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[SOLVED] Recommendations for Li-ion protection IC/Circuit

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Aussie Susan

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My current circuit has a wireless battery charger (BG51050B) that charges a single cell Li-ion/LiPo battery. That part works well.
I also have some circuitry on the 'other side' of the battery (a PyCom GPY and a GPS receiver) that are more than capable of working well below the appropriate Li-ion battery cutoff voltage. This means that I have ruined 1 battery by over discharging it.
What I'm looking for are circuit designs or ICs recommendations for something that will:
- allow the 'working part' of the device to be powered when the battery is above the minimum voltage (say 3.2V or whatever is the recommended lowest discharge voltage) - this also means that it should come on while the battery is charging on the wireless pad
- shut off the rest of the device when the battery is to low so that it will not discharge further (i.e. as low as possible stand-by current from the voltage monitoring hardware)
It is for a home-made GPS tracker for my dog and so it will only be used occasionally and I'm happy to put it on the charging pad before use. As my dog loves the water I am trying to make sure the container is as waterproof as I can make it so I don't want an external switch.
I've looked on the Internet and seen lots of designs for battery chargers so I could well be using the wrong searching terms.
Susan
 

BradtheRad

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A logic gate has high gain allowing it to provide abrupt shut-off to a PNP when the battery drops below 3.2V. A potentiometer adjusts volt level at the input.

battery shut-off below 3_2V via PNP invert-gate pot adjust.png
 

KlausST

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Hi,

there are RESET devices with fixed threshold. Add a MOSFET and it should work.

But the problem will be that as soon as you connect a load the voltage will drop --> the load will be switched OFF --> the voltage will rise --> the load will be switched ON.

So you need something with a fix switch_OFF_threshold and some hysteresis to switch ON.
A low power comparator, some resistors and a MOSFET could work.
But I guess there are ready to buy solutions.

Klaus
 

Aussie Susan

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Thanks for the responses.
It has taken me a little while to respond as I purchased an AP9101C protection IC and to took a little while to arrive. When it did it showed that it was working well except for......
For my purposes I want an IC that will restart when the battery level rises automatically. The AP9101C will stop ghe battery form discharging once the voltage falls below a certain limit BUT it needs to be manually restarted.
What I didn't realise is that there is an AP9101CA that does automatically restart. I have a couple on the way to test.
Lesson learned - read the data sheet CAREFULLY and make sure you understand the difference between the model numbers listed.
Susan
 

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