I am working on a project, the hardware I am using is a LILYGO TTGO T5 v2.3, it an ESP32 based board with a built in eink screen and charging circuitry for a lipo battery. The problem as far as I know anyway, is that it does not have any under voltage / discharge protection. If it does it could be as low as 2.4v which is no good.
Next to the lipo connector on the board there is a chip stamped LTH7, reading the datasheet https://www.sunrom.com/get/257069 I can't see any thing about low voltage cut off, regardless i've tested the board and it drains the battery down to 2.4v so no good.
I've ben reading allot about these DW01 chips, and there is some conflicting info out there about what they do. The regular DW01 only cut's out at 2.4v, but there is a DW01A and other variants that cut out at 3v. I have a bunch of these TP4056 lipo charge controllers, they have a chip marked DW01KA which I can't find anything about, not tested if these cut off at 3v or not yet. Then there is the built in protection to some of the lipo cells, I have a 800mah lipo, it has a DW01 chip, with a small A and Q at the end of the, I don't know if those are pin markings or if the chip is call DW01AQ, regardless I can't find any info on DW01AQ.
I am looking for a safe (and cheap) way to cut power coming from my battery, once it drops to 3v. My project already enters deep sleep at 3.3v as a precaution. I don't want to get into a situation where the battery voltage drops of a cliff and then the user try's to charge and worse case scenario it goes on fire!
In adition to the DW01, you would need a dual mosfet chip which is controlled by the DW01. I think you will find it simpler to use a protected battery, which would have all of that built in. But 2.4V is pretty much the typical cutoff voltage. And my DW01A datasheet says it's 2.4V as well. An alternate protection chip is the FS312F, which shuts down at 2.9V. But you would still need the dual mosfets. It sounds like your 800mah battery is protected, but that will be at 2.4V. There are billions of batteries out there with the DW01 2.4V cutoff. If you're already going to sleep at 3.3V, then I think you should be ok.
It's a fair point I think I have been looking at the over discharge release voltage as apposed to the over discharge protection voltage. What is meant by over discharge release voltage?
The release voltage is where the protection circuit will open back up again. If protection switches in at 2.4V under load, the battery voltage will recover somewhat when the load is removed. So you have to have some hysteresis to prevent it from cycling. I think the 0.6V hysteresis is usually enough so it will not turn on again until some charging has taken place. But it's possible the battery could cycle a few times before finally reaching the point where the no-load rebound no longer gets it back to 3V.
So one way to think of it is that cutting off at 2.4V under load really leaves the battery at something closer to 3V unloaded. So the 2.4V is not quite as bad as it sounds. And as a practical matter, I think the vast majority of batteries recover ok even if discharged to 2.4V unloaded. Your charger will limit the charge current to 1/10 of the maxium charge current until battery voltage goes above 2.9V, so it will be treated pretty gingerly until the voltage reaches a reasonable level.