2nd alternator

[avanti]

As I see it, your decision is pretty simple:
The prudent thing to do is to consult the OEM's upfitter's guide (or whatever Ford calls it); find out what they allow; and follow that advice. Far better to follow the advice of the engineers who designed the system over Some Guy on the Internet, such as myself.

As Booster suggests, this begs the question of how to automatically limit the current to the allowed amount. This is typically done using a DC-DC converter. Lots of people seem to use Sterling products for this purpose, although I have no direct experience. I would simply install the proper limiter and live with the consequences. You will soon find out whether or not you really need a second alternator.

 

[@Michael]

I have a 2017 Ford Transit with the heavy duty alternator and dual AGM chassis batteries, and have read most of the Ford builder documents. Ford has provisions for supplying customer accessible charging capability at high amperages.

Avanti, do you think continuously pulling 40-60 amps from the 2019 Ford Transit Heavy Duty 250 amp alternator would be too much of a continuous load for it to handle?

No. Not with a Ford Transit and the Heavy Duty Alternator.

This should translate to about 40-50 amps at 12 volts from the alternator needed to run to a 1,500 watt inverter to power the 5,000 BTU window air conditioner. Do you think this is long term sustainable on the 250 amp alternator? I can pull the 40-50 amps from the Ford CCP terminals.

Ford puts three 60A terminals for customer use for a reason, and I know that Jon and others are drawing more than 50A from them.

I changed to a 120 amp vehicle charger (with pain-in-the-butt larger wiring) and now I can run my rear rooftop AC with the HD alternator without running my battery down.
It's as good as having a second alternator.

--Mike

 

[avanti]

I have a 2017 Ford Transit with the heavy duty alternator and dual AGM chassis batteries, and have read most of the Ford builder documents. Ford has provisions for supplying customer accessible charging capability at high amperages.

How many amps do they permit?

 

[markopolo-ClassB]

2016 BEMM here: https://faroutride.com/wp-content/uploads/2017/03/Ford-Transit-BEMM-2016.pdf


Page 111, 250A possible. 180A seems almost routine (with the right setup).


Surprising but it's all detailed in the BEMM.

 

[avanti]

2016 BEMM here: https://faroutride.com/wp-content/uploads/2017/03/Ford-Transit-BEMM-2016.pdf


Page 111, 250A possible. 180A seems almost routine (with the right setup).


Surprising but it's all detailed in the BEMM.

Wow. That's fantastic. This is pretty strong evidence that the vehicle was engineered to support this kind of thing. Makes the Sprinter look wimp. I wouldn't hesitate to follow these guildlenes, absent specific evidence that it causes issues.

One note: The referenced document is from 2017, which was before the Transit update. They may well have re-engineered the charging system since then. It is possible that there are more restrictions in current production. I am guessing not, though.

This is good news.

 

[LostInWoods]

One note: The referenced document is from 2017, which was before the Transit update. They may well have re-engineered the charging system since then. I is possible that there are more restrictions in current production. I am guessing not, though.

I found the link (again) to the 2020 BEMM and it looks like this has been slightly modified (page 49):

"The previous 3 x Customer Connection Point (CCP) with 3x 60A fuses is replaced with a 1x 60A 'CCP1' power at all times stud and a 1x 175A 'CCP2' controlled stud."

https://madocumentupload.marketinga...bafecd216103ffdd3b4a3dc276fc3aa23e5a&v5=False

 

[@Michael]

2016 BEMM here: https://faroutride.com/wp-content/uploads/2017/03/Ford-Transit-BEMM-2016.pdf

Page 111, 250A possible. 180A seems almost routine (with the right setup).

Surprising but it's all detailed in the BEMM.

I think the intent is that the upfitter test the setup thoroughly:

The alternator
saturation voltage must be above 13.0V when
testing full load. AGM battery twin system
(OW5) must be fitted to the derivative. See
'Single and Twin Battery System' and 'Power
and Connectivity Usage Recommendation'
table in this section of the BEMM.

• A higher ampere alternator must be fitted if
long duration (greater than one hour) high
loads are required. See 'Single and Twin
Battery System' and 'Power and Connectivity
Usage Recommendation' table in this section
of the BEMM.

My read is the with the heavy duty alternator and twin AGM start batteries you can draw at high amperage (180A) as long as the alternator stays above 13 volts.

 

[booster]

2016 BEMM here: https://faroutride.com/wp-content/uploads/2017/03/Ford-Transit-BEMM-2016.pdf


Page 111, 250A possible. 180A seems almost routine (with the right setup).


Surprising but it's all detailed in the BEMM.

That is very interesting documentation, it sure would he handy if you were doing a DIY.


It certainly looks like they set it up for high power offload rates, and nice that you can turn off the special energy saving charging and go to conventional charging.


The alternators they show seem to to be rated at 240*F (p131) which is good as many are rated output cold. What I could not find is duty cycle at that output which is pretty critical if you are going to be running AC or long term big battery bank charging. The big question is can you really pull off 180 amps and run the van stuff which may be another 40-50amps over hours of driving without overheating the alternator? The second question is if the alternator has a temp sensor and turns itself down for self protection in conventional mode?


For me, I would be really interested in if the conventional charging mode would be able make it so you could run a parallel second alternator of the same size and type. If you could, it makes everything better, IMO, as it reduces the wear and tear on both from heavy use is redundant both directions unless one mechanically fails and locks up.



They have done a much better job of it all than the other brands we have seen in the newer models, I think, but a little more information would be nice to know.