LiPo connected to expansionboard, discharged, not charging

[Meirssv]

Hello,

When doing a battery test, an otherwise normally charging/discharging 1000 mAh LiPo got drained while being connected to an expansionboard with a LoPy on it. The LoPy was deepsleeping, waking up every minute, scanning BlueTooth devices for 5 seconds and sending a small payload with its battery level to a TTN Lora Gateway.

All was running fine until the LiPo level reached 3 volts, as may be expected, the LoPy did not start anymore.

But now, connecting USB power does not make the charging-led go on and the LiPo does not get charged. Even after 30 minutes or so. The battery was charging before, indicated by the charging led.

For our project, the LoPy needs to be in the field 'unattended' for a while, we could of course intervene when receiving low battery voltage from the monitoring we have set up but what if we do not get there in time? It's not really our intention to take out the lipo and charge it using another charger every time it gets drained.

Is there a possibility to set the LoPy into 'power off' mode so it does not start up anymore once we detect a safe minimum battery level so it doesn't get discharged beyond this "charging no-go" point?

[Meirssv]

I am using the expansion board 2.0. I have no deep sleep shield yet (Pycom forgot to send the deep sleep shield with the order of the lopy 2 weeks ago. They told me a deep sleep shield is on its way now)

We deinit the WLAN from start because we don't use it.

We charge just using the micro-usb cable. It is configured with the jumpers at 450mA charge current.

In the battery test we did, we intentionally drained the battery fully to see how long it would last. We expected the LoPy to stop working eventually, but expected we would be able to recharge it using the USB connection at that point.

Can the deep sleep shield -if used on the LoPy 1- recharge a drained battery by just plugging the USB-cable in after the battery was exhausted and shut off by the deep sleep shield?

[crumble]

@meirssv

When doing a battery test, an otherwise normally charging/discharging 1000 mAh LiPo got drained while being connected to an expansionboard with a LoPy on it.

The expansion board or PyTrack/PySense? The last two turn the whole LoPy off and use a second microcontroler to wake up the LoPy. Without the second microcontroller you have to switch off (deinit) all network related parts. Use an USB power meter to check it. If you have space in your case, you can add the deepsleep shield, which uses the second microcontroller as well. There is a thread in this forum, which already discussed which parts have to deinit.

A normal sleep seems to have no effect and will discharge your LiPo really fast.

How do you charge the your system? I hope that I can (re)use an old USB solar charger which is much too small to charge a phone in my region.