youtubeOne of the buzz words of the RV realm these days, and one that I am often asked about, is Lithium batteries. Many people want to know the pros and cons, and whether the high price tag is worth it. Let’s examine these questions in this article.

Lithium Ion (Li-ion) batteries have been used for many years in products such as cellular phones, electric cars, and laptop computers, but they are a relatively new technology in RVs. There are many different formulations of Li-ion batteries in use, but the most common for RV use is Lithium Ferrousphosphate (LiFePo4), although chemistry of Lithium batteries is outside the scope of this article.

One of the primary advantages of LiFePo4 batteries is the improved depth of discharge (DoD) over lead acid. Deep-cycle Lead acid batteries degrade if they are regularly cycled below 50% DoD. For example, if you have a 100 Amp-hour (Ah) lead acid battery, regularly draining the battery below 50Ah significantly reduces its life. Manifestation of this would include inability of the battery to hold a charge or charge up to its full capacity. Lithium batteries on the other hand, can be cycled down to between 0% - 20% capacity repeatedly without any degradation in performance. What this means is that Li-ion batteries have twice the operational capacity of lead acid batteries. In other words, a 100Ah lead-acid battery really only has an operation capacity of 50Ah, whereas a Lithium battery can be utilized for the entire 100Ah. This means that you only require half the number of Lithium batteries to achieve the same capacity in your coach. A typical RV battery configuration is four six-volt batteries. Six volt lead acid batteries are commonly 220Ah, resulting in a total capacity of 440Ah. A common Li-ion battery size is 100Ah, therefore two of these batteries contains basically the same capacity as the four lead acid.

Also, Lithium batteries are approximately half the weight of lead acid. This means the total weight of your RV house battery system with Lithium can be as low as 25% vs. lead acid, given both the weight difference as well as the increased capacity.

Lithium batteries are truly maintenance-free. Since the electrolyte is completely sealed into the system, monitoring of the “fluid” is unnecessary, and corrosion does not occur.

Due to a phenomenon known as Peukert’s Law, the added internal battery resistance caused by a load uses up the available energy faster at high loads than at low ones, reducing the advertised Amp*hr rating of the battery as the load increases. Lithium batteries are barely affected by Peukert’s Law because the internal resistance is very low. Therefore, the discharge rate of a Lithium battery is much more linear than Lead Acid. This results in a longer run time per Ah, especially at high loads. This is usually most relevant for inverter use. For example, by applying Ohm’s Law we know that current draw on the battery side of an inverter is twice that of the AC side. So, if you want to run a microwave oven at 12A, the draw on the battery is 120A while the microwave is running. With lead-acid, this would have a non-linear effect on the rate of discharge, whereas with Lithium, it doesn’t.

Another big selling feature is the life expectancy of Lithium batteries. On average, lead acid batteries last between five and seven years, whereas Lithium can last up to twenty. This is one of the ways to justify the much higher initial cost of Lithium batteries. LiFePo4 batteries can cost up to $1,500 or more, compared to the few hundred for lead-acid. Given the advantages in depth of discharge and the much longer lifespan, the sticker shock should not necessarily deter you from upgrading to Lithium.

However, there are a few disadvantages to adopting Lithium technology in your RV. The first is the charging requirements. Lithium batteries require a much different charging current profile than lead acid. This will require you to upgrade your entire charging system. Whether you use a converter-charger, inverter-charger, and/or solar charging, they will all need to be Lithium compatible. This can require a significant outlay of cash in order to upgrade the components. In the case of converters, drop-in modules are available for a few hundred dollars, and these are very easy to install, but upgrading a solar module or inverter is a much more expensive undertaking. Most components manufactured over the past several years are Lithium compatible. In the case of a motorhome, both the lead acid chassis batteries, as well as the alternator, will have to be isolated from the Lithium battery bank. This can be done using solenoids or a DC-DC converter.

Another little-known fact about lithium is that they cease taking a charge at temperatures below freezing. However, this relates to the core temperature of the battery and not the surface temperature. Some batteries, such as Briter™, largely mitigate this issue by incorporating a built-in control panel that generates enough heat to keep the battery warm. If you frequently use your RV in freezing temperatures, you may have an issue with your Lithium charging system. It is important to note that freezing temperatures don’t do any damage to the batteries and they will begin to function normally again once the temperature increases. Again, this refers to the battery core temperature, which will be significantly higher than the case temperature.

Lithium battery technology is not well understood by many RV sales or service organizations, so if you are considering this technology please be sure to do your own research, especially regarding charge requirements.

Questions? Comments? Please add your thoughts below.

Steve Froese
Author: Steve FroeseEmail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Steve Froese is a Licensed Professional Engineer in British Columbia, as well as an Interprovincial Red Seal RV Technician, which is equivalent to a Master Certified RV Technician in the USA. Steve was a personal friend and colleague of the late Gary Bunzer (“the RV Doctor”), and works closely with FMCA as the monthly “Tech Talk” columnist, as well as being a member of the Technical Advisory and Education Committees. Steve and his family are lifelong and avid RVers, mostly in the Pacific Northwest.

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