Eagle Eye Power Solutions

A Heated Discussion on Lead-Acid Batteries


Having just endured one of the hottest Julys on record, many people have been subjected to extremely hot environments lately. And, in some cases, where their bodies have produced or absorbed more heat than they could dissipate, people have been experiencing an abnormally high body temperature due to the failure of their body to thermoregulate. This is called hyperthermia.

In fact, as I wrote this piece, the outside temperature was 92°F with 65% relative humidity, which according to the NOAA chart, indicates a heat index of 108°F – in the “danger zone.” The National Weather Services will usually issue an alert when the heat index is expected to reach 105°F–110°F for two consecutive days.

Meanwhile, in the July 2020 issue of the IEEE Spectrum magazine, there is an article titled “The Year is 118 A.A.C. (After Air Conditioning).” After all, air conditioning (A/C) was invented in 1902 by Willis Haviland Carrier. But, did you know…

  • Of the more than 1.6 billion A/C units in the world, over half are in China and the U.S.?
  • It is estimated that cooling will account for over 30% of electric generation capacity at peak loads by 2050?
  • The growth of A/C units in high-population countries such as China, India and Indonesia will greatly increase the region’s emissions of carbon dioxide?

Personally having spent some time in the Middle East in the 70’s, using “water coolers” – window units that circulated water across a rotary fan – seemed like a much more efficient way to cool ourselves down than the typical evaporator/condenser unit.


So, we know excessive heat can cause damage to our bodies, but what does it do to batteries? Well, hot weather can in fact be more damaging to car batteries than cold weather. They typically perform adequately up to 90°F, but above that, the chemical reaction will accelerate, resulting in the loss of electrolyte, which can cause the battery to dry out and eventually fail.

The same is true for stationary lead acid batteries. With today’s AGM batteries, where water cannot be added, a 10% water loss in a VRLA battery can equate to a 25% loss in capacity. While VLA batteries handle heat better than VRLAs, because the electrolyte is always in contact with the cell container for better heat dissipation, VRLAs will also fail sooner when used in poorly ventilated UPS applications.

Even though a battery operating at a high temperature can show increased capacity at times, the life of the battery will always be reduced. For every 15°F-18°F above the ideal operating temperature of 77°F, the expected battery life is lowered by 50%. So, unless your battery is in a cool location with natural air flow or a rotary fan, it’s time to pay tribute to Mr. Carrier for the invention that will help maintain your batteries.

5 thoughts on “A Heated Discussion on Lead-Acid Batteries

  1. I don’t know what audience this is meant for. But, “For every 15°F-18°F above the ideal operating temperature of 77°F, the expected battery life is lowered by 50%” is too broad of a range., It’s common knowledge that heat affects batt-life. Beyond that, this info should be in the form of a graph for it to be informative. If this is for the layman, then you should also explain what VRLA, VLA, AGM, stands for. Changing temp away from ambient is not cheap/simple. Without a graph, one cannot appreciate how important this factor is. The cost/benefit ratio cannot be properly evaluated. Apparently you did the research; now give a better sales pitch. It’s too easy to dismiss this without further info.

    1. Hi Dennis. Thanks again for your interest in our articles – we always appreciate intelligent feedback like you’ve provided. We will take your suggestions into consideration on future content that we produce, and we also encourage you to register for our upcoming webinar “A Heated Discussion on Lead-Acid Batteries” which will go into greater detail when describing the affect of heat on batteries: https://zoom.us/webinar/register/WN_9o0nN_gpRFS0iXATFAunDg.

    2. I guess I was hoping for a meatier article. One of the critical issues I see is how well does a UPS compensate for temperature when charging? That has much more influence on battery life than the temperature itself.
      Evaporative cooling like those in the Middle East only work in arid climates. There, the evaporated water is not significantly raising the humidity of the room. Such units are useless in humid climates, for the water does not readily evaporate, and the added humidity from the evaporated water is doing the opposite of what is needed, which is a reduction in humidity.

      1. Thanks for your comments, Robert. For more information, or to ask the author any questions, please feel free to sign up for our upcoming webinar on this topic: https://zoom.us/webinar/register/WN_9o0nN_gpRFS0iXATFAunDg. And you’re exactly right about evaporative cooling in humid climates – it was meant solely as a light-hearted example of an alternative cooling method to A/C in the right climate. Again, we appreciate your interest in our material and look forward to hearing from you in the future.

  2. Anyone who works with VRLA should know the arrhenius equatiin based rule of thumb about every 10 deg C above nominal (20 C in Europe, 25 C in the US purely due to standards) will halve the service life. The accelerated aging is a combination of dry out and plate erosion. Worst case scenario in extreme cases is thermal runaway where damage to the physical infrastructure can occur. As for cost vs benefit analysis – there are variables well beyond the CAPEX cost of the battery, or the potential damage to infrastructure, in UPS standby battery applications often the most significant part of the cost equation is the downtime on the critical load supported by the battery! Plus business reputation when it fails!
    Bottom line is that VRLA need to be maintained in a controlled environment when failure is not an option!

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