Low power operation of nRF devices

[ThinkTransit]

I purchased some BLE beacons from aliexpress which contain a nRF51824. With the included firmware they operate at about 50uA, advertising a data packet every 500ms.

I installed micropython on one of these devices using openocd + an st-link. At the repl the device use about 1.2mA. I have tried reducing the power consumption by using machine.lightsleep/deepsleep but interestingly the current consumption went up during sleep.

import machine

while True:
    machine.lightsleep()

Has there been anything implemented in the nRF port for low power use?

Or should I be looking at using the zephyr port instead?

Thanks