I wanted to mention a test tool that I’d never used until last week, and now I am not sure how I managed without it.
I was recently asked by the organiser of the repair café I volunteer at (we’ll call him my boss, for the lack of a better term), for some ideas for new tools. We are entirely donation-driven; we do not charge at all for our time and only ask for costs to cover parts when they have had to be ordered specially. As such we occasionally have enough money in the donation pot to buy something new.
I suggested a few things, but one of those was a constant current load tester. These are not expensive in the scheme of things, but as I’d never got around to buying or building one of my own, it seemed like a good option.
My boss bought one, and last week I set it up and tried it out. That day I tested two battery vacuums, a switched-mode power brick/wallwart, a motorised e-scooter and a power tool. It quickly allowed me to quickly triage faults,
“Does this radio not work, or is it the wall wart?” – The supply voltage was OK, but as soon as any load was applied, it died. Nothing wrong with the radio at all, and we even found the owner an appropriate replacement in the store cupboard.
Likewise, the scooter had been brought in with a report that it charges fine but doesn’t go very far. Opening the scooter revealed two Lead acid batteries (a surprise as I was expecting a 37V 18650 battery pack like the “hoverboards” and e-bikes frequently have). A quick test on the dummy load proved that one of the lead acid batteries was entirely useless; the other I will do a further assessment on this week.
The final use case is the more “obvious”, I think, capacity testing recovered batteries. We see a number of dead laptops and power tools, things that are beyond our ability to revive or that are simply handed in as donor items. Assuming that they have died due to some non-power-related fault. I remove the battery cells and re-use them. I can now predict their health far better than I could before. First, we measure the load of the device they will be used in, and then we set the battery pack up in the dummy load, carefully setting the correct cutoff voltage. When the pack is drained, we can compare the rated power capacity to the actual and determine its usefulness.
I am glossing over the battery testing part here a bit. There’s a bit more to it to ensure you have balanced cells of equal quality, but there are entire YouTube channels out there talking about this!
The number of items that I see that are “broken” due to a dead battery or broken power supply means that this cheap little device will more than earn its keep in a very short amount of time.
Of course, now I’ve been asked to design and build/print a case for it!