Battery Notes

 

For Special Agent-in-Charge "John Smith"

 

 

Anyone in this business for any length of time will tell you that a battery dampens transient voltage spikes. Without this capacitance, perplexing drivability issues can result. I am not an electrical engineer so I will not get into ion diffusion, Randles equivalent cells, Tafel curves, Warburg Impedance, etc., but I do have my thoughts on the matter. As you know, a battery is quite complex with a multitude of electrochemical activities occurring simultaneously—charge transfer, ion diffusion—just to name two. Even back in the days of the Baghdad battery about 2000 years ago, we learned that if you place a metal electrode into electrolyte, the charge on the metal tends to attract ions of opposite charge within the electrolyte, and the dipoles align. It is this alignment which forms charging layers in both the metal and the electrolyte—the electrical double-layer, for lack of a better term. We know that electrochemical reactions occur within the double-layer. Any high school general science student knows that. All the atoms or ions that are reduced or oxidized must pass through this layer. That’s also Battery 101 Class.

            So, that basic information means the ability of ionic transfer through this layer controls the kinetics and the activation energy of the electrochemical reaction lies across this double-layer. I hypothesize that the damping ultimately occurs here. Of course, that is merely an uneducated guess. There are those who would have people believe that the capacitive term is not necessary and that the resistance is the only part that needs measuring, but I vehemently disagree. A battery simply is not resistive. There is also a capacitive component.

 

           Of course, what do I know? I'm just a lowly technician. Oh--what did they use batteries for, 2,000 years ago? To power the UFOs that the aliens knew to build the pyramids. Everyone knows that.

 

          Have a nice evening, "Agent Smith."

 

Jack McGinnis