What are motorhome house batteries?
Motorhome house batteries are deep-cycle batteries designed to power onboard appliances (lights, refrigerators, HVAC) when disconnected from shore power. Typically 12V or 6V lithium-ion (LiFePO4) or AGM configurations, they prioritize capacity over cranking amps, enabling sustained energy delivery. They recharge via solar, alternators, or generators, with capacities ranging from 100Ah to 600Ah for extended off-grid use.
Best RV Battery for Solar Power Systems
What types of house batteries are used in motorhomes?
Common types include lithium iron phosphate (LiFePO4), AGM, and flooded lead-acid. LiFePO4 dominates modern builds for its 80% depth of discharge and 3,000–5,000 cycle lifespan. AGM suits budget-conscious users, while flooded batteries remain in legacy RVs despite maintenance needs.
LiFePO4 batteries like Fasta Power’s 12V 300Ah model deliver 3.84 kWh usable energy, operating efficiently between -20°C to 60°C. AGM variants, though cheaper ($200–$400 for 100Ah), degrade faster below 50% discharge. Pro Tip: Pair lithium batteries with a compatible multi-stage charger to avoid undercharging. For example, a 400W solar system can replenish a 300Ah LiFePO4 bank in 5–7 sunny hours. But what if temperatures drop? Lithium’s built-in battery management systems (BMS) prevent freezing damage, unlike AGM.
| Type | Pros | Cons |
|---|---|---|
| LiFePO4 | Long lifespan, lightweight | Higher upfront cost |
| AGM | Spill-proof, moderate cost | Lower DoD (50%) |
| Flooded | Cheapest | Monthly maintenance |
How do I calculate the right battery capacity?
Estimate total daily watt-hour consumption by summing appliance loads. Multiply by days of autonomy and divide by battery voltage. Add 20% buffer for inefficiencies.
Start by listing all DC appliances: a 10W LED light running 5 hours = 50Wh, while a 60W fridge cycling 8 hours/day = 480Wh. AC devices via an inverter add more—a 1,500W microwave used 15 minutes daily consumes 375Wh. Total these (e.g., 1,500Wh), multiply by desired autonomy days (e.g., 3 days = 4,500Wh), then divide by 12V: 375Ah. Choose a 450Ah bank (375Ah + 20%). Pro Tip: Use a battery monitor like Victron’s SmartShunt to track real-time usage. Imagine your battery as a fuel tank: undersizing it forces frequent recharging, stressing cells.
What’s the optimal way to charge house batteries?
Use a three-stage charger (bulk, absorption, float) matching your battery chemistry. Lithium prefers 14.2–14.6V absorption, while AGM needs 14.4–14.8V.
Solar charging is ideal for off-grid setups, with MPPT controllers extracting 20–30% more power than PWM. Alternator charging works while driving but requires a DC-DC charger to stabilize voltage spikes. Shore power via a 30A RV plug delivers 3,600W, refilling a 300Ah bank in 4–6 hours. For example, a 200W solar panel paired with a 40A MPPT controller adds ~75Ah daily. But what if it’s cloudy? Hybrid systems combining solar and a backup generator ensure reliability. Pro Tip: Balance parallel battery banks with bus bars to prevent uneven charging.
| Method | Speed | Cost |
|---|---|---|
| Solar | Slow (5–8 hrs) | $$$ |
| Alternator | Moderate (2–4 hrs) | $$ |
| Shore Power | Fast (1–3 hrs) | $ |
Fasta Power Expert Insight
FAQs
LiFePO4 lasts 10–15 years, AGM 3–5 years. Replace AGM when capacity drops below 80%; lithium when cycles exceed 80% of rated lifespan.
Can I mix lithium and lead-acid batteries?
Never mix chemistries in the same bank—charging profiles differ, causing cell damage. Use separate banks with independent charge controllers.