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Discussion Starter #1
Equipment: 2020 Transit, factory dual alternators, factory dual 70Ah AGM chassis batteries, factory aux fuse panel, qty=5 parallel house BattleBorn 100Ah LiFePO4; my (new) build thread here Shirley the bicycle adventure van; garage-able pop-top all-electric build thread

My overall goal is simple: on a quick beer run from camp, I’d like to dump as much current into my house batteries as the alternators will manage (that is, get the greatest possible value from my high-current LiFePO4’s and my $845 upgrade to dual alternators and aux fuse panel). My house battery pack would be very happy with a 1C (500 Amp) charge rate for awhile, and .5C (250 Amp) indefinitely, though I completely understand that even 240 Amp total (120 Amp per alternator) for more than some number of minutes (maybe just 2 per the BEMM?) might overheat the alternators (and, 240 Amp might mean way more copper than I want to run).

My first design was to do alternator charging of the chassis batteries and my house battery bank with a Sterling alternator-to-battery charger (130, 210, or 400 Amps--as much as I can get out of my alternators). I was ready to precisely follow the Sterling schematic (Fig 8 here https://www.sterling-power-usa.com/library/Alternator to Battery Charger Owners Manual and Installation Instructions for model AB12130.pdf), and run new alternator + and - wires and an alternator thermocouple through the firewall directly to the alternators; and, connect the Sterling charger directly to the chassis batteries and my house batteries.

But then I did some more reading:
- 2020 BEMM 2020 OEM Wiring Diagram Manual
- @Vanpakr recommendation on B2B system: Dual alternator / dual battery in 2020 camper
- @Vanpakr info on “magic switch” to use Third Party High Power Mode 2020 dual alternator option. Anyone have it?
- Dual batt charging: Separating the dual batteries
- info about limited electrical system diagrams in the BEMM 2020 OEM Wiring Diagram Manual

I ended up feeling like following the Sterling schematic bypasses a lot of “smarts” installed at the Ford factory: the chassis battery pack has a Ford BMS; I think I understand that the alternators already have factory-installed thermocouples and some kind of charging management system; and, there are already power wires coming through the firewall from the alternators that I’d guess are rated for full current from the dual “250 Amp” alternators. The BEMM seems to indicate that the “Ford approved” way (figure E289272 page 89 of the Jan 2020 version) to hook up upfitter house batteries and charging differs significantly from the Sterling schematic.

So after all that preamble, I get to my questions for the experts:

1. What’s the best way to get the most out of the factory-installed dual alternators? Am I reading this right, that CCP2 (175A) or FPGB (200A, Ford Programmable Battery Guard GEN2, A540), and some kind of switching to turn on Third Party High Power Mode, is the most I can expect to get from dual “250 Amp heavy duty” alternators? I’m looking at BEMM section 4.5.3, page 85...

2. If that’s how I do it, what’s the best way to get a current-limited 200A (or 175A) max load to charge my LiFEPO4 house bank, and ideally allow me to pick a charge profile of 20-minute-minimum 14.3V bulk and 13.5V float? And, switch on High Power Mode if/when needed?

4. And then, going the other way, to allow my house batteries to top off my starter batteries, I think I understand that something like this simple device would work, connected from my house loads to the chassis ground and under-hood charging point (or maybe there’s a place more convenient?): Ultra TRIK-L-START Starting Battery Charger/Maintainer. Am I missing something simpler or more effective to ensure that my chassis batteries are always ready to go using my massive house bank?

I know that’s a lot of content and questions in a single post--thanks in advance for any help you can provide! Hopefully the answers will be helpful to more folks than just me, looking for advice on getting the most out of (and into) the factory systems that are (kinda) new for 2020.
 

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I ended up feeling like following the Sterling schematic bypasses a lot of “smarts” installed at the Ford factory: the chassis battery pack has a Ford BMS
There are other Sterling models that do not bypass Ford's battery charging "smarts", One model charges house batteries at 120 amps and two of these same models can be wired in parallel and charge at a total of 240 amps.


What are you going to do with all of this battery power? Run electric heat or air conditioning?
 

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Discussion Starter #3
No propane, no solar, so we have electric hot water, electric cooking, lights/fan/entertainment, and up to 3 days without shore power or driving. No AC at this point--not sure we'll really need it in the mid-/southwest, but it isn't out of the question as a future upgrade depending on how everything works and where our trip plans take us.

Thanks for the tip on the ProBatt-C
 

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Keith, congrats on the new van! Funny, you and I have been chasing the exact same idea. Unlike you, I intend to install solar panels. Everything else in our intended interior build is very similar. We ordered the same factory options on the van regarding electrical systems, and we hope to avoid propane. Our order has been on hold for a few months waiting for the power sliding door.

I have read the BEMM cover to cover once, and I'm now in the process of going back through it. Maybe it's just me, but I don't find it particularly easy to read. I'm a mechanical engineer, and I wish I had paid more attention during my couple electrical engineering courses. Ha!

My current, tentative plan is to connect a battery-to-battery charger to CCP2. We ordered the push-down parking brake, so the FPBG wasn't an option for our order, and I don't think it can be retrofitted in our case. Therefore, I'm leaning toward the Sterling 120-A battery-to-battery charger (12v to 12v Sterling Power ProBattC IP68 BBW12120 waterproof DC input battery to battery charger). If that ends up being insufficient, I can later add their 60-A version in parallel for a total of 180 A. That should be close enough to the 175-A rating of CCP2.

Out of curiosity, which hot water heater and stove are you considering? I haven't researched hot water heaters yet. Regarding electric stoves, I’m leaning toward one of the True Induction induction stoves. I'll most likely go with the Mini Duo, which is rated at 1800 W (Mini Duo Induction Cooktop). I would love to hear your ideas!
 

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Discussion Starter #5
@CincyBearcats , great minds think alike! I haven't quite read the BEMM cover to cover, but I'd agree that it isn't exactly an easy read. But, I'm starting to get used to the format and density of information, and will probably end up reading some key sections enough times that I'll be able to quote it verbatim soon!

Using that Sterling to CCP2 is probably something similar to what I'll do--I like the idea of paralleling a 60A with the 120 Amp. Are you going to do something to top off the chassis batteries with the house batteries also?

I've already got my water heater, and I used it this summer in my outdoor kitchen at my house--https://pantherrvproducts.com/isotherm-isotemp-601623-slim-square-4-2-gal-16l-electric-hot-water-heater/. It takes the better part of 1kWh to heat 4 gal up to hotter-than-you-need, and uses a mixing valve to make 6-ish gallons of just-hot-enough. The idea is to roll into camp the first night with full alternator-charged batteries, and some spare energy stored in the form of 160 deg F hot water. I'll be putting it on a timer switch, so I can turn it on for 30 or 60 minutes (before showering or doing dishes), but then not keep it on constantly.

For cooking, we'll probably take different appliances depending on our mood and space available, choosing from a combination of an immersion circulator, electric kettle, an insta-pot (on some trips--its kinda bulky), and an induction cooktop. I haven't researched induction cooktops yet, so I can't share any knowledge there. That Mini Duo looks cool though! I'm harboring an idea of having the ability to cook and use the kitchen sink both indoors and outdoors (under the awning), but my design isn't really final yet.
 

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I'm building a setup that is much smaller so I have no direct experience with your particular design. But I have become familiar with the BEMM and it is says you can connect a load (charger in this case) directly to the 12v+ battery lead as long as it is switched via a relay of the load shedding signal. It also states the load can be "up to alternator capacity". Obviously you would want a breaker to protect the wiring. It was not clear from my reading of the BEMM how the vehicle's charging system would react to that load regarding things like auto start/stop. I would think a large load would pull the voltage down on the coach batteries if the alternators stopped. I'm guessing the charging system would not allow start stop under a heavy load. I have seen a video of an F-150 where start/stop was cancelled as soon as a trailer with a 7 pin connector (or even a tester) was hooked up.
 

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The idea is to roll into camp the first night with full alternator-charged batteries, and some spare energy stored in the form of 160 deg F hot water. I'll be putting it on a timer switch, so I can turn it on for 30 or 60 minutes (before showering or doing dishes), but then not keep it on constantly.
If you insulate your hot water tank with 3 inches of high density foam, you will use a lot less energy for your hot water heating, and you won't be bleeding that unwanted heat into the living space.
 

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what’s the best way to get a current-limited 200A (or 175A) max load to charge my LiFEPO4 house bank, and ideally allow me to pick a charge profile of 20-minute-minimum 14.3V bulk and 13.5V float?
Great post keitho with well formulated questions. Please keep this thread updated as you figure things out. Regarding the above quoted part of your questions, Sterling sent me the following:

"We’re presently developing a bidirectional B2B that can do 12-12V, 12-24V, 24-12V or 24-24V at any current (in intervals of 5A) from between ~10A to 200A. To confirm, that will be 200A to 200A at both 12V – 12V and 24V – 24V. It hasn’t reached full production yet, but it is in active research and development. The core of it works, we just need to polish software and then get it through to production."
 

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Discussion Starter #9
My current, tentative plan is to connect a battery-to-battery charger to CCP2. We ordered the push-down parking brake, so the FPBG wasn't an option for our order, and I don't think it can be retrofitted in our case. Therefore, I'm leaning toward the Sterling 120-A battery-to-battery charger (12v to 12v Sterling Power ProBattC IP68 BBW12120 waterproof DC input battery to battery charger). If that ends up being insufficient, I can later add their 60-A version in parallel for a total of 180 A. That should be close enough to the 175-A rating of CCP2.
You don't happen to know if you can use one of their remotes to control two parallel B2B, do you?

If you insulate your hot water tank with 3 inches of high density foam, you will use a lot less energy for your hot water heating, and you won't be bleeding that unwanted heat into the living space.
Definitely a must! I was planning on at least a couple inches of XPS built into the cabinet...
 

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...
Are you going to do something to top off the chassis batteries with the house batteries also?
...
I've already got my water heater...
...
Thanks for the very detailed reply!
With the dual AGM starter batteries, I'm hoping that I won't ever need to use the house batteries to top them off. At one point, I was considering the Votronic Triple charger (combined mains/B2B/solar MPPT charger), and it has this capability built in. The Votronic Triple charger is a really fantastic device in an affordable, small package. Unfortunately, it can't handle an electrical system as large as I anticipate needing. For example, its largest version can do just 60 A of battery-to-battery charging.

You don't happen to know if you can use one of their remotes to control two parallel B2B, do you?
I don't actually know. Further, I don't know for sure that they can be used in parallel. However, it sounds like the new charger under development at Sterling is our best option. I hadn't heard of that until Ken mentioned it.
 

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Sterling sent me the following:
"We’re presently developing a bidirectional B2B that can do 12-12V, 12-24V, 24-12V or 24-24V at any current (in intervals of 5A) from between ~10A to 200A. To confirm, that will be 200A to 200A at both 12V – 12V and 24V – 24V. It hasn’t reached full production yet, but it is in active research and development. The core of it works, we just need to polish software and then get it through to production."
Ken, do you have any further details on this? Do you know when it might be available? Whom should I contact at Sterling to get more information? I'm very interested in this device. It sounds like the perfect solution for our situation. Thanks for sharing!
 

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Ken, do you have any further details on this? Do you know when it might be available? Whom should I contact at Sterling to get more information? I'm very interested in this device. It sounds like the perfect solution for our situation. Thanks for sharing!
No more info. That was the full reply from Sterling.
 

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It is always a balancing act.

____
On the battery pack end, a good target charge rate for LiFe packs is ~ C/2 (max), which is consistent with what multiple mfgs suggest.

Each BB battery is ~ 1 kW-hr, so (5 batteries) x (1 kW-hr) / 2 ~ 2.5 kW max charge rate on the battery side.

____-

I need to look again but I think that the sustained amps out of the dual 250 amp alternator system is ~ 125 amps x 12 volts, so ~ 1.5 kW.

Might be wrong, but that is what is in my mind at the moment.

____

On the efficiency side, you are nearly always better off taking as many efficiency hits as possible during the "charge cycle" when there is plenty of power around, vs on the discharge side when you are limited to what is in the batteries already.

In high load situations, running a higher battery pack voltage is nearly always more efficient than a typical 12 volt battery pack voltage. It also helps with keeping the batteries balanced if they are in series vs parallel.

That is why for higher powered systems (2 kW and up) we use 48 volts and for 1 kW applications we use 24 volts. 48 volt systems are a bit tricky but 24 volt systems use exactly the same components that you would normally use in a 12 volt system. Using them at 12 volts is a good idea, but you are not getting your money's worth.

Most appliances are available in 12 or 24 volts, some are dual. For the few that aren't - just use a 24 - 12 volt converter. Will give better results.

Boost that voltage up as soon as you physically can and life will be easier.

I have no idea why someone would need bi directional operation in a small system like a sub 10 kW-hr van aux battery pack but who knows.


The Orton method (alternator / battery pack ) - inverter - charger - (aux battery pack) might be interesting for a project like this. Certainly reduces the wiring requirements front to back of the van.
 

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Along these lines I have heard of people using heat exchanger hot water heaters where once taps into the engine coolant lines to heat water. They time their showers to just after they drive and insulation keeps the water fairly warm. Better to use energy that would otherwise be effluent than valuable battery power. In a way it's like having another battery bank dedicated to hot water made out of hot water.
 

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Discussion Starter #16
Along these lines I have heard of people using heat exchanger hot water heaters where once taps into the engine coolant lines to heat water. They time their showers to just after they drive and insulation keeps the water fairly warm. Better to use energy that would otherwise be effluent than valuable battery power. In a way it's like having another battery bank dedicated to hot water made out of hot water.
My electric HW heater has that capability, but I wasn't planning on using it, at least during my initial build. I'll have to see how we actually use our camper, and if the extra effort and complexity of running coolant lines back to the hot water heater might be worth it. The thing for me is that, when the engine is running and could be heating up coolant and heating water, it is also running two alternators and charging batteries, which is heating water--both ways puts energy into the hot water tank. The resistive heating element is less efficient, but it is easier for me to wrap my brain around running a wire vs running coolant lines!

Correct. Way too much to concentrate on at 8am Saturday morning. I don't think that hard at work 9-5.
I concentrate WAY more on my van build than I ever do at work! I thought that was the idea!
 

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keitho since you have used your water heater, do you have a feel for how long the water would stay hot if it is just sitting?
 

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Discussion Starter #18
In my outdoor kitchen, I didn't have it insulated, and it was plugged in to mains power. Even so, when I unplugged it after using it, a couple times i went back after a couple hours and it was still "shower hot". I'll get a lot better idea when I have it in the van, insulated, and am a lot more cognizant of power use when boondocking--sorry I can't give real-world info now. I choose the heater based on this article (and others, I can't find links at the moment) about of real-world use, which might be a lot more useful than my pre-installation testing: Hot water options in an electric van
 

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Discussion Starter #19 (Edited)
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

Equipment: 2020 Transit, factory dual alternators, factory dual 70Ah AGM chassis batteries, factory aux fuse panel, qty=5 parallel house BattleBorn 100Ah LiFePO4; my (new) build thread here Shirley the bicycle adventure van; garage-able pop-top all-electric build thread

My overall goal is simple: on a quick beer run from camp, I’d like to dump as much current into my house batteries as the alternators will manage (that is, get the greatest possible value from my high-current LiFePO4’s and my $845 upgrade to dual alternators and aux fuse panel).

...
So after all that preamble, I get to my questions for the experts:

1. What’s the best way to get the most out of the factory-installed dual alternators? ...

2. If that’s how I do it, what’s the best way to get a current-limited 200A (or 175A) max load to charge my LiFEPO4 house bank ...

4. And then, going the other way, to allow my house batteries to top off my starter batteries...
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:
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!
 

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I would love to see you just go for it and see how it all works out, but I do think you are a bit delusional when you list "simplicity" as an advantage. This probably sounds sacrilegious, but a simple system would just incorporate a separate 3kw generator and a strong inverter/charger that has configurable charging output. Sometimes old school makes sense.
 
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