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People spend a LOT of time talking about how various RV lithium batteries work in the cold.
- “How cold can you charge it?”
- “How do you warm it up if it’s cold?”
- “How long can it stay at X temperature?”
- “I can imagine my RV getting colder than yours, and so now I’ve given myself an excuse to ignore how lithium batteries are fifty-billion times better than lead-acid batteries because I could think of one special edge-case that would happen once every thirty-four years and would cause me a temporary inconvenience.”
You get the idea.
But for as much as people talk about lithium batteries getting hypothetically too cold, you don’t see the same amount of chatter about them getting too hot. Well, I’m talking about it today, because it happened to us… sort of.
When we installed the lithium battery in Lance in the first place, I wanted to make sure to keep it inside. My thinking was to avoid this too-cold/too-hot discussion altogether. Because, if it’s comfortable in the van for humans, it’s comfortable for the battery. But just putting the battery inside wasn’t enough. I hadn’t counted on two things.
First, the battery was installed inside a closed compartment. This keeps it somewhat (but not completely) isolated from the temperature inside the van. That’s what I rectify with the project in this video.
Second, I’ve learned that charging the battery – especially at rates of 100 Amps or more – can really cause the battery to heat up. In fact, charging the battery causes it to heat up more than dis-charging it.
So on a recent trip we were:
- driving across the desert
- charging the battery at over 100A
- keeping the battery sealed up in its compartment near the skin of the van.
And our battery got really hot. In fact, it got up over 131 degrees Fahrenheit, and the Battery Management System (BMS) shut the show down. When the battery’s internal temperature dropped back down to a safe level, it just turned itself on again. So I did some checking with Lithionics, who makes our battery, and found out that their BMS enforces two over-temperature conditions.
- At temperatures of 114 degrees Fahrenheit and above, charging the battery is not allowed.
- At temperatures of 132 degrees Fahrenheit and above, discharging the battery is not allowed.
It does this through a battery temperature sensor that is internal to the battery (not just surface temperature or the temperature in the battery compartment). These limits are set by Lithionics to prevent damaging the battery. I had no idea that our battery got that hot, but now I know. Time will tell how well my venting solution works.
The Key Takeaway
But here’s the big point. If my battery was NOT protected by the BMS, I could have done serious damage to it. SO – if you’re spending the money to upgrade to lithium batteries, it really pays to make sure that your batteries are protected by a solid BMS.
I know that the systems offered today by Winnebago and Coachmen (Volta and Xantrex systems, respectively) are protected by a BMS. Other manufacturers? Maybe, but I simply don’t know. Drop-in lithium replacements? I don’t know. “Roll your own” buy-a-bunch-of-cheap-cells-and-wire-them-together-yourself systems? Probably not.
So there you have it. I’ll be watching my battery’s internal temperature closely in the coming months, so we’ll see how well this mod works.