how to log and graph battery (cell) voltage over time?

[affinite]

I have 4 LiFePO4 cells wired in series to provide my 12v housebank.

What I want to do is to log the individual cell voltages (and overall battery voltage) and then display them as a graph of voltage against time.

Previously I used a celllog 8s with USB output to the LogView software, but my celllog died and they are now out of production. What was nice with that is it stored the data locally, and then I just exported it to my laptop to view when I wanted it. 

The first page on this thread https://forum.openmarine.net/showthread.php?tid=716 there is a graph of exactly what I want to do, but having read right through the thread I still cannot figure out exactly what I need to do.

Can anyone provide me with a step by step instruction of what I need to buy and do to get my cell voltages into a nice graph? I am sure I am not the only one who would appreciate this!

I am runing OpenPlotter 2 with OpenCPN on a raspberry pi 3

Thanks in advance.

Noel

Noel
There are several ways to do this but I chose to avoid a direct (physical) connection to my Pi/OpenPlotter
I use a combination of a NodeMCU ESP8266 microcontroller running firmware called ESPEasy and an Analogue to Digital converter called an ADS1115.
The ADS1115 is what measures the battery voltage. (In my case 3 separate battery banks)
The ADS1115 sends the digital voltage reading to the ESP8266 and then to the Raspberry Pi over WiFi (so no direct connection to the Pi) which puts the values into SignalK.
The Pi is on my boat in Greece and data is updated every second but, in addition, the data is sent every 10 minutes over the internet to my home in the UK where the battery measurements are stored in an InfluxDB database. A Grafana graph (see attached example) plots the data.

If you search this forum and Google these items you should be able to piece it together as I did but I am working on presentable "How I did it" write-up which I'll share when done.

PaddyB's posts on the sbuject were very useful for me and also take a look at Ole Saastad's project site here https://sites.google.com/site/olewsaa/ya...-raspberry
Ive shamelessly copied some of his ideas also.

Instead of using an ESP8266 you could connect the ADS1115 directly to the RPi and let OpenPlotter grab the data for you but, as I said, that's not the route I chose.
Best of luck