Chapter 11- The Morning Something Read Differently

On the ninth morning the pack voltage read three and a half volts lower than it had read on the previous eight, and Theo saw it in about four seconds.

Why he was reading it at all

Because it was the one genuinely useful number the adapter reached on that car, and because a number recorded once is not information yet.

He had recorded it on the first morning in the driveway alongside the state of charge, without knowing what he was going to do with it, and then every morning after that at the same point in the routine with the car at rest and the same state of charge on the display.

Eight mornings within about half a volt of each other. Then three and a half volts lower.

Three hundred and forty eight point six volts is not an alarming number. There is no manual anywhere that says an electric car is broken at that figure, and a person seeing it for the first time in their life would have no reason to think anything of it at all.

What made it meaningful was eight previous mornings of the same measurement on the same vehicle under the same conditions.

The number had not gone out of range. It had gone out of pattern, which is the sentence this entire series keeps arriving at, on a completely different kind of vehicle.

What he did, in order

Took it again. Same figure.

Checked the state of charge on the dashboard, which read four points lower than it had on the previous eight mornings.

Which was the answer, and it took about ninety seconds to find, and it is slightly embarrassing.

Pack voltage on a lithium battery varies with state of charge. That is not a fault, that is the fundamental physics of how a cell works. A pack that is four percentage points less full sits at a lower voltage, and the relationship between the two is a curve every battery has.

Theo had, on eight consecutive mornings, been comparing readings taken at effectively the same state of charge, because the car had reached a hundred percent every night. On the ninth morning it had not, for the reason in Chapter Nine: a power cut two nights earlier had left the charging pattern slightly disrupted and the guesthouse had been asked to switch the carport socket off at midnight to manage a load problem.

So the reading had moved because the state of charge had moved, and comparing the two directly had been the mistake rather than the finding.

Why this chapter is in the book

Because it is the only chapter in ten books where the method produced a false alarm, and leaving it out would misrepresent what keeping a log is actually like.

Theo spent about twenty minutes on the ninth morning genuinely concerned about a rental car's battery, on the basis of a comparison he should not have been making, and the reason he should not have been making it is that he had recorded the conditions and then not used them.

The conditions were right there in the notebook. State of charge, alongside every voltage figure, every single morning, because writing down the conditions with the reading is the rule from four previous books.

He had followed the rule and then not read his own notes properly, which is a considerably more common failure than not keeping the notes at all.

What Sarah said

He told her about it on the phone that evening, expecting sympathy, and got something more useful.

She pointed out that the method had worked exactly as designed. It flagged a deviation, he investigated it in ninety seconds using information he had already recorded, and he established that it was explainable and moved on.

"That is not a false alarm," she said. "That is the alarm working and the answer being boring."

Which reframed it, and which Mia put in the video, and which Theo now thinks is the single most useful sentence anybody has said about this method across five countries.

The correction he made

From that morning onward he recorded voltage and state of charge as a pair and compared only pairs, never a voltage on its own.

And he added one line to the notebook that has stayed there: a reading that moves with a condition you also recorded is not a finding, and if you did not record the condition then you do not have a reading, you have a number.

What They Learned

Pack voltage varies with state of charge, and that is fundamental physics rather than a fault. Compare pairs, never a voltage on its own.

A reading can go out of pattern without going out of range, and only a record shows that. That holds on an electric vehicle exactly as it does on an engine.

Record the conditions with the reading, and then actually read your own notes. Failing to use recorded conditions is a more common mistake than failing to record them.

An alarm that turns out to be explainable is the system working, not the system failing. Most of them will be.

This curated preview is provided for personal reading. Copyright remains with Nobo Astoria.