6 must-know answers about lithium batteries

This past week we've been camping in northern Arizona and New Mexico, with temperatures dipping down to 20°F at night. This was the kind of trip where we needed a lot of battery power, since the furnace was running a lot and we were sometimes camping with no power hookup.

It wasn't a problem. In fact, we hardly even thought about power, because a couple of years ago we upgraded from lead-acid batteries, to lithium batteries that yield about 3X as much power. (You can read the details in this guide, Diary of a Lithium Battery Upgrade.)

Why you should make the switch

Typically, a pair of Lithium Iron Phosphate (LFP) batteries that fit into an Airstream trailer battery box will yield 200 amp-hours (Ah) of power, or about 2,560 watt-hours (Wh) if you prefer that measure. Any way you measure it, that's so much power that, on many trips, we don't need solar panels or power connections. We can use all the electrical devices we want, including laptops, the inverter, TV/DVD, furnace, etc., without worrying about running out of power on a weekend.

Not only that, but lithium batteries weigh less, last longer, and recharge faster than lead-acid batteries. For RVers they are clearly superior – unless you never camp without an electric hookup and don't really use the batteries.

Yet despite the obvious advantages, we still hear a lot of misinformation about lithium batteries when we talk to Airstreamers and other brand RV owners. Let's address some of the most common questions:

1. Aren't lithium batteries a big fire risk?

No. Fortunately, this is not a worry for RV owners. To understand why, you need to understand that there are several types of "lithium" batteries in common use:

1. Lithium Nickel Cobalt Aluminium Oxide (NCA) and Lithium Nickel Manganese Cobalt Oxide (NMC) batteries are commonly used in e-bikes, laptops, electric cars, and other consumer devices. NCA batteries in particular are responsible for some of the eye-catching vehicle fires you may have seen. 
2. Lithium Iron Phosphate batteries–often referred to as LiFePO4 or LFP– are the type used in RVs (and a few electric cars).

The RV industry only installs LFP batteries in RVs, partly because they have an internal cathode made of phosphate, which won’t burn very easily. They also don’t have the "runaway" thermal problem that NCA batteries do. So they are highly unlikely to catch fire. 

2. Is it safe to install lithium batteries inside an RV – like under the beds or dinette?

Yes. Unlike lead-acid batteries, lithium batteries don't produce flammable gas, and don't contain dangerous acid. They're safe to be inside the trailer or motorhome.

3. I've heard you can't store lithium batteries at 100% without damaging them. Is that true?

Although it's true for some types of lithium batteries, it's not true for the LFP batteries that RVers use. You can charge your LFP batteries to 100% as often as you want, and even leave them in storage that way. The lifespan of a LFP battery isn't significantly affected by being kept at 100% charge.

If you read this "can't store lithium at 100%" myth online or hear it at a rally, you can tell the person that they are talking about other types of lithium batteries, not LFP batteries.

4. Can LFP batteries be damaged if they are used below freezing, without a built-in heater?

Not at all!

On our recent trip, we camped for many nights below freezing, and enjoyed plenty of battery power, despite the fact that our batteries are stored in the outside battery box and they don't have heaters.

You can use a LFP battery to power your Airstream below freezing without a problem, all the way down to 0° F. You just can't charge them much below freezing.

If you try to charge LFP batteries below freezing, the charging process will automatically be shut off to protect the battery. That’s because any good LFP battery has “smart” technology, in the form of a Battery Management System (BMS) that works to prevent the battery from being damaged. When the temperature drops to about 25°-32° F, the BMS will shut off charging. When the sun rises and the temperature climbs above 32°, the BMS will accept a charge again.

Because of the "smart" BMS technology, you won't damage your LFP batteries by camping in freezing temperatures. They simply won’t charge until it gets warmer. Since you're probably using solar panels to recharge them you won't even notice this, because you're not trying to charge the batteries at night.

If this is a problem based on how you travel, you can get LFP batteries with little built-in heaters that enable you to charge the battery in sub-freezing temperatures. They run about $40-50 more per battery and brands such as Battle Born and Renogy offer them.

Most Airstreamers don’t need heated LFPs. Only if you need to charge when you're in places where the temperature stays below freezing both night and day do you really need them. If that's not how you travel, you can save about $100 by purchasing unheated LFP batteries.

5. How do I winterize my lithium batteries?

Easy! As long as you don't live in an area where the temperatures drop below -10°F, you can just make sure the batteries are fully charged, and then disconnect the negative cable from the batteries. (The "Battery Disconnect" switch in your RV may not fully disconnect everything, which is why disconnecting the negative cables is better.)

Lithium batteries don't "self-discharge" nearly as much as lead-acid batteries do, so you can leave them in this state for 3-4 months without any problem at all. If your batteries have a "storage mode" or "shelf mode", follow the manufacturer's instructions to activate it and they'll last even longer.

6. Which lithium battery brand should I buy?

Stick with reputable brands that are commonly used in RVs, like Battle Born, Renogy, Expion 360, Victron, and Lithionics. Watch out for "bargain" lithium batteries. If the battery you're considering is half the price of a well-known brand, there's a reason. They may have skimped on the BMS (which can be dangerous), they might be using inferior cells, the warranty may be short, and there probably isn't any US-based support from the manufacturer.