Temperature is such an easy thing to measure you’d wonder why we don’t measure it more often and in more places. Battery monitoring is no exception to this and even today there are few systems that take advantage of this easy-to-measure yet very informative parameter.
Canara’s own system has always measured every jar temperature and, in monitoring hundreds of thousands of batteries worldwide, it really is surprising the range of problems that we regularly detect and warn of because of this data. Here are a few examples…
Cooling Equipment Failure
The first and most obvious of these of course is the failure of cooling equipment. It may be through chiller failure, fan or other mechanism, but whatever it is it inevitably results in a rise in temperature of the batteries and, in some cases, can even cause a thermal runaway event if not addressed quickly enough. You can see from the chart below that the temperature rises 20 degrees in about 24 hours!
The ability to monitor individual jar temperature has also taught us another thing that you may not realize – there can be a very wide variation in temperatures of batteries even within a single cabinet. The stratification of temperatures across a string can be quite striking and well beyond what you might at first imagine. Strings of wet cells in large battery rooms on racks have shown spreads of over 10 degrees F while batteries within cabinets can display a huge spread of over 20 degrees F!
Knowing this, it stands to reason that if you have some areas of your battery cabinet at 77 degrees F that it is quite possible that you could have other areas at 97 degrees F and therefore most definitely in the thermal runaway danger zone.
Without individual jar temperature, this, unnoticed spread of temperatures, means that a cabinet of batteries can be vulnerable to thermal runaway without you ever realizing it.
For us the forewarning of thermal runaway is the singular most urgent of conditions we must act on, and warn of, and we see batteries in the thermal runaway zone all the time.
The chart below shows a recent real-world incident where a customer did not take action when notified of likely thermal runaway condition. The batteries were virtually new but the combination of high float voltage and warm temperatures meant thermal runaway conditions were likely. From our Monitoring Operations Center, we were able to notify the customer of the impending event 10 days prior to the actual event taking place.
Discharge is another occasion where measuring temperature can be a useful indicator. While there are few systems that measure temperature when the batteries are discharging, a discharging battery can generate large amounts of heat and looking at this heat signature can give us early signs of a change in battery condition or a change in connector conductance.
So what does all this mean?
Without individual jar temperature monitoring, you are not able to ensure that your batteries are not on the edge of thermal runaway. The majority of battery monitors do not have the capability to detect individual jar temperature and any other symptoms that can only be seen by skilled personnel paying close attention to these subtle indicators and act quickly upon them.
At Canara, we are actively monitoring close to 300,000 batteries worldwide every day and are regularly reminded that, as well as all the other parameters, individual jar temperature is a highly critical factor in keeping batteries healthy and your critical power flowing.