Posted: 06:41am 21 Sep 2023
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LRAT Newbie
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Howdy,
I am replacing my current weather station with something smaller. The brain of the weather station is going to be an ESP32 as I want to use the WiFi capabilities. The project will be charged by a 10W, 12V solar panel. I live in Melbourne and we can have many days of overcast conditions, so, I'll need redundancy in battery capacity. I did the sums and I probably need 4x 18650 Li-ion cells in parallel. But because I also need a stable 5V output for my sensors I probably need to double the batteries so that I can put them in series to achieve 8.4V (If that makes sense). I will also need protection against over- and under-voltage. Anyway, I did my research and I think the following is going to be my best option:
The 12V solar panel will be connected to a CN3795 MPPT Li-ion charge control module. I will put a Schottky diode to prevent drainage overnight. I then will connect two Mini360 switching power regulators. One will be set to 3.3V and the other to 5V with common ground
I am not an electronics specialist and I would like to receive some constructive feedback if my thinking process is in the right direction. I've been looking for off-the-shelf MPPT chargers but I can't find anything for multiple 18650 cells in parallel. Most chargers are for lead-acid battery technology but I want to switch to Li-ion batteries as they are common, cheap and long-lasting (When treated correctly).
Also, I've been told that it's possible to buy 18650 Li-ion batteries with inbuilt BMS; Is that correct? If yes, where do I find these? I don't want to skimp on quality and reliability so brands like Samsung or Panasonic would be the best.
Anyway, I hope somebody can give me a nudge in the right direction. Many thanks in advance for your help/advice! Cheers,
Luke |