Perhaps a small Battery level indicator within the Sphero app (just a small battery level icon in the corner of the screen or something) so we can better judge when the battery needs charging,
Thanks for your suggestion. It would be great to know how much juice your Sphero had left.
Unfortunately,the type of battery Sphero uses actually prevents us from adding this to the app. Sphero's battery essentially gives us a message that the battery is running at full all the way until the last few minutes before the battery dies. Therefore, we can't pull a current running time battery status from Sphero.
If one were to graph Sphero's battery levels at it reports to us, it would look like a long straight line at 100% with a sharp dive down to zero at the end. That is why currently Sphero will only show his battery is low, as opposed to a level indicator.
I hope that clarifies things, and we will take this into consideration for future product decisions.
What if instead of reporting the actual amount of power left you wrote it to estimate based on how long sphero has been running between charges?
I think this is still a good idea since most modern devices usually have a power indicator so users will typically expect to have this so they better utilise and plan battery usage of that device.
From my understanding, Sphero uses a standard Li-ion battery (similar to smart phones). I have read in other forums that Li-ion batteries don't have a sensor, so smart phones are not able to directly measure the charge either. It is actually a microprocessor in the control circuitry that measures the charging and discharging currents when it is full and nearly empty and uses that to estimate the battery level. That is why there are many articles online related to Li-ion battery maintenance that will advise to "recalibrate the battery" by doing a full dischage and full charge every 1-3 months or so. Based on this, I see no reason why this can not be implemented for the Sphero too. as suggested by Matthew and Trish.