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Lithium leisure battery for campervans – are they worth it?

Contents

You’ve heard the rumour: there’s a flashy new type of leisure battery that outshines the old alternatives by miles. Your van friends say you have to get a lithium leisure battery, but you’ve seen how much they cost and you’re not convinced! Are they really worth that extra big price tag?

This article will explain how a lithium leisure battery works, compare them with the much-loved AGM leisure battery, and discuss whether they’re the right choice for your campervan set-up. 

For an overview of campervan batteries, take a look at our leisure battery page. This short guide can help you pick the perfect battery for your van.

Need to clue-up on some basic campervan electrics first? Have a read of our campervan electrical system guidebook page to bring you up to speed. 

What is a lithium leisure battery?

There are a few different types of leisure battery available, all with their own pros and cons. The lithium-ion battery is the most recent to join the leisure battery market. 

campervan leisure battery types lead acid agm gel lifepo4 lithium

How does a lithium leisure battery work?

Lithium-ion batteries produce electricity through the movement of lithium ions and electrons. Throwback to that all-important high school chemistry lesson: an ion is created when an atom has gained or lost an electron, and therefore has a negative or positive charge. 

how does a lithium leisure battery work lithium ions and electrons

A lithium battery takes advantage of the fact that the lithium ions and free electrons are compelled to join back together because they are in an ‘unstable’ state. If some sort of load is connected across the terminals, the ions and electrons travel from the anode to the cathode. The battery uses a separator that forces the ions to travel through the battery and the electrons to flow around the circuit. This creates the current needed to power the load. When the battery is recharged, the process is reversed and the lithium ions and free electrons are replaced in the anode. 

how does a lithium leisure battery work chemistry diagram showing anodes and cathodes lithium ions during discharge

The first lithium battery came to market in the 1970s and revolutionised the battery industry with its high energy capacity and low weight. They were first used for small devices such as cameras and mobile phones, but have recently become available as a leisure battery and are becoming increasingly popular.

Different types of lithium battery

You may have come across a variety of names for lithium ion batteries: Li-ion, LiFePO4, LFP, NMC, NCM. This is because there are a few different types, depending on which material has been used for the cathode or the anode.

NCM batteries have a cathode made from Lithium Manganese Cobalt Oxide and are the most widely used type of lithium battery. Their high power output makes them the perfect choice for use in power tools, e-bikes and electric vehicles, and they’re also used in some portable powerbanks.

For a leisure battery, LiFePO4 is the name you want to look out for. LiFePO4 (or LFP) use Lithium Iron Phosphate for the cathode material and their high current rating, long cycle life and tolerance to misuse make them ideal for use in campervans. They also have good thermal and chemical stability, making them slightly safer than NCM batteries. 

What is the usable capacity of a lithium leisure battery?

Fully draining a conventional lead acid battery will significantly shorten its lifespan and can cause irreparable damage. This means you can’t use all of the battery’s rated capacity and you’ll need to account for this when you design your electrical system. With a lithium-ion battery, all of the battery’s capacity is available to use.

But how much difference does this really make? And should you really drain a lithium battery 100%?  Let’s get into the nitty-gritty of battery capacity and the difference between lithium-ion and lead acid batteries. 

Not a fan of maths and just want to know if a lithium leisure battery is the right choice for you? Go on then, you can skip to the end.

Useful definitions

Depth of Discharge (DoD): How far a battery is discharged relative to its capacity. 

From a 100Ah battery, if we power a light that draws 2A for 10 hours (20Ah), the depth of discharge will be 20Ah/100Ah = 20%. 

lithium leisure battery depth of discharge graphic

Cycles: How many times a battery has been discharged and recharged. If we power that 2A light for 10 hours, then fully recharge the battery, we have completed 1 cycle at 20% DoD.

graphic showing 1 cycle of a leisure battery charging and discharging lithium lifepo4

Lifespan (or ‘Design Cycle Life’): How many cycles a battery can perform until it becomes unfit for purpose. Most manufacturers define this as the point at which the battery only holds 80% of its original capacity.

How far can a lead acid battery be discharged?

The lifespan of lead acid batteries are significantly influenced by how deeply they are discharged. Regular deep discharges will have a negative effect on the number of cycles the battery will be able to perform.

Agm leisure battery lifecycle based on depth of discharge graphic showing cycles

Because lead acid batteries are so affected by the depth of discharge, many of these batteries, particularly flooded lead acid batteries, only have a maximum DoD of around 50%. AGM and gel batteries are also lead acid and can typically be discharged more than this, but just how far is down to personal choice and the consideration of how long you want the battery to last.

Some high-quality AGM and gel batteries can withstand very deep discharges, but most lead acid batteries will be irreparably damaged if they are fully discharged.

So what about lithium leisure batteries?

Can lithium batteries really be discharged 100%?

Short answer: Yes!

Even though an increase in the depth of discharge does decrease the battery’s lifespan, a good-quality lithium battery can still achieve 1000s of cycles at 100% DOD. This means you can use all of that available capacity, and the lithium battery will still outlive a lead acid battery by years.

lithium leisure battery lifecycle based on depth of discharge graphic showing cycles

Most manufacturers advise against regularly discharging your lithium battery to 100% DoD. When you’re designing your electrical system, we recommend you plan to use up to 90% of your lithium leisure battery’s capacity.

If you’ve ever relied on lead acid batteries as your source of power, you’ll know the twitchy feeling of constantly checking your battery voltage, trying to guess how much power you have left, dimming the lights and turning the fridge down a few clicks. Hopefully you haven’t experienced that sinking feeling when your lights suddenly cut out because you’ve run your battery completely flat! With a lithium battery, if you’re running low on charge, you have the luxury of using that extra battery capacity without the worry of any real damage.

Total beginner when it comes to wiring electrical components? We have loads of advice to give on how to wire a campervan electrical system.

How long will a lithium leisure battery last for?

How long a lithium leisure battery will last for will depend on the quality of the battery, how often you use it, and how deeply you discharge it on a regular basis. But even the shortest lifecycle of lithium batteries at 100% DoD is more than enough for most off-grid applications.

Example

You’ve chosen a battery which should last you 3 days off-grid without charging before you need to recharge. So the estimated time for one cycle is 3 days. TN Power’s 12V lithium leisure batteries last for ~2,500 cycles at 90% DoD.

This means the battery could last for 2,500 x 3 = 7,500 days. This equates to 20 years if you’re using your van 365 days of the year! Weekend warriors will cycle their battery much less frequently and get an even longer lifespan.

Scratching your head and bored of all this maths? Try Nomadic Energy, our our free electrical system design service where we’ll do all the calculations for you! All you need to do is answer a series of questions about your usage and we’ll take care of the rest. We provide a bespoke proposal for your system for free, and when you purchase your components through us, we’ll also provide a free bespoke wiring diagram.

Our free electrical system design service makes off-grid energy simple.

How much does a lithium leisure battery cost?

A lithium leisure battery costs anywhere between around £370 to over £1,000 for a 100Ah battery. This number can vary pretty wildly based on the quality, lifespan and features of the battery. You can generally expect to pay around £100 extra per battery for a heated lithium battery (more on that soon).

We only stock high-quality lithium leisure batteries. Our favourite is the Fogstar Drift. They boast an incredible combination of functionality and affordability. Firstly, the price per Ah is almost unbeatable. Not only that, but they have a suite of impressive features. As standard, all Drift batteries include a heater, a built-in Bluetooth app and a 10 year warranty. Plus, Fogstar are the UK’s leading lithium battery manufacturer.

If you have a higher budget and you’re looking for a battery from a well-known brand, then you’re in safe hands with Victron. The Victron lithium batteries will integrate with the rest of a smart Victron system, and will no doubt outlive your van several times over. Alternatively, RELiON batteries boast the most impressive lifespan figures and also have a 10 year warranty.

However, at almost 3 times the cost, it’s quite hard to justify these choices! We believe the Fogstar batteries offer the best combination of performance and cost.

If the price of a lithium leisure battery is simply out of budget for you, AGM batteries are generally more affordable and offer the best balance of cost and performance for many campervan owners.

If you will not use your campervan full-time, then it’s likely a lithium battery will outlive your campervan. On the flip side, if you use your camper every single day, you will probably need to replace an AGM leisure battery every 2-4 years. So, lithium might be a better option.

A few years ago, lithium batteries used to be around 4 times more expensive than AGM. And if we look at Victron dual-purpose AGM vs Victron lithium batteries, that’s still the case. However, with brands such as Fogstar paving the way for more affordable lithium batteries, the price gap is closing. A 105Ah Fogstar Drift battery is less than double the cost of a 100Ah Victron AGM battery. So, this may well make lithium a more viable option for many more.

AGM vs lithium leisure batteries

Lithium batteries are:

  • lighter
  • smaller
  • last longer

but are more expensive than AGM batteries.

Example

You’ve calculated that you will use 70Ah of power per day, and you would like to be able to spend up to 3 days off-grid without charging. So you will need 210Ah of usable battery capacity.

Let’s base our calculations on someone living in their van full-time. So we would typically recommend that a lithium leisure battery is discharged up to 90% DoD, whereas an AGM battery is only discharged by 65% DoD. This is because, in the case of someone using their van full-time, it will help to prolong the lifespan of the battery.

Comparing 12V batteries, you could either buy:

230Ah lithium battery

Fogstar Drift

@ 90% usable capacity

or

2x 165Ah AGM batteries

Victron AGM

@ 65% usable capacity

When comparing TN Power’s lithium and AGM batteries, for the same usable capacity, the AGM batteries weigh 3.4 times more than the lithium batteries.

The lithium batteries have 4.7 times more cycles than the AGM batteries.

But the lithium batteries are 1.6 times more expensive for the same usable capacity. 

Leisure battery discharge rate

Other than the available capacity (Ah), a significant difference between lithium and lead acid batteries is in how much current (A) can be drawn at any one time. This is referred to as ‘discharge rate’. A large current will discharge the battery faster, and for AGM batteries, a faster discharge will reduce the total Ah capacity. This is called the Peukert effect.

Battery manufacturers rate the capacity of lead acid leisure batteries based on a 20 hour discharge, called the C20. For example, a 100Ah battery will be able to provide 5A for 20 hours. However, if we discharged the same battery faster, say at 50A, we wouldn’t get 2 hours from the battery as you might expect. Instead, we might only get 1 hour of current at 50A, which is only 50Ah – around 50% of the 100Ah capacity.

Lithium batteries are much less affected by fast discharge and so can handle large currents better than AGM batteries. This is why we always recommend lithium batteries if you’re planning on installing an induction hob, or any other high wattage appliances that draw a large amount of power.

Most lithium batteries specify a maximum discharge current of around 1C (100A from a 100Ah battery, or 200A from a 200Ah battery), and Victron Smart batteries can supply as much as 2C, or 200A from a 100Ah battery!

However, it’s important to check the max discharge current of any lithium battery before purchase. If you have a large inverter (e.g. 3000W), this will draw a max of 250A. So, you will need a lithium battery with a higher discharge current. Alternatively, you can connect two batteries with a lower discharge to access a higher max discharge.

Lithium battery use-case examples

We design campervan electrical systems for new customers every day, so we thought we’d share some typical cases where we have recommended lithium leisure batteries.

Example 1

This customer was planning on using their van both off-grid and on campsites. Additionally, they would be using their van for several months at a time on longer trips.

Appliances

Fridge

Phone chargers

Laptop chargers

Hairdryer

Speaker

We recommended a single 280Ah lithium leisure battery, which would give them 3 full days off-grid without recharging. So, this meant they could spend a few days in one place even in bad weather.

Example 2

This customer was planning on using their van both off-grid and on campsites. Additionally, they would be living in and working from their van full-time. Finally, they had a high wattage appliance (a hairdryer) which required a high discharge current.

Appliances

Fridge

Phone chargers

Laptop chargers

WiFi router

Speaker

Blender

Hairdryer

We recommended a 460Ah lithium leisure battery bank. As a result, they would have 3.5 full days off-grid without recharging. So, they wouldn’t need to worry about running out of power whilst working, even if the sun wasn’t shining.

Example 3

This customer was planning on using their van fully off-grid. Additionally, they would be living in their van full-time.

Appliances

Fridge

Phone chargers

Laptop chargers

We recommended a 230Ah lithium leisure battery. As a result, they would have 3 full days off-grid without recharging. So, they would never need to worry about running out of power whilst off-grid.

Lithium leisure batteries in cold temperatures

Other than the price tag, there’s just one other major downside to lithium batteries that might be the deciding factor for you: most of them can’t be charged below 0oC. If you have big plans to travel through sub-zero temperatures, you may have to do a little extra thinking to keep your lithium battery alive and well.

Most lithium battery manufacturers limit the operating temperature to around 0oC-50oC for charging and -20oC – 60oC for discharging. That means you can discharge them below 0oC, but you can’t recharge them. Most good-quality lithium batteries come with some form of built-in protection that will automatically prevent charging below 5oC. Without this protection, a lithium battery in sub-zero temperatures may appear to charge as normal, but plating of metallic lithium will occur on the anode which will permanently degrade the performance and safety of the battery.

But don’t despair! If you think your lithium battery might reach sub-zero temperatures, you still have a couple of options. Firstly, are now lithium leisure batteries on the market which can be charged in sub-zero temperatures. Secondly, there are several ways of heating a leisure battery to keep it at a safe operating temperature. 

Low temperature lithium leisure batteries

RELiON have developed a new series of lithium leisure batteries which can be charged and discharged in temperatures as low as -20oC.

This extra functionality comes with a cost, but if you need to use your lithium battery in low temps, the RELiON LT (low temperature) series will give you everything you need. 

Heated lithium leisure batteries

TN Power and EcoTree have developed a self-heated 12V lithium ion battery which includes a built-in heater, keeping the battery above 5oC when charging. These come at a little extra cost but can be used in temperatures below 0oC.

All of the Fogstar Drift batteries have a built-in heater. So, you don’t need to worry about cold temperatures when charging your leisure batteries.

DIY battery heaters

Wrapping an electric heating pad around a lithium battery can be a cheap alternative to the self-heated battery. Heat pads which have been designed for campervan water tanks even have their own built-in thermostat and will only kick in at certain temperatures.

If you choose to use a heat pad, be careful of overheating! Keep an eye on your battery’s thermometer reading and make sure the BMS will react to any overheating.

The need for a battery heater will depend heavily on where the battery is located in your van. If you plan on travelling in cold climates, try and install your battery somewhere warm and well-insulated. So long as your van’s interior is at a sensible, ambient temperature, then your batteries should be too. This will improve the battery’s efficiency when it’s cold and could remove the need for a heating pad even when the outside temps are sub-zero. For example, if the battery is installed in the garage, consider adding a heater outlet into the garage to avoid creating a cold, damp environment. Adding a heater outlet to any large ‘non-living’ spaces is also a good way to keep the mould at bay!

Insulating the space around your battery will be equally relevant if you’re planning on visiting really hot climates; keeping the battery within the cool, insulated part of the van will improve efficiency and prevent overheating.

Fogstar lithium batteries w. 250A busbar 12V kit - Pick from 280Ah-560Ah battery bank
Leisure battery kits

Our leisure battery kits include everything you need to fully install a battery subsystem. Pick AGM or lithium, busbar size, and we’ll provide everything you need. Plus, we’ll send you a wiring diagram and detailed installation guidance.

Do I need a lithium leisure battery?

We now have all the information we need to decide if a lithium battery is right for you. The numbers don’t lie – lithium batteries out-perform their lead acid counterparts by miles. However, they do cost anywhere from 1.5 to 4 times more than their AGM counterpart. So, you really need to justify spending that extra chunk of your van conversion budget.

Here’s the main reasons you might opt for lithium:

Weight and space are really important to you

If you need quite a large battery bank, lead acid batteries can eat into a large chunk of your storage space and limited weight allowance.

You’re planning on needing a lot of power

If you’re going to use a lot of high-power appliances, like a hairdryer or an induction hob, a lithium battery will be able to sustain these high current discharges without losing capacity due to the Peukert effect. We normally recommend lithium batteries if you need a battery bank over 460Ah, due to the weight of an AGM battery bank of this size.

You’re planning to live in your van full-time

If you’re going to be using your van for weekends and holidays, the lifespan of an AGM battery will probably be more than sufficient, and a lithium battery would be overkill (unless you fall into one of the buckets above). If you’re planning on living in your van full-time, the lifespan of your battery becomes a lot more important and you could run through an AGM battery bank pretty quickly.

Example

You’ve worked out your average daily power usage to be around 40Ah/day and you’ve decided that you want to last off-grid for at least 2 days before you need to recharge. That means the batteries complete 1 full cycle in 2 days.

High frequency Medium frequency Low frequency
Days per year
365 days
144 days
70 days
Cycles per year
183
72
35

AGM lifespan

700 cycles

3.8 years
9.8 years
20 years

Lithium lifespan

2,500 cycles

13.7 years
> 20 years*
> 20 years*

*other aspects of the battery will degrade over time making it very unlikely for any battery to have a lifespan over 15-20 years

If you want your battery to last for at least 10 years, then an AGM battery provides enough cycles for low-medium frequency use. But if you’re planning to live in your van full-time, an AGM battery will begin to lose capacity after 3 or 4 years and may no longer meet your daily usage requirements.

We recommend lithium-ion batteries to most customers who want to experience full-time van life without the hassle of battery degradation after 3 or 4 years.

We also recommend lithium leisure batteries to any customers who would need an AGM battery bank larger than 460Ah, due to the size and weight implications!

Still not sure if a lithium battery is right for you? Try our free electrical system design service where we’ll do all the calculations for you!

Our free electrical system design service makes off-grid energy simple.

Which lithium leisure battery should I buy? 

As you’re searching online, you’ll find all sorts of leisure batteries for sale, with unfamiliar brand names and enticingly cheap price tags. However, it can be hard to tell the difference between a bargain and a knock off.  To give you peace of mind, we only stock batteries we would be happy to install in our own campervan conversions.

When it comes to lithium leisure batteries, our favourite brands are TN Power, RELiON, Victron Energy, and Transporter Energy. They all have a good lifespan, battery protection and a respectable warranty.

Here’s a quick summary to help you choose between these brands:

Fogstar Drift lithium batteries

  • Best balance of performance and cost
  • All include a heater by default
  • 10 year warranty
  • 4,500 cycles at 80% DOD
  • Connect up to 4 batteries in series and parallel

Fogstar Drift are our lithium leisure battery of choice in all of our Nomadic Energy electrical systems. We think they provide the best balance of cost and performance. As Fogstar are the UK’s leading lithium battery manufacturer, this feels like safe choice.

Victron Energy lithium batteries

  • 2,500 cycles at 80% DOD
  • 3 year warranty
  • Smart models have built-in Bluetooth – wireless monitoring and control via an app
  • Smart models have no built-in BMS – must be purchased separately
  • Connect up to 4 batteries in series and 5 batteries in parallel

Victron Energy are a well known, high-quality electrical component brand. For those looking to buy their lithium leisure battery from a reputable brand with a long history, the additional cost of Victron batteries is worth it.

RELiON lithium batteries

  • 7,000 cycles at 80% DOD
  • 10 year warranty
  • LT (low temperature) models can be used in sub-zero temps (down to -20oC)
  • HP (high peak amp) model can provide up to 800A and can be used for starting a motor or generator
  • Connect up to 4 batteries in series and 4 batteries in parallel

RELiON are a trustworthy, reputable brand, and their numbers speak for themselves. RELiON LiFePO4 batteries boast an impressive 7,000 cycle lifespan, and they all come with a 10 year warranty. RELiON are our go to premium choice for those looking for a high quality battery.

Transporter Energy (Battle Born Batteries) lithium batteries

  • Most expensive lithium leisure battery
  • 5000 cycles at 80% DoD
  • 10 year warranty
  • Connect up to 4 batteries in series and infinite batteries in parallel

Transporter Energy are the rebranded battery of the well known US brand Battle Born Batteries. Despite their price tag, they are a popular lithium battery choice.

One of the big selling points of the Battle Born Batteries is that there’s no limit to how many you can connect in parallel. This means you can make your battery bank as big as you need it to be.

Lithium battery brands – a direct comparison

RELiON and Transporter Energy are definitely the most expensive batteries, but you can see how this is justified when we compare the lifespan and warranty that comes with each battery brand:


Cycle Life (at 80% DOD)Warranty

Victron

2500 cycles3 years

Fogstar

4500 cycles

10 years

Transporter Energy

5000 cycles10 years

RELiON 

7000 cycles10 years

Finally, your decision might also depend on the shape of the batteries themselves. If you have a really specific space to fill with your leisure battery, you can browse the dimensions of each product in the Specification tab on our website to find the size that works for you. 

tn power 216ah lithium leisure battery lifepo4 200ah

Debunking lithium leisure battery marketing claims

We’ve noticed that some companies manufacturing lithium leisure batteries have been making some fairly outrageous marketing claims. They are trying to suggest that lithium batteries are the only sensible choice for a leisure battery. However, for many people, AGM batteries will be more than good enough to suit their needs.

Lithium batteries are the right choice for some, but we want to debunk some of these claims so that you can make an informed, unbiased decision without spending more than you need to.

Recharge time 

Claim: “20 x faster charging”

Lithium batteries can receive a higher current than AGM batteries, which allows them to charge faster. However, if you’re using your leisure battery in a campervan off-grid, you won’t be able to generate high charging currents. Subsequently, you won’t see a significant difference between lithium and AGM. 

Let’s compare a 160Ah Victron lithium battery and a 230Ah TN Power AGM. If we choose a sensible depth of discharge for full-time van life such as 90% for the lithium and 65% for the AGM, these two batteries give a similar usable capacity, therefore, are comparable.

This lithium battery has a maximum charge current of 320A per hour.

This AGM battery has a maximum charge current of just 36A per hour

So, the lithium battery is theoretically able to accept far more current than the AGM, allowing a much faster charge. However, the rate of charge will also be limited by how much current is actually available for charging. When you’re travelling off-grid, the majority of charging will come from solar power or from a battery-to-battery charger, both of which will only provide a relatively small charging current.

Recharging from solar

For example, a large solar array of 400W would only provide around 320W on a really sunny day, which equates to 23A per hour of charging power once it’s been transformed down to the correct voltage for charging. 23A is below the maximum charge current of both batteries, therefore, they would both charge at the same rate.

Recharging as you drive

When it comes to charging your leisure battery from the vehicle’s alternator, the current will be limited by the battery-to-battery charger. The largest Victron B2B charger is rated to 30A. If you have very high power usage, you may want to connect two in parallel to give you 60A per hour of charging power.

Since the AGM battery can only accept 36A, in this case, the lithium battery would charge twice as quickly when you’re driving. So it is faster, but not 20 times faster!

Therefore, you will only really benefit from the faster charging capabilities of the lithium leisure battery when you’re plugged into mains power.

Although, even when charging from mains power, the incoming current will still be limited by your battery charger. Even from a really big charger like the 3000W Victron MultiPlus, you still wouldn’t reach the lithium battery’s maximum charging current of 320A. 

You would only likely charge at a current close to the maximum in a non-campervan setting. Quoting the maximum charge current for lithium batteries being used in campervans is unfair, as it’s incredibly unlikely you will charge even close to this maximum.

Claim: “Charge from 0 to 100% in just one hour!”

To charge a battery so quickly, we encounter the same problems as above: off-grid charging methods won’t produce this kind of power.

Consider a 300Ah battery which can be discharged by 90% – that’s 270Ah. To fully recharge in 1 hour, we would need 270A of charging power. This could only be achieved with an absurdly large solar array (around 4000W!) and it wouldn’t be possible to consistently draw that amount of power from your vehicle’s alternator. 

For some lithium batteries, this claim might be true when charging from mains power, but you won’t get anywhere near these speeds with off-grid charging methods. The 3000W MultiPlus has a recharge current of 120A, and realistically this is the fastest charging you would have in a campervan electrical system. So unless you have a 130Ah lithium leisure battery, you will not be able to fully recharge in an hour.

Lifespan

Claim: “10x longer lifespan”

Lithium batteries last for many more cycles than their AGM equivalents, which means that they will last longer. However, for many campervaners, these extra cycles aren’t really needed!

For example, if you’ll be using your campervan for weekends and holidays, an AGM battery will last ~8-10 years. In this instance, you probably don’t need a lithium battery which could last 80-100 years! 

Nevertheless, if you are planning to use your camper for full-time van life, your leisure battery will reach the end of its lifespan much more quickly. For example, a campervan which uses around 100Ah per day will run through a 250Ah AGM battery bank in just 2 years. If you used a lithium battery bank instead, this would last for ~15 years.

For this reason, we would always recommend lithium batteries for anyone looking to live in their van full-time.

In reality, it is very unlikely that any battery will last for more than 15-20 years. This is because batteries degrade over time due to corrosion of the positive plate, which happens as a battery is charged. This is a slow but continuous process over the lifetime of a battery, and will eventually disintegrate the positive battery plates.

Usable power

Claim: “AGM batteries can only be discharged by 50%”

Some lithium battery manufacturers will claim that AGM batteries only have 50% usable power, but this is simply not true. Most AGM batteries can be discharged regularly by 80% without causing damage, and some, such as the Victron Super Cycle AGM batteries, can be discharged by 100% without causing damage.

Cost comparison

Claim: “Lithium batteries are 7x cheaper per Ah”

Some manufacturers have claimed the cost of a lithium battery is 7 times cheaper per Ah when you take into account their much longer lifespan. However, this is based on calculations which assume that AGM batteries can only be discharged 50%, which, as we’ve mentioned, is not correct.

To compare the two types of battery, we need to account for the fact that they can be discharged to different depths, and the fact that each battery will last for a different number of cycles.

Example

Let’s compare the cost of a 100Ah lithium battery and a deep cycle, 125Ah AGM which can be discharged to 80% (both from TN Power). 

The 100Ah lithium battery can be discharged 100%, giving us 100Ah for every cycle. 

The cycle life of this battery is 2000 cycles, which means we’ll get 2000 x 100Ah from the battery over its lifespan: that’s 200,000Ah.

The 125Ah AGM battery can be discharged by 80%, which also gives us 100Ah for every cycle. The cycle life of this battery is 600 cycles, which means we’ll get 600 x 100Ah from the battery over its lifespan: that’s 60,000Ah.

Here’s a breakdown of the cost:


Price Total Ah over lifespan

Cost per 1,000Ah

Lithium

£1,549.78

200,000Ah

£7.75

AGM

£439.78

60,000Ah

£7.33

From this example, it’s clear that there isn’t a significant difference in cost between the two batteries. In fact, lithium batteries are much more expensive to buy initially, but that expense is matched by the larger usable capacity and longer lifespan.

Did we debunk the claims? 

Lithium leisure batteries are a great choice for some people, but it’s important to be wary when you see these big, confident claims with very appealing numbers attached to them! There’s always a hidden caveat.

We’ve chosen to tear these claims apart because we believe lithium batteries are great, but we want you to really understand the numbers before you can justify the extra cost.

Lithium batteries are not the right choice for everyone, and it’s important to understand the real numbers so you can make an informed decision.

Our free electrical system design service makes off-grid energy simple.

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6 Responses

  1. Wow, what an amazing source of information! We are absolute beginners with A Hymer Free S 600 arriving next month. It has just the one leisure std battery so looking at possibly adding a second as well as a solar panel with dual controller and running with that for a while. We dont anticipate being off grid on our planned travels…….just yet!! I definitely understand a good deal more after reading your article, we live in France otherwise I’d be beating a path to your door.

    1. Hi Mick, good luck with the install! Unfortunately France is the only country we’re not currently able to deliver to – if you know anyone in a neighbouring EU country we can deliver there! Best wishes

  2. We have a lunar clubman caravan with 180 watts worth of solar panels on top and currently have a gel battery (3 years old). The on board display has over the last few months been slowly decreasing until it showed less than 11 watts which I’m advised means it’s more or less dead. Van is outside all day and no power is being used. And so I was wondering if a lithium battery would be a better choice as they can be discharged to within about 20% and can be guaranteed for up to 10 years but would my 180 watts be enough to top it up every day. And then there is also the minimum charging temperature (0 deg) which kill’s an average lithium battery. Temperatures can drop that low overnight even in summer ! So does that mean each night I would have to isolate the panels from the battery when temperatures drop and turn them back on the next day ? If anyone can give me some advice that would be great. Thanks.

    1. Hi Andy! Oh gosh, it does sound like your battery is fit for recycling! When changing over to lithium there are a few things to consider, especially when it comes to charging sources. Not all solar chargers are lithium compatible and as you say, they should not be charged below 0 °C. Some battery management systems (BMS) have built-in heaters to protect them and are clearly marked on our website under the lithium battery section, which could be of use! If you need any further information you can always reach out to our team of engineers here 🙂

  3. Thanks for all this, very useful.

    Can I ask about useful capacity Gel vs Lithium… If I had a laptop charger drawing 80w at 12v, how long would a fully charged 100ah Gel and Lithium last before they were considered safely flat and needed recharging?

    1. Batteries can be a boring way to spend your money, but you do really get what you pay for. The Ah rating of an AGM/Gel battery changes drastically based on the rate of discharge and temperature. In a car, the faster you drive the lower your fuel efficiency. The same applies to most batteries, except Lithium, which is still efficient even with a larger draw like a laptop. Lithium batteries can also be discharged further without decreasing their cycle life, making them more cost-effective in the long run.

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