I’m using a LiFePO4 100 Ah battery to power amateur radios in my 2020 KIA Telluride vehicle. I have the Orion-Tr Smart Isolated DC-DC charger (12-12 18 A). I presently have the charger’s input hooked to the engine battery’s positive terminal and the vehicle frame near the engine battery (the vehicle’s “ground” connection). I didn’t want to bypass the engine computer’s monitoring shunt in the vehicle’s battery return line (between the engine battery’s negative terminal and the vehicle frame). Apparently, I have a “Smart” alternator. Being new to this whole activity, I was surprised (alarmed, actually) to see charger input currents of over 40 A (fortunately, I now have AWG 6 wiring for the charging circuit). Have I defeated the charger’s “smart” interaction with the vehicle’s charging system by connecting to the vehicle frame instead of the engine battery’s negative terminal? The charger’s input is isolated, so I presume I could do that. I just don’t know what the consequences would be, particularly for the vehicle. Given the “rating” of the charger, the 40 A concerns me. It all works - it charges the battery - but that seems like a lot of current. I now understand that the high charging currents are typical of these lithium batteries, but I don’t know what is limiting that current. I followed the diagram. Everything is fused where it should be. It’s just where that charger input return should be connected - the engine battery negative terminal or the vehicle frame? Have I connected the charger input wrong?
Where are you seeing 40a at? does the telluride have a built in shunt? if so i would assume 40a is the full draw of the system not just the dcdc.
I’m seeing the 40 A in the input to the charger. I have my own ammeter shunt in the charger’s input return line to measure that current. The 40 A is just the charger input. I believe the vehicle does indeed have its own built-in shunt between the battery negative terminal and the vehicle frame to which everything else is referenced. I have another ammeter shunt in the charger’s output return, showing slightly less current being sent to the lithium battery.
Interestingly, the ammeters I have also show power. The input indicates about 570 W, and the output shows about 490 W (going into the battery being charged), with the 80 W difference presumably being dissipated in the charger. Once the battery is more fully charged, the charger eventually comes down to just a few Amps.
The input and output voltages are also important, if it has to boost from 12.4 to 14.4V then it needs 16% higher input current than output. If you are outputting 490W then that is circa 33A so with losses and voltage boost it is no surprise it is pulling 40A. There have been other comments that some of the DC to DC chargers will output more current than nameplate. Just make sure that it is able to dissipate the heat.
Everything about this system seems to be working. I get the voltage boost and the battery charges—it’s just that surprisingly large charging current. Since the charger is in a somewhat ventilation-restricted area, I already installed fans on the heat sink, and they seem to have the heat sink temperature well under control.
Thinking about this more, I see that the way I have it connected now, the charging current is going through the vehicle’s shunt. The path back to the engine battery positive terminal is from the charger to the frame, to the engine shunt, to the battery negative terminal, and through the battery back to the positive terminal. So, the engine computer “knows” about all this excess current. Perhaps that’s what’s limiting it with the “smart” alternator (about which I am very concerned). I need to find out what its rating is.
By the way, thank you all for the astute questions, comments, and observations. This is a learn-as-you-go experience for me. Please keep them coming.
In full disclosure, the path through the frame is about 2 inches. The engine battery has only one big cable (with the shunt at the battery’s negative terminal) screwed into a threaded hole in the frame in the engine compartment. My return AWG 6 wire is screwed into the threaded hole right next to that connection. I did not disconnect the engine’s battery from the frame to fasten them together. The lithium battery and the charger are in the very back of the vehicle, hence the long AWG 6 wiring, both supply and return. The vehicle’s battery is an AGM type, and its voltage is often in the 14 V range when the engine runs. With only half a volt or so drop in the cabling, even at that high current, the charger’s boost arrangement doesn’t have to work too hard.
And the charger is only enabled when the engine is running…
I am also using a 100 Ah LifePO4 battery in the trunk of my 2017 Hyundai Sonata for POTA ham radio activations. The. Orion-Tr 18A turns off and on while I am driving even with engine detection set to smart alternator. if I set the shut off voltage to 12.3 V it does not do this but continues to charge the battery when I shut the engine off as my car battery is above 12.3 V. While driving, It seems the voltage measured at the battery can drop pretty low with the on-demand smart charging system. Can anyone tell me what parameters I should use or if I am missing something?Thanks, Pete.
Thanks Ludo
I was hoping to not have to mess with additional wiring but I looked at the manual and will do this.
Pete
Just completed this Ludo and it works great.
Thanks - Pete
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