You may have heard that lithium deep cycle batteries, including the Lithium Iron Phosphate (LFP or LiFePO4) variety, will be damaged if you charge them in cold weather. Is it true, how big of a deal is it, and what should you do about it?
Yes, it is true that charging lithium batteries whose internal temperature is less than freezing will cause permanent damage. This is because the chemical reaction inside the battery cannot take place properly resulting in free lithium ions attaching themselves to the surface of the anode instead of being captured by the anode. This is called plating and will lead to a decrease in performance and/or capacity of the battery.
How big of a deal is it? Well, this phenomenon doesn't deserve the mass hysteria it is causing in the industries and hobbies where LFP deep cycle batteries have become common, such as the boating, RV, and off grid living communities. Many consumers are passing over perfectly good batteries because they don't have this feature. The reality is, it is rare for a battery to get that cold and in over 5 years of selling tens of thousands of batteries in the upper midwest, MillerTech has only run into one report of one of their batteries being damaged by cold charging. It just isn't that common. Here are some reasons why:
First, they are almost always kept within a box, such as a bulkhead, storage compartment, or cabinet. This insulates the battery somewhat even without a heat source.
Second, most people in the RV, off grid, or boating communities or industries are not using their batteries outdoors in those conditions. And it isn't the use of the battery that will damage it, it is the charging of the battery. So even if a fisherman goes out on the lake in freezing temperatures and uses his trolling motor, he isn't charging those batteries in those conditions.
And third, remember that the internal temperature of the battery has to be below freezing. Not the ambient temperature or the temperature of the battery case. The cells inside the battery have to be that cold. Typically, the internal temperature of the battery will be at least a few degrees warmer than ambient.
So if you are still concerned, what can you do to make sure this damage doesn't happen to your lithium battery investment? The free method for any lithium battery of any brand is to simply charge the battery indoors.
If you don't want that hassle or if you can't bring the battery into a warmer environment to charge, like a solar powered camera or something, buy a battery that has cold charging protection built into the battery management system (BMS). For example, all MillerTech batteries have cold charging protection capabilities built in to the BMS. Cold charging protection will keep track of the inside temperature of the battery and disallow charging, even if a charger is connected to the battery. But that doesn't give you the ability in really cold weather because it can't be charged.
So the bulletproof solution if you really need to use your battery and charge it in the cold is to find a battery with an internal heating function and cold charging protection. For example, the Jericho Battery Company battery that we carry has a built-in heater that engages to heat the internal temperature of the battery above freezing before it automatically allows the charger to do its job. Even if it is below freezing outside you can rest assured that you can still charge the battery without any intervention or worry on your part.