charging lipo batteries

Anything not related to STM32
GonzoG
Posts: 113
Joined: Wed Jan 15, 2020 11:30 am
Answers: 8

Re: charging lipo batteries

Post by GonzoG »

ag123 wrote:
Sun Oct 18, 2020 12:53 pm
average voltage of 4.2v is maintained.
No. It's not average 4.2V. It's maximum 4.2V.
And with capacitor you'll definitely get more.
mrburnette
Posts: 483
Joined: Thu Dec 19, 2019 1:23 am
Answers: 2

Re: charging lipo batteries

Post by mrburnette »

cjcj1949 wrote:
Sun Oct 18, 2020 1:26 pm
...
They can be made to burn if abused.
Another plus for LiFePO4. Hopefully, the energy density for these low-risk cells will continue to improve.
ag123
Posts: 867
Joined: Thu Dec 19, 2019 5:30 am
Answers: 5

Re: charging lipo batteries

Post by ag123 »

thanks all, i did a little google (re)search on the topic and stumbled into many articles
apparently the most common charging strategies for lithium ion batteries is constant current below 4.2v and constant voltage 4.2v at the end.
there are quite many articles around the internet
https://en.wikipedia.org/wiki/Lithium-i ... _discharge
https://www.electronics-notes.com/artic ... arging.php
https://www.eetimes.com/current-voltage ... -charging/#
https://www.eetimes.com/current-voltage ... ng-part-2/

apparently a large influence factor on the durability and hence safety of the battery is the temperature !
https://www.nature.com/articles/srep12967

charging at 1 C is actually pretty high it translates to 1 ampere for 1 hour for a 1 AH battery.
i think more commonly currents are lower for the average usb connection more like 250-500 mA (there are many better chargers these days that can supply in the ranges of amps, most likely some buck converters) and for small solar cells / panel getting 100-500 mA is good on a sunny day.

hence with solar cells we'd get an coincidental 'constant current' charging simply due to the limited solar power that can be delivered

what would be somewhat curious is can pwm mimic the constant current, constant voltage charging that's typically done with possibly analog circuits.
if that pwm CC CV charging is possible, stm32 can be its own li-ion battery charger with just a single mosfet say from a usb power source. i think the main aim of the CC charging phase is to limit the heating of the battery, that can be done by simply reducing the pwm duty cycle
apparently, this isn't really all that new, some have been there done that
https://www.embedded.com/managing-devic ... odulation/
https://www.microfarad.de/li-charger/

interestingly found an app note from ST
https://www.st.com/resource/en/applicat ... ronics.pdf
in the proposed circuit, it is basically a buck converter, driven by the mcu using pwm, but it is quite interesting
there is actually some incentive for doing all these, the mcu is both the charger and columb counter, it manages the complete state of the battery and can give indications of the battery state and even estimated power remaining and estimated charging time, while still doing other things
ClarkWu
Posts: 1
Joined: Wed Jun 16, 2021 7:23 am

Re: charging lipo batteries

Post by ClarkWu »

Hi...In the event that you have a charger that shows battery inner obstruction, watch that first prior to doing anything to the batteries, they should be 1-4 milliOhm.

Whenever left depleted, set charge to in a real sense the most minimal charge rate and stream them for two to four hours, check the batteries. In a ton of cases you may need to stream them for some time. When you get them to capacity voltage, release them to cutoff and afterward endeavor 1c equilibrium charge rate.

Whenever left completely energized, again check interior opposition. In the event that alright, release them at 1 amp and continue to release them at 1 amp until cutoff, check battery, assuming alright, run a Storage charge the battery, then, at that point release at 2-3 amps, check interior opposition and last completely balance charge and trial, continue to screen the battery.
mrburnette
Posts: 483
Joined: Thu Dec 19, 2019 1:23 am
Answers: 2

Re: charging lipo batteries

Post by mrburnette »

NOT AN ADVERTISEMENT OR SALES RECOMMENDATION.

But, I have been testing out this charging board and it appears to work well:
https://www.amazon.com/dp/B089Q1HBXL?ps ... ct_details
ag123
Posts: 867
Joined: Thu Dec 19, 2019 5:30 am
Answers: 5

Re: charging lipo batteries

Post by ag123 »

@ray
nice, i'd guess the prevalence and low costs of these li-po charging modules these days gives little incentive to do 'custom' li po charging, they are nearly priced 5 pieces to 1 stm32f103 blue pill board. but i'm just thinking a lot of times the timers on stm32 are simply 'idle' they could be used for instance to charge a lipo battery via pwm

a note about those 'mobile power bank' styled 5v battery chargers though i noted some of them requires that you draw rather significant milliamps of current or it'd shutdown the port. i've once tried using a 'power bank' which apparently doesn't power up a blue pill board, but if i connect a higher load such as a 100 ohm resistance across vcc - gnd power comes on.
mrburnette
Posts: 483
Joined: Thu Dec 19, 2019 1:23 am
Answers: 2

Re: charging lipo batteries

Post by mrburnette »

ag123 wrote:
Sat Jun 19, 2021 6:30 am
...
a note about those 'mobile power bank' styled 5v battery chargers though i noted some of them requires that you draw rather significant milliamps of current or it'd shutdown the port.
...
Yes, I noted the same behavior.
I use LiFePO4 chemistry for "lite" uC loads and the charging requirements of those cells are very simple.
Post Reply

Return to “Off topic”