The lithium battery in motorhomes is becoming more and more popular. And with good reason, lithium-ion batteries have many advantages, especially in mobile homes. A lithium battery in the camper offers weight savings, higher capacity and faster charging, making it easier to use the motorhome independently. With our upcoming 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 lithium RV batteries.

Why a lithium battery in the motorhome?

Conventional lead-acid batteries (and their modifications such as GEL and AGM batteries) have been installed in mobile homes for decades. They work, but these batteries are not ideal in the mobile home:

• 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, 12v lithium battery have increasingly found their way into mobile homes. 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 mobile home. We will report on this in detail, but of course we did a lot of research in advance, 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 mobile homes, one inevitably comes across the somewhat cumbersome term LiFePo4.

LiFePo4 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 mobile homes.

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 mobile home 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 mobile home.

“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.

That’s a lot more than conventional lead-acid batteries can do.

Advantages of a lithium battery in the mobile home

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!

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 charging booster 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 mobile home spoil you with great charging comfort.

BMS

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.

Bluetooth interface

Many lithium batteries for mobile homes offer a Bluetooth interface. This allows the battery to be monitored using a smartphone app.

We are already familiar with this option from our Renogy solar charge controllers and the Renogy 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 12v inverter. 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 anyway.

Save weight with lithium batteries in the mobile home

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”!

More capacity with a lithium battery in the mobile home

As a result of the fact that a lithium battery is lighter and smaller than a lead battery with the same capacity, you can of course turn the whole thing around and instead enjoy more capacity with the same space and weight. Space is often still saved even after a capacity increase.

With our upcoming switch from AGM to lithium batteries, we will triple our usable capacity while taking up less space.

Lithium battery life

The lifespan of a lithium battery in a mobile home can be quite enormous.

This starts with the fact that correct charging is easier and less complicated, and that it is not so easy to affect the service life through incorrect charging and deep discharge.

But lithium batteries also have a lot of cycle stability.

Example:

Suppose you need the entire capacity of a 100Ah lithium battery every day. That means you would need one cycle daily. If you were on the road all year round (i.e. 365 days), then you would get by with your lithium battery for 3000/365 = 8.22 years.

However, the vast majority of travelers are not likely to be on the road all year round. Instead, if we assume 6 weeks of vacation = 42 days and add a few more weekends to a total of 100 travel days per year, then we would be at 3000/100 = 30 years of life. Huge, isn’t it?

It must not be forgotten: The specification refers to 90% DoD. If you need less power, the service life is also extended. You can also actively control this. Do you know that you need 100Ah daily, then you could just choose a battery that is twice as big. And in one fell swoop you would only have a typical DoD of 50% which would increase lifespan. Whereby: A battery that lasts longer than 30 years would probably be replaced because of the expected technological progress.

The long service life and the high, usable capacity also put the price of a lithium battery in a mobile home into perspective.

Example:

A Bosch AGM battery with 95Ah currently costs around $200.

Only about 50% of the 95Ah of an AGM battery should be used, i.e. 42.5Ah.

A Liontron RV lithium battery with a similar capacity of 100Ah costs $1000.

At first that sounds like five times the price of the lithium battery. But with the Liontron, over 90% of the capacity can be used. In the example, it corresponds to two AGM batteries.

Now the price of the lithium battery, adjusted for the usable capacity, is still more than double.

But now the cycle stability comes into play. Here the manufacturer’s information varies greatly – if you can find any at all (with ordinary batteries).

• With AGM batteries one speaks of up to 1000 cycles.
• However, LiFePo4 batteries are advertised as having over 5000 cycles.

If the lithium battery in the mobile home actually lasts five times as many cycles, then the lithium battery will overtake the AGM battery in terms of price-performance.