I just can’t do it Captain, I just don’t have the power!

Unfortunately, today has turned into a bit of a failure.

This morning brought with it the final component I needed I start on the battery monitor project. At lunchtime, I quickly assembled the relevant bits and connected the battery…


One of the battery monitor’s features is its ability to power it’s Arduino component from the battery being tested – but of course, this only works if the battery in question has at least a trickle of power – it would appear that mine doesn’t.

I still don’t fully understand the mechanisms behind this, but a battery’s state of change is measured via its voltage output. On a 12-volt battery, a voltage of 12.6 is fully charged, while anything below 10.5 is empty.

Multimeter probes in hand, I measured the voltage on mine: 2.37. This is severely under voltage, and I’d imagine probably beyond repair. I can’t even get an LED to light up using it.

Although I can’t be sure, I think this is very possibly related to the broken charge controller I mentioned yesterday, and if nothing else, this is a hard-learned lesson about leaving unused batteries connected.

Checking back in with the Arduino for a moment, when supplied with power via the USB port it sprung into action and showed a reading of 4.34 on the display, while also making the buzzer sound off. This appears to be expected behaviour, as the script is set to activate the buzzer on anything less than 11.7 volts.

With a bit of tweaking to the Arduino, provided I maintain power via the USB, I think I can use this to measure the capacity of some 3-volt coin cells I have. I’ll try that later today, and if I’m successful I’ll post an update.

So what do I do now? Frankly, I’m a bit fed up with the idea of charging batteries (via solar, pedal, or even directly from the mains), so I think it might be time to invest in a bench power supply. I know nothing about them, but it appears models suitable for home enthusiast cost anywhere from about £50 to £100, which unfortunately means waiting for another payday.

But fear not, for I won’t be spending the next month twiddling my thumbs – instead, I’ll see what I can make of the e-textile and circuit sticker goodies I have.

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