Installing a Victron Energy Orion Tr Smart DC-DC Charger 12-12 30A Isolated

N6WT
N6WT Registered Users Posts: 2 ✭
in Caravan, Recreational Vehicle, and Marine Power Systems #1
I am about to install 4 12v LiFePO batteries in my class A DP motorhome. I will be installing a Victron Energy Orion Tr Smart DC-DC 12-12 30A Isolated charger to protect my alternator. My question is where do I install the DC to DC charger? If I look at the schematic of my motorhome it shows a wire going from the chassis batteries to the house batteries but there is a "bi-directional isolator" inline which I cannot find. Should I just bypass the isolator and run a new set of wires from the chassis batteries through the DC to DC charger then to the house batteries??

Thanks
Kent
N6WT
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #2
    We have a similar Victron product discussion where a member was having some issues:

    https://forum.solar-electric.com/discussion/356329/buck-boost-flashing-led-lights-no-power

    If you cannot verify the existing cabling, you may have to install new.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • N6WT
    N6WT Registered Users Posts: 2 ✭
    #3
    Bill

    I have just been lazy. I need to take a few things apart in the storage bay to verify the cabling. The only thing that is kind of strange is the wiring diagram shows a "bi-directional isolator" inline. I would have thought it would be somewhere in the storage bay. I don't think it would be in the wire chase. Again I need to take some things apart. Thanks for the info!

    73 Kent N6WT
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #4
    Depending on what the "Isolator is"--If it is a true buck+boost charge controller--Then usually you want them near the house battery bank to have low voltage drop from regulator to battery bank, and be at the same temperature as the battery bank (for lead acid batteries, temperature compensated charging voltage).

    https://www.solar-electric.com/victron-energy-orion-tr-smart-12-12-30a-dc-dc-charger.html

    Looking at the specs... Yes, you want near your house battery, and the longer cable run back to the vehicle battery/alternator...

    The long wire run will have lots of voltage drop, and while you want to keep the drop "low", in practice, sending 12 volts any sort of distance is a tradeoff between lots of heavy copper cabling (to keep voltage drop low) and accepting higher voltage drop (to keep copper cable costs lower).

    For example, the unit you are looking at(?) accepts 10-17 volts... And lets say that you want at least 12 volts at the converter, 30 amps input, and the two/vehicle outputs 14.0 volts running. Or ~2 volts maximum drop, and guess at 10 foot one way wire run (for this calculator)...

    Note that the manual says to use 60 amp fuse--So a 60 Amp cable using the NEC cable ampacity chart (simplified)--We see that need at least 6 AWG (maximum AWG for converter cable connections)... 

    https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm (this is a conservative chart--You will find Marine wiring charts that allow much higher current--Your choice).

    Playing with the numbers in the voltage drop calculator we get:

    https://www.calculator.net/voltage-drop-calculator.html?necmaterial=copper&necwiresize=4&necconduit=pvc&necpf=1&material=copper&wiresize=0.4066&resistance=1.2&resistanceunit=okm&voltage=14&phase=dc&noofconductor=1&distance=10&distanceunit=feet&amperes=30&x=69&y=24&ctype=nec

    Result

    Voltage drop: 0.29
    Voltage drop percentage: 2.10%
    Voltage at the end: 13.71

    Which, for my guess at your cable length, looks like a nice solution for any reasonable wire run...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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