Should RV battery be on when connected to shore power?

Yes, RV batteries should generally remain on when connected to shore power to enable proper charging through the converter and maintain DC systems like refrigerators or propane detectors. However, use a battery disconnect switch if storing the RV long-term to prevent parasitic drain. Lithium batteries handle continuous charging better than lead-acid, but always verify your converter’s voltage compatibility.

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Why keep RV batteries active during shore power use?

Shore power charges batteries via the RV’s converter-charger, which requires an active circuit. Turning batteries off disrupts charging, risking sulfation in lead-acid models and leaving DC systems unpowered. Lithium-ion packs need periodic top-ups to avoid BMS sleep modes.

Beyond basic charging, RV converters often power DC loads directly from shore electricity while simultaneously maintaining the battery. If the battery is switched off, critical systems like CO detectors or emergency lighting lose backup power. For example, a Norcold fridge might draw 12V for control panels even on AC mode—disabling the battery could cause malfunctions. Pro Tip: Set lithium batteries to 13.6V float charge when plugged in long-term to prevent overcharging. But what if your converter lacks a lithium profile? Upgrading to a modern multi-stage charger (like Progressive Dynamics) ensures compatibility.

Can shore power overcharge RV batteries?

Modern three-stage converters (bulk/absorption/float) prevent overcharging, but outdated units lacking float modes can damage batteries. Lithium systems with integrated BMS are safer, disconnecting at 14.6V vs. lead-acid’s 14.4V ceiling.

Practically speaking, overcharging risks depend on battery chemistry and charger intelligence. Flooded lead-acid batteries in RVs with basic converters might experience water loss if left plugged in for months. AGM/gel types are more susceptible to swelling from voltage creep. Lithium iron phosphate (LiFePO4) batteries, however, tolerate indefinite 13.6V float charging. A real-world test showed Trojan T-105 lead-acid batteries lost 18% capacity after 6 months of unregulated charging, while Battle Born LiFePO4 packs retained 99%. Pro Tip: Install a battery monitor like Victron SmartShunt to track state of charge—alerts prevent overcharge disasters.

How does shore power interact with inverter systems?

Inverters bypassed when shore power is active, but inverter/charger combos (e.g., Victron MultiPlus) use AC to recharge batteries. Always keep batteries on to maintain inverter functionality for pass-through loads and surge protection.

When you plug into 50A shore power, the inverter typically stops inverting and becomes a battery charger. However, some advanced systems like Xantrex Freedom X use “power sharing” to simultaneously power AC loads and charge batteries. If the battery switch is off, the inverter can’t stabilize voltage spikes—imagine a brownout damaging your TV’s circuitry. Pro Tip: For rigs with residential refrigerators, ensure the inverter remains battery-connected to handle brief shore power interruptions seamlessly.

Do lithium RV batteries need special shore power settings?

Yes—lithium requires 14.6V absorption and 13.6V float versus lead-acid’s lower voltages. Outdated converters may undercharge lithium packs (stopping at 13.6V), causing capacity loss. Use a lithium-specific charger or DC-DC booster if needed.

Consider this: A Progressive Dynamics 9200 converter set to “lead-acid” mode only delivers 13.6V, leaving LiFePO4 batteries at 80% SOC. Pairing it with a $50 Renogy DC-DC charger boosts voltage to 14.6V for full charges. RV owners report 30% longer cycles after making this tweak. But why risk it? Upgrade to a lithium-smart converter like IOTA DLS-55/Li for set-and-forget operation. Pro Tip: Lithium batteries self-discharge just 2-3% monthly, so disconnecting them during short shore outages (<1 week) won’t harm performance.

What parasitic drains persist on shore power?

Even with shore power, LP gas detectors (0.3A), clocks (0.1A), and phantom loads in entertainment systems draw 5-10W continuously. Over a month, this can drain 7-15Ah from batteries if the converter fails.

Imagine leaving your RV plugged in at a seasonal site—defective converter combined with parasitic drains might kill a 100Ah battery in 10 days. Install a Blue Sea Systems battery switch to physically disconnect loads without losing converter charging. Real-world example: A 2022 Grand Design Solitude lost both chassis batteries because its 12V radio module stayed active on shore power. Pro Tip: Use a Kill-A-Watt meter to identify stealth loads; unplug devices not in use.

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