Tutoring high school chemistry includes electrochemistry.  The tutor shares some reflections about auto batteries as winter approaches.

 
I recall more than one mechanic talking about how a device might work fine for a long time but have a hidden weakness. When that device is, for whatever reason, put under abnormal stress, it likely fails. The failure is surprising: hasn’t it worked for months (or years) with no problems? Why, then, does it suddenly fail, at a time you really need it to work?

From my experience, auto batteries can give that “false sense of security.” It’s not the battery’s fault, of course; it’s just the life cycle in most of North America (ie, summer to winter).

From purchase, an auto battery of good quality is likely strong and reliable for a few years anyway. Depending on driving habits, it may maintain its vigor much longer than that. However, time is working against the battery: potentially, the chemical process of sulphation, among other factors.

So, the battery likely weakens over time, yet continues starting the car just as expected. Let’s imagine the battery becomes considerably weaker in late May. The driver likely won’t even notice: from late spring through early fall, the weather is warm. In the heat, the car’s oil might be more agreeable to letting the engine turn over. The days are bright, warm, and dry: the driver doesn’t use the headlights, heater, or wipers as much. Life is easy for the battery. Yet, during those carefree months, the battery may already be too weak to start the car in the cold.

When the inevitable “first winter storm” comes, the car may not start. The driver is surprised. (I’ve been there.) Really, though, the driver’s been on borrowed time for weeks or months already. The battery just wouldn’t reveal its weakness until put under stress.

I’ve been reading up on auto batteries lately (just for the pictures, of course:). In coming posts I’ll discuss some of my findings about this fascinating topic we all depend on.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.