I'm at my wit's end trying to figure out the proper wiring for my 2019 Newmar after upgrading to lithium batteries with a Victron system including a BVM-712 battery monitor, Orion XS DC-DC charger, and Cerbo GX. I've been going in circles for weeks!
The main issue is I can't figure out how to properly integrate my existing boost switch with the new DC-DC charger setup while maintaining the ability to trickle charge chassis batteries. Currently, my Orion XS DC-DC charger flows only one way from engine alternator to lithium batteries. Should I replace the existing BIM with a LI-BIM, which would be in series with the 2/0 cable? Is there a control wire on the Orion XS that will allow flow from lithium to chassis batteries while on shore/inverter power?
I'm considering adding a 120V battery tender for chassis batteries, but want to confirm what modifications might be needed to my existing BIM. Can someone provide guidance on the correct wiring approach?
Keep boost switch wiring separate from DC-DC charger circuit. Add dedicated chassis battery charger or use DC-DC second output for trickle charging. Boost switch remains for emergency use.
SAFETY WARNING: Always disconnect battery negatives first and work with proper electrical safety procedures. Turn off all electrical systems and shore power before beginning any battery or charging system modifications. Battery and DC electrical systems can pose fire and explosion hazards - ensure proper ventilation and use appropriate personal protective equipment.
For your 2019 Newmar Newaire lithium conversion with the Victron Orion XS DC-DC charger, you'll need to replace your existing BIM with a Victron LI-BIM 400 and add a separate 120V battery tender for chassis battery maintenance. The Orion XS doesn't have bidirectional capability - it's designed as a unidirectional charger from alternator to house batteries only. Your current BIM should be disconnected once you install the LI-BIM, as running both could create conflicts in your charging system. The control wire on the Orion XS (terminal H) can be used for remote on/off but won't reverse current flow.
The main challenge you're facing is common in lithium conversions - traditional BIMs aren't designed for lithium profiles and can contribute to issues with your new Victron system. Your existing BIM likely uses lead-acid charging parameters that could damage lithium batteries or prevent proper charging. The Orion XS is specifically engineered as a unidirectional DC-DC charger, meaning it only flows power from the alternator/chassis battery to the house batteries, never the reverse.
Many RV owners assume they can keep their original BIM alongside new lithium equipment, but this often creates voltage conflicts and charging inefficiencies. The boost function you want to preserve requires a different approach when lithium batteries are involved, as they can't safely provide emergency starting power without proper voltage management.
Shore power trickle charging becomes an issue because your new lithium setup isolates the chassis batteries from the house system during charging. Without active management, your chassis batteries will slowly discharge during extended shore power stays, potentially leaving you stranded.
WARNING: This modification involves high-current DC systems that can pose fire and electrical shock hazards. Ensure all power sources are disconnected and use proper personal protective equipment.
Before starting this modification, you'll need a Victron LI-BIM 400 - correct part for your model (verify with dealer) which costs around $200-250. This intelligent BIM is designed specifically for lithium house battery systems and will work properly with your Orion XS. You'll also need a quality 120V battery tender for your chassis batteries - I recommend a NOCO Genius or Battery Tender Plus rated for your chassis battery capacity.
Gather your tools: wire strippers, crimpers, heat shrink tubing, electrical tape, and a multimeter. You'll need properly sized cable (verify gauge requirements based on current load and cable run distance - often 2/0 AWG for high-current applications), plus smaller gauge wire for the battery tender installation. Print out the wiring diagrams for both the LI-BIM 400 and your Orion XS to reference during installation.
Document your current BIM wiring with photos before disconnection. Note which terminals connect to chassis positive, house positive, and any control wires. This documentation will be crucial if you need to troubleshoot later. Check your chassis battery voltage and load test them while you're at it - old batteries may not be worth preserving in your upgraded system.
Start by disconnecting both chassis and house battery negative terminals for safety. Remove your existing BIM after verifying it's not integrated with other systems - some 2019 Newmar models have BIMs integrated with other functions. Consult your specific model documentation before removal. The LI-BIM 400 installs in parallel with your Orion XS circuit, with both devices connected to chassis battery positive. The LI-BIM manages isolation while the Orion XS handles charging - consult Victron wiring diagrams for proper parallel installation.
Wire the LI-BIM 400 according to Victron's specifications: follow Victron LI-BIM 400 wiring diagram for proper terminal connections to chassis battery positive, Orion XS input, and chassis ground. Torque all connections to manufacturer specifications (consult Victron LI-BIM 400 installation manual for specific torque values). The LI-BIM manages battery isolation between lithium house batteries and chassis batteries, preventing voltage conflicts. For emergency start functionality, you'll need a separate emergency start relay or manual switch, as the LI-BIM does not provide automatic boost capability.
For chassis battery maintenance charging, install a 120V battery tender with a dedicated connection. Route the tender's DC output directly to your chassis batteries with an inline fuse rated at or slightly above the battery tender's maximum output current. Mount the tender's AC plug near your shore power connection for easy access. This tender will maintain your chassis batteries during extended shore power stays without interfering with your lithium charging system.
Configure your Orion XS remote control terminal (H) to connect to your Victron Cerbo GX if desired, but understand this only provides on/off control, not bidirectional charging. The LI-BIM handles the emergency start function automatically based on voltage sensing. Test the entire system by starting your engine and verifying the Orion XS activates, then check that shore power properly charges both battery banks independently.
Call a professional if you're uncomfortable working with 2/0 AWG cables or high-current DC systems. These installations require proper crimping tools and techniques - poor connections can cause fires or system failures. If your chassis charging system includes alternator temperature compensation or other complex controls, professional installation ensures proper integration.
Seek help if you discover your alternator output exceeds the Orion XS input rating (typically 30A continuous) or if your existing wiring doesn't meet Victron's installation requirements. Some 2019 Newmar models may have varying electrical configurations that require specific documentation - consult your specific model documentation.
Professional consultation is recommended if you're planning to integrate this system with solar charging or other power sources. Complex multi-source charging systems require careful coordination to prevent conflicts. Additionally, warranty considerations on your Newmar may require professional installation documentation for coverage preservation.
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