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Questions &/or issues related to products in the Power category should be posted in this forum.

Recently, I have tried using 8266 module connected with battery Babysitter; D1-->SDA, D2-->SCL.
They work well together.
However, when I used Moter shield Node MCU ESP8266 board with battery Babysitter, D1-->SDA, D2-->SCL.
It just didn't work.
Couldn't I2C work with D1 and D2 outpins of Moter shield Node MCU ESP8266 board?

Thank you,
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Hi Maggie,

We cannot really help with using SparkFun boards with non-SparkFun products so our support here is limited. That said, my guess is the Motor Shield is using D1 and D2 for some other functionality and you are not able to use pins those for SDA and SCL. I would refer to the schematic of the Motor Shield to confirm this.

The ESP8266 does not really have any hardware I2C pins so you can adjust which pins you want to use for SDA and SCL by defining them in your Wire.begin(SDA, SCL); function. This should fix the problem but you may also need to adjust those pins in the variants.h file for your NodeMCU board. If you are using Arduino, you can find that file in your Arduino AppData folder. On Windows, the file path would be something similar to this: C:\Users\mark\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.5.0-beta2

I hope this helps explain the issue and gets the Battery BabySitter working in your circuit.