components. I wanted the option for those rare occasions when I have limited shore/generator power available and don't want to manage loads.

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I looked at those since I already have a Xantrex Freedom in my rig but If I recall correctly the SW need a piggyback unit for the assist feature which makes them really expensive

InMyImage said:

I looked at those since I already have a Xantrex Freedom in my rig but If I recall correctly the SW need a piggyback unit for the assist feature which makes them really expensive

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I don't believe that's the case but I'm not certain.

K8MEJ said:

I don't believe that's the case but I'm not certain.

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It use the “Sequence Power Manager” to provide the intelligence for power management functions.


”Together with the Freedom SW Inverter/Charger, System Control Panel (SCP) and Automatic Generator Start (AGS), the Freedom Sequence provides a complete integrated power management solution for RVs. The Freedom Sequence enables you to monitor and control all the power components from a single, easy to use System Control Panel, rather than multiple, mismatched, control panels. When used with the Freedom SW Inverter/Charger and the Automatic Generator Start, the Freedom Sequence provides automatic generator starting and stopping and automatic inverter assist support for maximum load usage, all behind the scenes. These power components that form a single, cohesive ‘Freedom SW Power System’ are manufactured by Xantrex and are able to communicate with each other.

The Freedom Sequence automatically manages RV power needs while helping to minimize the nuisance caused by tripping of circuit breakers.”

As I read it, that is more of an automatic load-shedding transfer switch. I wasn't aware of that accessory so it's good to know about. However, in the manual for the Freedom SW:

Generator Assist
The Freedom SW Series of inverter/chargers can operate in tandem with a generator (or shore power) to temporarily assist power loads with large start-up demands such as air conditioners, water pumps etc. A Xanbus AGS is not required for this feature to work when shore power is present to assist the Freedom SW but the AGS is needed if a generator were to be used in assisting the Freedom SW.
When the Gen Support mode is enabled and the generator’s or shore power’s current capacity defined (in amps), the inverter will come on-line and assist the generator or shore power with starting and operating the load (drawing power from the battery). The battery bank must be well charged in order for the inverter to engage this mode. For more details, see “Gen Support” on page 67.

Anyway, I'm not sure if that's what you're looking for or not. Like I said, I ultimately went with Victron so I don't have practical experience with Xantrex.

K8MEJ said:

As I read it, that is more of an automatic load-shedding transfer switch. I wasn't aware of that accessory so it's good to know about. However, in the manual for the Freedom SW:

Generator Assist
The Freedom SW Series of inverter/chargers can operate in tandem with a generator (or shore power) to temporarily assist power loads with large start-up demands such as air conditioners, water pumps etc. A Xanbus AGS is not required for this feature to work when shore power is present to assist the Freedom SW but the AGS is needed if a generator were to be used in assisting the Freedom SW.
When the Gen Support mode is enabled and the generator’s or shore power’s current capacity defined (in amps), the inverter will come on-line and assist the generator or shore power with starting and operating the load (drawing power from the battery). The battery bank must be well charged in order for the inverter to engage this mode. For more details, see “Gen Support” on page 67.

Anyway, I'm not sure if that's what you're looking for or not. Like I said, I ultimately went with Victron so I don't have practical experience with Xantrex.

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It’s an interesting contradiction, fortunately I don’t need to worry about it any longer. Just pulled the trigger on the new Victron MultiPlus-II 12/3000/120-50 2x120V through @the_colorist. The design focused on RV’s including 50amp RV’s was just too much to pass up.

Thanks to @snoobler for making me aware of it.

InMyImage said:

The Self Consumption is sort of the opposite, it can be configured to use power from your own PV array before using any grid or generator source.

”Power Assist” actually supplements available grid power from your batteries when the grid based power might be insufficient for your loads. This is pretty common in campgrounds that have 30amp power but you are trying to power a 50amp RV as is my case.

Click to expand...

The radian says, " In the event that you lose utility power, the Radian will take over by keeping your house powered". Which mean you either have power or you dont on the grid. It does not talk about assisting to bring up the amps to a certain level.

Victron's 'Power Assist' is a little more than just load shaving which some hybrid inverter/chargers can do.,

Normal load shaving waits until input current reaches max AC input current you set on inverter before inverter supplements input current.

Victron's 'Power Assist' will start the supplementing of AC output load when AC current starts to rise, then backs down the supplement to what is needed or max AC input current setting. It provides a 'jump' on supplementing any startup surge current like starting an air conditioner compressor. It means it is less likely any sudden initial startup surge current will make it through inverter to your generator.