100Ah vs 200Ah vs 300Ah: Which Battery Size for Your Van?

Choosing the right battery size is one of the first major decisions in a campervan electrical build. Go too small and you will be constantly worrying about power. Go too large and you have wasted money and added unnecessary weight. This guide breaks down the three most common LiFePO4 battery sizes for UK campervans — 100Ah, 200Ah, and 300Ah — with real usage data so you can make the right choice for how you actually use your van. For a full overview of battery types and selection, see our campervan battery guide.

The right battery size depends on three things: what appliances you run, how long you stay off-grid between charges, and how much solar or alternator charging you have. Rather than guessing, the best approach is to calculate your actual daily energy consumption and work backwards. Our calculator does this for you automatically — enter your appliances and it recommends the right size.

Quick Summary

Understanding Usable Capacity

The rated capacity on the battery label is not what you actually get in practice. LiFePO4 batteries should be discharged to 20% state of charge for optimal lifespan, giving you approximately 80% usable capacity:

• 100Ah rated = 80Ah usable = 1,024Wh
• 200Ah rated = 160Ah usable = 2,048Wh
• 300Ah rated = 240Ah usable = 3,072Wh

All the run time estimates in this guide use these usable figures, not the rated capacity.

What Does Each Size Actually Power?

100Ah LiFePO4 — The Weekend Battery

Usable energy: 1,024Wh

A 100Ah LiFePO4 battery is sufficient for minimalist setups and short trips. Here is what a typical day looks like:

At 475Wh per day, a 100Ah battery (1,024Wh usable) lasts approximately 2.2 days without any charging. With 100-200W of solar in summer, you can extend that significantly.

Where 100Ah falls short: Add a diesel heater (150-200Wh/night), a laptop (195Wh), and inverter standby (200Wh), and you are suddenly at 1,000Wh+ per day — exceeding the battery's usable capacity in a single day. If you plan to use any of these regularly, 100Ah is too small.

Best 100Ah option in the UK: The Fogstar Drift 105Ah at around £299 offers excellent value with built-in Bluetooth monitoring.

200Ah LiFePO4 — The Sweet Spot

Usable energy: 2,048Wh

A 200Ah battery is the most popular choice for UK campervan builds, and for good reason. It covers the majority of use cases without being excessive.

At 950Wh per day, a 200Ah battery (2,048Wh usable) lasts approximately 2.2 days without charging. With 200W of solar in UK summer (generating 600-800Wh per day), you offset 60-80% of daily use, extending off-grid capability to 4-7 days.

Where 200Ah works well: Weekend trips, week-long holidays, and occasional longer stays. If you have solar and/or drive regularly (DC-DC charger), 200Ah handles most UK van life comfortably.

Where 200Ah struggles: Full-time van life with heavy use (remote work, induction cooking, electric heating). Extended winter off-grid stays with limited solar.

Best 200Ah option in the UK: The Fogstar Drift 230Ah at around £549 is technically 230Ah but sits in this category. It offers the best value per Ah in the UK market.

300Ah LiFePO4 — The Full-Timer

Usable energy: 3,072Wh

A 300Ah battery is for those who need extended off-grid capability or run heavy loads daily.

At 1,538Wh per day, a 300Ah battery (3,072Wh usable) lasts approximately 2 days without charging. With 300-400W of solar in summer, you can be largely self-sufficient.

Where 300Ah shines: Full-time van life, remote working, extended off-grid stays, and winter use where solar input is limited.

Best 300Ah option in the UK: You can achieve 300Ah+ by pairing two Fogstar Drift batteries (e.g., two 230Ah units for 460Ah total). Single 300Ah batteries are available from brands like LiTime and Renogy but are less common in the UK market.

How to Choose: Decision Framework

Choose 100Ah if:

• You use the van for occasional weekends only
• You have minimal power needs (no laptop, no heater)
• Budget is the primary concern
• You are building a small van (VW Transporter, Caddy) where weight and space are critical
• You always have access to shore power or drive daily

Choose 200Ah (or 230Ah) if:

• You use the van for weekends and 1-2 week holidays
• You run a fridge, lighting, heater, and occasional laptop use
• You have or plan to install 200W+ of solar
• You want a balance of capability, cost, and weight
• This is the right choice for most UK van builds

Choose 300Ah+ if:

• You live in the van full-time or do extended trips (2+ weeks off-grid)
• You work remotely and need to charge a laptop daily
• You run heavy loads (induction hob, large inverter, electric heater)
• You travel in winter regularly and need reserves for low-solar periods
• Weight and cost are secondary to capability

The Impact of Charging Sources

Your battery size decision should not be made in isolation. Your charging sources dramatically affect how much battery capacity you need:

Solar

In UK summer conditions, expect 3-4 peak sun hours per day. A 200W panel generates approximately 600-800Wh per day. In winter, this drops to 1-2 peak sun hours (200-400Wh). Solar reduces the effective battery drain but cannot be relied upon as the sole charging source in the UK, especially in winter.

DC-DC Charger (Alternator)

A 30A DC-DC charger delivers approximately 385Wh per hour of driving. A 2-hour drive replenishes about 770Wh — roughly a third of a 200Ah battery. If you drive daily, your DC-DC charger can be your primary charging source.

Shore Power

A 20A mains charger delivers approximately 250Wh per hour. Overnight on a campsite with hook-up, you can fully charge almost any battery bank. If you frequently use campsites with electric hook-up, you need less battery capacity.

Sizing With Charging

If you drive every day and have solar, you can get away with a smaller battery because it is constantly being topped up. If you park for days without driving and have no solar, you need a larger battery to bridge the gap.

Cost Comparison (UK, 2025)

The Fogstar Drift 230Ah hits the sweet spot of price, capacity, and quality for the UK market. For budget-conscious builders who need 300Ah+, the LiTime 300Ah is worth considering but has less UK market presence and support.

Weight and Space Considerations

In a campervan, every kilogram matters against your payload limit. Battery weight adds up quickly:

For smaller vans like VW Transporters, Vauxhall Vivaros, or Ford Transit Customs, space and weight are at a premium. A single 200-230Ah battery is usually the practical maximum. For larger vans (Sprinter LWB, Ducato LWB), two batteries in parallel are feasible.

Use our calculator to determine the right battery size for your specific appliance usage, then choose based on the options available in your budget and space constraints.

FAQ

Is 100Ah enough for a campervan?

For occasional weekend use with minimal loads (lights, fridge, phone charging), 100Ah LiFePO4 is adequate. For anything more — diesel heater, laptop, longer trips — it is too small for comfortable use without daily charging.

Is 200Ah enough for full-time van life?

It depends on your usage. If you have good solar (300W+), drive regularly, and are mindful about power use, 200Ah can work for full-time living. For heavy users or those who want comfortable margins, 300Ah+ is recommended.

Can I start with 100Ah and add another later?

You can, but it is not ideal. Batteries wired in parallel should be the same brand, model, and age. Adding a new battery to an older one causes uneven loading. It is better to buy the right size from the start.

What about 400Ah or more?

For large full-time setups (especially those running induction hobs or air conditioning), 400Ah+ is appropriate. This typically requires two batteries in parallel. See our guide on wiring batteries in parallel for details.

Does a bigger battery charge slower?

At the same charge rate (e.g., 30A from a DC-DC charger), a larger battery takes proportionally longer to charge from empty to full. However, in practice you rarely drain a properly sized battery below 40-50%, so charge times are similar. A bigger battery also means you can charge opportunistically — even a short drive adds a useful amount.