Hi,
I am using a battery babysitter board (PRT-13777) to charge/discharge/monitor a single 18650 Li-Ion cell (Murata INR19/66). I have noticed that even though I have set the dip switch to a 1.5A charging current I can’t get above 300-400mA during charge, it can even get as low as 250mA…
I am charging the battery using a generic 5V/2A wall adapter using a USB-C cable connected to a 5V trigger board such as https://www.amazon.com/ANMBEST-Connecto … 091CRLJM2/ which is then connected to the Vin pins of the battery babysitter. I have checked the charging current by using a USB voltmeter.
I have set the dip switch according to the hookup guide to get 1.5A but to no avail, I have also tried the other configurations and nothing gives 1.5A. I measured the ISET resistor and it has the correct value (590 Ohms).
Could you help me figure out why I can’t get to 1.5A ?
Thank you in advance !
How low is the battery when you charge it? If it’s not very low the charger will sense that and drop the current.
Your battery might also have current limiting built in that drops current.
Also, your power supply, even though it’s rated for 2 amps might not be able to deliver all that current. Or it may drop it’s voltage under load to a point where the charger can’t compensate and then the charger drops it’s output.
Could also be a bad board but check those other things first, they are more likely where the issue is.
Thanks for the quick reply !
I tested the charger by charging a power bank and it seems to work according to its specs. I am using a bare cell so there are no additional circuitry on the battery that would limit the current.
I tried charging a cell which had a voltage of 4.06V, for that one the charging current was ~350mA.
I tried charging a cell which had a voltage of 3.67V and for that one the charging current was 980mA (still far from 1.5A).
It looks like it’s just the BQ24075 limiting the current towards the end of charge but my understanding from the datasheet was that would start at 4.2V not before (see attached charge cycle graph from the datasheet, VBatREG is 4.2V).
