Power Banks

Ultramic384K BLE can work as autonomous unattended recorder.

Unfortunately the commercial power banks used to recharge smartphones, have got a circuit that stops the power at a defined minimum level of current.

This happens when the UM384k in scheduled mode sleeps between two recordings and the current falls below 1 mA.

Here you can find a way how to modify a standard power bank

Use of USB power bank with Ultramics

Another solution is the use of battery holder for standard not rechargeable batteries size D, C or AA connected with a USB voltage converter.

Here you can find the off the shelf solution for your battery pack.


Battery holder comparison

3 x size AA battery holder



3 x size D battery holder


3 x size D battery holder opened

3 x size AA battery holder opened