Lithium battery built in protection circuit - Page 1
Forum section: electronics / projects

author: LittleRain
author_rank: Contributor
timestamp: January 23, 2020, 06:23:42 am
content: I got some batteries that I am using for a project, they have a small board on them, but I cant tell if they have any protection IC's on them due to it being folded over.All I can see is its wires, but I'm pretty sure it does.Even if it does have protection IC's, do I still need to add a charging circuit to my board?The battery is just a standard 600mAh lipo,theone in this picture.I was going to use this IC to handle its charging, but I'm not sure if I need it.I have no idea what the protection IC's on lipos are, I'm guessing short circuit and over current, but does it handle charging as well?The IC I plan to use is the LTC4054,here is link to datasheet.So I guess what I need to know is, do I need to add that charging IC?

author: Siwastaja
author_rank: Super Contributor
timestamp: January 23, 2020, 06:27:05 am
content: Yes, even if it has a protection circuit, you'll need a charger circuit, which actively controls charging current and voltage, and hopefully monitors temperature to prevent low-temperature charging.The usual protection circuits just cut off completely with severe overcurrents, and with slight overvoltages, and have no means to actually limit current to safe values, just act like a resetable fuse in case they are greatly exceeded. Also, the protection voltages tend to be a bit over the normal operating values (like 4.25V or 4.30V instead of 4.20V) so that they won't trig at normal, intended operation.

author: MarkF
author_rank: Super Contributor
timestamp: January 23, 2020, 01:21:21 pm
content: It may be cheaper to just buy a charger...For example:Mini-USB jack:https://www.adafruit.com/product/1905Micro-USB jack:https://www.adafruit.com/product/1904

author: LittleRain
author_rank: Contributor
timestamp: January 23, 2020, 09:58:34 pm
content: Ok thanks Siwastaja, very helpful.MarkF, I'm not building a charger... I'm building a HID USB/Bluetooth device that charges via USB.

author: LittleRain
author_rank: Contributor
timestamp: January 24, 2020, 05:15:42 am
content: Do I also need to provide under voltage protection?

author: kjr18
author_rank: Regular Contributor
timestamp: January 25, 2020, 06:34:27 pm
content: Typically these protection circuits are based on DW01 chip (or some other) and double mosfet package. They protect from overcharge, and overdischarge. But I think not every of them has them. I saw on YT some time ago, that someone took it apart and board was used only for soldering cables to it. You could check this by discharging battery, if it will go below 3V it's probably not overdischarge protected (I know that some variants of DW01 trigger at a lower voltage, even around 2.5V, but i never saw it in battery)For charging you can use these small TP4056 boards with builtin protection. It won't hurt to be sure.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 25, 2020, 06:39:12 pm
content: Quote from: LittleRain on January 24, 2020, 05:15:42 amA good design should have its own protections, and should not rely on the battery internal protection.

author: LittleRain
author_rank: Contributor
timestamp: January 25, 2020, 09:54:13 pm
content: Quote from: kjr18 on January 25, 2020, 06:34:27 pmSpace is very critical, I'll see try to incorporate it into my board. If not that IC, another one.Quote from: RoGeorge on January 25, 2020, 06:39:12 pmPoint taken, will do.

author: kjr18
author_rank: Regular Contributor
timestamp: January 27, 2020, 08:00:45 am
content: Quote from: LittleRain link=topic=226796.msg28ltc4057-4.287388#msg2887388 date=1579989253You can use TP4057 or ltc4057-4.2 if you need space. As charging current in those is lower you can get by with smaller boards. As for protection you can look for protection IC's with integrated mosfet's. I'm sure there are enough of them.