The lithium battery in motorhomes is becoming more and more popular. And with good reason, lithium-ion batteries have many advantages, especially in RVs. A lithium battery in the camper offers weight savings, higher capacity and faster charging, making it easier to use the motorhome independently. With our impending conversion in mind, we’re taking a look around the market, considering the pros and cons of lithium, and what needs to change in the existing RV for lithium.
Why a lithium battery in the motorhome?
Conventional lead-acid batteries (and their modifications such as gel and AGM battery) have been installed in RVs for decades. They work, but these batteries are not ideal in the RV:
- they are heavy
- With an unfavorable charge, they have a short service life
- They are not well suited for many application scenarios
But conventional batteries are relatively cheap – although an AGM battery has its price.
In recent years, however, lithium RV batteries have increasingly found their way into RVs. Lithium batteries in the camper are still a certain luxury, since their price is a lot higher than the price of ordinary rechargeable batteries. But they have many advantages that cannot be dismissed out of hand, and which also put the price into perspective. But more on that in the next few sections.
We had received our new van in 2018 with two AGM on-board batteries. We didn’t want to dispose of them right away and had actually planned to only switch to lithium at the end of the life of AGM batteries. However, plans are known to change, and in order to make room in the van for the forthcoming installation of our diesel heater, we now preferred to install a lithium battery in the RV. We will report on this in detail, but of course we did a lot of research beforehand, and we would like to present the results in this article.
Lithium battery basics
First, a few definitions to clarify the terminology.
What is LiFePo4?
In connection with lithium batteries for RVs, one inevitably comes across the somewhat cumbersome term LiFePo4.
LiFePo4 battery is a lithium-ion battery in which the positive electrode consists of lithium iron phosphate instead of lithium cobalt oxide. This makes this battery very safe as it prevents thermal runaway.
What does the Y mean in LiFePoY4?
In exchange for safety, early LiFePo4 batteries had lower wattage. Over the course of time, this was counteracted by various methods, for example by using yttrium. Such batteries are then called LiFePoY4, and they are also (rarely) found in RVs.
How safe is a lithium battery in an RV?
Like many others, we wondered how safe lithium batteries actually are when used in motorhomes. What happens in an accident? What happens if you accidentally overcharge?
In fact, there are safety concerns with many lithium-ion batteries. That is why only the LiFePo4 variant, which is considered safe, is actually used in the RV sector.
Cycle stability of lithium batteries
In the course of battery research, one inevitably comes across the terms “cycle stability” and “DoD”, which are related. Because the cycle stability is one of the great advantages of a lithium battery in the RV.
Cycle stability indicates how many times a battery can be discharged before it loses a certain percentage of its capacity.
“DoD” (Depth of Discharge) now indicates how much the battery is discharged. So the degree of discharge. Because of course it makes a difference whether I discharge a battery completely (100%) or only 10%.
The cycle stability therefore only makes sense in connection with a DoD specification. Because if I only discharge the battery to 10%, it is easy to reach many thousands of cycles – but that should not be practical.
Marine batteries deep cycle currently achieve about 80% residual performance after 5000 cycles or more.
That’s a lot more than conventional lead-acid batteries can do.
Advantages of a lithium battery in the RV
As already mentioned, a lithium battery in the camper offers many advantages.
- Light weight
- High capacity with the same size
- High usable capacity and resistant to deep discharge
- High charging currents and discharging currents
- High cycle stability
- High security when using LiFePo4
Usable capacity and deep discharge resistance of lithium batteries
While ordinary batteries should only be discharged to about 50% in order not to severely limit their service life, lithium batteries can and may be discharged to 90% of their capacity (and more).
This means that you cannot directly compare capacities between lithium batteries and ordinary lead-acid batteries!
A 100Ah lead-acid battery only offers a de facto capacity of around 50Ah. Any discharge beyond this is at the expense of battery life. With a 100Ah lithium battery, on the other hand, almost 100Ah can actually be used. In addition, the BMS prevents harmful deep discharge in the lithium battery.
Faster power consumption and uncomplicated charging
While conventional batteries can only be charged slowly and, especially towards the end of the charging cycle, hardly want to consume any more current, lithium batteries do not have this problem. This allows you to load them much faster. This is how a DC charger really shows its advantages, but also a solar system runs up to new top form with it. Because ordinary lead-acid batteries “brake” enormously when they are already quite full. However, lithium batteries literally suck up the energy until they are full.
While lead-acid batteries have the problem that they often do not get full from the alternator (because of the low current consumption towards the end of the charging cycle) and then their service life suffers, lithium batteries in the RV spoil you with great charging comfort.
Lithium batteries integrate a so-called BMS, a battery management system. This BMS monitors the battery and protects it from damage. In this way, the BMS can prevent deep discharges by simply preventing the current from being drawn. The BMS can also prevent charging at temperatures that are too low. In addition, it performs important functions inside the battery and balances cells.
This happens comfortably in the background, as a pure user you don’t normally have to deal with it at all.
Many lithium batteries for RVs offer a Bluetooth interface. This allows the battery to be monitored using a smartphone app.
We are already familiar with this option from our MPPT solar charge controller and the battery monitor, and have come to appreciate it there.
Better for inverters
Lithium batteries can deliver high currents without a voltage drop, which makes them ideal for use in inverters. So if you like to use electric coffee machines in the motorhome or want to operate the hair dryer, there are advantages with lithium batteries in the motorhome. If you want to cook electrically in the camper, you can hardly avoid lithium phosphate anyway.
Save weight with lithium batteries in the RV
Lithium batteries are much lighter than lead batteries with a comparable capacity. This is a great advantage for many troubled motorhome travelers who have to check the weighbridge before every trip to ensure that they are still on the road in the legal area.
Calculation example: We originally had 2x 95Ah AGM batteries. These weighed 2×26=52kg. After our lithium conversion we only need 24kg, so we save 28kg. And that’s another flattering comparison for the AGM battery, because we’ve tripled the usable capacity “by the way”!
There is no doubt that lithium batteries are the best choice for RVs. If you have no financial pressure, be sure to equip your windmill with lithium batteries. This means you’ll be comfortable when you’re out and about without worrying about running out of power in your RV. If nothing else, after decades of use, your lithium battery will still work well, and you will be happy with the choice you made in the first place.