Charging - Auxiliary Alternator vs. DC-DC/B2B. Which is Better?

[Vance Vanz]

Hi All,

I wanted to provide some follow up information that may be helpful to those who decide to go with an auxiliary alternator. This is just from my experience, which may not represent what others have encountered, but I think it is also important to speak to the customer service vendors provide. This is not intended to start a wildfire of bashing on vendors while also derailing the original intent of the thread, so please do not take it down that road.

American Power Systems:
They spent quite a bit of time with me on the phone, answered all of my questions, have 12, 24 and 48V output voltage options and will also incorporate the Balmar MC-614 or the Wakespeed WS500 alternator regulator in their package.

Nations Alternators:
Called and sent emails, several times, to both their sales staff and their more tech savvy guy and did not get a response. Poor customer service.

 

[vtsoundman]

That has been my experience as well (Nations vs APS).

Sent from my Pixel 4a using Tapatalk

 

[mechengrsteve]

Hi All,

I will be starting my complete build this coming winter 2022, similar specs to an EarthRoamer LTi. We will eventually be traveling from Alaska to South America if COVID permits-full time living in the rig for 18-24 months.

I have already read many of the threads in the “Power Systems” section of this forum and did a bit of digging online. Maybe I already know the answer to my question (Auxiliary Alternator is the best choice given my power system), but I would like some additional clarity on the pros/cons, or which is better, related to charging a 900Ah lithium battery bank using an additional auxiliary alternator or a DC-DC/B2B charger.

I’ve already owned a camper van with a similar off grid power system, slightly smaller, and it had an auxiliary alternator. I know most of the custom build shops in the campervan industry pretty much only run auxiliary alternators for lithium offgrid power systems. It appears that most DIY’s in the Expedition Portal prefer/are running the DC-DC charges. Given my power requirements, and need to primarily charge when driving, I’m assuming the auxiliary alternator is best. Please educate me if I’m missing something.

Truck:
2022 F550 Lariat, 7.3L Gas, 397A dual alternator, 78A dual battery.

Significant Electrical Specs-Camper:
900Ah lithium battery bank, 12-1,300W solar, A/C unit, Induction cooktop, fridge/freezer, combo microwave/convection oven, puck/under cabinet lighting. Heating/hot water will be off of gasoline (Rixon unit) from the truck, or shore power if present. No generator or LP. This will be an offgrid system, all electric, except for the few items noted coming off of gasoline. We are not planning on using much if any shore power.

Auxiliary Alternator:
I’m currently looking at the Nations kit, 280A [$1,999] or 370A [$2,199] alternator, which comes with a MC-614-H Balmar regulator/temp sensor and all the additional/needed mounting brackets, belts, etc. I’m open to other alternators/kits that anyone may be aware of and recommendations on the 280A or 370A noted above.

DC-DC/B2B:
It appears Sterling (Waterproof 12-12V 120A IP68) has the highest rated DC-DC/B2B charger, 120A, and you can wire two of them together to get a total of 240A [$625 x 2 = $1,250]. I’m also open to other/higher rated DC-DC/B2B charges that anyone may be aware of.

Thanks in advance for your time and wisdom !

I have a dual alternator system with the second running a 220A/24V to my 17kwh Nissan leaf Battery bank. I have some prejudices against the Balmar reg. Got one sitting on my desk in front of me and not in my truck....Instead of typing along string, I will refer you to some of my YT videos, and blog....there is also a separate forum here that is just about dual alts/lithium in which I have posted thoughts. My short thoughts; finding an OEM 2nd alternator 'take-off' from a wrecked truck is what I typically recommend. It will be far cheaper and spares more intenationally available if you need it. Search eBay for your truck years (not sure what the 2022 overlaps with) using 'second alternator' to find someone scrapping one out and offer to buy 2nd alt system as a kit. Since you ahve a newer truck, you will also be victim to the 'variable voltage' alternators on newer trucks. I would not think letting the ECU run your 2nd alternator is good for you power produftoin but this also means, operating the 2nd on a separate power system, totally separate from the vehicle. I like B2B but due to the power you want, am not that hot on them. I use my 2nd alt as a backup (950W solar is primary) so maybe you might want to truly consider if you need a back up at this much capacity. If you want to stay with 12V, you end up with huge amperage and heat generated in the alternator. Any possibility going to 24/48V? you can get 2x-4x the power out of the same alternator at the same amps. Slinging a lot of amps around is a pain. I think that using the 2nd alternator completely separately form you primary is a good idea as it permits more efficient connection to the battery (so you can use a charging regulator) and not potentially interfere with your vehicle operation.

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My YT channel has build videos. See 'workingonexploring' some links are in the above blogs.

 

[Vance Vanz]

Hi All,

I thought I would come back around and provide some additional information that may be helpful to others.

I ended up going with a Nations third alternator kit, separate from the factory alternators, for the 810Ah lithium house battery bank. A Wakespeed WS500 alternator regulator will be used for the third auxiliary alternator. Nations and American Power Systems were the only two vendors I could find that provide a kit for the 2022 Ford F550's running a 7.3L gas engine. Leece Neville, US Alternators, Mechman and Balmar Alternators were not options.

Per the Ford Builders support line, the 2022 Ford Lariat F550 7.3L gas has two alternators standard from the factory. The primary alternator is 240A and the secondary is 157A, a total of 397A. Under normal conditions, there is roughly 90-100A’s in reserve for the alternators. If ambient temp is high, air conditioner is on, defrost/heaters are on during a cold day, auxiliary devices are being used, etc., this reduces the 90-100A reserve. They don't recommend pulling more than 50-60Amps off the factory alternators from a DC-DC charger(s)/auxiliary device. You might be able to get away with pulling 80-100 amps from a DC-DC charger, but if other factory systems/loads/conditions noted above are on, the truck may/will start shutting down factory loads/components.

I also inquired about upsizing the factory secondary alternator, so the factory power system and house power system could be charged by just two alternators. I could not get a straight answer from anyone (Ford Builders Support line, Ford Dealers, Nations Alternators, American Power Systems) on how to do this to ensure there would be no issues or alarm codes on the truck.

All the best!

 

[john61ct]

That's going to be a fantastic electric powerplant. With a high-Ah LFP House bank, will support lots of mod cons, big freezer, all electric galley...