Axial Flux generators

[avanti]

Just before they folded, Great West Vans was starting to offer rigs with underhood generators built by Mobile Electric Power Solutions. These are based on a technology called "axial flux generators". This is a very interesting approach that generates power using very simple brushless underhood generators with rotors containing permanent magnets. As I understand it, unregulated 3-phase power is passed via a 3-wire cable from the alternator to a custom electronic unit which converts this current directly to 120VAC. Another manufacturer using this technology is Aura Systems.

This technology seems to be very popular in military vehicles, and looks to have a lot of advantages, including good performance at low RPMs and good temperature characteristics. It has been around for awhile, and comes up from time to time in the RV world, but it has never seemed to have caught on. Does anybody have any insights as to what the pros and cons of this approach are?

[gregmchugh]

I recall a video about that...

https://www.youtube.com/watch?v=Ac7G7xOG2Ag

[VanFan]

Originally Posted by gregmchugh

I recall a video about that...

I've got one of those things sitting out in the barn. We've been using it for a feed trough, but I could hose it off and it should be good as new. If anyone wants it, I'll let it go for $1,000,000. Firm.

[VanFan]

Originally Posted by avanti

Does anybody have any insights as to what the pros and cons of this approach are?

I contacted both Mobile Electric and Aura before starting my current build. They're both pretty pricey. I don't recall what they quoted, but the difference between them and a couple of high output alternators was enough to scare me off.

[Winston]

Originally Posted by avanti

Does anybody have any insights as to what the pros and cons of this approach are?

We like this concept as a replacement for 'the RV generator' but prefer a system that directly outputs to our 'off-grid' electrical battery system . . . and for the time-being, that's 12 VDC. Yet, with a simple 12v charger, this approach has merit.

[avanti]

Originally Posted by Winston

We like this concept as a replacement for 'the RV generator' but prefer a system that directly outputs to our 'off-grid' electrical battery system . . . and for the time-being, that's 12 VDC. Yet, with a simple 12v charger, this approach has merit.

Yes, that is the approach I took as well. Literally everything in our rig is native 12VDC, except for the obvious high-current items.

But, the key phrase is "for the time-being". I brought this up in the context of this thread because if 48VDC makes sense, maybe 120VAC makes even more sense. The recent discussion about the apparent surprising efficiency of the current generation of "dorm fridges" adds credence to this. The idea of an ALL-AC van is interesting.

Obviously, one would need DC between the battery and the inverter/charger, but maybe some day that will be it. Some of the axial flux systems I referenced have integrated battery interfaces at various voltages.

[Winston]

Originally Posted by avanti

But, the key phrase is "for the time-being". I brought this up in the context of this thread because if 48VDC makes sense, maybe 120VAC makes even more sense . . . The idea of an ALL-AC van is interesting.

The time doesn't seem ripe for 48 volts. We'd like to avoid running parallel 12 & 48 volt systems. As our lithium-based house electrical system, including second Nations alternator, is completely separate (and never interconnects with) the vehicle system, we could have gone 48 volts. But until more 48 volt appliances are available, we'll stick with 12 volts, and its inefficiencies.

Speaking of ALL-AC, we have gravitated in that direction. We have 8 duplex outlets spread throughout our DIY Promaster 159" HT Class B with a Magnum 2812 inverter/charger running 24/7 (except when on shore power). We no longer shop for 12 volt power supplies for our computers, power tools, and other gadgets, instead, we just plug their supplied wall chargers into one of these distributed 120 VAC outlets. Yes, this arrangement carries a fairly steep 'overhead', say, 2kwh/day. But with a large array of solar (800 watts), that 2nd alternator and 500ah of lithium, why not?

[gregmchugh]

Originally Posted by Winston

The time doesn't seem ripe for 48 volts. We'd like to avoid running parallel 12 & 48 volt systems. As our lithium-based house electrical system, including second Nations alternator, is completely separate (and never interconnects with) the vehicle system, we could have gone 48 volts. But until more 48 volt appliances are available, we'll stick with 12 volts, and its inefficiencies.

Speaking of ALL-AC, we have gravitated in that direction. We have 8 duplex outlets spread throughout our DIY Promaster 159" HT Class B with a Magnum 2812 inverter/charger running 24/7 (except when on shore power). We no longer shop for 12 volt power supplies for our computers, power tools, and other gadgets, instead, we just plug their supplied wall chargers into one of these distributed 120 VAC outlets. Yes, this arrangement carries a fairly steep 'overhead', say, 2kwh/day. But with a large array of solar (800 watts), that 2nd alternator and 500ah of lithium, why not?

What would be the components of your overhead estimate of 2kwh/day ?

Parasitic power and conversion inefficiencies on the Magnum?

Anything else?

[Winston]

Originally Posted by gregmchugh

What would be the components of your overhead estimate of 2kwh/day ?

Our Battery Management System draws about 1 amp.

Our Midnite Solar Classic draws, when resting, about 1 amp. If we're tight on power (rarely), we have a breaker to disable this at night.

We've not documented the Magnum with absolutely nothing connected, but with the various 'things' that are always connected, it draws about 5 amps. These things include a router, a Ubiquiti WiFi modem/antenna, a WeBoost, an Asus file server (NAS) and various small chargers that we leave plugged in whether charging or not, a NovaKool R4500 frig which, when running, draws 4-5 amps, LED lighting of 1 amp, maybe more, one or more laptops/tablets . . . which can runs for hours at over 100 watts (8 amps).

Then there's the 125 amp hot pot which runs in 4 minute spurts, the 125 amp induction stove, again, limited time durations.

Truth is that we probably average closer to 3kwh/day. The good news is, during these long days at reasonable latitudes we can generate 4-4.5kwh/day.

But if we get hit with a couple of overcast days, it's either shore power or the 2nd alternator.

[gregmchugh]

Originally Posted by Winston

Our Battery Management System draws about 1 amp.

Our Midnite Solar Classic draws, when resting, about 1 amp. If we're tight on power (rarely), we have a breaker to disable this at night.

We've not documented the Magnum with absolutely nothing connected, but with the various 'things' that are always connected, it draws about 5 amps. These things include a router, a Ubiquiti WiFi modem/antenna, a WeBoost, an Asus file server (NAS) and various small chargers that we leave plugged in whether charging or not, a NovaKool R4500 frig which, when running, draws 4-5 amps, LED lighting of 1 amp, maybe more, one or more laptops/tablets . . . which can runs for hours at over 100 watts (8 amps).

Then there's the 125 amp hot pot which runs in 4 minute spurts, the 125 amp induction stove, again, limited time durations.

Truth is that we probably average closer to 3kwh/day. The good news is, during these long days at reasonable latitudes we can generate 4-4.5kwh/day.

But if we get hit with a couple of overcast days, it's either shore power or the 2nd alternator.

OK, I was confused, I thought by overhead you were referring to the penalty for using 120v vs 12v devices and the requirement to keep the inverter running to support them...

[VanFan]

Originally Posted by Winston

The good news is, during these long days at reasonable latitudes we can generate 4-4.5kwh/day.

So you mean you generate that much through solar alone, right? If so, that's impressive for a Class B. What size/capacity are your panels?

[kite_rider]

Originally Posted by Winston

The time doesn't seem ripe for 48 volts. We'd like to avoid running parallel 12 & 48 volt systems. As our lithium-based house electrical system, including second Nations alternator, is completely separate (and never interconnects with) the vehicle system, we could have gone 48 volts. But until more 48 volt appliances are available, we'll stick with 12 volts, and its inefficiencies.

Speaking of ALL-AC, we have gravitated in that direction. We have 8 duplex outlets spread throughout our DIY Promaster 159" HT Class B with a Magnum 2812 inverter/charger running 24/7 (except when on shore power). We no longer shop for 12 volt power supplies for our computers, power tools, and other gadgets, instead, we just plug their supplied wall chargers into one of these distributed 120 VAC outlets. Yes, this arrangement carries a fairly steep 'overhead', say, 2kwh/day. But with a large array of solar (800 watts), that 2nd alternator and 500ah of lithium, why not?

I think you miss the point about 48V DC if you are looking for 48V DC appliances. You already say you are gravitating to an all AC direction, and that is what 48V+large lithium battery+large inverter enables. 48V DC as a second alternator and wiring solution makes so much more sense than a second 12V alternator.

[Winston]

Originally Posted by gregmchugh

OK, I was confused, I thought by overhead you were referring to the penalty for using 120v vs 12v devices and the requirement to keep the inverter running to support them...

Yes, we understand . . . and agree that the term "overhead" better defines power required to operate or maintain the system in a 'ready' state and not otherwise providing useful work. Your comments inspired us to answer the question: "What is our real overhead?"

With the inverter on, but providing no power, our total current is 3.6 amps (47 watts @13volts). Our BMS draws 1 amp (13 watts), leaving 34 watts of overhead for an inverting inverter, not under load. After a short while, the inverter goes into standby, but constantly 'checks' to see if a load has been applied. Our digital ammeter couldn't follow this jumpy activity, but we saw readings as low as 1.2 amps with peaks over 2 amps.

As a practical matter, we always have some loads on the inverter, so we consider the inverter overhead to be a steady 34 watts.

Thanks again for providing the incentive for us to learn more about our system.

Originally Posted by VanFan

So you mean you generate that much through solar alone, right? If so, that's impressive for a Class B. What size/capacity are your panels?

We have 3 Kyocera 270 watt panels that mostly fit on the roof of our 159" standard length ProMaster - - leaving just enough space for a Fantastic fan.

Originally Posted by kite_rider

I think you miss the point about 48V DC if you are looking for 48V DC appliances. You already say you are gravitating to an all AC direction, and that is what 48V+large lithium battery+large inverter enables. 48V DC as a second alternator and wiring solution makes so much more sense than a second 12V alternator.

We’d agree if the only function of DC was that of an ‘intermediary’ between engine-drive alternator and 120 VAC inverter. But there are too many ‘things’ that scream “we want DC” - - and that DC is uniformly 12 volts. The advantages of 48 volts, for us, do not justify running a second, parallel DC system.

[Davydd]

By leaving our inverter own all the time I estimate the "overhead" is a draw of about 72 amp hours off the batteries in a 24 hour period. That's about a 15 minute drive to replenish with our Delco second alternator producing 280 amps. With an 800ah lithium single battery bank that is negligible considering the transparency of how our van performs electrically with all 120vac all the time whether off-grid or on shore power. Consequently, we rarely use shore power even when available. We use our Keurig coffee maker, electric induction cooktop and microwave/convection oven liberally and on our last trip we added a 3 qt. Instant Pot. We also have no propane and I am beginning to question whether we need solar at all even though we have 420 watts.

I might add leaving the inverter all the time is because the microwave clock is the most prominent readout that doesn't have to be set each time the inverter is turned on and our 120vac operated electric articulating beds are at our disposal all the time.

[VanFan]

Thanks for describing your solar set up. It's impressive.

[kite_rider]

Originally Posted by Winston

We’d agree if the only function of DC was that of an ‘intermediary’ between engine-drive alternator and 120 VAC inverter. But there are too many ‘things’ that scream “we want DC” - - and that DC is uniformly 12 volts. The advantages of 48 volts, for us, do not justify running a second, parallel DC system.

I'm glad we've got some common ground here on what we agree upon. Where we don't see eye to eye is that I think there are too many things that scream "we want 120V AC". Davydd has many great posts that show an all-AC system backed with big battery and inverter works great with common low cost and widely available 120V AC appliances.

But here is where I get confused; you already have a second parallel DC system with your second 12V alternator! What I don't like about the Nations system is that it's big, bulky, expensive, and has very thick cables.

My opinion (based on theory and not a lot implementation.. yet ) is that you can get a similar amount of power to your li-ion battery with a smaller (in size) 48V alternator with smaller and easier to work with cabling as opposed to the Nations solution that's being currently used.

I really want to hack the voltage regulator on a commodity 90 Amp alternator to produce 58V rather than the common 14.4V. Theoretically I think this will work. If so, I think it would open the floodgates to single fuel, all 120V AC van designs.

[booster]

Others may have more intimate details, but I don't think anything you can do to the regulator would make you get much higher voltage. When they test the alternators, they bypass the regulator with straight in 12-13v input, and rarely get much past 17v in the ones that I have seen.


There probably are applications that use the higher voltage systems, so you might be able to find an alternator and do the adapting to the mounting and case. It is very possible the Volta alternator is from one of the major suppliers, with a private label for Volta.

[booster]

Like this?


https://www.bruceschwab.com/high-out...rs/alternator/

[avanti]

Originally Posted by kite_rider

My opinion (based on theory and not a lot implementation.. yet ) is that you can get a similar amount of power to your li-ion battery with a smaller (in size) 48V alternator with smaller and easier to work with cabling as opposed to the Nations solution that's being currently used.

HEY! You guys are hijacking my thread. I'm shocked. SHOCKED!

The premise of my original post is that MEPS and others have systems which go directly from unregulated 3-phase output from these fancy alternators DIRECTLY to 120VAC. That is the innovation that I was hoping to discuss here. Such a system would have no DC at all, beyond the bare minimum implied by the battery system (whose voltage would be more or less irrelevant).

The system looks generally like this:



The diagram shows a DC load, but that is obviously optional.

[kite_rider]

Sorry to hijack the thread Avanti. I guess I would ask why you would want to produce 120V AC in the first place? The advantage might be that you could use the engine as the 'generator' for your AC appliances. That sounds like it might work, but what about the 60 Hz cycle that is common for utility power? Seems like it would be complicated (or inefficient) to replicate this over the rpm range of the vehicle engine.

I think the general thought is that it's a much better design is to have a big energy bank (batteries) and then convert that energy to 120V AC via an inverter. You would need this system anyway for times when the engine is off and you charge batteries with DC.

I was just about to reply to booster and get into alternator theory and why the electromagnets on a common automotive alternator rotor and why they should be able to easily produce a 60V output; but yea, this is an axial flux generator thread I guess