Axial Flux generators

[kite_rider]

Originally Posted by Winston

You say "too large an alternator" and "too large wire size". Ok. But, so what? Yes, that Nations alternator hanging 'under' our ProMaster seems precariously low and, we admit, we're just waiting to whack it someday. And the required wire gauge is ungainly . . . but once installed, it's over (unless we succeed in whacking the alternator). For the minor inconvenience of that initial installation, we gain the huge benefit of having a virtually limitless supply of 12 volts.

Welcome back Winston, now let's get back to hijacking this thread!

I guess I would say life is full of "good, better, and best" solutions. Plain Jane class B systems are good (AGM, solar, and propane..), the solution you have described is 'better' in many ways. But for a brand new build the 52V with lithium style battery regulation would be 'best' I think. This forum helps me think through these ideas and provides some great suggestions. For example, Booster added a link on this thread earlier that had a lithium ready 56V alternator regulator. It might be perfect for the build;
https://www.bruceschwab.com/wp-conte...al-2011-01.pdf
I'm now looking into ways to use this regulator with a smaller 'normal' sized alternator.

I'm also in the process of 'ruggedizing' my Promaster, so this means moving as much of the low hanging stuff under my van as possible. Then I'll add a lift kit and some larger and more rugged tires. It turns out that my existing van doesn't need a second alternator, but I really don't like the way the Nations solutions sticks so far down and in front on the Promaster. So that would be an issue for me. I'm thinking I would do this build on either a 4x4 Sprinter or a 4x4 converted Transit van.

Anyway, I'm just thinking that if you are going to go through the trouble to put in a parallel DC system; it would be better to make it 48V (52V) than 12V.

[Davydd]

Winston,

I no longer have a Nations alternator. I replaced it with a Delco Remy alternator which is much more robust than the Nations. Advanced RV has a video on the difference. Also, it is twice the size so I suspect it will not fit in a Promaster. Also the Delco does not use the MB provided brackets as they have to be custom brackets. That's how I consistently get 280a output tested over one hour of continuous driving at 50 mph on the Natchez Trace. The test ended when I reached 99% SOC. I have a 4/0 wire from alternator to battery bank and inverter.

I stated about a 3a draw leaving the inverter on. In the garage I can gauge it more accurately without any solar and the compressor refrigerator turned off. However, there are some other draws I realized such as our wifi ranger system that is active inside with a router and antenna outside on the roof. I don't know how much parasitic loss there is from alarms, the two intermittent cooling fans, and I am unsure about my two Pioneer units and Trik-L-Start. I did turn on and off yesterday the main bank of LED overhead lights and LED light strips in the ceiling and baseboard and that drew 4a when on. And of course, SOC readouts are to the 1% increments. However, the 72ah off the battery is still the maximum overhead when unoccupied with the inverter on.

BTW, the 48v Volta system as tested out be Advanced RV is really 56 volts.

[Winston]

Originally Posted by booster

Winston, how do you get the Nations down to 125amps? The largest turndown I have found in the Balmar is 50% . . .

. . . our two in parallel (560 amps) of alternators . . .

It is hard for us to say anything good about the Balmar regulator other than it works. We have ours mounted 'inside' under the glove box and requires a mirror to see its difficult-to-interpret 7-segment display. And tapping that red dot with the magnetic wand in the precise time-synchronization required to program, can be an exercise in frustration. Then there's the hopeless charging 'algorithms' all tied to lead-acid's 'bulk/absorption/float' protocol and further aggravated by its reliance on 6 minute (or multiples thereof) time intervals.

We operate the Balmar in a manual mode and have programmed it for a multi-hour 'bulk' charge - - it being our intention that it never switches out of 'bulk' mode. We turn it on, and leave it on, until our other instrumentation tells us that we have reached the desired State-of-Charge for the lithium pack.

It's been awhile since we programmed it . . . as we recall, we did not use the Balmar 50% cut-back feature, rather, we set the bulk charging voltage to a level that produced the desired current. As with all 'low voltage' chargers (as distinguished from solar PWM or MPPT controllers), we see the normal current 'sag' as the battery charges. Less than ideal, but in the absence of a more sophisticated programmable regulator, we get by.

Incidentally, we do not utilize the battery temperature feature of the Balmar believing that the comparatively low temperature/voltage coefficient of lithium does not warrant it.

560 amps of alternator output?! That's a definite 'wow'. Why so much?

[Winston]

Originally Posted by kite_rider

I'm just thinking that if you are going to go through the trouble to put in a parallel DC system; it would be better to make it 48V (52V) than 12V.

Arguably good advice for one in the planning stages. Ours, of course, is a fait accompli.

We like your "good, better, best" analysis . . . but, here, the competing systems each have advantages so the dividing line between 'better/best' isn't as sharp, in our opinion, as you suggest.

Curiously an argument in favor of 56 volts that we haven't heard in this discussion is battery chemistry. Doesn't the chemistry employed in the 56 volt systems have a higher energy-density? Don't you get more 'bang' for the size/weight?

[booster]

We wound up with the 560amps kind of by default. Our Chevy doesn't have a fancy alternator PCM control, so we can parallel the engine alternator and the add on. We had started with a 250amp DC Power alternator in the stock place as the upgrade when we had 260ah of wet cells, but when we went to the AGMs at 440ah, it ran too high an output to give us the amps we wanted, and it heated up too much. We added a second 280amp DC Power/Nations alternator in parallel, and run them so the don't get too hot. In our Chevy, heat is probably more of an issue than in Sprinters or Promasters as the alternators sit behind the radiator, more on top of the engine. AT 180 amps, the alternators and batteries seem to both be happy, and at 280 amps for 20 minutes, we get well over 1 days recovery if the batteries are getting low.


The Ample Power regulator is very nice, as not only do you have two different turndowns that you can get off of remote switches, you also get the option of forcing the stages with a remote switch. We force it to bulk until we see low enough amps to the batteries for them to be full, or low enough for the solar to top them off, then just let it go to float. Works very well for us.

[kite_rider]

Originally Posted by Winston

Curiously an argument in favor of 56 volts that we haven't heard in this discussion is battery chemistry. Doesn't the chemistry employed in the 56 volt systems have a higher energy-density? Don't you get more 'bang' for the size/weight?

I went into the chemistry discussion in some detail back in that post I referenced about my 'new lithium build' idea in December. Another forum member, nebulight, made the case that the iron phosphate (LiFEPO4) was better because it was safer and lasted for more cycles. Recent data from Volta PR material seems to claim that NMC (Nickel Manganese Cobalt) is better.

NMC does have higher energy density and is the choice for most lithium applications (Ecars, Ebikes, laptops, etc..). It has a nominal voltage of 3.7V and a charge voltage of 4.2V. This is in contrast to the iron phosphate chemistry which has a nominal voltage of 3.2V. The redeeming quality of that voltage is that it fits well into the existing 12V world with a 4S configuration (common in power sports and other automotive Lithium designs).

I would refrain from calling any of these systems "56V". But maybe I'm missing something here with that name...

We in the Ebike world often call our 14 Series NMC batteries "52V" because the nominal voltage is 51.8V. The charge voltage is 58V. Most 48V E*bikes use 13 Series NMC batteries. Since others have mentioned the Volta system is charged at 58V and that they say they are NMC, I would conclude that they are 14S configuration.

[Winston]

. . .

Originally Posted by booster

when we went to the AGMs at 440ah . . .

In our former CaRV (a VW Jetta*) we had a massive AGM battery (size 8, 245ah) weighing-in at 160 lbs. Hard to imagine your 440ahs . . . .

* We called it a CaRV by reason of the shore power receptacle we mounted in the back bumper. When we got to our campsite we could plug-in just like the big boys.

Originally Posted by kite_rider

Most 48V E*bikes use 13 Series NMC batteries. Since others have mentioned the Volta system is charged at 58V and that they say they are NMC, I would conclude that they are 14S configuration.

It seems that 48 volt systems have a dual standard: 13S and 14S. We trust that appliances designed for these systems can accommodate both - - we'd hate to see another Betamax/BluRay war.

[VanFan]

Originally Posted by avanti

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).

As I mentioned in an earlier post to this thread I looked into the MEPS/Aura options before beginning my custom build and decided on dual high output alternators instead, because of the cost difference. But there was a little more to that decision, so here is the complete thought process:

Alternators generate alternating current (hence the name, I suppose) which is then converted to direct current internally before being output to the loads. That's the main difference between generators and alternators. Generators have no internal converter, so they output alternating current directly to the loads. This means the only real innovation is the fact that the MEPS/Aura units are generators driven by the main propulsion engine, instead of a generator driven by a separate engine. I'm not minimizing the coolness of that, just saying from a technical point of view everything that happens downstream from the MEPS/Aura unit is virtually identical to an RV with a separate generator.

If memory serves, there's not as much price difference as one might expect between a dedicated genset and the MEPS/Aura options, but of course there are significant space advantages to the MEPS/Aura, not to mention significantly less maintenance by omitting that second engine. So between those choices, I think the MEPS/Aura wins easily, especially for a Class B.

But what about high output alternators?

The cable size and line loss between a 120v generator and a charger is much less than the cables required to run a comparable current straight to the batteries from a 12v alternator. So that's a check mark in the MEPS/Aura column. But that difference can be mitigated by placement of the batteries, and with intelligent design on a Class B we're never talking about a wiring run of more than a ten feet from power source to batteries, give or take.

Once the cable size and line loss issues are dealt with, everything else is much the same. You need a charger along with the alternators if you plan to plug into shore power. And of course with the 120v output from the MEPS/Aura option your need for a charger is even greater. And unless you're willing to fire up your engine every time you have a 120v load, either way you still need to buy an inverter to step the voltage back up and produce an alternating current.

So as with the self-contained genset option, the MEPS/Aura option offers no real equipment savings over high output alternators once you get past the initial power source, except perhaps minimal savings in wires.

Back when I considered MEPS and Aura generators, the prices they quoted were several thousand more than a pair of high output alternators. (I don't remember the exact price difference, but I think it was $2000 to $3000). So as I mentioned, that was the main reason I went with alternators. But there was also the logic I just went through above, and nothing I've learned since then has changed my thought process.

[avanti]

Originally Posted by VanFan

Alternators generate alternating current (hence the name, I suppose) which is then converted to direct current internally before being output to the loads. That's the main difference between generators and alternators. Generators have no internal converter, so they output alternating current directly to the loads. This means the only real innovation is the fact that the MEPS/Aura units are generators driven by the main propulsion engine, instead of a generator driven by a separate engine. I'm not minimizing the coolness of that, just saying from a technical point of view everything that happens downstream from the MEPS/Aura unit is virtually identical to an RV with a separate generator.

If memory serves, there's not as much price difference as one might expect between a dedicated genset and the MEPS/Aura options, but of course there are significant space advantages to the MEPS/Aura, not to mention significantly less maintenance by omitting that second engine. So between those choices, I think the MEPS/Aura wins easily, especially for a Class B.

But what about high output alternators?

The cable size and line loss between a 120v generator and a charger is much less than the cables required to run a comparable current straight to the batteries from a 12v alternator. So that's a check mark in the MEPS/Aura column. But that difference can be mitigated by placement of the batteries, and with intelligent design on a Class B we're never talking about a wiring run of more than a ten feet from power source to batteries, give or take.

Well, your comments above are essentially an examination of the merits of a traditional genset vs an underhood engine-driven alternator or generator. The has been discussed a lot here, and it hinges mostly on the merits of charging while you are driving vs having to run a genset (and camping in a place that allows this.) I agree that in this regard there is little difference between a DC second engine generator and the MMEPS/Aura approach, except for the pragmatics of wiring, as you say.

Once the cable size and line loss issues are dealt with, everything else is much the same. You need a charger along with the alternators if you plan to plug into shore power. And of course with the 120v output from the MEPS/Aura option your need for a charger is even greater. And unless you're willing to fire up your engine every time you have a 120v load, either way you still need to buy an inverter to step the voltage back up and produce an alternating current.

So as with the self-contained genset option, the MEPS/Aura option offers no real equipment savings over high output alternators once you get past the initial power source, except perhaps minimal savings in wires.

I don't think I agree with this. My understanding is that the MEPS/Aura have the intrinsic ability to run in "inverter" mode, converting battery power to 120VAC. That certainly seems to be implied by the box labeled "bi-directional power supply" in the first diagram I posted. I don't know whether they can accept shore power, but even if not, a simple 3-stage charger is fairly trivial. The Aura ECU seems to be an "all in one" box (which admittedly can be both good and bad).


But, all this really misses my main goal, which is to examine the merits of going toward a 120VAC-oriented house, rather than the current DC-centric systems. The trend is to go towards higher voltage DC systems, driven by the efficiency gains so achieved. My question is: If we are going in that direction anyway, why not go all the way to 120VAC. You don't need axial flux generators to do this, it is just that the MEPS/Aura systems would fit well into such a system.


P.S. -- There are a lot of good reasons for wanting to have your house batteries toward the back of the van. I don not consider your "10 feet max" claim to be realistic in general. The run from my second alternator to the batteries that it charges was more than twice that, and I do not consider my layout to be foolish.

[Winston]

Originally Posted by avanti

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.

This thread was moving fast enough that we missed some of its posts . . . so let us respond and try to 'unhijack' the thread . . .

In one of our earlier posts we noted that we've "gravitated" to 120 VAC - - which your proposed system addresses well. And while 'we're not there yet' concerning your comment that "DC loads . . . (are) optional", for argument, let's accept that we don't need DC loads. But, unless you intend on running your engine continuously, DC is hugely important as the means of storing energy to run your inverter when parked. And it is that "bi-directional" power supply that charges the battery from the 3-phase "alternator" when the engine is running and generates the 3-phase output necessary to drive the 120VAC inverter when the engine is not running.

It's hard for us to appreciate how this arrangement simplifies . . . you need, in essence, three high power charger/inverters: 1) to convert the three phase alternator output to DC to charge the battery; 2) to convert the DC battery voltage back to 3-phase; and, 3) to convert the 3-phase (from either the alternator or the battery-to-3 phase inverter, to 120 VAC.

What we need here is an AC battery!

[VanFan]

Originally Posted by avanti

My understanding is that the MEPS/Aura have the intrinsic ability to run in "inverter" mode, converting battery power to 120VAC....

This surprised me, so I went back and reviewed the marketing material Aura sent when I was considering their system. The meaning of "bi-directional" is not immediately apparent in their brochure (or if it is, I missed it) but I wonder if that isn't simply the marketing department cooking up a term that sounds more interesting than "alternating" which of course refers to the fact that the current flows both ways in an AC circuit. In any event, it appears the "bi-directional power supply" is one of several separate devices you can buy in addition to their generator to build a user-specific system, so from a cost and system complexity perspective that's tantamount to adding an inverter to an alternator powered package.

While I was at it, I went ahead and dug up the quote for the MEPS generator that I received. The generator alone, plus pulley and mounting bracket, was $6,033. To compare, I paid $2,500 plus tax for an OEM replacement high output alternator plus a second high output alternator and mounting bracket. So that's a $3,500 argument for going with alternators.

And once I really started thinking back, I remembered that both the Aura and the MEPS generators are significantly larger than the second alternator I used (which is a Balmar I believe, although frankly I've forgotten). The second alternator was a very tight squeeze as it is, so there was a real question whether the generators would fit. [/QUOTE]

Originally Posted by avanti

But, all this really misses my main goal, which is to examine the merits of going toward a 120VAC-oriented house, rather than the current DC-centric systems. The trend is to go towards higher voltage DC systems, driven by the efficiency gains so achieved. My question is: If we are going in that direction anyway, why not go all the way to 120VAC. You don't need axial flux generators to do this, it is just that the MEPS/Aura systems would fit well into such a system.

I'm sorry I misunderstood your main goal. By asking about the "pros and cons" I thought you were looking for a comparison to other systems.

You're certainly correct that the generator approach begins to make sense functionally if the goal is a 100% AC van. But as mentioned above, the generator alone is just a substitute for alternators or a genset. So financially, once you add their other components to their system I suspect the cost difference between it and a more traditional approach will rise into the low five figures. Can't say that for sure because once I found out what they were asking for the generator alone I moved on.

EDIT: I know you're aware of this, but just to make sure all the facts are on the table, there is no such thing as a 100% AC system. As far as I know, there is currently no way to store AC power as AC power long term, so until such an invention comes along there will always be DC batteries in every system, which means there will always be converter/chargers and inverters of some sort. There may be several types of devices that accomplish those same functions, but even if every load on board is 100% AC, there will still be devices of some kind managing DC power.

Originally Posted by avanti

P.S. -- There are a lot of good reasons for wanting to have your house batteries toward the back of the van. I don not consider your "10 feet max" claim to be realistic in general. The run from my second alternator to the batteries that it charges was more than twice that, and I do not consider my layout to be foolish.

Not knowing anything about your layout I certainly didn't mean to imply that it's foolish, and I'm very sorry I left that impression. What I was trying (poorly, apparently) to say is that given the fact that the cables required to conduct 300+ amps are very large, and the amperage loss can be significant, if one is concerned about those issues an intelligent solution is to put the batteries close to the alternators.

All design involves balancing the user's priorities against each other to arrive at the best possible compromise. Different priorities lead to different compromises. So it's certainly not foolish to put batteries in the rear of the van. It just means you prioritized something else more highly than I did. I'm sure your set of compromises is the most intelligent response possible to achieve your unique set of priorities.