Hey guys I am using 5 lithium ion cell (18650) in parallel config to get 4.2V 10Ah supply. However, I am having a problem in finding suitable regulator that can provide 3.3V as the battery pack voltage drops from 4.2V. Any module will be good. Or any IC that can be hand soldered. Or any solution which is good.
I was first using an approach where I was boosting the voltage to 5V and then regulate to 3.3V but the boost converter was consuming 50mA which was very high for our application. So any suggestion will be appreciated.
Regards,
You want what is called an LDO, or low drop-out voltage regulator. Something like the LF33ABV, which provides 500mA max current at 3.3 volts with a drop-out voltage of .2 volts. This means it will stop outputting voltage somewhere around 3.5 volts input. Alternatively, you could use a DC/DC power supply like the TSR 3-0533, which can take 2.5-5.5 volts input and supply 3.3 volts at 93% efficiency, but it's a bit more pricey.
Thanks for your reply. It seems good. My current level is 300mA. So it is sufficient.
But my concern is that the lithium ion cells discharge up to 2.7V or atleast 3V safely. So if I use the IC it will only regulate up to 3.5V. i want to use my battery pack capacity to 80-90%. How do I know at 3.5V how much battery capacity has been consumed, provided the current is 300mA max that my circuit takes when it wakes up. And the rest it is in sleep mode.
Regards,
Workaholic:
Thanks for your reply. It seems good. My current level is 300mA. So it is sufficient.
But my concern is that the lithium ion cells discharge up to 2.7V or atleast 3V safely. So if I use the IC it will only regulate up to 3.5V. i want to use my battery pack capacity to 80-90%. How do I know at 3.5V how much battery capacity has been consumed, provided the current is 300mA max that my circuit takes when it wakes up. And the rest it is in sleep mode.
Regards,
You will need to provide sufficient datasheets for the battery cells to answer your questions on % of battery capacity. There is often a graph that will answer this question. However, if you wish to output 3.3 volts DC continuously while the battery fluctuates between 4.2 and 2.7, you probably want to go with the more expensive DC-DC power supply or one similar. You will pay more but you will get more.