Lithium vs AGM vs gel: which leisure battery is right for your motorhome?

Choosing the right leisure battery for your motorhome is one of the most crucial decisions you will make. It is the heart of your off grid electrical system, quietly powering everything from the lights to the refrigerator. For years, the choice was a complex balance of cost and performance between traditional lead acid technologies. However, the landscape has changed dramatically. Today, the decision primarily revolves around three key players: Absorbent Glass Mat (AGM), Gel, and the increasingly dominant Lithium Iron Phosphate (LiFePO4).

As a technical writer in the motorhome space, my goal is to provide you with clear, accurate, and trustworthy information. This article will move beyond marketing claims and delve into real world data to compare these three battery technologies across the metrics that truly matter: lifespan, usable energy, charging requirements, and overall cost. We will dissect the specifications to help you invest in the right technology for your travel style, ensuring you have reliable power wherever your journey takes you.

A quick look at the technology

Before we compare them, let's briefly understand what we are working with. Both AGM and Gel batteries are types of Valve Regulated Lead Acid (VRLA) batteries, meaning they are sealed and maintenance free. In an AGM battery, the electrolyte is absorbed in a fine fibreglass mat pressed between the lead plates. This design makes them robust and excellent at delivering high currents when needed, for example, to power an inverter.

Gel batteries also use a sealed design, but here the electrolyte is mixed with silica to create a thick, gel like substance. This construction gives them a slight edge in terms of lifespan and performance in a wider range of temperatures compared to their AGM cousins. Lithium batteries, specifically LiFePO4, are a completely different chemistry. They are significantly lighter and can handle much deeper discharging and faster charging, all managed by an essential onboard computer called a Battery Management System (BMS).

Lifespan and cycle life: the long game

A battery's lifespan is not just measured in years, but in cycles. A cycle is one full discharge and recharge. How many cycles a battery can endure before its performance degrades significantly is a key indicator of its value. Here, the difference between the technologies is stark. A high quality AGM battery can typically provide between 600 and 1,200 cycles when discharged to the recommended 50% depth, while a Gel battery often delivers around 1,000 to 1,200 cycles under the same conditions.

Lithium batteries operate in a different league entirely. It is common for a LiFePO4 leisure battery to be rated for 4,000, 6,000, or even more cycles. This means a lithium battery can realistically last ten years or more, potentially outliving the motorhome it is installed in. Data from Victron Energy's own testing confirms that Gel batteries consistently outperform AGM at every depth of discharge, but neither comes close to the endurance offered by lithium.

Usable energy and depth of discharge

Perhaps the most misunderstood, yet critical, specification is a battery's usable capacity, which is determined by its recommended Depth of Discharge (DoD). To preserve their lifespan, it is widely recommended that you do not discharge AGM or Gel batteries below 50% of their rated capacity. This means a 100 amp hour (Ah) AGM or Gel battery only provides you with 50Ah of usable power before it needs recharging.

This is where lithium technology presents its most compelling practical advantage. Lithium batteries can be regularly discharged to 80% or even 100% of their capacity without any negative impact on their lifespan. Therefore, a 100Ah lithium battery provides at least 80Ah of usable energy. In real world terms, to get 100Ah of usable power, you would need a 200Ah AGM or Gel battery bank, whereas a single 125Ah lithium battery would suffice, saving both space and significant weight.

Weight: a factor that really adds up

Weight is not just a convenience issue for motorhome owners; it directly impacts your payload allowance. A typical 100Ah AGM battery weighs between 27 and 32 kg, while a Gel equivalent tips the scales at 30 to 35 kg. A lithium battery of the same capacity weighs a remarkably light 11 to 14 kg. That is roughly a third of the weight of its lead acid counterparts.

When you factor in the usable capacity advantage, the weight saving becomes even more dramatic. To achieve 100Ah of usable energy, you would need around 60 to 70 kg of AGM batteries compared to just 11 to 14 kg of lithium. That is a difference of around 50 kg, which is a meaningful amount of payload you could use for water, food, or equipment instead.

Charging: speed, efficiency, and system compatibility

How you replenish the energy in your battery is just as important as how you use it. AGM batteries are relatively robust in their charging requirements and can be charged at a reasonable rate, often taking around 6 to 8 hours for a full charge. Gel batteries are more sensitive; they require a slower, more controlled charge with a slightly lower voltage to prevent the gel electrolyte from being damaged by overheating. A typical Gel battery needs 8 to 10 hours for a full charge, and overcharging can cause permanent, irreversible damage.

Once again, lithium batteries excel here. They have a very high charge efficiency, close to 99%, compared to the 80 to 85% efficiency of lead acid types. This means almost every watt of power from your solar panels or alternator goes into the battery rather than being lost as heat. They can also be charged much faster, often in just 2 to 4 hours, provided you have a compatible charger. It is crucial to note that your motorhome's existing charging system, including the split charger, solar controller, and mains charger, must be lithium compatible or replaced to safely and effectively charge a LiFePO4 battery.

Cold weather performance: the lithium caveat

This is the one area where lead acid technology holds a genuine advantage. AGM and Gel batteries can both charge and discharge in sub zero temperatures, although their performance is reduced. Gel batteries, in particular, handle temperature extremes slightly better than AGM, with Victron Energy's data showing a longer service life at elevated temperatures.

Lithium batteries have a well documented limitation: they should not be charged below 0°C, as doing so can cause permanent damage to the cells. Discharging in cold weather is generally fine down to around minus 20°C, but the charging restriction is a real consideration for winter motorhome use. The good news is that many modern lithium leisure batteries now come with built in heating elements that warm the cells before charging begins, effectively solving this problem for a modest additional cost.

The cost factor: upfront investment vs lifetime value

There is no denying that lithium batteries come with a higher initial purchase price. A 100Ah AGM battery might cost between £120 and £180, while a 100Ah Gel battery typically falls in the £180 to £250 range. A 100Ah lithium battery, by comparison, will likely set you back between £200 and £350, although prices have been steadily decreasing over recent years as manufacturing scales up.

However, the story changes completely when you analyse the lifetime cost. By dividing the initial cost by the number of expected cycles, we can calculate a cost per cycle. For an AGM battery, this works out to roughly 19 pence per cycle. For a Gel battery, it is about 20 pence. For a lithium battery, the cost plummets to as low as 6 pence per cycle. This simple calculation reveals that while the upfront cost is higher, a lithium battery provides far greater value over its operational life. When you also factor in the potential need to replace an AGM or Gel battery two or three times during the period a single lithium battery would still be going strong, the financial case becomes overwhelming.

Putting it all together: a direct comparison

To make the differences as clear as possible, the table below summarises the key specifications for a typical 100Ah leisure battery of each type. This data is based on extensive research of manufacturer datasheets and real world market pricing in the UK for 2025/2026. This visual guide should help consolidate the information and highlight the distinct advantages and disadvantages of each technology.