If you’ve ever tried to do anything, whether it’s packing and moving, machining a new part, or building a shed, you’ve learned that everything takes longer than you think it will. A good rule of thumb is to estimate your time requirements, then multiply by 2.
Why? Because of unexpected setbacks. You find some items that are heavy/hard to move/hard to pack. Or you make a mistake machining and have to start over or create a workaround. Or you realize it takes a lot longer to level the ground and place shed footings, and there’s a rock where you wanted to place a footing. A car-sized rock.
Successfully shipped – USB, Hacker
The FlexVolt Hacker Arduino Shields started shipping over a month ago and the FlexVolt USB models started shipping two weeks ago! It took much longer than expected, but it’s still very exciting. By now many FlexVolt customers have received USB models or Arduino shield models and are using them to measure there muscle signals!
Delayed shipping – Bluetooth
The FlexVolt Bluetooth models were destined to ship last week, but then a faulty battery stopped everything. Lithium-Ion batteries are great – high energy density, good cycle life, minimal memory-effect – but they have been known to fail through overheating. So when one of the assembled units got warm and the battery failed, I stopped all Bluetooth shipping to learned why. This failure resulted in me being extremely concerned about the integrity of the rest of the batteries and of the charging circuit. I could not ship defective products that might overheat! So I stopped preparing for shipping, unpacked devices that were already packed and ready to ship, and extensively (even more so) tested each battery and charging system. Thermocouples were placed inside cases to monitor temperatures during charging. Batteries were stressed and monitored, but no problems were seen.
Eventually, it became clear that the problem was inside the failed battery, not with the design of the battery charge controller circuit. I learned that one type of manufacturer’s defect in a Lithium-Ion battery is an internal partial short-circuit. This short can lead to internal energy loss through heating, which can damage the battery and lead to further heating, which can damage the device! I am currently developing and performing quality control tests for the batteries, the charging circuits + batteries, and the assembled devices, to make sure devices are not shipped with a defective battery that could overheat. Shipping of FlexVolt Bluetooth models will resume when I am convinced the problem is solved.