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Newby* wants to monitor a 12v battery level and a bit of temperature reading - which board should I go for? - I thought they'd all be basically the same ..... or are they?
* Done some stuff with RPi's and python but I want a proper low lower consumption solution to put on a boat - plus it's only got to do 2 jobs so another Pi seems overkill.
A Wemos D1 mini if you don't need too many GPIOs. Can be had for less than £2 a pop if you buy a couple from AliExpress.
they are all much of a muchness, NodeMCU is a popular one with lots of GPIOs or as above D1 mini if you don't need many. They all have only 1 analog input pin AFAIK which you can probably use to measure the 12v battery although you'll need a voltage divider as per here: https://www.engineersgarage.com/nodemcu-battery-voltage-monitor/
as you're already using your only analog input you'll want a digital thermometer for the temp, DS18B20 is pretty much the standard. https://thepihut.com/products/waterproof-ds18b20-digital-temperature-sensor-extras?variant=27740417873
potentially I might choose one of these for this kind of project as an off-the-shelf solution rather than an ESP - which doesn't need any programming (eliminating one potential area of failure, at least for me 😂): https://shellystore.co.uk/product/shelly-uni/