Due to some intermittent voltage drop issues on the first revision of PowerShield I refactored the design and released a new PowerShield R2 based on the LTC3525 fixed 5V booster that should address this issue. This is a much more expensive chip than the TPS61220, others have used the Linear Technology boosters with success so hopefully it’s more reliable, but price will reflect this. It also means there is no switching between 3.3V and 5V output any more. For 3.3V projects, a Lipo can be connected directly to Moteino and the onboard regulator will provide up to 250mA of current to the Moteino itself and any other peripherals attached. There are also some other changes, notably the charging current has been set to 212mA (4.7K PROG resistor on the MCP73831), down from 500mA (2K PROG). The battery connector has been rotated 90 degrees and a notch underneath it was added to allow the wires to be flush to the enclosure sidewall. The rotation was done to allow the USB charging side to be inserted in the wall of an enclosure without the wires interfering with that. This should be ideal for MotionMotes or similar projects where a PowerShield+small Lipo are used instead of a 9V battery. Then the MotionMote could be plugged in and recharged whenever it runs out of juice, without opening the box.
The “voltage monitor” has been kept on pin A7 on the side Moteino header. The prototyping area has been enhanced to connect the bottom row into all GND and all the columns pins connected. You can get a 5V boost from single AA/AAA cells (for light low power loads) or a solid efficient 5V boost from 2xAAs or even better from Lipos. The LTC3525 is rated at 400mA output but to get that you would need to use at least a Lipo battery that is fully charged. You will NOT get even close to that much juice from a single AA cell. See datasheet for more details on the limits and what to expect.