What is the ideal external voltage for an Electron?

The Electron can accept up to 12V at Vin – but what would the ideal configuration be for maximizing useful life? I’m assuming maybe the regulators do better (more efficient) at one voltage vs another.

Higher voltage with lower capacity, or lower voltage at higher capacity?

For example… Assume a D cell is 2500mA @ 1.5V … is it best to have 9 D cells in series for a 2500mA @ 12V supply as your Vin? Or 3 paralleled strings of 3 giving 7500mA @ 4.5V?

Or is the difference really just in the noise?

I have an environmental monitor that I’d like to survive for 1 year doing reporting every 3 hours with approximately 2-3 minutes of uptime including the comms. Solar and other renewables or mains power aren’t an option, but annual swapping of a set of alkalines (or lithium as the temps may drop) is OK.

The closer you are to 5v the more efficient the DC to DC conversion is going to be.

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I did some research regarding this topic. It seems a supply voltage of a little less than 5V is ideal. You can find it here: Particle Electron PMIC Efficiency

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Hi Lawolf,

Thank you for linking those details!

Given that 5V appears to be the most efficient, I think in my situation two parallel strings of 4 D cells would seem ideal. That would give me 6.4V with fresh cells dropping toward 4.2V as the cells die.

I mistyped above when I said 2500mA per cell, it’s more like 12000mA per cell for D’s… so I’d have about 144Wh of power which is about 9-10x what I have with the 4.4Ah lithium ion pack now which yields over 45 days.

…and with a small divider network connected to an ADC pin sunk to another pin set low I should be able to monitor the voltage of the pack and shut myself down permanently when the voltage starts to get too low (I’m not sure if brownouts are bad with Particle devices?)

@ems, brownouts ARE bad for Electrons and Photons and have been linked to units wiping themselves clean. Do remember that alkaline and Lithim Ion batteries have a very different discharge curve, with the latter being flat for most of its discharge. Running trials will provide the necessary data. It would be great if you published your results here!