If You Buy an RV Lithium Battery, You’ll Need a Converter to Go With It!

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  • Post category:Electrical / Guide
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This is your last chance. After this, there’s no turning back.

You stop reading this article about lithium batteries, and the story ends. You go back to your RV and believe whatever you want to believe.

You keep reading this article, you stay in wonderland – and I show you just how deep the rabbit hole goes.

Yes, I shamelessly borrowed the blue pill/red pill script from The Matrix (thanks, Morpheus). But the truth is that after you realize what lithium batteries can do for you, you’ll start sneaking in snide remarks about lead-acid batteries, and soon you’ll just become flat-out rude to them.

  • Sometimes, I link to an affiliate product because A) I think it’s the bee’s knees or B) I’m saving you the hassle of online shopping. If you click the link and purchase, I may receive a small commission at no extra cost to you. (Thanks for helping me to not live under a bridge.) For more information, you can read the site privacy policy or peruse my open letter about how this site makes money so you can read this awesome free content! And while I’m shamelessly hawking and peddling, have you checked out my recommended lists of RV membership clubs or RV gear??

Table of Contents

Um … I Have Batteries?

(If you’re new to RVing, please read this 2-minute primer on RV batteries and electricity. Otherwise, skip ahead.)

All RVs have two electrical systems: 12-volt direct current (12VDC) and 120-volt alternating current (12VAC). Small items, like lights and fans, run on 12VDC. Larger appliances, such as your microwave and air conditioner, run on 120VAC.

You get 120VAC power by plugging into shore power at a developed campground or house. You get 12VDC power from onboard “house” batteries.

Your RV has at least some ability to connect the two systems.

Almost all RV batteries from OEMs and dealers are some type of lead-acid battery, whether flooded, AGM, gel, etc.

  • Psst . . . if you’re reading this content anywhere besides Ask The RV Engineer, it’s been illegally “scraped,” and you’re probably on a spam website. So please be careful! Don’t share any private information, and come back to us at www.askthervengineer.com!

Bid Farewell to Lead-Acid Batteries

Battery Terminals Close Up

Before we roll out the red carpet for lithium batteries, let’s bid farewell to the old guard: the lead-acid battery.

By the 1950s, the familiar flooded 12-volt lead-acid battery had established itself as the battery of choice for the automotive and RV markets. And since then, it really hasn’t changed much.

It’s a simple affair: Two plates (anode and cathode) are submerged in an aqueous sulfuric acid solution (electrolyte). A separator plate keeps the plates from touching. Electrons flow between the two due to a chemical reaction, and wallah! – you have electricity.

For more information, see our Ultimate Guide to Your RV Batteries.

This technology remains fundamentally the same in today’s batteries. More advanced construction types, such AGM and gel batteries, overtook the market 20 years later, in the 1970s, but the basic technology is steadfast.

Today, most RVs are still equipped with these 12-volt lead-acid batteries. Common upgrades include:

  • Moving from flooded/wet batteries to sealed/valve-regulated construction (e.g., AGM).
  • Purchasing deep-cycle batteries with sturdy lead plates for deep discharges and more usable capacity.
  • Upgrading to heavy-duty, long-lasting 6V batteries wired in series for a system rating of 12V.

All of these improvements are useful and well worth the money. But lithium batteries may soon render them all footnotes.

What’s All This Hullabaloo Around Lithium Batteries Anyway?

In order to understand the appeal of lithium batteries for RVs, you need to understand the one BIG limitation of lead-acid batteries.

You can’t discharge a lead-acid battery all the way.

Even the best RV deep-cycle batteries really aren’t designed to be discharged more than 50-60%. Beyond that, sulfates form, plates crack, mats flake, electrolytes freeze, and catastrophe reigns.

Full battery discharges drastically shorten battery lifespan and can even ruin a battery in one go. That’s why your car starting battery often kicks the bucket a few months after you left your headlights on all night.

For even more information on lead-acid battery state of charge, read this deep dive article.

In order to understand the appeal of lithium batteries for RVs, you need to understand the one BIG limitation of lead-acid batteries.

You can’t discharge a lead-acid battery all the way.

Even the best RV deep-cycle batteries really aren’t designed to be discharged more than 50-60%. Beyond that, sulfates form, plates crack, mats flake, electrolytes freeze, and catastrophe reigns.

Full battery discharges drastically shorten battery lifespan and can even ruin a battery in one go. That’s why your car starting battery often kicks the bucket a few months after you left your headlights on all night.

For even more information on lead-acid battery state of charge, read this deep dive article.

Meanwhile, lithium batteries can be repeatedly, safely, FULLY discharged.

Lithium batteries can be discharged to 0-20% of their state of charge.

So you basically get twice (2x) as much usable power as a true deep-cycle battery and three times (3x) as much usable power compared to a hybrid marine/RV battery!

Oh, and high-quality LiFePO4 batteries discharge at a constant voltage. So you get a constant supply voltage throughout the entire cycle. No more dimming lights!

Actually, I’m such a fan that I created this list of lithium battery benefits.

Lithium batteries can be discharged to 0-20% of their state of charge.

So you basically get twice (2x) as much usable power as a true deep-cycle battery and three times (3x) as much usable power compared to a hybrid marine/RV battery!

Oh, and high-quality LiFePO4 batteries discharge at a constant voltage. So you get a constant supply voltage throughout the entire cycle. No more dimming lights!

Actually, I’m such a fan that I created this list of lithium battery benefits.

Big Benefits of a Lithium Battery for Your RV

Here, at a glance, are the many benefits of converting your RV to lithium batteries!

  • Can be fully and safely discharged to 0-20% of capacity!
  • Good for 3,000-5,000 lifecycles (5-10x that of a lead-acid battery!)
  • Can last well over 10 years! Manufacturers may even offer 10-year warranties, which are underhead of for lead-acid batteries.
  • Weighs just one-third that of a comparable lead-acid battery.
  • No periodic water replenishment (so no need to go hunting for distilled water).
  • No flammable or explosive fumes while charging or discharging.
  • Can be safely stored and used inside an RV.
  • Constant voltage throughout discharge cycle.
  • Quickly and efficiently recharged without overheating. Very fast charge rate!
  • Almost fully recyclable.
  • Don’t contain environmentally dangerous metals.
  • Terminals don’t corrode like lead-acid batteries!

Can you tell I’m a believer?

I’ve already highlighted the big benefit of lithium batteries, which is the extra usable power.

But I’d like to highlight another one: charge rate. Lithium batteries have far less internal resistance than lead-acid batteries, so they can accept a charge much, much faster.

Compare that to a lead-acid battery, which charges quickly up to 70-80% and then slowly, sloooooooowly tapers off to 100%. None of that wasted time with LFP batteries!

What Are the Differences Between Using Lithium or Lead-Acid RV Batteries?

Lithium (LiFePO4)

Cost
$$$$
Weight
Only weighs one-third as much as comparable lead-acid!
Charging Rate
Fast
Discharge Rate
Fast
Environmentally Hazardous
No
Recyclable
Yes
Maintenance
Low

Lead-Acid

Cost
$$
Weight
Heavy! 50-75 lbs per battery on average.
Charging Rate
Medium
Discharge Rate
Slow
Environmentally Hazardous
Yes
Racyclable
Yes
Maintenance
Medium/High

You should be aware that lithium batteries are a completely different chemical beast.

  • A 12V LFP battery uses four cells at 3.2 volts each for a total of about 12.8 volts
  • The battery is charged with a Constant Current Constant Voltage (CCCV) profile rather than the standard 3-stage bulk-absorption-float for a lead-acid battery.
  • LiFePO4 batteries should not be stored at full capacity, just 50-60% charge. So no trickle charger required over the winter. How nice is that?!

If you know anything about lead-acid batteries, you know that all these numbers, facts and requirements are totally different!

So yes, lithium batteries require a learning curve. But the benefits are well worth it.

Note: You’ll need a lithium-compatible converter and (if present) solar charge controller in order to convert your RV to lithium batteries! See the last section of this article for more information.

Don’t Lithium Batteries Explode?

Unfortunately, a few publicized stories of consumer laptops or smartphones catching on fire due to their lithium batteries put the kibosh on early adoption in the RV industry.

Some linguistic housekeeping: There are several chemistries of “lithium” batteries.

For our purposes, any reference to an RV lithium battery refers to Lithium Iron Phosphate (LiFePO4) batteries, also known as LFP batteries.

LiFePO4 is a type of lithium-ion battery. But there are quite a few more!

RV lithium house batteries are NOT the same as the other lithium-ion (li-ion) batteries found in consumer electronics.

The lithium batteries in your cell phone have much higher energy density and faster discharge rates. They’re perfect for the daily use and abuse of smartphones and tablets.

But yes, the alchemy of cobalt, nickel, manganese and silicon in a smartphone battery makes them combustible. They can be subject to runaway high temperatures, which increases the risk of explosive ignition.

There are other lithium-ion chemistries as well, like lithium-nickel-cobalt-aluminum oxide. But we don’t need to get into those.

The chemistry inside an RV lithium battery is simply not subject to the runaway heat and combustion issues of smaller smartphone batteries.

Now, yes, lithium is a reactive metal. If major physical damage ever occurred to the battery housing, a battery could catch on fire or explode. This is a genuine risk, but it’s extremely low.

And all listed LFP batteries are required to be sold with an integrated Battery Management System (BMS) to prevent overcharging and similar dangerous conditions. The BMS acts as a “brain” to control all aspects of charging and discharging.

Do Lithium Batteries Work in Cold Weather?

This is a half-myth. It is true that RV lithium batteries cannot be charged at temperatures below freezing. In fact, the optimum charging temperature is around 65 degrees Fahrenheit.

However, very few campers consistently camp in freezing temperatures. So this limitation has no impact on most recreational RVers.

Now, if you do find yourself in frigid conditions, you have two options.

1 Regulate the ambient temperature around the batteries. In this case, RVers often install the lithium batteries inside the coach itself! Unlike a lead-acid battery, lithium batteries don’t off-gas explosive fumes when overcharged.

2 Regulate the temperature of the battery itself. There are many aftermarket solutions, such as battery box blankets and battery box pads, that will heat up a battery. You’ll either need to be plugged into power, however, or the battery will drain trying to keep itself warm!

Fun fact … lead-acid batteries can be used in freezing weather, but they can freeze at low temperatures, too! In fact, the more discharged a lead-acid battery, the quicker it freezes!

How Much Do RV Lithium Batteries Cost?

If you’re wondering why all RVs don’t come with these wonderful batteries, it’s because RV manufactures are cheap b*st*rds.

… Well, the full truth is a bit more complicated.

If you only camp in developed campgrounds, then the extra $X,XXX required for lithium batteries probably isn’t worth it to you. So why should you fork over the cash for a standard feature you don’t need?

It’s true that LFP batteries have a high upfront cost (quite a bit more than those triple A’s you’ve stashed in your desk).

  • Brand-name lithium batteries, such as BattleBorn or Renogy, cost $700-$1,100 for a 100-Ah 12V battery.
  • Knock-off lithium batteries cost at least $400 for a 100-Ah 12V battery.

That’s roughly 2.5-3x as much as a comparable AGM lead-acid battery. Certainly not chump change!

But let’s look at overall lifecycle cost.

Lithium batteries can endure several thousand charge/discharge cycles. Renogy states their 100Ah 12V smart lithium iron phosphate battery will last about 4,000 cycles until the efficiency of the battery drops to 80% (which is still pretty good!). Some batteries are rated up to 5,000 cycles!

Lifecycle for deep-cycle lead-acid batteries ranges from 400 to 1,500 cycles, with better-built brands offering a longer lifespan.

A lithium battery can last up to 10x longer than a lead-acid battery! Comparing topnotch lead-acid batteries to brand-name LFP batteries, you can expect a 4-5x longer lifecycle – yet the battery only costs 2-3x as much!

So the lifecycle cost of a lithium battery is much lower than a lead-acid battery. In fact, your lithium battery will probably outlive your camper! Some manufacturers claim a 30-year lifespan. You could include your batteries in your last will and testament.

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How to Upgrade My RV System for Lithium Batteries?

Even though LiFePO4 batteries have been around for RVs for several years, many RV owners have been scared away by the complexity of your RV electrical system.

Unfortunately, in 95% of RVs, you cannot simply replace your conventional lead-acid batteries with lithium batteries.

Here’s how to retrofit your RV for lithium ion batteries.

Step 1: Replace the Converter

First, because LFP batteries are generally charged at 14.0 to 14.6 volts rather than 13.2 to 13.6 volts like a lead-acid battery, you’ll have to replace the converter charger.

You need a converter compatible with LiFePO4 batteries.

  • WFCO and Progressive Dynamics make lithium-compatible converters.
  • Magnum and Xantrex make even nicer units usually bundled as part of an inverter/charger.

You can either buy a dedicated unit or a convertible converter capable of charging both battery chemistries. These dual-purpose converters are more popular. All it takes is the flip of a switch.

By the way, what happens if you don’t change out your converter?

Well, you might damage your $1,000 lithium battery! However, most LFP batteries BMS’s will prevent any serious damage.

And even if you don’t, you’re wasting effort – a conventional charger can only charge a lithium battery to 70-80% capacity, so you don’t get to use all that extra capacity you paid for!

Step 2: Replace the “Shortstop” Breaker

Your main battery power line is protected by a “shortstop”-style inline breaker, usually a Type 1 (auto reset thermal cycling).

You’ll want to replace the inline breaker with a manually resettable circuit breaker (e.g. Bussmann CB 185) rated for at 120% of the charger or load current. Because LFP batteries generally charge at a faster rate than lead-acid batteries, you’d quickly burn out your original shortstop breaker.

Of course, if your battery cables have a gauge too small to safely accept a higher current, you’ll need to replace the cables and terminals, too.

STEP 3: Review Battery Monitor and/or Solar Charge Controller

If your rig has a built-in battery monitor and/or solar charge controller, you’ll need to ensure they are compatible with lithium batteries. You’ll probably need to program them to a different mode, too.

STEP 4: Review and Rewire If Necessary

Lastly, you need to review all affected aspects of your 12V system. Obtain a schematic of your rig’s 12V wiring system and ensure no wires are being overloaded. Don’t replace any circuit breakers or fuses without fully understanding the downstream impacts!

As a rule, AWG wires are capable of carrying the following currents at 12V nominal:

  • 18AWG: 7 amps
  • 16AWG: 10 amps
  • 14 AWG: 15 amps
  • 12 AWG: 20 amps
  • 10 AWG: 30 amps

No wire or cable should be protected by a breaker or fuse in excess of its current-carrying capacity. Additionally, high heat conditions or extra-long runs may reduce wire current capacity.

Although to be honest, if this is news to you, then perhaps you should seek professional assistance when upgrading your RV battery system. Electricity is extremely dangerous. Electrical shorts are responsible for over a third of all RV fires. Play it safe!

Ross

RV engineer by day, intrepid blogger by night (and occasionally weekends). This website is all about how RVs work, and sometimes why they don't. Bookmark pages that you find helpful, and join my email list for exclusive monthly awesomeness.