Electronics > Power/Renewable Energy/EV's

Charging a Li Ion battery: 3.7V, 4400mAh

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Peabody:
I just don't think it's safe to use the DW01 to terminate charging.  I've never seen that done in any circuit.  And of course it doesn't terminate at all if the voltage doesn't quite get to 4.3V.  You can't continue to apply 4.2V or higher to a fully charged lithium battery.  I would just urge you to use your charger chip, which will handle this correctly.  You might also look at the J5019 module, which is a TP4056 charger plus an adjustable MT3608 boost converter on one tiny board.  It has no protection, but you already have that.

fourfathom:

--- Quote from: Peabody on September 23, 2022, 03:31:36 am ---I would just urge you to use your charger chip, which will handle this correctly.  You might also look at the J5019 module, which is a TP4056 charger plus an adjustable MT3608 boost converter on one tiny board.  It has no protection, but you already have that.
--- End quote ---

Thanks for the heads-up on that J5019 -- pretty much exactly what I need and stupidly cheap from China.  I need an enable for the boost, and I didn't notice one on that board.  I just sent out my little charger / boost board for fab (JLCPCB, $8 for five bare boards, delivered) and I already have the parts, but I also ordered a couple of the J5019 boards from ebay to try them out. 

Peabody:
The boost chip on the J5019 does have an ENable pin, but it's not brought out on the module.  But it looks like there's a way to wire into the ENable:

https://www.andersknelson.com/blog/?p=765

Not a solution for production stuff, but should work ok for hobby projects.

Edit:  With the boost converter disabled, unboosted current will still flow through the coil and the schottky diode, and it looks like the chip will still draw about 65uA.  So for a real shutdown, it may be better to use separate charger and boost modules, with a switch or mosfet in the middle.

Faringdon:
Since your solar is so weak, 5v and 2w.....it just seems overkill to do it with a charger.
I mean...you coudl just shovel the solar into the battery.....and have a voltage clamp circuit in there....which only kicks in if the batt voltage starts straying above say 4.3v..........this voltage clamp cct woudl be pretty well out-of-cct when the batt voltage was low....so it wouldnt incur losses.....because with a small weak solar like you have  , you dont want big losses as you appear to be well aware

fourfathom:
I considered a clamp but it would have been dissipating about 2W once the battery was charged. That power would have been wasted anyway,  but I didn't want to deal with the thermal on the shunt transistor.

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