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Part Number: BQ51050B
I want to charge a small LiPo battery of 3,7V. Can it be charged with the BQ51050B component?
As I can see, the output voltage options are around 4,2V.
1 - How the component can notice that the battery is completely charged at 3,7V?
2 - How the component will stop charging the battery?
3 - How the charging ending can be notified? I see that CHG can do that, but as long as I have test it, CHG is always high (both charging or not)
I am measuring the currents with an INA219 between the battery and the BQ51050B. Using the 3,7V battery, I checked that it was charged to 4,096V. Afterwards, it started decreasing the voltage in a constant negative current of -70mA (consuming from the battery). Which could be the reason for that?
Thank you so much in advance,
Bill Johns, Applications Engineer
Texas Instruments Inc
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In reply to Bill Johns:
1 - I have been monitoring the charge of the 3,7V battery, and I could check it was charged to 4,242V. But then, without taking away from the Qi transmitter, it started discharging continously. Which could be the reason for that?
At 4,1V I was seeing voltage in ILIM, but from 4,2V and in the discharge, there is no voltage there.That showed that the charge was finished, didn't it?
3 - I attach two images. The first one is CHG when the battery is charging. The second one is obtained in CHG when it is not charging. Should that be the correct performance?
In reply to Gerardo L:
Thank you so much for your information.
1 - Please, find attached the schematic used below. Vcc is the V of our system. However, the battery is discharging faster than the usual discharge in a normal operation. Therefore, I suppose it is related with Qi.
In addition, our coil is not completely tuned with C14, C15, C16, C17 and C18 to the Qi frequencies. Could that be a reason for the discharge?
2 - Is there a way to calculate the exact current charge from the voltage in ILIM? Is it proportional to VIlim?
3 - I do not have it pulled up. It goes to a GPIO port in a microcontroller, with the purpose of notifying when the system is being charged and when the charge is finished. Is it necessary to be pulled up?
It works using a 4,7KOhm resistor to pull-up. CHG started to work perfectly then.
However, I see in the datasheet that the minimum charging current is 500mA. For the batteries I am using, the maximum charging current is 85mA.
1 - Is there any way to charge at 85mA? Can I modify Rilim to get such current?
2 - How that overcurrent can affect the batteries?
3 - If the batteries have a Protection Circuit, does the overcurrent affect them? Or does it protect them from such problem?
Thank you so much,
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