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Discussion Starter #1
It's a shame when a pickup truck has to deal with recreational vehicle cycling batteries and the ECU could care less. But the ECU does not permit direct substitution. Something needs to go into the A field circuit feed to the ECU to satisfy it enough not to go into open-loop limp-home mode. Has anyone done any research on this and pray tell, developed a work-around to allow a "smarter" voltage regulator to be employed? -Thanks!
 

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Sorry, it's not clear to me what's happening, and what you want to happen. Can you explain it a different way?
 

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Bob Lincoln said:
Sorry, it's not clear to me what's happening, and what you want to happen. Can you explain it a different way?
Im with BOB, Is it under charging, Over charging. Charging but cycling too much? or just the battery light on the dash?
Then we can try and help you out.
 

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Is this a diesel Ram with the dual-batteries? Are you using deep-cycle gel batteries? There is not enough information here as stated.
I can't see a charging issue putting the PCM EFI system into limp-in default and if it did, what are your fault codes? I think that you may have another electrical problem with the truck.
Are you trying to charge external batteries as you drive? Are you using an aftermarket battery isolator?
The charging voltage regulator can't be fooled by inserting a static 13.7 volts, as it has to see 'field voltage action/battery voltage reaction' in order to confirm the charging system tests.
 

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Discussion Starter #5
With RV batteries, they are meant to be discharged to around 50% of capacity then recharged. But the truck ECU charges at 14 volts only for a little while, a very little while, then backs off to 13.5 volts. It takes roughly eleven hours of driving to recharge a couple of RV batteries at that rate of charge. When going from one bookdocking site to another this is impossible. It really gets nuts when the campsites do not allow use of a generator. Solar planels don't work too hot in the shade, and parking in the sun many times means a rig temperature of a hundred ten degrees.

Is there public access data that furnishes parameters that the ECU demands to see without generating a fault code and going into limp-home mode? The data would include alternator field current in relationship to battery voltage, voltage failing to or too slow rising, too high, etc. Putting on a second alternator seems to be out of the question. No room, and modifying pulleys and building a custom bracket would cost thousands of dollars.
 

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I think what you want first is charging specifications (amperage rate and voltage) for the RV batteries. Then look into how to buy or rig a charging system for them. Without knowing, it may be appropriate to charge them more slowly than you think. Fast charging is always harder on batteries than a slower rate.

Can you rig solar cell blankets on top of the RV, and have them charge the batteries while you drive? I've seen a blanket size panel put out 21 volts and many amps, so that a regulator is needed to keep the batteries from boiling. That way the batteries can be charged by the time you reach your destination.
 
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