Lithium Battery Sizing for Full-Time Van Life: 200Ah vs 300Ah

The single most common question from people building out a van for full-time living is: how big should my lithium battery be? The two most popular capacities — 200Ah and 300Ah LiFePO4 — sit at a sweet spot between price, weight and real-world usability. But choosing between them is not as simple as “bigger is better.” Your actual daily consumption, solar setup, driving habits and budget all feed into the decision. This guide walks through the numbers so you can size your battery with confidence rather than guesswork.

1. Why battery sizing matters

Oversizing wastes money and adds weight your van does not need. Undersizing means running out of power on cloudy days, cutting usage short, or relying on hookups that defeat the purpose of going off-grid. The goal is to match your battery to your actual consumption pattern with enough margin for bad-weather days — but not so much margin that you are hauling around capacity you never touch.

For full-time van lifers, the stakes are higher than for weekend warriors. Your electrical system is not a convenience — it is infrastructure. A fridge that shuts off overnight because the battery ran low means spoiled food. A diesel heater that cuts out at 3 a.m. in January means a cold, miserable night. Getting the sizing right is one of the highest-impact decisions in a van build.

2. Understanding usable capacity

The number on the label is not the number you can use. Every battery chemistry has a recommended depth of discharge (DoD) that balances daily usability against long-term cycle life:

Throughout this article, we use 80% DoD for LiFePO4 calculations. This is the industry-standard recommendation that most manufacturers use for their cycle-life ratings (typically 3,000–5,000 cycles). If you regularly discharge to 100%, expect shorter battery life — closer to 2,000 cycles on many models.

At 80% DoD:

• 200Ah LiFePO4 = 160 usable Ah = 1,920 Wh
• 300Ah LiFePO4 = 240 usable Ah = 2,880 Wh

That 80 Ah difference — roughly 960 Wh — is the real gap you are deciding on. Not 100 Ah, but 80.

3. How to calculate your daily Ah consumption

The formula is straightforward:

Ah/day = (watts × hours/day) ÷ battery voltage

For a 12V system, a 60W laptop running for 3 hours consumes 60 × 3 ÷ 12 = 15 Ah. If you run the laptop through an inverter, add 10–15% for conversion losses: 15 × 1.12 ≈ 16.8 Ah.

Do this for every appliance you run daily, then add them up. The result is your daily Ah budget — the number your battery must cover each day.

4. Appliance-by-appliance consumption table

These are real-world averages measured from popular campervan appliances. Your numbers may vary by model, but this gives you a reliable planning baseline.

5. The 200Ah profile: who it suits

A 200Ah LiFePO4 battery (160 usable Ah) is the most popular choice in the campervan market, and for good reason. It covers the needs of the majority of van lifers without the cost and weight penalty of a larger bank.

200Ah works well for:

• Couples or solo travellers with a moderate electrical setup: fridge, lighting, phone charging, water pump, vent fan. Daily draw: 60–85 Ah.
• Solar-supported builds with 200–300W of panels. In sunny conditions, 200W of solar can put back 50–80 Ah per day, making 200Ah more than sufficient for continuous off-grid living.
• Vans that drive regularly. A 30A DC-DC charger running for 2 hours of daily driving adds ~42 Ah. Combined with even modest solar, 200Ah rarely bottoms out.
• Budget-conscious builds. A quality 200Ah LiFePO4 costs €500–900 — a significant saving over 300Ah.

200Ah gets tight if:

• You run a diesel heater on high for extended periods (adds 30–55 Ah/day).
• You work remotely and run a laptop + Starlink all day (adds 30–70 Ah/day).
• You have multiple cloudy days with no driving — no recharge means one bad day depletes the bank.
• You regularly use high-draw 230V appliances through an inverter (hair dryer, coffee machine, electric kettle).

6. The 300Ah profile: who it suits

A 300Ah LiFePO4 battery (240 usable Ah) gives you 50% more buffer. That extra 80 Ah is not about running more appliances — it is about riding out bad days without changing your habits.

300Ah is the right call if:

• You work remotely from the van. Laptop + Starlink + monitor can draw 50–90 Ah/day on top of your baseline. With 300Ah, you have room for a full work day plus all your domestic loads without anxiety.
• You camp in cloudy or northern climates. Scandinavia, Scotland, Pacific Northwest, UK winter — where you might get 2–3 consecutive days with minimal solar yield.
• You use a diesel heater heavily. Winter full-timers in cold climates can easily draw 100–140 Ah/day once the heater runs on medium or high.
• You prefer longer stays without moving. 300Ah gives you 2–3 days of autonomy versus 1.5–2 for 200Ah, meaning fewer forced drives just to recharge.
• You run 230V appliances regularly. A morning coffee ritual through an inverter, occasional use of a hair dryer, charging power tools — these short bursts add up.

300Ah is overkill if:

• You travel in sunny southern Europe and have 300W+ of solar. Your battery will rarely drop below 50%, meaning you are paying for capacity you never use.
• You drive every day. Regular alternator charging keeps even a 200Ah battery comfortably topped up.
• You have a minimal electrical setup (no inverter, no heater, basic lighting). A 200Ah or even 100Ah battery would suffice.

7. 200Ah vs 300Ah: side-by-side comparison

This comparison uses mid-range LiFePO4 batteries from reputable European brands. Prices are approximate as of mid-2026.

Key takeaway: the price per usable Ah is roughly the same for both capacities. The decision is not about value for money — it is about how many days of buffer you need between recharges.

8. Real-world autonomy scenarios

Three full-time van life profiles, each with different consumption patterns. All numbers assume 80% DoD on LiFePO4 and a 12V system.

Scenario A: Minimalist couple (southern Europe, summer)

• 200Ah: 160 ÷ 44 = 3.6 days without recharge
• 300Ah: 240 ÷ 44 = 5.5 days without recharge
• With 200W solar (southern Europe, ~5 peak sun hours): 200 × 5 × 0.85 ÷ 12 = 71 Ah/day. Both batteries stay full indefinitely.

Scenario B: Remote worker couple (central Europe, spring/autumn)

• 200Ah: 160 ÷ 117 = 1.4 days without recharge
• 300Ah: 240 ÷ 117 = 2.1 days without recharge
• With 300W solar (~3 peak sun hours): 300 × 3 × 0.85 ÷ 12 = 64 Ah/day. Net deficit: 53 Ah/day.
• 200Ah autonomy with solar: 3.0 days. 300Ah autonomy with solar: 4.5 days.

Scenario C: Winter full-timer (Scandinavia / Alps)

• 200Ah: 160 ÷ 140 = 1.1 days — essentially no buffer at all.
• 300Ah: 240 ÷ 140 = 1.7 days without recharge.
• With 300W solar (winter, ~1.5 peak sun hours): 300 × 1.5 × 0.85 ÷ 12 = 32 Ah/day. Net deficit: 108 Ah/day.
• 200Ah autonomy with solar: 1.5 days. 300Ah autonomy with solar: 2.2 days.
• Add DC-DC alternator (30A, 2h driving): +42 Ah. Net deficit: 66 Ah. 300Ah autonomy: 3.6 days.

9. Cost analysis: price per usable Ah

Battery prices have dropped significantly since 2023. Here is where popular brands land as of mid-2026 for 12V LiFePO4 models with integrated BMS and Bluetooth:

Two patterns emerge:

• The cost per usable Ah is slightly lower on 300Ah models. Manufacturers spread the fixed cost of the BMS and casing across more cells. The saving is small — 2–7% — but it means you are not paying a premium for going bigger.
• The absolute price difference is €200–400. That is the real question: is the extra buffer worth €200–400 to you?

For context, a single night on a campsite with hookup costs €15–30 across Europe. If 300Ah saves you even 10–15 hookup nights per year because you can stay off-grid longer, it pays for itself in 1–2 years.

10. When to go bigger (400Ah+)

If 300Ah still looks tight for your consumption, you have two paths:

• Single 400Ah battery. Brands like LiTime and Ampere Time offer 400Ah 12V LiFePO4 batteries at €900–1,200. Gives 320 usable Ah at 80% DoD. The trade-off is weight (35–45 kg) and size.
• Two batteries in parallel. Two 200Ah batteries give you 400Ah total (320 usable) with the added benefit of redundancy. If one fails, you still have 200Ah. Cost is typically €1,000–1,800 for the pair — more expensive than a single 400Ah, but with a safety net.

Parallel setups work best when both batteries are the same brand, model and age. Mismatched batteries can lead to uneven charging and shortened lifespan. Use identical cable lengths and gauge to each battery to ensure balanced current flow.

Going above 400Ah in a 12V system is unusual. At that point, consider whether a 24V system makes more sense — it halves the current for the same power, allowing thinner cables and smaller fuses. Several 24V 200Ah LiFePO4 batteries are now available from brands like Ective and Victron.

11. The sizing formula

Here is a step-by-step formula to calculate your ideal battery capacity:

1. List every appliance with its wattage and daily hours of use.
2. Calculate daily Ah for each: (watts × hours) ÷ 12. Add 12% for inverter loads.
3. Sum the total — this is your daily Ah budget.
4. Decide your buffer. How many days of autonomy do you want without any recharge? For full-time van life, 1.5–2 days is a practical minimum.
5. Divide by DoD. Use 0.8 for LiFePO4.

Formula: Battery Ah = (daily Ah × days of autonomy) ÷ DoD

Example: 90 Ah/day × 2 days ÷ 0.8 = 225 Ah. A 200Ah battery is slightly undersized; a 300Ah gives comfortable headroom.

Example: 60 Ah/day × 2 days ÷ 0.8 = 150 Ah. A 200Ah battery is well matched.