Low battery cutoff voltage?

#1

I am working with V2 of the ESP32 WiFi / BLE kit.

I’m making a LiPo-powered device that will be only intermittently connected to USB power to charge. I’d like to make sure that I don’t damage the LiPo battery by excessive discharge. I’ve seen a schematic (not up to date with the part I have, since it specifies pin 13 instead of 37 for VBAT) that says that the battery charge controller chip is a TP4054. The datasheet I found for the TP4054 indicates VUV of 3.4-3.8V which is a wide range and much higher than I would expect for low-battery cut-off, and I think is VIN undervoltage lockout, not VBAT low voltage shutdown. But I see no mention in the datasheet of a battery low voltage cutoff to protect against over-discharge of the attached LiPo. Discharging a LiPo to less than 3.0V generally will damage the LiPo, and my application requires many charge cycles without battery replacement, so I want to preserve battery life.

I’m testing my unit to see if it will shut down before the battery reaches 3.0V, but based on the datasheet it’s not clear that it will.

I’m not sure that the datasheet I found is authoritative. Should I expect the battery charge controller on this device to implement excessive discharge protection?

If it should, do you have a link to an authoritative datasheet for the charge controller in use?

If the battery charge controller does not have excessive discharge protection, how is the user expected to avoid excessive battery discharge in an application?

Thanks!

#2

It looks like it has no battery excessive discharge protection. I inadvertently left it alone for a while and when I came back it was a 2V, so I almost certainly killed the LiPo cell I was testing with.

So given that the battery is directly connected, how do you protect against excessive discharge? Turn off all wakeup sources, go into deepest possible sleep, and just hope that someone plugs in to recharge in time?

#3

Some LiPo battery drive boards have battery excessive discharge protection.

1 Like
#4

@Xiao-H oh, good point, thanks! I wonder whether the 2V I read on the LiPo I was using was a presence signal from the charge control circuitry on the board? I didn’t think of that, so I didn’t put a load on it to test.

Yes, this cell has a 2.75V low cut-off.