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Old 09-21-2017, 03:57 PM   #21
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Originally Posted by boywonder View Post

Are the alternator vendor links in post 1 reputable brands or examples of hype?
As to the other brands not sure. DC Power claims to be selling into DoD & Military/Police applications. They are pretty solid on the phone and also make a secondary '270-280A' kit for Sprinters. (It is their alternator and uses MB style brackets). I liked what I heard - they source only Grade A rotors into their high current applications and make most of their own internals/parts. The cases are all generic. Pulley size would depend on final design, but they also use a clutch pulley.

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Originally Posted by Wrinkledpants View Post
Like others, I'd be concerned with something that heavy producing that much power having reliability issues elsewhere.

SMB is not going to install that if it goes against the MB regs (which it sounds like it will).
Agreed...and frankly I don't need/want such a massive unit. I wonder if Advanced RV has worked obtained MB permission for the 40SI case.

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Maybe I'm missing something in your math, but a nations alternator will put out 150 amps at idle, and 230 at driving speed (or high idle). That's registering at the battery by other folks that have this setup. ...
These are good data points - thx.

And yes, assuming I can find a way to limit battery current into the lithium stack while the AC is running...an acceptable outcome could be simply confirm a Nations' style alternator is just fine for the application.

Nations datasheet/literature spec'd 198A-200A @ 'idle' - idle in the alternator industry for 2250 alternator shaft RPM. Typical hot vs cold rating is about 15% diffential with hot being less. If they are only hitting 150A, then the alternator isn't quite hitting 2250 RPM @ MB engine idle.

Most of the secondary alternators are going to be a Denso Style Case - MB OEM style. There are small case and large case. The ones in these applications are considered a 'large case' alternator for automotive applications. If it is a Denso case, then it is a newer 6phase hairpin design with a modern/latest rectifier/output regulator concept.

My numbers from before (30-40% of full rating were based on the older case designs, some 3phase, some older rectifier designs). Newer style windings with a higher phase count - we may see 50-65% of full rating at idle. (Alternators are actually variable frequency AC generators with a DC rectifier output stage).

In alternator design, there is a tradeoff between total/max output and idle current. Realistically, a '270A' alternator and '370A' (in this case size) will have a similar output current at idle RPMs levels. It isn't until the alternator RPMs start to increase is when difference really starts to appear.

In an ideal world, and in my application a system controller would observe the current flowing into the batteries, sense load current, and alter the alternator output voltage. (The batteries' current is controlled by its ability to accept charge and by the charging voltage).

By controlling the system voltage (via the alternator's field current), we can regulate/reduce current into the batteries. The load will continue to draw what it needs...all with the goal of not straining the alternator (and increasing/decreasing the amount of current into the batteries).

Since my application is running an electric A/C AND charging batteries, I could be cranking for hours. Example: I went to Phx in August through Southern CA. The only time it dropped below 105 was at night....mostly it was 110 LA Area to Queen Creek. The A/C on my jeep was on high the entire drive time trying to keep it cool in the back for the kiddos & dog. For the sprinter, I won't really know until I try and I don't want to throw away $900, when $1400 would have solved the problem.

I could also be overthinking this...
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Old 09-21-2017, 03:58 PM   #22
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One concern I have about SMB and 2nd alternators is that they don't use the Balmar Voltage Regulator with their Nations Starter alternators (at least at SMB North). In fact, when I talked to the SMB tech, he didn't seem to even know what the Balmar regulator was. This seems important to me first to provide the proper charging profile for the batteries but also as a safety device to monitor the alternator temperature (if you use the optional temperature sensor) to maintain safe operating temperatures for the alternator.

Does anyone have any thoughts about using a 2nd alternator without using the Balmar voltage regulator?
There are all sorts of opinions on charging profiles and voltages. I won't get into that here....Most of the external regulators are time based -> they will cycle through different set points based upon time.

A decent dedicated battery charger will use both time and current when cycling through the different charging phases for AGM and lithium systems.
For AGM, typically, a timer is started once the battery has dropped out of bulk (dropped out of CC to say 0.05C and is now onto CV mode). It will maintain a higher voltage for a period of time, say 14.7 - but it will also look at current. Once the current drops below some level, the charger will drop the output voltage into float, say 13.6-13.88.

Alternators are actually pretty good chargers and not too bad at self-regulating - and are not too bad at being a CC/CV device. They will only output to a set voltage ... too much demand, voltage will drop. Too much demand for too long, however, and the alternator gets cooked.

But if they were so good at self-regulating, why are we hearing reports of alternators being cooked in these applications?

Too big of an alternator (too much current), one can actually damage AGM and other deep cycle batteries. Full River AGMs (220aH 6V DC200s) only want to see about 0.35C - or 0.35*220ah = 77A. My Jeep's 180A alternator can slam well over 100A-130A into them while cruising down the interstate (typical draw w/o cooling fan for my jeep is around 50-70A). Too much current and outgassing starts. Imagine what a 280A or 380A alternator would do...

Field current increases to maintain that voltage. At some point, the demand will exceed the ability for the alternator to produce power, and more field current won't help. The voltage will drop. Temps will start to rise in the alternator.

The problem with an alternator based charge controller is its inability to differentiate between load current and battery charging current - so all of the demand looks the same. For lithium systems (where we are trying to maximize battery life) we need is a BMS that can command the alternator voltage thereby controlling the amount of current flowing into the battery stack.

RE Temp Compensation
Many of the higher quality aftermarket alternators will have internal temp compensation - and will throttle the alternator output. It really depends on where that thermal compensation set point is...

RE Balmar vs No Balmar
Depends on your application. Simple AGM, my gut tells me not to worry about it too much PROVIDED the alternator's setpoint is around 14.4-14.5 AND has internal alternator temp compensation. There is some benefit if the Balmar's temp sensor function is utilized as it will vary the output voltage bit. Balmar's programming is based on time & alternator current only. So if it is in the Calaculated Bulk stage and you kick on a load (like your inverter/AC), it will remain at Bulk Voltages regardless of what the battery needs.

Lithium? That requires more precise voltage control. In my case, with a heavy AC load that may be running for quite a while, the benefit of the Balmar's field current/time base is limited.
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Old 09-21-2017, 04:10 PM   #23
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Cool Videos on Decoupler Pulleys

Still trying to understand which kits include an OAD pulley...

Here are some cool videos on pulleys.





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Old 09-21-2017, 04:30 PM   #24
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I could also be overthinking this...
I think this is a case of just that, lol. You're not blazing a new trail here with running rooftop A/C and charging lithium batteries. Plenty of OEM RV makers, as well as DIY folks, have been doing this for quite sometime without issue.

Heat is going to impact any alternator unless it's liquid cooled. I'm still struggling to understand how your need is drastically different from what we're doing, or what others have done. Is your A/C unit some type of high-power commercial setup made to turn the van into a meat locker? Do you have data that indicates a nations alternator is not able to accomplish what it says it can do? Maybe there's a backstory to this that I missed.

I fully anticipate driving all over this country in all kinds of heat and cold, and I'm not worried that we can't run the A/C and recharge the batteries. Dometic Penguin II on the roof, large inverter, 300 AH of lithium. If there are short periods of time when the alternator is a few amps short of maintaining the A/C, then power will just get pulled from the batteries for a bit. It's not going to be significant, so once we're underway with higher RPMs and airflow, we'll be back to recharging.

Let me know if I'm missing something.
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Old 09-21-2017, 05:08 PM   #25
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What is insane is trying to run the AC compressor from batteries.
Actually it's not. The insane part is doing it at 12 volts.

There are all kinds of high energy tasks being done these days but done at a much higher voltage of DC. Even something as mundane as the A/C in my Chevy Volt car uses 3k watts off the lithium pack on high, but at 300 volts. I'll go out on a limb here and say that as the large lithium packs find there way into more RV applications the systems and their equipment (A/C, refrigerators, inverters, 2nd alternators, generators, ect) will operate at much more efficient higher voltages. And be isolated from the vehicles. Or not, what about a hybrid propulsion system for boost going up hill and a re-gen system that harvests the power for house needs. I realize this doesn't help your current goals. I hope you keep on this pursuit this IS crazy and awesome.

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Old 09-21-2017, 05:35 PM   #26
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Lets see, to keep the dogs cool for one hour would require one half gallon of gas idling your engine and running the dash AC. You keep your batteries charged as a free extra. No setup required just turn it on....

There are debates over idling but that is why I have a gas engine in my Promaster.
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What is insane is trying to run the AC compressor from batteries.
Are you aware that in a couple of weeks Elon Musk is going to announce a Tesla battery powered semi tractor? Cummins already announced theirs, but Tesla seems to be much farther into development. Things have changed. Much of it is due to Musk who also is now landing SpaceX rockets on a tail of fire back at Cape Canaveral or on a little barge out in the ocean and then re-flying them. Old paradigms are dissolving. Britain and France have mandated that new vehicles of all types be completely electric by 2040. The time to embrace the future is now.

https://electrek.co/guides/tesla-semi/

https://www.forbes.com/sites/joannmu.../#7aa6feee78f1
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Old 09-21-2017, 09:08 PM   #27
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Are you aware that in a couple of weeks Elon Musk is going to announce a Tesla battery powered semi tractor? Cummins already announced theirs, but Tesla seems to be much farther into development. Things have changed.
Things are changing but a lot of the new stuff is not ready for prime time. There are better batteries coming. Here is one that you don't have to charge at all. Just feed it from the diesel tank (3kw).

https://www.trucknews.com/sustainabi...pu/1003060195/

I was just pointing out that objectives can be met in simple ways. Avoiding all this complexity.
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Old 09-22-2017, 10:19 AM   #28
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For us in some of the towns we are visiting it would not be feasible to run the van while we are away for 2-3 hours in town. I don't think main street Winthrop WA would appreciate a diesel running @ high idle.

It is then about enough amp hours to run the Dometic a/c for the time we're away from the van with dogs inside. It is somewhat ironic though that this one issue has taken up the majority of our time on designing the builds... But it's all from experience while camping out of the back of our Tacoma for years where we will sometime drive around for an hour looking for a shady enough spot to park while we're in town.

If I can I will absolutely run the van while we're away. But I don't see that happening in most small western towns we visit. And of course it's only for the hot days where the roof vent isn't going to keep the van cool enough.
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Old 09-22-2017, 11:08 AM   #29
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I think you might underestimate how cool you can keep a van with good insulation and insulated window covers. We have no problems keeping comfortable in a friends promaster with good insulation, no windows, and dual max fans. Stays much cooler in the van than outside. It’s a white van, though, so he’s got everything working for him.
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Old 09-22-2017, 01:27 PM   #30
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I've gone back and forth many times on the issue. We are getting the extra insulation, also ordered with our production order with MB. I'll also have insulated panels for the windows. We'll have one MAX fan/vent.

I've agonized about going with the standard SMB electrical with 2 4D AGM's, no rooftop a/c and a 2nd Max fan in lieu of the a/c. The basic guy in me wants that. Especially considering the use of the rooftop a/c and lithium set-up is probably under 5% of total use. At best.
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