Charging LED on Feather HUZZAH blinking despite no bat

[valenceelectron]

Hi there! Newbie here.

I've developed a program for a "Feather HUZZAH with ESP8266". Testing/developing was done with it attached to my computer via USB.
Now that I'm finished I've attached the USB cable to a regular 5V power supply and the feather works well, however, the charging status LED is constantly blinking. At first I was worried this might indicate a problem but it seems to work so far. The constantly blinking LED is a little annoying though. Oh and of course there is no battery attached.
All my wiring is a connection to a BEM680 breakout (I2C) and GPIO16 to RST for deep sleep.

Is there a problem because the LED is blinking with no battery attached? Is there a meaning to it?
And ultimately: how to turn it off?

Thanks in advance!

[adafruit_support_mike]

It's normal for the charging LED to blink when no LiPo is connected. It just means the LiPo charger is reacting to random voltage fluctuations on the BAT pin due to things like parasitic current in the components and static charge accumulation.

Any time BAT goes below the threshold for starting a new charge cycle, the LiPo charger will try to send current to the pin, and that will bring the pin up to the correct shutoff voltage almost instantly. Then the charger shuts down and lets the pin voltage drift again.

It's harmless.

[eeriedescent]

Harmless or not, how can I turn this off? I find it pretty annoying as well.

Can I short this to a GPIO pin pulled high?

[adafruit_support_mike]

You can connect a 10uF capacitor between BAT and GND. The LiPo charger will charge that to 4.2V, and the capacitor will hold the voltage stable against random leakage currents.

A GPIO pin will only take the BAT voltage to 3.3V, which is about 0.9V too low. Connecting to 5V would damage the LiPo charger's output, and trying to make a 4.2V voltage divider would be iffy. LiPo chargers have to hit their target voltage within about 4mV to operate safely.

[eeriedescent]

That makes sense. Thank you!

[tinkerdave]

Hi there,

This may be the wrong thread for dealing with the charge LED flicker issue for other controller boards but I'm currently having this issue using a Feather nRf52 Bluefruit LE without a battery.

I tried the cap solution above, but all it did was delay the flicker until the cap charged, then it starts to flicker again. Looking at the Feather nRF52 schematic, I see there is already a 10mF cap connected between VBAT and GND. I tried putting a 1 meg resistor between VBAT and GND, and the flicker stops. What I don't know is if this causes any harm to the LIPO charger chip long term. I assume the current through that resistor will be extremely small , so I'm not too worried, but I really don't know. Does anyone have any insight?

Thanks.

[adafruit_support_mike]

That will work, and won't hurt anything. The 1M resistor just gives the LiPo charger a few microamps worth of DC connection to GND.

[jensbjorgensen]

I tried this (putting 1M resistor across BAT & GND) on my Feather nRF52840 Express but still got the blinking light. Maybe this feather doesn't already have the capacitor and the combination is what makes it settle?

[disgustipated]

I'm seeing this on a huzzah32 but not on any of my 8266 huzzahs... at first i thought i bridged something on the pins when soldering the headers on but it seems to be working ok... that esp32 chip is MUCH closer to the pins when soldering.

[adafruit_support_mike]

I tried this (putting 1M resistor across BAT & GND) on my Feather nRF52840 Express but still got the blinking light. Maybe this feather doesn't already have the capacitor and the combination is what makes it settle?

There’s no built-in capacitor between BAT and GND.

If you add a capacitor, it acts like a really small LiPo.. the charger can send current into it, and can monitor the capacitor voltage. It’s usually good enough to make the status LED stop blinking.