Do I need a charging circuit for this 3.7 lipo battery, or does it have one?

Thread Starter

bmbouter

Joined May 29, 2021
55
Here's a 3.7V lipo battery on aliexpress. It clearly states it has a built-in protection circuit, but do I also need to externally provide a charging circuit, e.g. TP4056?

I asked them and the vendor was just as unclear as the page is. Either they don't know or it's lost in translation. After several rounds of questions, all I could get was a claim from they for me to "just use 5V and everything is fine".

I think I need a charging circuit and this is just a battery protection IC. What do you think?
 

ericgibbs

Joined Jan 29, 2010
16,370
hi bm,
A battery protection IC just covers the following clip, you do need a suitable lipo battery charger, I would say a 5Vdc charger as the supplier suggested will be OK.
E

Clip:

Lithium-ion battery protection ICs protects the lithium-ion battery packs from overcharge, overdischarge, overcurrent and short-circuit condition.
 

Thread Starter

bmbouter

Joined May 29, 2021
55
Thanks for the replies. I do have one, so I can test it locally.

When you say "a suitable lipo charger", do you mean just a 5Vdc and DC power supply, or do you mean more like a TP4056?
 

Audioguru again

Joined Oct 21, 2019
5,166
The protection circuit is not a charger circuit.
Of course you need a charger circuit designed for the single-cell 1500mAh Li-Po battery.
The charger circuit does the constant current then constant voltage (then detect a full charge and turn off the charging) that the protection circuit does not do.
The battery is sold as a replacement for a product that already has a charger circuit.

Did anybody say what the 3rd wire is for?? An over-temperature warning to an external charger circuit?
 

Ya’akov

Joined Jan 27, 2019
6,561
I often use my bench supply to charge LiPo cells. But I use the constant current mode to prevent overcurrent. Combined with the protection board, the CC of the supply means I can just set it at 4.2V and somewhere between 500mA and 1.5A depending on how much of a hurry I am in or how much I want to increase battery life. Usually, I charge at 1A, and the protection board happily shuts isolates the battery at 4.2V automatically.
 

Audioguru again

Joined Oct 21, 2019
5,166
I think a Li-PO battery is too dangerous to guess that it "might" be safe to use oddly (without a proper charger circuit).
Especially when it came from a Seller for AliExpress in China.
 

Thread Starter

bmbouter

Joined May 29, 2021
55
Thank you for all the replies and discussion.

The safety arguments I agree with completely, but that aside, using some magnification I can see the IC numbers here. It's indeed just a DW01 protection IC and another IC that has the two mosfets for it. It matches the design from this video also perfectly. So yes, to do this right I do need something like a TP4056. Thanks everyone!
 

Audioguru again

Joined Oct 21, 2019
5,166
"When a battery cell is being charged, the Protection Circuit disconnects it when its voltage reaches 4.2V to avoid overcharging".
But that is wrong because when the battery reaches 4.2V then the charging should continue with Constant Voltage of 4.2V until the charger circuit detects a full charge (low charging current).
 

crutschow

Joined Mar 14, 2008
30,790
Here is a typical proper charge sequence for a Li-ion battery (from Battery University):
It's similar to the sequence for a lead-acid battery except it terminates the charge at the end, rather than going to a trickle charge mode.

1668286182114.png
 
Last edited:

Ya’akov

Joined Jan 27, 2019
6,561
For the record, though it is hard to read, it looks like the protection board on the cell is using a DW01A protection chip. The DW01A including overdischarge, (optionally overcurrent), and overcharge protection. The chip will shut off charging using the MOSFET it controls if the cell voltage reaches 4.25V~4.35V ±50mV. If a constant voltage supply is used with a capacity of no more than 1A, or a CV/CC supply set to 4.2V@1A~1.5A, the DWO1A will stop the charging if the voltage rises above the limit. If the supply voltage is accurate, the cell itself will reach equilibrium with it and current will stop.

I have had very good success and no failures using this method when the DW01A is present but I don't suggest anyone use it who doesn't already understand why it would work, or more to the point fail, so that a mistake is not made in the setup. The DW01A is as reliable as any charge controller IC, the key is an appropriate power supply.
 

Thread Starter

bmbouter

Joined May 29, 2021
55
@Ya’akov thanks! I think I understand. You're saying that if I used a power supply that was the right voltage (4.2V) and not too high of a current 1.0 - 1.5A, the DW01A will appropriately act as a charging circuit because the over-current limiter interrupts charging when the battery reaches equilibrium. Alternatively, I could use a higher voltage, e.g 5V with a max of 1A. I'm a little unclear on how the DW01A works in the case of a 5V, 1A power supply.

What I definitely should not do is to use a power supply outside of these bounds, e.g. I should not use a 5V, 2A power supply!

I'm going to still use the TP4056 for my design, but I'm enjoying learning about this. Since it's using a micro-USB style port it will be 5V and I can't assume everyone will use a <= 1A USB power supply with it. It's nice to learn though.
 

BobTPH

Joined Jun 5, 2013
5,762
A USB 5V phone charger is not a current limiting supply. It has a certain capacity, but, if you exceed the hat, it might be damaged.

The kind of supply that ya’akov is talking about has a current limit control that will lower the voltage to keep the current within the limit.
 
The TP4056 is a battery charger circuit for a Lithium-Ion or Li-PO battery. We do not know if the module you purchased matches the charging current needed by your battery.
Unless the LEDs are disconnected then the battery will not charge or it will not charge correctly.
 
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