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Review of Caravans Plus Service
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AGM batteries were the preferred choice of deep cycle batteries for the Caravan and RV Market for many years and would still be the most commonly found today. Lithium Batteries have been around for a number of years now and while their performance was always undoubtedly superior, concerns about safety and affordability have resulted in a slow acceptance by seasoned travellers.
The advancements in the renewable energy sector have been responsible for a vast improvement in the affordability of safe, high quality Lithium Batteries. As more and more new caravans are being outfitted with Lithium Batteries the real world benefits are being observed by fellow travellers creating a push in the aftermarket sector.
Lithium batteries outperform their lead acid cousins in every metric - Size, Weight, Capacity, Lifespan, Output, Charging Time and Cost.
Yes, that's right when we break it right down to the cost of every usable Amp Hour over the life of the battery the Lithium saves you money.
It is without a doubt the age of Lithium.
Lithium Batteries are nearly 50% lighter than Lead Acid Batteries, which is a huge advantage in the RV application where every kilo counts. At half the weight you can increase your battery bank capacity allowing you to remain off-grid more comfortably for longer.
Lithium Batteries provide around 60% more usable power than Lead Acid Batteries due to their ability to be safely discharged to lower levels.
As a general rule AGM batteries should not be discharged to more than a 50% State Of Charge(SoC). This means that you will only get 50Ah from your 100Ah battery.
Why is this so? This industry recommended level was created by the battery manufacturers to standardise battery specification such as lifespan. Choosing a lower acceptable SoC would reduce the expected lifespan of their batteries which is a bad look. Lithium Batteries can be discharged safely to at least 20% SoC meaning you are getting 80Ah from your 100Ah Battery
A fully charged AGM Battery will supply a voltage of around 12.8V which reduces in a linear curve to around 12.1V at the recommended maximum 50% SoC. Yes you can discharge further at the expense of battery health, but the voltage will also continue to drop reaching insufficient levels for most items at around 30% SoC.
A fully charged Lithium Battery produces a voltage of above 13.5V with more constant voltage reducing to around 12.5V at 20% SoC after which the voltage drop is extreme.
The colour coded table indicates the safe levels of SoC and when the damaging effect on the battery health begins.
As they say your Caravan is your "home away from home" and we are seeing more and more of the creature comforts making their way into our mobile living experience. Coffee Machines, Hair dryers, Air Conditioners and other 240V appliances are now commonplace in caravans and while they are great when you have access to mains power they can become impractical off grid.
Inverters require a high current source to power such items which can cause issues with traditional Lead Acid Batteries. While AGM batteries do have a very high peak discharge rate it is limited to 5 sec, they are not designed for continuous discharge at higher levels. Lithium Batteries on the other hand have a high continuous discharge rate making them ideal for hungry inverters running your AC appliances.
Generally speaking AGM Batteries can accept a max charge current of 20-25% of the battery capacity. Lithium can accept up to around 50-60% for short periods (30min) but for longevity around the 30-40% mark is recommended.
The bulk charging profile of AGM batteries is up to around the 80% mark before entering the absorptions stage which can last a few hours, while Lithium Batteries accept high levels of charge up to 95% before tapering off. The most noticeable example of the charging advantage of Lithium over AGM is during DC to DC Charging, either from your tow vehicle when driving or solar input. A 100Ah Lithium battery can realistically be fully charged while driving over around 3 hours or will be able to accept any available solar all day. Meanwhile AGM batteries charge at a slower rate and even if they get to the 80% they enter the absorption stage and any available source is wasted, an AC Charger is the only practical way to achieve a full charge. With the last 20% of an AGM accounting for nearly half its recommended usable output, having less efficient charging dramatically shortens the amount of time you can spend off-grid.
The end result is you can fully charge your Lithium Battery in around 3-4 hours (from DC or AC sources) while an AGM will take 10+ hours (usually requiring AC to achieve a full charge)
All batteries have limited lifespan which is referred to as cycles (rechargers). This lifespan is directly affected by the level to which a battery is discharged before charging, this is known as the Depth of Discharge (DoD).
As noted earlier the AGM rated lifespan is based a 50% DoD while Lithium is generally at 80% DoD
Discharging to a lower level than recommended will reduce the lifespan of your battery which is a common occurrence with the 50% AGM limit. This is because it is generally impractical to carry the extra batteries required to cover the shortfall, this is less of an issue with the Lithium 80% limit. As a general rule of thumb you can expect a Lithium Battery to last around 4 times as long as the standard AGM equivalent.
ie. Four times the number of cycles at the recommended DoD.
There is no hiding the fact that Lithium Batteries cost more upfront than AGM's, but is the initial cost recovered over their life? Using the expected lifespan and price of both types of battery we have calculated the actual cost per Amp Hour at different levels of Depth of Discharge. As you will see even when we use the best case AGM scenario regardless of how impractical, Lithium is still substantially cheaper.
100Ah AGM Battery Costing $300
100Ah Lithium Costing $900
$0.0066 vs $0.0051 | The AGM Battery is 29.5% more expensive than the Lithium Battery.
Manufacturers Recommended DoD
$0.0080 vs $0.0037 | The AGM Battery is more than DOUBLE the cost of the Lithium Battery at 116%.
As with most things there is no one right choice, while Lithium Batteries outperform traditional Lead Acid Batteries they are not for everyone.
For those who spend only a small percentage of their time away from mains power & don't utilise an inverter AGM's are most likely still a more economical choice.
The advantages in performance of Lithium Batteries are only an advantage if your style of travel utilises them.
While the initial cost of Lithium Batteries is more than recovered over the life of the battery, the cost benefit could take years for some to achieve.
For those who travel frequently, enjoy the freedom of more remote sites and the ability to power your creature comforts anywhere there are definite advantages to Lithium Batteries.
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1 Comments
Ian
Very interesting article. I have Full River AGMs at but will change when these come to the end of their life. Interesting information.