The local Poundland (called Dealz on the Isle of Man) had some portable power units that house an Amazon Echo unit so you can make it portable. They claim to contain a 10,000mAh cell, so I thought I'd get one for the £5 they were selling them at to check out the cell capacity.
I'm guessing that they are probably discontinued stock to be sold for £5 given the complexity of the circuitry inside.
I did spend a LOT of time trying to fathom out the circuitry, but it's surprisingly complex due to the way it can charge the 8.4V lithium cell from a USB input with a boost converter or the original power supply with a buck converter. The circuit board is three layer which made tracing things a lot harder. I was actually thinking how useful the soft contact brush mentioned by Mike of mikeselectricstuff would be for hunting down ends of tracks.
I couldn't quite fathom the apparent dual boost circuit for the output, unless I'm just missing some useful detail.
The lithium battery is a stack of two cells with a protection board. Not a balancing board, just protection. I guess it relies on the cells being charged to a similar level for most of the item's useful working life.
The twin-stack cell accepted a charge of 10,348mAh which is a good result. It does mean that in its original form it was actually a 5000mAh 8.4V battery.
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14 окт 2024
