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hello /diy/,
so the usual chinese suppliers have this led clock that runs on 5V DC over USB, and can work off a 3V coin cell if not connected.
how would i go about making a battery and charging system that would charge the battery from the USB when connected? i have some hobbyist electronics knowledge, and am pretty confident in my soldering, but this is somewhat above my knwledge level. google mostly sends me to some instructables from 2008 with crappy pics and drawings...
here's the board, if anyone would like to know which chips it uses. surprised it's not some chip-on-board plastic drip...
If you're using a proper li-ion cell (i.e. one that goes to 4.1V or 4.2V at top of charge), then you can wire one of these in parallel with it:
http://www.ebay.com/itm/5pcs-TP4056-5V-Micro-USB-1A-Lithium-Battery-Charging-Board-Charger-Module-/191677384222?hash=item2ca0dcc61e:g:NS4AAOSw0JpV4nuS
They typically ship set up to charge at 1A constant current, but this can be adjusted by changing the value of one of the surface-mount resistors. Requires some delicate soldering.
>>951812
Adding: you would then use the USB port on the TP4056 board to charge the cell. The come in mini and micro USB.
is this okay?
here are some beauties from the description:
>The first time you access the battery, it may no voltage between the output OUT + and OUT-, then access 5V voltage charge your energy can activate the protection circuit, and the battery from the B + B-, then draw a line on the short open also need recharged to activate the protection circuit.
> The charge should disconnect the load OUT terminal on the positive and negative can not be wrong, please according to specifications, otherwise it will damage directly.
can anyone decipher this?
