High voltage alternator

CappyJax

Member
I keep finding that charging a 48V battery bank from the alternator is quite the challenge on many vehicles. Stock alternators maybe give you 2500watts max, then you have to convert it. I was thinking what if we exchanged the stock alternator with a high voltage alternator like 56V 60V or 72V and 100+ amps to give us something closer to 7500W. Then dumping that into an MPPT controller to charge your battery bank. A 48V to 13.8V converter would then be used to recharge the chassis battery and provide for the vehicle loads.

What do you all think about this idea?
 

NatersXJ6

Explorer
I’m guessing you will have challenges transmitting 7.5 kW through a regular automotive style serpentine belt and might need another drive system. Finding the brackets and pulleys might require so much customization that you cost yourself a fortune and end up with a non field-repairable alternator. It feels like a step away from reliability.

Maybe if it was PTO driven?
 
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CappyJax

Member
I’m guessing you will have challenges transmitting 7.5 kW through a regular automotive style serpentine belt and might need another drive system. Finding the brackets and pulleys might require so much customization that you cost yourself a fortune and end up with a non field-repairable alternator. It feels like a step away from reliability.

Maybe if it was PTO driven?

How much power can you transit? This is far a sprinter and they already make a 5,000W second alternator kit, so add that to the stock alternator, and that is close to 7,500W. Is the limit based on each individual pulley?

PTO won’t work as this is for recharging the house batteries while driving.
 

Alloy

Well-known member
What are you running that you'd need 7.5Kw of charging?

 

CappyJax

Member
What are you running that you'd need 7.5Kw of charging?

Battery charging.

I am aware of the 48V alternators. They are ridiculously expensive. Here is a 56V alternator with 75% more power that is less than 1/3 the price. https://enginepartssuperstore.com/Category/MG976/Mahle-New-Alternator-AAN8217-56V-150A/

I am planning a 20kWh pack in the sprinter, but when I build my F550 Expedition vehicle, it will have a 40kWh pack.
Fwiw.
7.5kW is basically 10 horsepower.
Probably need a cogbelt to work even if
space is available for that giant lump of copper.
Assuming a PTO is available for the chassis, that could work.
Otherwise, perhaps drive from the crankshaft. Fit the alternator on the front bumper like a concrete truck does for its hydraulic pump.

I did some research and I see what you are saying. Max wattage is generally around 750W-1000W per rib on the belt. i guess that limits me to a 4500W to 6000W max alternator.
 

CappyJax

Member
The other way I was thinking of doing this is to simply have a 120V inverter that sends AC back to the inverter charger generator input. I would be limited to the max idle output unless I had someway to increase the inverter load with RPM. The would probably limit me to about 3000 watts with dual alternators.
 

NatersXJ6

Explorer
. Fit the alternator on the front bumper like a concrete truck does for its hydraulic pump.

I think I’ve seen fire trucks do similar with various pumps.

Even if this was impractical, it would definitely be geek-chic cool! 😎

Bonus points if you incorporate a winch and air compressor!
 

MontySquareo

Active member
Get a 56 volt alternator and keep your factory 12v alternator. If your van doesn't have rear a/c you can mount your extra alternator there. If your belt isn't big enough to turn the alternator at full load, somehow keep your batteries/charge controller from drawing full alternator load.
 

1stDeuce

Explorer
It seems the FAR easier solution is not to run a 48v house battery setup... ??? If the chassis is 24v, that would work fine but why 48V on an auto/RV chassis? It would be better for running A/C, but for how long?? I don't get why you would want a 48v house battery setup in an RV, so some enlightenment for me might be in order...

If you must run a 48v house setup, then the correct charging voltage would be 56v, so that alternator could charge the house batteries directly, which I think is what you were suggesting.

I'm not sure an MPPT charger is going to like charging the 12v chassis batteries though... Most have a top limit to what they can handle for input, and your high amp/voltage alternator is going to be able to roast the charge controller if there is 12v demand...

Why not add the 56V alternator as a second alternator and have it ONLY charge the house batteries while letting the stock alternator charge the chassis batts.

I still think not running a 48v setup is the real answer, and it lets you easily emergency jump the chassis using the house batteries, which is nice...
 

Jogrnot

New member
Having a 48V or 56V alternator system, that would also support the existing 12V is perfect for charging EV bike batteries, induction stove, heater, ETC. I understand that the new Cyber truck has a 48V architecture, so we'll see soon enough about the potential downsides.
 

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