I'm planning a lithium battery upgrade for my motorhome's house bank and trying to decide between dual purpose lithium batteries versus dedicated deep cycle lithium batteries. I understand that dual purpose batteries are designed to handle both starting and deep cycling applications, which sounds convenient for an RV setup. However, I'm wondering if there are performance trade-offs when using dual purpose lithium batteries specifically for coach/house battery applications where they'll primarily be doing deep cycling to power lights, water pump, refrigerator, and other 12V systems. Would I be better off with dedicated deep cycle LiFePO4 batteries for my house bank, or do dual purpose lithium batteries offer sufficient performance for typical RV boondocking and daily use? I want to make sure I'm getting the best cycle life and value for my investment in a house battery system.
Dual purpose lithium batteries work for coach use but dedicated deep cycle lithium is better for house banks. Dual purpose compromises between starting and cycling. For RV house batteries, deep cycle LiFePO4 provides better value and cycle life.
Dual purpose lithium batteries can work for motorhome coach applications, but they're not the optimal choice. While they'll provide power for your lights, water pump, and 12V accessories, dual purpose batteries are designed as a compromise between starting and deep cycle performance. For a motorhome coach bank where you need reliable deep cycling capability for extended boondocking and consistent power delivery, dedicated deep cycle lithium batteries like Battle Born 100Ah or Renogy 170Ah models will serve you much better. The dual purpose design means you're giving up some deep cycle capacity and longevity for starting ability you don't need in a coach application.
The main issue with dual purpose lithium batteries in coach applications stems from their hybrid design philosophy. These batteries sacrifice some deep cycle performance to maintain cranking amps for engine starting. In a motorhome coach setup, you're primarily drawing steady loads over extended periods rather than high-amp bursts, which is where dedicated deep cycle batteries excel.
Dual purpose batteries typically have higher internal resistance than pure deep cycle units, leading to voltage drops under load and reduced efficiency when powering inverters or high-draw appliances like microwaves. They also tend to have shorter cycle life ratings - often 2000-3000 cycles versus 4000-6000+ for quality deep cycle lithium batteries.
Cost considerations also come into play. Dual purpose lithium batteries often carry a premium price due to their versatility marketing, but you're paying for starting capability you won't use. Pure deep cycle batteries frequently offer better amp-hour value for coach applications.
Before making any battery decisions for your motorhome coach, calculate your actual power needs by listing all 12V devices and their amp draws. Include LED lights, water pump, furnace fan, refrigerator (when on 12V mode), slides, leveling jacks, and any inverter loads. This determines your minimum battery bank size regardless of battery type.
Check your existing charging system compatibility with lithium batteries. Your converter/charger needs appropriate lithium charging profiles, typically 14.4V absorption and 13.2-13.4V float voltages. Older converters may need replacement or reprogramming. Solar charge controllers should be MPPT type with lithium settings.
Verify your motorhome's battery compartment ventilation and mounting system. While lithium batteries don't need ventilation like lead-acid, they do need protection from extreme temperatures. Most lithium batteries have built-in Battery Management Systems (BMS) that shut down charging below 32°F and above 120°F, though many can continue discharging at lower temperatures.
Budget for the complete system upgrade, including new batteries, potentially new charging equipment, and proper monitoring systems. Quality lithium coach batteries range from $800-1200 per 100Ah unit, while dual purpose versions might run $900-1400 each.
If you decide to proceed with dual purpose lithium batteries despite the limitations, start by selecting reputable brands like Battle Born, Renogy, or Victron that offer robust BMS systems and good warranties. Avoid cheap imported units that may lack proper safety features or customer support.
Install the batteries in your existing coach battery compartment, ensuring proper securing and cable routing. Use marine-grade tinned copper cables with proper fusing - typically 100-150A fuses for 100Ah batteries. Connect batteries in parallel for 12V systems, maintaining equal cable lengths to prevent imbalanced charging.
Configure your charging system for lithium profiles. Most modern converters have lithium settings accessible through DIP switches or programming modes. Set absorption voltage to 14.4V, float to 13.2-13.4V (check manufacturer specs), and disable equalization modes. If your converter lacks lithium capability, consider upgrading to units like Progressive Dynamics 9200 series or WFCO 8900 series.
Install a battery monitor system to track state of charge, amp hours consumed, and charging status. Quality monitors like Victron BMV-712 or Battle Born's 712 Smart provide Bluetooth connectivity and detailed battery information. This is crucial with lithium batteries since voltage alone doesn't indicate state of charge as clearly as with lead-acid.
Test the complete system under normal loads before your first camping trip. Verify all charging sources work properly and the BMS functions correctly by monitoring charging cycles and load responses.
Contact a professional RV technician if your current charging system is older than 10 years or if you're unsure about lithium compatibility. Many converters from the early 2010s and before lack proper lithium charging profiles and could damage expensive lithium batteries or fail to charge them properly.
Get professional help for any 12V electrical work if you're not comfortable with high-current wiring, fusing, or troubleshooting charging systems. Improperly installed lithium batteries can create fire hazards or expensive equipment damage. RV electrical shops typically charge $500-800 for complete lithium battery installation and system setup.
Consider consulting with lithium battery manufacturers' technical support before purchase, especially for dual purpose applications. Companies like Battle Born and Renogy offer pre-sale consultations to ensure their products match your specific needs and existing equipment.
If you experience charging issues, unexpected shutdowns, or BMS error codes after installation, contact the battery manufacturer immediately rather than attempting repairs. Lithium battery BMS systems are sophisticated and require specialized knowledge to diagnose and repair safely.
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