Orion DC to DC not charging Lithium batteries

My boat is wired such that the alternator is connected to an Isolator, which has 2 outputs - one to the starter battery (12V AGM, 100Ah) and the other to my bow thruster batteries (2x 12V AGM 100 Ah). All of these AGM batteries are charging fine off the alternator. The alternator is 115A. The starter battery is connected as the input to an Orion DC-DC charger, 30A. The output of the Orion is connected to my house bank directly, which are 2 Lithium batteries, 12V, 330Ah each. The Lithium batteries are about 4 feet from the Orion.I also have solar panels connected to these 2 Lithium batteries via 2 50A MPPT controllers. The MPPT outputs don’t go directly to the Lithium batteries, they connect to a smart battery protect device. The alternator used to charge by house bank (albeit, it wasn’t all that fast), but now it doesn’t. It seems like once the starter battery is charged (which happens quickly), the Orion goes quickly into Absorption, then after we hours into Float. So the input and output of the Orion is showing 14.2V, but there is very little current going to my house bank. There is also very little current (2A) coming out of my alternator when the Orion hits absorption. Has the Orion gone bad? A few months ago, the Isolator failed (one of the diodes blew), so I replaced it, and everything was working again, although it seemed like after that I would sometimes get charge to the Lithiums, but sometimes it didn’t seem to be. Since we are a sailboat, we don’t tend to run the engine for very long, so it would often be hard to tell.

Your first thing to check here is your wiring between the Orion and the batteries. If the output of the Orion is going up to 14.2V, then that is correct, but not delivering current suggests a poor connection or high resistance between the Orion Outlet and the Battery. If the Orion was struggling to generate current on the output it would not be able to lift the output voltage to 14.2V, it would register the battery voltage. Do you have a multimeter to try and trouble shoot where the poor connection is. Check each crimp, terminal, bolt, fuse and breaker.

Do you have any of the cheap resettable breakers between the Orion and the batteries, if so these often fail giving poor contact.

Thank you for the response, I really appreciate it. I checked the cabling from the output of the Orion to the battery and with the Orion off and the House batteries not receiving charge from any other source, the resistance in the cable is about 0.3 ohms and the voltage is the same on both ends of that cable, in this case with the Orion off and no other charging source on the Lithium batteries, I had 13.24V in this case because it was night and therefore no solar panel charging source. Also there are no fuses or breakers from the Orion to the bus bar for the house bank, should there be? I didn’t do this installation, so I don’t have full details on it.

Much too high…

Go back when it is trying to charge with your multimeter on volts and try to find where the voltage drop occurs. Measure on lugs, terminal bolts, crimps, exposed end of wire. Remember, this can be a bad negative connection as well as positive. This could be the Orion negative connection or the negative connection between starter and house batteries if the systems are non-isolated. You do not say if you have an isolated or non-isolated Orion.

For testing set the orion to power supply @ bulk voltage.

Then you’ll have current flowing …

Hmm, ok, when the Orion is on (in charging mode), I see 14.2V at the Orion output but 13.5V at the bus strip for the Lithium batteries. I checked on the bus bar, and the cable crimp terminal, and they are both the same voltage. There is no exposed wire on the cable, since there is heat shrink around it. Note that when I made this measurement, the solar chargers (MPPTs) were connected and charging the Lithium house batteries. When the Orion is off, I see exactly the same voltage on the Orion output as I do at the Lithium battery (house bank) bus bar. Is this what should be expected? I have been wondering if the other charging source (the solar input), is causing some issue with the Orion output?

My Orion is a non-isolated. It is wired with the single ground input connected to the negative terminal of the starter battery. And of course the negative terminal of the starter battery is connected to the engine block. This arrangement is also something I have been wondering about if it was the correct way to have the grounding done.

Another thing I just tried, since we just pulled into a marina today for the first time in months was this: with the Lithium house bank at 13.2V and no solar input (it was dark out), I connected the boat to shore power but turned off the charger going to the house bank, but turned on the separate charger (a Phoenix charger, which is an older Victron product). So with the shore power supplying the Phoenix charger and no other charging source to my house bank, I switched my battery switch on (this is setup as a trigger for my Orion) and after a few seconds, the input voltage to the Orion went up to 14.5V, the Orion turned on and the output rose to 14.2V (this took a few seconds), and on my Lithium house bank monitor I could see the input current to the house batteries went to 16A (it probably went to 30A, the max output for the Orion, but things were happening fast so I couldn’t see everything going on) and then the input dropped a few seconds later to 12.6V, which tripped the low voltage shut off on the Orion. Then the input voltage (starter battery voltage) rose again to 14.5V, as if the Phoenix charger was having trouble “keeping up” with the drain of current going to the Lithium house batteries. So does this prove the Orion itself is working, so I can rule out a faulty Orion?

So you have a large voltage drop in the wiring.

You need to find and fix it yourself, nobody will do this online for you.

As i wrote above, set the orion as power supply with 14.4 volts, then you have a stable and constant behavior for testing.

You can not maintain a voltage difference of 0.7V between two connected components and not have current flow, if there is no measurable current flow something is odd. The charging from shore power confuses the issue but shoes the Orion can deliver some current. I was going to state that you need to make sure that your negative connection between house and starter batteries needs to be in good condition also.

All we can do as Ludo says is advise you to get your meter out and check the system. If you can get current flowing feel for warm connections, leads etc as this will indicate voltage drop.

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