Li - Ion Smart / Battery Charger - Page 1
Forum section: electronics / projects

author: StreetRooster
author_rank: Newbie
timestamp: March 22, 2019, 10:27:11 am
content: Hi EveryoneI have a number of 3.7V 6600mAH Li batteries, and am asking if anyone has a circuit for a smart charger for my batteries.

author: aldi
author_rank: Contributor
timestamp: March 22, 2019, 05:34:53 pm
content: We need more specifications, such as:Input voltage, charge current, interface (I2C or just pins?). Any need for protection? And what do you mean with "smart"?

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: March 22, 2019, 05:38:50 pm
content: I've done several designs, it's best to use an IC dedicated to charging Lithium batteries, Texas Instruments have several. What is the maximum charge current?

author: StreetRooster
author_rank: Newbie
timestamp: March 25, 2019, 09:06:02 am
content: Thank you or replying to my post.What I mean by " Smart " is that when I start charging the battery the charger will be able to detect the battery's Voltage.In my case these are 3.7VIt will then start charging in CC mode, in my case that will be 3A as these batteries are 6000mAH.When the 3.7V is reached the charger then reverts to CV mode.It will remain in this mode until a residual charging current of +- 150mA is reached and then switch off.

author: Daixiwen
author_rank: Frequent Contributor
timestamp: March 25, 2019, 09:47:30 am
content: What you describe is what most dedicated Li-Ion charging chips do. Just pick your manufacturer and any reference that can charge 1S batteries (meaning one element, and not several in series).Double check your voltage though. 3.7V is most probably your cell nominal voltage, but its charging voltage is more likely 4.2V. If you charge it only to 3.7V you'll only get about half its capacity.

author: StreetRooster
author_rank: Newbie
timestamp: March 25, 2019, 09:58:33 am
content: Thank youMaximum charge current will be 3A.Battery Voltage 3.7V

author: StreetRooster
author_rank: Newbie
timestamp: March 25, 2019, 10:00:53 am
content: I follow, the 3.7 V is whats printed on the battery.

author: KL27x
author_rank: Super Contributor
timestamp: March 26, 2019, 02:42:17 am
content: 3.7V is printed on the battery because that's the nominal output voltage under load. The charge/float voltage would be 4.2V. Daixiwen was generously allowing for the possibility that you live in an alternate universe.

author: AlienRelics
author_rank: Unknown
timestamp: March 26, 2019, 06:48:21 pm
content: Which chemistry? Most have a terminal charge voltage of 4.20V, but not all.https://batteryuniversity.com/learn/article/types_of_lithium_ionWay more information on Lithium Ion cell charging:https://batteryuniversity.com/learn/article/charging_lithium_ion_batteriesIt really is a wise idea to select a chip dedicated and designed for Lithium Ion charging.

author: KL27x
author_rank: Super Contributor
timestamp: March 27, 2019, 08:06:21 am
content: In an alternate universe, those other chemistries might be relevant. That info is 20 years old* when those cells still showed (or at least more recently had shown) potential. One of those...(LiFeO4 ? Something like that) is still alive and used in some applications like EV's. But if the cells are marked 3.7V, you know exactly what it is. It's the one that is 99.9% of the li ion battery industry.*I not only read about these chemistries nearly 20 years ago, I read it from this exact site. This site has not changed much in the interim.