AGM vs Lithium Battery Lifetimes
Ah, the age-old question. How long will your campervan leisure batteries last? It can be a minefield researching battery lifetimes, numbers of cycles, discharge depths, and capacities.
But what difference does all this make to your van conversion? Will you have to replace AGM batteries before lithium? Or is lithium worth the extra cost?
Campervan Leisure Battery Terminology
We’ll break down a battery lifetime assessment and show what it could mean for you and your van conversion. But before we do, here is a quick explainer for those new to battery terminology. If you’re already a battery wiz, skip ahead to our assessment.
- Capacity – measured in amp-hours (Ah), the total energy the leisure battery can hold at any one time
- Cycles – a single discharge and charge of your batteries (similar to what your phone battery experiences each day)
- Lifetime – the total number of cycles that your battery can handle before it degrades
- Depth of Discharge (DoD) – A percentage figure describing the amount of energy drained from your leisure battery (Ah) during each cycle. The DoD is relative to the battery’s capacity. (50% DoD for a 100Ah battery is a 50Ah discharge)
Which Campervan Leisure Batteries Have We Used?
For our assessment, we’ve used batteries we have experience with and verified their quality. Our AGM example is the 100Ah TN Power Deep Cycle AGM, and our lithium example is the Victron Energy LiFePO4 100Ah offering. We’ve used the manufacturers’ information on how long these batteries are expected to last.
Battery Lifetime Case Study
For our battery lifetime assessment, we have created three profiles for people that have campervans. Each has a different use for their campervan and, as such, has different campervan electrical systems. To make the comparison easy, all our van users will have a 100Ah campervan leisure battery.
Three Example Campervan Users:-
Monica - Small Usage
- How does Monica User Her Campervan? – Monica uses her van for day trips and the occasional overnight trip and only needs a few 12V appliances.
- What electrical system has Monica got? – Monica has a small electrical system in her campervan. She has a 140W solar panel, a 12V fuse box and one 100Ah leisure battery. On her travels, she uses lights, a fridge and 12V USB chargers with a daily consumption of 30Ah. The equivalent of a 30% DoD for a 100Ah battery.
Joey - Medium Usage
- How does Joey use his campervan? – Joey uses his vans to go on weekend trips around the UK. He particularly enjoys exploring the north of Scotland as he is away for weekends and needs a way to heat his van and charge his laptop.
- What electrical system has Joey got? – Joey has a medium-sized electrical system in his campervan. Joey has a 215W solar panel, an 18A DC-DC charger, a 100Ah leisure battery, a 375W inverter and a 12V fuse box. Joey needs a bit of juice to power his lights, USB sockets, roof fan, gas heater, laptop and projector. His daily consumption is 50Ah, with his 100Ah battery – equivalent to 50%DoD.
Graeme - Large Usage
- How does Graeme use his campervan? – Graeme is what we call a full-time van-lifer. He lives in his van all year round and thus needs a lot of energy to power all his appliances, particularly his larger appliances like his microwave and blender.
- What electrical system has Graeme got? – Graeme has a large campervan electrical system. It contains a total of 450W of solar, a 30A DC-DC charger, a 100Ah leisure battery, a 12ooVA Multiplus and a 12V fuse box. He needs to make sure he can power his van daily, as he has a daily consumption of 80Ah – equivalent to 80% DoD for a 100Ah battery.
We have done our best to represent some standard scenarios but everyone’s campervan electrical system is different. Lets have a look at how each persons batteries will do over time…
Depth of Discharge
One crucial fact to remember is that the maximum number of cycles your batteries will handle before degrading depends on the depth of discharge. Battery manufacturers agree that deeper cycling will wear out the batteries in fewer cycles.
Your batteries will perform more cycles at 30% DoD than 80%. The typical lifetimes of AGM and lithium batteries are shown below.
Using the three van user examples, we can see how many discharges each person will get from their campervan leisure battery.
Monica will get 600 cycles from a Deep Cycle AGM battery and 5000 cycles from a Lithium battery.
Joey will get 500 cycles from a Deep Cycle AGM battery and 3500 cycles from a Lithium battery.
Graeme will get 400 cycles from a Deep Cycle AGM battery and 2500 cycles from a Lithium battery.
Great, but how does the number of cycles relate to how long my campervan leisure battery will last? Using Monica, Joey, and Graeme, let’s look at this.
Our battery lifetime assessment is shown below. We have compared how long we expect batteries to last, in years, based on how many days they are used per year. At the lower end, 48 days use a year works out to four days a month or two weekends. At the higher end, 365 days corresponds to full-time van life. This should show how long a 100Ah battery could last in your van based on how you intend to use it.
Battery Lifetime - AGM vs Lithium
By comparing the AGM and Lithium graphs above we can make a few observations:
- Lithium batteries will last longer than Deep Cycle AGM batteries, between 20 and 3 years longer depending on your usage
- Deep Cycle AGM batteries degrade a lot quicker than lithium batteries if you are using a lot of cycles
We have not discussed this here, but Lithium batteries are usually 2-3 times more expensive than deep-cycle AGM batteries. So the extra performance that comes with lithium batteries does come at a cost!
How Long Will Batteries Last For our Three Campevan Users?
Monica - Small Usage
We estimate from our plots above that Monica’s 100Ah AGM battery could last around 7-8 years. This is pretty good going. However, if she chooses a Lithium battery, it would last her 35 years. Monika realises she does not need her battery to last 35 years, so the added cost of lithium batteries means the Deep Cycle AGM battery is best for Monica.
Joey - Medium Usage
We reckon Joey’s 100Ah AGM battery will last 3.3 years. Not bad, but if he intends to keep his van for the foreseeable future, it may be worth investing in lithium, which we think could last 23.3 years.
Graeme - Large Usage
We estimate Graeme’s lithium batteries will last around seven years, whereas an equivalent AGM will last around a single year. It’s, therefore, a no-brainer to invest in a superior lithium battery
How Much Will a Campervan Leisure Battery Cost?
Now for the juicy part – how does this affect your wallet? For our 3 van-owning friends above, we’ve looked at what they could expect to spend on batteries if they owned their vans for 5, 10 or 15 years.
When assessing the cost, it is essential to look at the cost of batteries across the whole life of your campervan. Based on our research, we have assumed, on average that AGM batteries last 7 years, whereas lithium batteries last 15 years.
As you can see from the table, how often and for how long you intend on using your van changes whether AGM or Lithium leisure batteries are the best investment for your campervan adventures.
If you are a day tripper like Monica, AGM will be the cheapest option across the van’s lifetime.
If you think you are similar to Joey and will head out for most weekends, deciding whether Lithium or AGM is best can be trickier. We suggest considering how long you think you will keep your camper.
Finally, lithium leisure batteries are the clear winner if you are a full-time van lifer. Your high usage and hence the high number of cycles means you will need a lithium battery to keep up with the pace of your exploring.
What Else To Consider When Choosing a Campervan Leisure Battery?
Our battery assessment is reasonably simple and excludes a few factors. We’ll discuss each of these and what we’ve assumed below.
Larger Leisure Batteries
We’ve only modelled 100Ah batteries above to make the maths easier. If a larger 200Ah battery is used compared to 100Ah, then your DoD for each daily cycle will decrease. An 80Ah consumption from a full-time van lifer is 80% for a 100Ah battery, whereas it is 40% for a 200Ah battery. In effect, larger batteries will last longer as they will have a lower depth of discharge for the same daily power consumption.
Lithium batteries are known to have issues when things get closer to freezing temperatures. They can’t be charged if the temperature drops below zero, and some batteries won’t begin charging again until it reaches five °C to protect the batteries.
Maximum Depth of Discharge
Historically, AGM batteries have been limited to as low as 50% depth of discharge. However, current manufacturers claim deep cycle AGM batteries can be discharged 100% without causing significant degradation. Others claim 80%, and the same variation exists in lithium battery suppliers. Lithium is believed to be the safer option for deep discharging, but it depends on who you ask!
High Discharge Currents
High discharge currents can also cause quickened degradation of batteries. This applies mainly to large inverter systems with significant power draws. If you intend to use an inverter 2000W or larger, we recommend lithium batteries to help protect you.
How long Will My Campervan Leisure Battery Last Summary
Lithium batteries can cost significantly more than AGM batteries, and we’ve discussed the pros and cons briefly in a previous blog. However, we take from this assessment that lithium batteries are well worth the added expense if you expect your van and electrical system to see heavy use or value longevity.
Lithium batteries typically cost three times that of AGM but can handle at least five times as many cycles, even under worst-case conditions. AGM will likely offer you the optimum solution if your van is intended for weekends only.
It’s worth bearing in mind that estimating how long a battery will last you in the real world is very difficult, and all batteries will degrade after Around ten years, regardless of how much use they have seen. Lithium batteries are far superior to AGM but carry a heavier price tag.