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Discussion Starter #21
Fair enough, kenryan, it is definitely delusional to call my crazy approach simple. If I were planning on sitting for days in camp, I can definitely see bringing a generator; but I can't imagine bringing an extra generator along with me for weekend adventures and <1 week trips, since my dual alternators are already a very competent ~~3kW generator (as long as I'm planning on moving the van around a bit--to/from camp, trailheads, sights, etc.).
 

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Put a litre of water in the microwave for 10-15 minutes while driving. Mix with a bit more cold water in a small handheld weed/fertilizer/multipurpose hand pressurized sprayer. Wet, lather, rinse as you go to avoid soap drying on you.

Perfect temperature and quantity for daily cleaning without fuss.

I modified the lid of a rectangular plastic container with small holes to let steam/pressure out while keeping water in during the drive.
 

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I'm still in the throes of design mode, so I wanted to summarize where I was so far and ping the very helpful contributors of this thread one more time for a sanity check. First, the original questions I was after:

minor edit below in bold in response to the first reply



From the responses above, plus other research I did, the best battery charging options I could find never really got up to a 200-Amp charger that I really wanted. There's a very nice 100-Amp Victron DC-DC buck/boost, a couple 100- and 125-Amp Sterling DC-DC units, and the 225-Amp battery-to-battery switch that Battleborn recommends (not a buck/boost or current regulator, just a switching battery combiner). I found a couple of ACR devices that were battery combiners, but also not really current regulators. So, there I was, still trying to figure out how I can safely get a nice current-limited 200 Amp out of my running engine and dual alternators, when my beast of a Victron 3000 Watt Multi-plus inverter/charger showed up, and gave me an idea.

OK, stay with me here. I'm looking for some devil's advocates to tell me why I'm crazy. And, it might be very easy to tell me I'm crazy. That beast of a Multi-plus is already a current limited charger. It takes up to 30 Amps of AC shore power, and passes a lot of it straight along to AC loads in the van, and puts up to 120 Amps of it into charging the house battery bank. It can be set to limit how much current it draws from a small generator or limited capacity shore power plug. So, why not just put a separate 3000 Watt inverter on my starter battery bank, and let my beast of a Victron be the current regulator and my only charger? It sounds a little crazy to me too, at first--I'm going DC starter/alternator to AC into the Victron and back to DC...here's a block diagram:
View attachment 133522

So, with a dash switch I'd turn on High Power mode, allow the inverter to supply power to my Victron Multi-plus, and switch from shore power to vehicle power as the Victron's input. I wouldn't need a separate DC-DC charger, I'd just be using the Renogy inverter AC output to supply the Victron charger with input; the Victron would be the current limiter that would ensure that I get just the right amount out of the vehicle's alternators, but not too much.

So, obviously, some cons:
  • inefficiency of going DC/AC/DC to charge my house batteries--that system might only be 75-80% efficient
  • still only charges my house batteries with max 120Amp
The pro's I see:
  • price--the Renogy inverter seems to be pretty burly, and is only $315 right now (3000W 12V Pure Sine Wave Inverter), compared to the high-Amp DC/DC chargers that hover around a kilobuck
  • conceptual simplicity: only one charger on board (I kinda love my Victron); only one charging controller and system to program (Victron) [though, in fairness, there are many more simple charging approaches]
  • lower Amp: by dealing in AC, my control relays only need to handle 30Amp AC, not 200 Amp DC
  • Victron AC handling--it only passes 120Amp to the house batteries, but can pass along additional AC directly to AC loads--specifically my hot water heater. So, when I'm making a beer run from camp or driving from the trailhead back to camp, I can be charging my batteries and also heating up a tank of water (and running an air conditioner if I ever decide I need one)
So, convince me I'm crazy to try this kind of system. Don't be gentle--I need to know if I've gone bonkers and I'm missing something. Thanks!
It isn't crazy at all. In fact it is essentially an upgraded version of the concept that Dave Orton promotes.

The added control that you gain from having the adjustable charge rate on the primary inverter is potentially beneficial.

As far as renogy - well I can't honestly recommend their stuff but there are other brands out there for inverters.

Two possible additional items to consider:
  • Consider to make the battery pack 24 volts instead of 12. That will help reduce wire requirements and slightly improve efficiency - especially when running the inverter.
  • Look again at the continuous rating of the dual alternator setup in the manual - IIRC is is ~ 125 amps "sustained" but my memory is subject to error. Ford might be derating to deal with high temperatures.
If the 125 amp number is correct, then in theory you could replace the 3000 watt alternator inverter with a 1 kW one if you buy a good one vs probably needing a 3000 watt one if you buy an aims or renogy.

The victron 3000 is listed in VA - not watts, so while it is an impressive unit, it is really closer to 2500 watts if that matters.

Don't get too crazy on charge rates and imagine that 1C is really possible with those batteries. If you want to dump as much power as possible into the pack - get 6 batteries instead and stick with ~ 0.5 C. Keep in mind that not everyone who drives the van will be as aware of the details as you are, or might be tired. Mistakes will happen so plan for the mistakes, not just ideal situations.

The relay for choosing the power source (generator / grid / alternator inverter) can work but you do have to watch how the neutral / ground switch. For example:
  • a typical home plug is ground - neutral bonded at the breaker box
  • A typical honda generator is not ground - neutral bonded at all, so you have to create this G-N bond yourself
  • Some inverters are G-N bonded and some are not.
There are transfer switches for dealing with this behavior and some are more sophisticated than others. For example the Victron 5000 is substantially more sophisticated than the 3000.

Again - not criticizing at all, just a few items to double check.
 

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Discussion Starter #25
...
As far as renogy - well I can't honestly recommend their stuff but there are other brands out there for inverters.
...
  • Look again at the continuous rating of the dual alternator setup in the manual - IIRC is is ~ 125 amps "sustained" but my memory is subject to error. Ford might be derating to deal with high temperatures.
The victron 3000 is listed in VA - not watts, so while it is an impressive unit, it is really closer to 2500 watts if that matters.

The relay for choosing the power source (generator / grid / alternator inverter) can work but you do have to watch how the neutral / ground switch.
...
harryn, thanks so much for the reply. Very good points on the VA vs watts, grounding of relays, and other points.

Any recommendations for a reliable 3kW inverter? I still think the most I'd ask from the inverter in the real world will be 200A ([email protected] 13.0V).

For the rating of the dual heavy duty alternators, I keep re-reading the BEMM (2020 version dated Jan 2020), and get something new each time. I've been through the electrical section at least 6 times! This time, I searched for the 2 instances of "sustained" and the 104 instances of "alternator", and came away with what, in 2020, seems like a relatively squishy recommendation on max continuous alternator rating (emphasis all mine):
  • Table page 81, engine state "engine run loads," Power Usage "very high continuous PTO (power take off)," "up to twin alternator capability," the Recommended Specification includes "using the load-shedding system...up to alternator limit...consider using Third Party High Power mode."
  • Page 83, "High electrical loads should also be grounded directly to the vehicle body and not the negative battery terminal"
  • Page 85, "Any peripherals added to the power supply must be connected in one of the following ways:...Up to alternator limit - direct from battery, when controlled using load-shed signal and Third party switch For loads greater than 175A (CCP2) or 200A (FPBG), up to 240A can be connected from the battery cable for short term use, less than 2 minutes."
  • Page 89, "In the event a current requirement greater than 175A but less than 250A peak loading (maximum fuse value third party installed), connecting to the rear battery +12V clamp 6mm stud is permitted in conjunction with a disconnect relay controlled by the load-shedding signal."
  • Page 90, "For a long duration (greater than one hour continuous), the fuse must be no higher rating than the alternator fitted to the vehicle...For long duration continuous power applications such as High Power Inverter, the Mega fuse must not exceed the rating of the alternator fitted to the vehicle. The alternator saturation voltage must be above 13.0V when testing full load"
  • Page 91 figure E294170 shows "3rd party" cable wired to + battery terminal
  • Figure E284685 shows that the peak alternator torque (gas engine, 250A-rated each) comes at alternator RPM between 1900 and 3200; that is engine RPM between 700 and 1200 per note on page 109, "For equivalent engine revs per minute (rpm), the alternators revolutions, axis (B) should be divided by the following factor: 2.7 for Gas Engines."
  • Figure E183977 shows "alternator output" [I take this to mean "alternator limit" as used in previous paragraphs] at different temps by alternator RPM; 700 engine RPM (1900 alternator RPM) looks to be between 125-155A per 250A alternator; 2000 engine RPM (5400 alternator RPM) looks to be between 180-255A per alternator.
They say a lot of limits--"alternator limit", "240A for 2 minutes", "250 amps peak". "Alternator limit" isn't precisely defined, but it seems to indicate that the performance is what you'd expect: dependent on RPM and alt. temp. It's confusing to me, because they say "up to the alternator limit" in a couple places, which could mean over 500Amp in some conditions; but, they also say "240A for 2 min" and "250A max." I'd never try a crazy 500 Amp load, but it still seems confusing that, in the same manual, they wouldn't just put the actual limit, worded in the same way, in every section; or, chop off the alternator performance graphs at the vehicle upper limit (at least a horizontal line to show where the alternator performance exceeds the vehicle limits).

So, what are my current (pun intended) conclusions? I'm open to input--I can't claim that I fully understand the BEMM...
1. My plan is to use real-world data to sneak up on my actual limit. That is, I'll keep monitoring voltage and alternator temp at increasing loads on some hot days this summer, and find how far I can go while still keeping my alts below 220F and the voltage above 13.0. Based on the BEMM, assuming 60A vehicle loads with my AirCon and stereo blasting on a hot day at idle, my dual alternators when hot might only be able to provide the inverter with 190 Amps (or less) total. Whatever I find, I'll back off of the max for some safety margin. If I get really slick, I'll build in a temp control relay--above an alternator temp of 220F it shuts off the inverter and tells me with a buzzer that I should be boiling water with the summer sun rather than electricity!

2. Inverter Hookup: positive to the + battery terminal, - to the body (probably multiple points), and use a load-shedding relay to shut off the inverter load if the vehicle decides it isn't liking it.
 

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No question the BEMM is inexcusably confusing. It would be great if one of the electrical engineers on this forum would chime in and tell us what it all means (or if it is gibberish to them as well).
 

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If it is anything like past Bemm commentary the best you will get are semi educated Bemm guesses.

You are on your own.

Be happy, The 2020 Bemm is more complete then any of the other year Bemm.
 

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Why not just get a 400 amp alternator to battery charger? Manufacture link below, distributors are about $100 cheaper. It is rumored that the Sterling dc to dc chargers have an ac component internal making it really a dc-ac-dc charger in the end.

 

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Discussion Starter #30
Why not just get a 400 amp alternator to battery charger? Manufacture link below, distributors are about $100 cheaper. It is rumored that the Sterling dc to dc chargers have an ac component internal making it really a dc-ac-dc charger in the end.

That's a good thought sportcoupe. I am still considering those Sterling models. The negative I see is that I'm pretty sure they don't have current regulation built in. So, I'd have to go with a 400-Amp with some kind of additional current regulator, or a 200-Amp. And, as I mentioned above, there might be cases when I really want to limit myself to 190 amp or less--I'm a little too much of a scientist to not want to do some real-world test conditions to characterize my particular vehicle. What I like about the Sterling is the remote. The Sterling manual seems to have been written by someone who used to write the Ford BEMM, but was fired for being too confusing even for Ford. (In fairness to Ford and Sterling, I am acutely aware that the best engineers are usually terrible writers, and decent writers are usually terrible engineers--manual writing is a rare skill for which almost no company will successfully hire and train.) But, I think I gathered that you can use their remote to set whatever "charge" and "float" voltage you want. So, if I want to treat my batteries gently, I can be conservative with my charging. Too bad it doesn't seem to have the one extra function that I'd really need to treat my alternators and vehicle wiring gently--adjustable current regulation. It seems a little hard to believe, since their electronics are very capable of pulling the source down to whatever voltage they need.

I'll send them an email to confirm--maybe there is some trick to use the remote to limit current that I'm just not picking up in their manual. I'll share their response here; they've been responsive to me before, so I'll wait a few days to see what they say.
 

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I'll send them an email to confirm--maybe there is some trick to use the remote to limit current that I'm just not picking up in their manual. I'll share their response here; they've been responsive to me before, so I'll wait a few days to see what they say.
Sterling's very fast and very succinct response to "can you control current with the AB12400" was "No there is not."
 

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As far as the 12 V (-) return path, my speculation is that they suggest using the vehicle ground path because that is what the (-) of the alternator is tied to. (the alternator mount stud). I really don't like using the vehicle as the (-) path due to historical reasons, but it might make sense to consider running a heavy wire to the alternator mount like the audio people do.

Inverter - if you mount the inverter under the hood, then your earlier idea of using a high wattage rated inverter might be better than my earlier suggestion because they de rate at higher temperatures - at least 40%. Maybe just use another victron 3000? Otherwise magnum or outback make good inverters. In fact I think that outback makes some sealed models IIRC.

The load capability of any system is always a balance of things. Standard vs factory vs 3rd party wire upgrades, pulling from as close to the alternator as possible, built in relays, etc.

Mechman alternators has some good example resources for things that people have done to enhance vehicle wiring and installations.
 

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Discussion Starter #33
As far as the 12 V (-) return path, my speculation is that they suggest using the vehicle ground path because that is what the (-) of the alternator is tied to. (the alternator mount stud). I really don't like using the vehicle as the (-) path due to historical reasons, but it might make sense to consider running a heavye ch wire to the alternator mount like the audio people do.

Inverter - if you mount the inverter under the hood, then your earlier idea of using a high wattage rated inverter might be better than my earlier suggestion because they de rate at higher temperatures - at least 40%. Maybe just use another victron 3000? Otherwise magnum or outback make good inverters. In fact I think that outback makes some sealed models IIRC.

The load capability of any system is always a balance of things. Standard vs factory vs 3rd party wire upgrades, pulling from as close to the alternator as possible, built in relays, etc.

Mechman alternators has some good example resources for things that people have done to enhance vehicle wiring and installations.
Yeah, I was thinking of at least running the inverter to multiple vehicle ground points, if not all the way to the alternator. Inverter is going to be mounted right next to the driver pedestal, to make the + cable run about 2'; I think the closest vehicle ground point might be the brake lever bolt, but I haven't studied that part of the BEMM yet. I can wage at least a little battle, if not a war, against ground loops and poor - connections with at least a couple of runs of heavier gage wire to other grounding points to tie them together better.

But that brings up another point that Orton made when he did his DC-AC-DC setup--completely isolate the house batteries, and don't rely on vehicle ground for the house bank. I can't say I'm a fan of relying on the chassis...
 
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