The battery sockets, and which pin is plus
Two sockets in this kit take a cell, and they are wired opposite ways round. A plug that is right for the shield's LIPO BTT socket is reversed in the board's own socket, and the other way about. The + printed beside each socket is the only thing to trust.
Two sockets, opposite ways
Look down on the board or the shield with the USB end towards you.
- On the board, the + is printed beside the left pin of its battery socket.
- On the shield, the LIPO BTT socket has its + on the right.
So one plug cannot be right for both. Try it:
Cell leads are no help here. They are not standardised — the same red and black pair comes wired both ways round, depending on who assembled it — so the only safe habit is to find the + on the socket and the red wire on the plug, and check they meet, every time.
The third socket
The shield's TO ESP32 socket has its + on the left, the same as the board. It is not for a cell: it is where one of the kit's six cables starts, and the other end goes into the board's socket. Red to + at both ends.
Check with a meter
Before a new cell's first use, set a meter to DC volts and touch the probes to the two metal contacts inside its plug. Red probe on the contact that will meet the + mark: a healthy cell reads between 3.0 and 4.2 V. A minus sign in front of the number means that plug is reversed for that socket.
Swapping the pins
A JST PH plug holds each wire's contact with a small plastic tab. Lift the tab with a needle, slide the wire out, and push it back in the other hole until it clicks. Do one wire at a time, so the two bare contacts never touch.
When it does not work
Unplug it at once. Then power the board from USB alone, with no cell, and run the blink sketch. If it works and nothing is warm, carry on with the cell the right way round. If the cell got hot or has swollen, do not use it again.
JST PH plugs only fit one way up: the ridge on the plug meets the latch on the socket. Turn it over rather than pushing harder. If it still will not seat, it is probably a different connector family — see the cell to buy.
There is nowhere to do that by accident: on a shield, the board's own socket is taken by the cable from TO ESP32. A cell goes in LIPO BTT on a shield, or straight into the board's socket without one, never both.
What the regulator does as the cell runs down, and where to stop.
From the cell to 3.3 V →Edit this page — content/books/esplipo/which-pin-is-plus.mdx
Questions about this product
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ESP32 LiPo Dev Kit: 3 Boards with LiPo Charger + 3 Shields
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