LI ion batteries

[jason0l]

Think there should be some kind of cut off protection for the batteries for when they run too low. If the batteries don't have any protection circuitry, drawing more power than they can provide can damage the cells.
Maybe consider a 2S lipo pack with protection circuitry or adding a protection circuit to the two 18650s.

[olivervogelreed]

Thank you for bringing this issue up, just a bit of background. We decided to choose the 18650 due to a higher ubiquity of a standard sized cell and they fact that they can be easily charged but clearly missed some things. Let us know if you had any particular solution that comes to mind.

@Yo5001 is currently developing a second iteration of the circuitry so I will make sure he is aware of this and we'll have a look into making sure this is fixed in the next iteration.

[jason0l]

A simple solution would be to just add a voltage divider across the two batteries and have the Arduino read the voltage of the batteries. When the batteries get too low, you can let the user know to charge the batteries before they can use it.

Ideally, you would want some kind of dedicated circuitry for protecting the batteries but it will add more to the cost and complexity. You can find these on places like eBay if you search "2s battery protection"