I've been discussing plans for an animated solar lantern with people online. The Adafruit bq24074 solar BMS looks to be an excellent battery controller to drive my lantern day and night.
Some people online claim that the unit requires a fuse to protect the rest of the board. They even suggested that the entire board would erupt in flames.
However, the Adafruit documentation doesn't mention the fuse precaution. Then I got silence from Libera.Chat, no further clarification there. So I am asking here that the wider community could help me to understand better.
Does it matter if the battery is planned to be a Samsung flat top 18650 Li-Ion nominal 3.6V, max 4.2V? The Adafruit product page stresses using Adafruit branded batteries at nominal 3.7V, max 4.2V.
The lantern scheme in question:
Matters not the voltages involved. What does matter is the current the battery will supply IF, for any reason, wires are shorted together. Will enough heat be produced to melt the wire insulation? If so, then a fuse is needed and the fuse current rating needed will be somewhat above what your entire system will draw from the battery, so measure the current normally used.
As long as you use 6V solar cells and the temps do not get to hot or down to freezing and you need no more than 1.8A you should be OK.
I use a PWM charge controller with a 12V LiFePo4 that works down to -40F.
I tried using a regular 18650 Li, the physical conditions are very difficult for a Li. The Li lasts about 4 months between the heat and the cold. My LiFePo4 has been going for 1 year 5 months.
I do not use a fuse.
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