AGM vs GEL vs Lithium: Which Leisure Battery for a Campervan?

Choosing the wrong battery chemistry can cost you hundreds of euros in replacements — or leave you stranded with a dead bank on a cold morning. AGM, GEL and lithium each have real trade-offs in usable capacity, lifespan, weight and price. This guide puts the numbers side by side so you can pick with confidence, not marketing hype.

1. Why battery chemistry matters

A leisure battery is not a car starter battery. It needs to deliver steady power over hours — lighting, fridge, USB charging — then accept a slow recharge from solar or alternator. That cycling behaviour is where chemistries diverge.

The three numbers that define real-world performance are:

• Depth of discharge (DoD) — how much of the nameplate capacity you can actually use without damaging the cells.
• Cycle life — how many full charge-discharge cycles the battery survives before dropping below 80% of its original capacity.
• Energy density — how much usable energy you get per kilogram of weight.

A 100 Ah AGM and a 100 Ah lithium have the same label, but they deliver wildly different amounts of usable energy over their lifetime. Understanding those differences is the key to making the right investment.

2. AGM: the affordable workhorse

Absorbent Glass Mat (AGM) batteries are a type of sealed lead-acid. The electrolyte is held in fibreglass mats between the lead plates, making them spill-proof and vibration-resistant — a big upgrade over flooded lead-acid for a moving vehicle.

Strengths

• Low upfront cost — a quality 100 Ah AGM costs around 150 to 250 euros.
• Widely available — you can find one at almost any auto parts store or marine supplier, even in remote areas.
• Simple charging — works with any standard lead-acid charger, B2B or solar controller out of the box.
• Proven reliability — well-understood technology with decades of track record.

Weaknesses

• 50% DoD limit — regularly discharging below 50% dramatically shortens lifespan. A 100 Ah AGM effectively gives you only 50 Ah.
• Heavy — around 28 to 32 kg for 100 Ah. Two in parallel for 200 Ah means 60+ kg.
• Shorter cycle life — typically 400 to 600 cycles at 50% DoD, which translates to roughly 2 to 3 years of daily use.
• Voltage sag — output voltage drops noticeably as the state of charge decreases, which can cause some appliances to cut out before the battery is truly "empty".

3. GEL: heat-resistant and maintenance-free

GEL batteries use a silica-based gel instead of liquid acid. This makes them completely sealed, very resistant to vibration, and better suited to high ambient temperatures than AGM.

Strengths

• Excellent heat tolerance — degrades more slowly in hot climates (Southern Europe, Africa, Australia) where AGM cells lose capacity faster.
• Slightly longer cycle life than AGM — typically 600 to 800 cycles at 50% DoD.
• Very low self-discharge — retains charge well over months of storage.
• Zero maintenance — no watering, no gas venting.

Weaknesses

• Same 50% DoD as AGM — usable capacity is still halved.
• Sensitive to overcharging — requires a GEL-specific charge profile. Overcharging dries out the gel permanently.
• Pricier than AGM — typically 20 to 40% more for similar Ah, without the leap in performance that lithium offers.
• Same weight penalty — lead-acid chemistry is inherently heavy.

4. Lithium (LiFePO4): the van life standard

Lithium Iron Phosphate (LiFePO4) has become the default for serious campervan builds. It is lighter, stores more usable energy, and lasts far longer than either lead-acid chemistry — but it demands compatible charging equipment and a higher budget.

Strengths

• 80 to 90% DoD — a 100 Ah lithium battery delivers 80 to 90 Ah of usable energy, versus 50 Ah from lead-acid.
• 2000 to 5000+ cycle life — at daily use, that is 5 to 14 years before meaningful degradation.
• One-third the weight — a 100 Ah LiFePO4 weighs around 11 to 13 kg, versus 28 to 32 kg for AGM.
• Flat voltage curve — delivers a steady 13.2 to 13.4V from full down to nearly empty, so appliances run consistently.
• Fast charge acceptance — can absorb high charge currents without damage, which means solar and alternator fill it faster.

Weaknesses

• Higher upfront cost — a quality 100 Ah LiFePO4 costs 400 to 800 euros. Budget brands exist below 300 euros but BMS quality varies.
• Cold sensitivity — most LiFePO4 cells must not be charged below 0 degrees Celsius. Higher-end models include a heated BMS to handle freezing conditions.
• Requires compatible chargers — your DC-DC charger, shore-power charger and solar controller must have a lithium / LiFePO4 profile.
• Not a drop-in for every rig — old vehicles with basic alternator regulators may need a dedicated B2B charger upgrade.

5. Head-to-head comparison table

Here is every spec that matters, normalized to a 100 Ah nameplate battery.

6. Cost per cycle: the real price comparison

Upfront price is misleading. What matters is cost per usable Ah over the battery's lifetime — the price of each amp-hour you actually get to use before the battery dies.

Let us run the numbers for a 100 Ah battery in each chemistry:

Lithium costs roughly three times less per usable Ah over its lifetime — even though it costs three times more up front. The break-even point typically arrives after 1.5 to 2 years of daily cycling.

7. How to choose: decision framework

Rather than a one-size-fits-all answer, match the battery to your usage pattern:

8. Charging compatibility

Switching from lead-acid to lithium is not just swapping the battery. Your charging sources must match the chemistry.

• Solar charge controller (MPPT) — most modern MPPT controllers (Victron, Renogy, EPEver) have a LiFePO4 preset. Set it to 14.2 to 14.6V absorption, 13.6V float.
• DC-DC / B2B charger — mandatory if your vehicle's alternator regulator does not output the right voltage. A dedicated B2B charger (Victron Orion, Renogy DCC series) isolates the leisure battery and charges at the correct profile.
• Shore-power charger — ensure it has a lithium mode. Most multi-stage smart chargers do.

If you keep AGM or GEL, make sure your solar controller is set to the correct chemistry. GEL especially is sensitive to overvoltage — a wrong profile will permanently damage the cells.