Hi,
I have a NCR18650 LI battery and I'm designing a circuit that can charge it from a low power source ( solar, TEG, piezzo), as well as USB when the low power source is not available. The circuits will always be connected to a load that is switched on/off as needed.
For the low power circuit part, I am using a BQ25570RGRT nano power booster and have the circuit designed as per Texas instruments' application notes.
For the USB part, I am using an MCP73833 charge management controller from microchip that is recommended for USB charging.
Both chips would supply around 4.2V to charge the battery.
The questions that i need help with are:
1- is it ok to have both charging circuits connected to the battery as shown below? Each circuit eventually has a VBAT output that connects to the +side of the battery. Is there any risk connecting the two charging circuits in parallel like that? Both circuits will be charging at the same voltage level. If the USB power is connected, and the low power energy source is supplying power as usual, will the battery be charged from both sources? will it be charged by the source that can deliver more current?
2- When the load is connected to the circuit while one or both charging circuits are active, my assumption is that the charging circuits will still try to charge the battery, but the latter will be drained because the current consumption of the load is higher than what the charging circuits can supply. Is that a correct assumption?
3- Should I put some diodes between the VBAT pins and BAttery to make sure no circuit forces current into the other? each VBAT is already connected to a FET transistor as show in the picture below.
Thanks a lot for your support.
I have a NCR18650 LI battery and I'm designing a circuit that can charge it from a low power source ( solar, TEG, piezzo), as well as USB when the low power source is not available. The circuits will always be connected to a load that is switched on/off as needed.
For the low power circuit part, I am using a BQ25570RGRT nano power booster and have the circuit designed as per Texas instruments' application notes.
For the USB part, I am using an MCP73833 charge management controller from microchip that is recommended for USB charging.
Both chips would supply around 4.2V to charge the battery.
The questions that i need help with are:
1- is it ok to have both charging circuits connected to the battery as shown below? Each circuit eventually has a VBAT output that connects to the +side of the battery. Is there any risk connecting the two charging circuits in parallel like that? Both circuits will be charging at the same voltage level. If the USB power is connected, and the low power energy source is supplying power as usual, will the battery be charged from both sources? will it be charged by the source that can deliver more current?
2- When the load is connected to the circuit while one or both charging circuits are active, my assumption is that the charging circuits will still try to charge the battery, but the latter will be drained because the current consumption of the load is higher than what the charging circuits can supply. Is that a correct assumption?
3- Should I put some diodes between the VBAT pins and BAttery to make sure no circuit forces current into the other? each VBAT is already connected to a FET transistor as show in the picture below.
Thanks a lot for your support.