We are all attached to our mobile equipment and devices, but we really don’t want them to be attached to anything, like a power cord. This requirement for mobile power has put a lot of focus on reliable and long-life battery performance. Batteries are temperature-sensitive devices: they don’t operate when it’s very cold. And when it’s very hot, their performance degrades. Moreover, excessive heat from thermal runaway conditions can even result in fires or explosions (you’ve seen the videos).
This need to keep batteries in a safe temperature-operating zone is of growing interest and has even spawned some new terminology - “Intelligent Battery Cooling.” In a general sense, Intelligent Battery Cooling is an active powered solution that heats the battery when it’s too cold, and then cools it down when it’s too hot. It essentially uses some programmed intelligence to monitor and control battery temperature and apply heat or cooling whenever required.
Pretty cool, right? Sure – it’s nifty and complex. But any active control system like this also has potential issues:
1. They use up some of the available power from the battery and
2. Moving parts (pumps, fans, etc.) will malfunction sooner or later
Here at Advanced Cooling Technologies, we too are coming across more and more battery thermal management challenges. But we are also finding there are some very reliable passive options (no moving parts and no power) that provide similar performance to the more conventional “intelligent battery cooling” solutions, without the drawbacks just mentioned. Qualifies as “intelligent-er battery cooling,” we think!
Most of these solutions use some variations of Heat Pipes. Heat pipes are very reliable heat transfer and heat spreading devices that are ubiquitous, most commonly used in laptops and cell phones, but also used in high performance medical and military devices. They have been known to provide reliable and power-free heat transfer for decades. In its most common battery thermal management solution, they are embedded in the battery pack frame and move heat away from a hot spot in a battery module. See a Battery Cooling Case Study. This heat spreading is very effective at delaying or avoiding thermal runaways.
For more sophisticated battery thermal management challenges where over-cooling can be a concern, there are Variable Conductance Heat Pipes (VCHPs). VCHPs are essentially heat pipes with a reservoir of non-condensable gas that throttles the ability of the heat pipe to move heat at low temperature, which may cause the battery to become too cold. Like their Heat Pipe cousins, VCHPs are also very reliable and completely passive. VCHPs provide heat transfer when the batteries are too hot and stop heat transfer when the batteries might get too cool. They take advantage of very reliable and well-defined physical properties. No programming required.
So, if you are facing battery thermal management challenges and think an “intelligent battery solution” is what you need, rethink what “intelligent” really means. Simple and reliable is intelligent too!