Category Archives: Batteries

I was in a meeting this morning when I was told a battery pack had insufficient capacity to meet a 24 hour backup time requirement. While in the meeting, I grabbed a specification for the battery the test engineer was using, did a quick calculation of the backup time results that the test engineer should have expected, and what needed to change in order to pass the backup time requirement. While I have discussed different kinds of battery calculations in numerous blog posts, I thought this one was more typical than most and reflects the kind of work done daily by battery engineers. Continue reading →

Many battery manufacturers do not specify the Ampere-Hour (AH) ratings for their automotive products because Cold Cranking Amperes (CCA) more important in automotive applications than AH ratings. Car applications tend to focus on the ability of the battery to crank the engine when both the battery and car are cold. While reading a post on an automotive forum about batteries, I saw the following statement made about the relationship between a battery's CCA and AH ratings. Continue reading →

My Montana-based son mentioned that his wife's 2016 Honda CR-V (Figure 1) will not turn-over after sitting in the garage for seven days. No starting problems had occurred prior to early November. Unfortunately, I have had my share of car electrical problems and some of these problems have been hard to find. However, this is a new car and under warranty, so I recommended that he just take it into the dealer. He took the car into the Honda dealer, who told him that this is the result of the current drain imposed on his car battery by his aftermarket remote start system, which was verified to be within specification –the car was operating normally. Continue reading →

In this post, I will be looking at how these ventilation calculations are performed. My focus here is on standard wet-cell batteries, which simply release any gases generated during charging. Other battery types, like Absorbed Glass Mat (AGM), will attempt to recombine the H2 and O2 released during charging. The AGM battery's internal gas recombination will reduce the amount of H2 released by these batteries – example shown here. I will compare the output of my model to those generated by a number of web-based and textbook sources. The results are in good agreement. Continue reading →

I am doing some work with lead-acid batteries and their state of charge versus their H2SO4 electrolyte concentrations. While we normally use specific gravity to assess a battery's state of charge, some folks use molality (m), molarity (M), or mass fraction (w). These concentration metrics are all related by relatively simple formulas (Figure 1). Continue reading →

Quote of the Day If the tiger ever stands still the elephant will crush him with his mighty tusks. But the tiger does not stand still. He lurks in the jungle by day and emerges by night. He will leap … Continue reading →