RV Lithium Battery Upgrade Near Me

LiFePO4 vs AGM Battery Chemistry - What Changes When You Switch

Lithium iron phosphate batteries differ from AGM in four ways that matter to RV owners. First, usable capacity: AGM batteries are typically cycled to 50% depth of discharge to preserve calendar life, so a 100Ah AGM gives 50Ah usable. A 100Ah LiFePO4 from Battle Born or Renogy is safe to 80% DOD, yielding 80Ah usable - 60% more usable energy from the same nameplate. Second, cycle life: AGM rated at 300 cycles at 50% DOD versus 3,000 - 5,000 cycles at 80% DOD for quality LiFePO4 cells. Third, charge acceptance: AGM batteries taper to under 10A at 90% SOC, slowing the last 10% of charge significantly. LiFePO4 accepts full current up to 95% SOC, then tapers sharply - full recharge in a fraction of the time. Fourth, voltage sag: AGM voltage drops from 12.7V at full charge to 11.5V at 50% DOD under load, causing the inverter to see lower voltage and potentially shut down. LiFePO4 holds between 13.2V and 12.8V from 100% to 20% SOC - the inverter sees stable voltage and runs more efficiently.

BMS Compatibility and Charger Reconfiguration Requirements

Swapping AGM for LiFePO4 without reconfiguring the charger is the number one lithium upgrade mistake. Every quality LiFePO4 battery has an internal Battery Management System that protects cells from overcharge, overdischarge, excess current, and temperature extremes. A charger running at AGM absorption voltage (14.4V - 14.7V) into a lithium battery will not damage the cells in most cases because the BMS disconnects at 14.6V, but the cycling disconnect-reconnect as the charger over-targets and the BMS trips causes premature BMS MOSFET wear and erratic charge termination. Correct lithium charge profiles: absorption 14.2V, float 13.5V, equalize mode disabled. On Victron inverter/chargers this takes 5 minutes via VE.Configure. On Progressive Dynamics PD9100 series converters, the PD9105V Charge Wizard module adds a lithium-compatible 4-stage profile for $65.

Battery Bank Sizing - How Much Lithium Do You Actually Need

Over-sizing is common in lithium marketing and it adds unnecessary weight and cost. We size lithium banks from a logged consumption baseline, not from rule-of-thumb estimates. A Victron BMV-712 Smart battery monitor installed for 24 - 48 hours before the upgrade gives exact amp-hour consumption data. Typical Florida boondocking loads: a CPAP (ResMed AirSense 10 at 55W average) consumes 27Ah over 6 hours. A Dometic CRX-65 12V compressor fridge consumes 30 - 45Ah per day depending on ambient temperature. LED interior lighting consumes 10Ah over 5 hours of evening use. Total for a typical couple dry-camping: 75 - 100Ah per day. With a 200Ah LiFePO4 bank usable to 80% DOD (160Ah), that covers 1.5 - 2 nights before needing recharge.

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Case Study: The two Interstate DCM0075 AGM batteries had been discharged below 50% depth of discharge on an estimated 180 out of 420 cycles - mostly during boondocking trips where the owner consistently ran loads until the inverter shut down. At 180 sub-50% DOD cycles on an AGM rated for 300 cycles at 50% DOD, the batteries were at end-of-life with internal sulfation reducing usable capacity to approximately 58% of nameplate.

1. Consumption Baseline: Connected the Victron BMV-712 for 24 hours to log actual overnight draw - measured 48Ah total from CPAP (80W x 6hr = 28Ah), Keurig (900W x 10min/day = 7Ah), LED lighting (3A x 4hr = 12Ah), and miscellaneous 12V loads (1Ah).
2. AGM Removal: Disconnected and removed both Interstate DCM0075 batteries from the front pass-through bay - total weight 116 lbs for the pair.
3. Lithium Bank Installation: Installed two Renogy RBT100LFP12S-G1 100Ah LiFePO4 batteries (50 lbs total for the pair) with internal Daly BMS rated for 100A continuous discharge. Wired in parallel using 2 AWG tinned copper cable with tinned lugs to maintain polarity and minimize voltage differential between cells.
4. Converter Reconfiguration: Reprogrammed the existing Victron MultiPlus-II 12/2000/80 via VE.Configure 3 - changed absorption voltage from 14.4V to 14.2V, float voltage from 13.6V to 13.5V, disabled equalization mode (destructive to lithium), and set charge current to 80A (within the Renogy BMS 100A charge limit).
5. Shore Power Charge Profile Verification: Confirmed the Winnebago's OEM Progressive Dynamics PD9130 30A converter was also reconfigured to lithium profile (14.2V/13.5V) using the PD9105V Charge Wizard plug-in module.
6. Capacity Verification: Discharged the new lithium bank to 10% SOC using a 50A load then recharged to 100% - confirmed 182Ah total capacity per BMV-712 log, matching nameplate specification for the parallel 200Ah bank.
7. Runtime Test: Ran CPAP (80W) and lights (36W) for a simulated 8-hour night - bank reached 71% SOC at end of test, with 58Ah consumed and 142Ah remaining.