DC to DC troubleshooting

[Olive2Roam]

So we have had a DC to DC charging system on our LE I for a year now. It worked very well, but has become inconsistent and unreliable. The system was installed by a local inverter service center with a solid reputation. They actually are the supplier for some parts, such as solar panels, to Oliver. The tow vehicle is a 2024 Pathfinder with a "smart" alternator. The charger is a Victron Orion 50 amp. 

Using the Victron app I can see that the voltage on the input side of the charger is sitting between 12.2 and 12.4 volts. Aside from a brief spike on start up to 14.4 or so, it remains there. When driving the voltage remains that low and occasionally jumps to 14.4 or so and occasionally that casues the bulk charging to start. But this lasts only for a short time (seconds) and the voltage drops, and the charging stops.

Bottom line is that the batteries are not being charged. The inverter service center has worked with me to make sure all of the parameters are correct, but there is still something wonky that we can't figure out. Out of curiosity I had the tow vehicle battery tested by a couple of battery shops and all looks good there. 

12.2-12.4 seems very low for the output from the TV battery. In fact, the Victron parameters require 13.3 volts (default) and we have dialed that down to 12. 9. Any thoughts as to why the voltage from the tow vehicle would be that low? Also, does anyone know a DC to DC charging resource/expert that I could connect with to trouble shoot this?

Thanks,

Bob

Edited 17 hours ago by Olive2Roam

[jd1923]

18 minutes ago, Olive2Roam said:

12.2-12.4 seems very low for the output from the TV battery.

Yes Bob, this voltage is very low! An automotive LA battery after sitting overnight or sitting for a few days should read 12.5V minimum and more like 12.6V with a newer battery. When towing or at highway speeds, voltage across the battery with the alternator running should produce 13.6V min and more often 13.8V to a max 14.2V.

The term Smart battery bothers me unless it's smart enough to know you have the DC-DC charger attached. Check a Nissan truck forum, search for "alternator" or "towing."

If you have been DC-DC charging adequately for some time and now nothing, you could have blown something in the Nissan alternator. Perhaps it did not have +50A available.

Your DC-DC charger installation is likely fine. Instead of "inverter service" test your alternator or take it to an electrical shop that rebuilds alternators and starters,

Before I installed our Orion 50A charger, I installed a HD alternator rated at 50A greater capacity. Let us know. Best wishes, JD

[Olive2Roam]

2 minutes ago, jd1923 said:

Yes Bob, this voltage is very low! An automotive LA battery after sitting overnight or sitting for a few days should read 12.5V minimum and more like 12.6V with a newer battery. When towing or at highway speeds, voltage across the battery with the alternator running should produce 13.6V min and more often 13.8V to a max 14.2V.

The term Smart battery bothers me unless it's smart enough to know you have the DC-DC charger attached. Check a Nissan truck forum, search for "alternator" or "towing."

If you have been DC-DC charging adequately for some time and now nothing, you could have blown something in the Nissan alternator. Perhaps it did not have +50A available.

Your DC-DC charger installation is likely fine. Instead of "inverter service" test your alternator or take it to an electrical shop that rebuilds alternators and starters,

Before I installed our Orion 50A charger, I installed a HD alternator rated at 50A greater capacity. Let us know. Best wishes, JD

Thanks, JD. This is the best description of the smart alternator that I have found. https://www.thefastreligion.com/mr-smart-alternator-function What I have seen on a couple of other forums (https://www.pathfindertalk.com/threads/disabling-vvcs-voltage-variable-control-system.45074/) is that some choose to disable the variable voltage control system and make the alternator act like they always have and just pump 13.4 V to the battery 100% of the time. 

I will definitely have the alternator looked at. There might be something going on there. 

Thanks for your thoughts.