I want to create 5V power supply for a portable lighting project, using 18650 batteries.
The power supply needs to provide power to an arduino (which can take 3.3V to 13V input) and some addressable LED strips, which would take 5 volts input ideally, but a somewhat lower voltage is acceptable.
The project would draw a maximum of 2 Amps (10 watts) with all LEDs on.
I’d like to use 18650 batteries as the power source, which are nominally 3.7V but which I believe would provide an actual voltage rannging between around 4.1V (when fully charged) down to maybe 2.5V (at which point they would be considered discharged).
The options I’m considering are:
- 2 18650s in series, with a buck converter to step the voltage down to 5v.
- a single 18650, with a buck booster to bring the voltage up to 5v.
I’m aiming for around 3 hours of battery life. I think the average draw of the project would be maybe 5 watts, so I need ~15Wh of capacity. A good quality panasonic 18650 provides around 12Wh, so if I went with the boost option I’d consider adding a second 18650 in parallel. Perhaps this means I’d also need a BMS?
I don’t believe that an LDO voltage regulator is a good approach - it would be pretty inefficient and would need a lot of heat dissapation support, given the wattage of the LEDs.
Are there any majors pros or cons between these options? Are there other options I haven’t considered?
My main decision factors are efficiency (for longer battery life) and cost.