Calculate the charge time for the Nordic thingy 91


I am trying to calculate the charge time for the nordic thingy 91. I followed this website to calculate the charge time but ~13 hours just did not seem right to me. Can someone let me know if I am on the right track for calculuating this? I have attached my calculations, the link for the thingy, and the website where I got the calculations. The battery capacity is 1440mAh.

-nordic thingy 91



The referenced resource on charge time calculation is what I would describe as Bad Information; it makes a lot of very big assumptions without clearly explaining them or describing the limitations of the ideas that are offered. It’s not totally inapplicable to this case, but it’s close…

Documentation for the thingy suggests that an ADP5360 is used as a charge controller/battery manager. That device offers software-programmable charge management, so until one learns how it’s been programmed to behave, one cannot know what to expect of it.

One could guess that the designer would have aimed to minimize charge time, and noting that the ADP5360 docs indicate a charge current output of up to 320mA, one could guesstimate a 0~100% charge time of around 1.44Ah/0.32A=4.5 hours.

However, lithium batteries of this sort do not accept a charge in an entirely linear fashion, one will not always start at zero charge, and there’s no way of knowing up front whether “100%” is actually the finish line, as opposed to 95% or 90% or something like that. Again, the device in control of things here is programmable, so one can’t really know how it’ll behave without knowing what it’s been programmed to do.

It’s probably a fair guess that most charge events will complete in around 4.5 hours or less, but that’s just a guess. Making measurements on an actual device would probably be the easiest way of acquiring more concrete information on the subject.