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Discussion Starter · #1 ·
Amp clamp glad I got one.

idle 24-28
now add
  • low beams 40-42
  • high beams 49-52
  • wipers on fast 25-29, may have to recheck that one
  • blower on high 49-51 radiator fans on 88-90
  • a/c on high 53-55 radiator fans on 93-96
  • everything on 118-124
 

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Way more thorough than me. My base idle value (28) matches yours. And your 120 for everything would seem to indicate there isn't much room left for additional loads at that point. I think I'd turn off my DC-DC in that situation, just to be safe.
 

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Post #49 of this thread has some related estimates of power usage.


The post was made by @adamjameshendren

I am just copying in the info for convenience. Probably there is an easier way to do this but I don't know how to do it.

___

Hope Ram's latest response is enlightening to you all and i'm making sure to close the loop on this conversation. Here's @RamCares response. This makes me feel as though having 3 orions is definitely doable and having one that can be turned off when a heavier load is on the alternator would mitigate any risk/issues.

Thanks for raising a request for 'Maximum allowable draw for aux battery charging' with Ram commercial team for body builder's guide. Our engineers have analyzed the request and provided the solution below.

Request Id: 10844
Request Subject:Maximum allowable draw for aux battery charging

Request Description:Hello,

I'd like to understand the maximum allowable draw I can place on the 220a factory alternator. More specifically, after accounting for the draw required for standard operation of the vehicle and charging the starter battery, how much left over amperage do I have to work with for charging an auxiliary battery bank. Thank you

Response:That is dependent on the loads that are running in the vehicle. If you are designing for worst case, max vehicle load can be around175 amps, and that courting on a reasonably charged battery. If yo are also trying to charge a low battery, it will go up from there. I don't have charge current numbers for the battery. Here are the numbers for the vehicle loads.

ABS 3A
Front Fog Lamps 9A
Wiper motor - high 6A
Turn Signal 2.5A
IP Cluster 2.5A
Head Lamps - Low Beam 9A
Marker Lamps 8A
Rear Fog 3.2A
Stop Lamps (With CHMSL) 3.4A
Engine 12A
Radio 4A
TBM 0.75A (Plus the load of the trailer Lights)
Heated Mirrors 4A
Heated Seats 10A
HVAC Blower 23.5A
Rad Fan 65A
 

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It is always interesting trying to reconcile real measurements vs text book estimates with electricity.
 
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Discussion Starter · #7 ·
idle with radiator fan

jumps to 60 amps when the fans kick in
 
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2018 159 High Roof gas, BC, Canada
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Amp clamp glad I got one.

idle 24-28
now add
  • low beams 40-42
  • high beams 49-52
Good info, Phil. I wonder why your high beams draw more power than the low beams. I believe they are both H7 bulbs.

Response:That is dependent on the loads that are running in the vehicle. If you are designing for worst case, max vehicle load can be around175 amps, and that courting on a reasonably charged battery. If yo are also trying to charge a low battery, it will go up from there. I don't have charge current numbers for the battery. Here are the numbers for the vehicle loads.

Marker Lamps 8A
Rear Fog 3.2A
Thanks, Harry. I think the part of the comment that I highlighted is important. From my big external battery charger (max 25A), I can tell that a depleted battery draws more than 25A. And thus a battery in that state will consume quite a large chunk of your alternator's output. (This is why I always use an external battery charger when I can whenever I come across a low battery situation: to reduce wear and tear on the alternator.)

The fact that the marker lamps use 8A is an incentive to replace them with LED. That's a large amount of current being burnt up for not a particularly useful piece of electronics. (I mean, what are the marker lamps really for anyways??? [I like their look though!])

And what are "rear fog" lamps??? Are they what are normally called "tail lights"?
 
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Discussion Starter · #10 ·
IIRC in Europe (at least Italy) a single bright red light was mounted on the rear for fog, I assume it's connected to the front fog lights.

Seems like they're just using Ducato specs.
 

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Good info, Phil. I wonder why your high beams draw more power than the low beams. I believe they are both H7 bulbs.



Thanks, Harry. I think the part of the comment that I highlighted is important. From my big external battery charger (max 25A), I can tell that a depleted battery draws more than 25A. And thus a battery in that state will consume quite a large chunk of your alternator's output. (This is why I always use an external battery charger when I can whenever I come across a low battery situation: to reduce wear and tear on the alternator.)

The fact that the marker lamps use 8A is an incentive to replace them with LED. That's a large amount of current being burnt up for not a particularly useful piece of electronics. (I mean, what are the marker lamps really for anyways??? [I like their look though!])

And what are "rear fog" lamps??? Are they what are normally called "tail lights"?
I wish that I were responsible for the content as it is quite helpful, but I just copied and pasted it over from the linked post of @adamjameshendren .

It is possible that some of these lights are already LED - I am not sure.

In my mind, one of the big insights is that it might make sense to switch on / off the Battery to Battery charging so that it is not running at the same time as the radiator fan.
 

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Discussion Starter · #12 ·
Say you use a DC to DC rated at 50 amps, it would only surge to 110 amp for a few seconds, I don't see it as a problem considering the OEM upfitter is 70 amps.
 

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Discussion Starter · #13 ·
Worse case scenario, trying to charge a battery on a dark back country road while it's raining cats and dogs, and it's hot/humid.

Basically understand the limitations, DC to DC guys will be better off vs free flow guys.
 

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Worse case scenario, trying to charge a battery on a dark back country road while it's raining cats and dogs, and it's hot/humid.
Then add in that an oblivious vanlifer could then start cooking with electricity whilst playing a 3D first-person shooter on a gaming laptop inside a brightly lit-up coach area.
 

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Discussion Starter · #15 ·
Then add in that an oblivious vanlifer could then start cooking with electricity whilst playing a 3D first-person shooter on a gaming laptop inside a brightly lit-up coach area.
I'd like to think they're not driving :)
 

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Hopefully not! But that'd only save the headlights' amperage. :)
Well, if there were house batteries, they wouldn't need to run the engine while gaming :) and save another 12A

More to the point, I am going to redouble my effort to replace all halogen bulbs with LEDs (did the headlamps already). I wasn't thinking so much about saving energy as I was about maintenance. Guess I'll do the DRL and other running lights next.
 

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Heated mirrors comes with power retract side rear-views and run off dashboard HVAC controls rear window defrost switch, so switch controls -something- even if no rear defrosters... but it'd have to be below 50*f or somesuch to draw current according to owners manual?
 

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Well, if there were house batteries, they wouldn't need to run the engine while gaming :) and save another 12A
No, the point of the thread was that the alternator might be struggling with some loads so the engine would be running.

I was only joking (a bit), but I could see people inadvertently piling more and more things onto an alternator when it'd be not only running the van's "stuff" but also charging the coach batteries--and THEN, somebody could inadvertently start other loads, even major ones like cooking with electricity.

This can easily happen because things generally "just work" and so we (me too!) could mindlessly add more load.

I mean this happens at home. My wife frequently has something in the toaster oven and then she'll try to get some water boiling in the electric kettle that's on the same circuit. The circuit breaker then blows. Fortunately, she knows exactly what to do (resets the breaker then waits to boil water).

Unfortunately with the alternator, the problem is not so apparent. It could get searing hot trying to handle what someone's tasked it to do and the person wouldn't know. The "circuit breaker" could be the alternator...frying...
 
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There is of course the question of how much of alternator capacity is available for continuous use, especially at low RPMs.

Alternators rely on rpm to run their internal cooling fan, and almost none of them are designed for anything close to 100% duty cycle, especially on a hot day.
 
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