2024-03-27 02:14 AM
I have a STM32F429, It is possible to know the batteri state ?
I would like to know from RTC register or other if the battery is near the low voltage level, and needs to be replaced it
Thanks
Stefano
2024-03-27 02:28 AM - edited 2024-03-27 02:29 AM
Hello,
You can do it with ADC CHANNEL18:
See RM0090:
2024-03-27 02:35 AM - edited 2024-03-27 02:37 AM
Other information that you need to take care about when you need to monitor your battery with ADC:
From the datasheet:
2024-03-27 03:07 AM
Well, that measures the battery voltage - which may or may not be a good indication of its state-of-charge...
😋
2024-03-27 04:28 AM - edited 2024-03-27 04:28 AM
> Well, that measures the battery voltage - which may or may not be a good indication of its state-of-charge...
There's no magic method to determine state of charge of a battery anyway. You can coulomb-count, but that of course has its drawbacks, too.
While some chemistries have a rather steep end-of-life V-t curve, they also quite universally have increased internal resistance by that time. Loading it by the divider thus results in lower voltage than what it's unloaded. In other words, when the measurement using the divider shows some reasonably low voltage on the V-t curve, there's still some life left in the battery.
JW
PS. Don't leave the resistor divider connected to VBAT longer than absolutely necessary, as that would drain it very quickly.
2024-03-27 07:15 AM
@waclawek.jan wrote:Don't leave the resistor divider connected to VBAT longer than absolutely necessary, as that would drain it very quickly.
^^^ This! ^^^