Author Topic: Lithium battery built in protection circuit  (Read 1999 times)

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Offline LittleRainTopic starter

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Lithium battery built in protection circuit
« on: January 23, 2020, 06:23:42 am »
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?
 

Online Siwastaja

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Re: Lithium battery built in protection circuit
« Reply #1 on: January 23, 2020, 06:27:05 am »
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.
 

Online MarkF

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Re: Lithium battery built in protection circuit
« Reply #2 on: January 23, 2020, 01:21:21 pm »
It may be cheaper to just buy a charger...
For example:

  Mini-USB jack:  https://www.adafruit.com/product/1905
  Micro-USB jack:  https://www.adafruit.com/product/1904
 

Offline LittleRainTopic starter

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Re: Lithium battery built in protection circuit
« Reply #3 on: January 23, 2020, 09:58:34 pm »
Ok thanks Siwastaja, very helpful.

MarkF, I'm not building a charger... I'm building a HID USB/Bluetooth device that charges via USB.
 

Offline LittleRainTopic starter

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Re: Lithium battery built in protection circuit
« Reply #4 on: January 24, 2020, 05:15:42 am »
Do I also need to provide under voltage protection?
 

Offline kjr18

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Re: Lithium battery built in protection circuit
« Reply #5 on: January 25, 2020, 06:34:27 pm »
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.
 

Offline RoGeorge

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Re: Lithium battery built in protection circuit
« Reply #6 on: January 25, 2020, 06:39:12 pm »
Do I also need to provide under voltage protection?

A good design should have its own protections, and should not rely on the battery internal protection.

Offline LittleRainTopic starter

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Re: Lithium battery built in protection circuit
« Reply #7 on: January 25, 2020, 09:54:13 pm »
For charging you can use these small TP4056 boards with builtin protection. It won't hurt to be sure.
Space is very critical, I'll see try to incorporate it into my board. If not that IC, another one.

Do I also need to provide under voltage protection?

A good design should have its own protections, and should not rely on the battery internal protection.
Point taken, will do.

« Last Edit: January 25, 2020, 10:03:44 pm by LittleRain »
 

Offline kjr18

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Re: Lithium battery built in protection circuit
« Reply #8 on: January 27, 2020, 08:00:45 am »
Quote from: LittleRain link=topic=226796.msg28ltc4057-4.287388#msg2887388 date=1579989253
Space is very critical, I'll see try to incorporate it into my board. If not that IC, another one.

You 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.
 


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