'Intelligent' charger LiPo battery detection problem

[Brexei]

Hello everyone!

This is my first post and i am very very excited that such a forum exists! I really did not expect so much information on electronics and i am very happy to join. I am not an electrical engineer, but a physicist with a keen interest for electronics (as a hobby).

Now, i would like to ask if anyone has an idea on how "smart" chargers identify lithium battery types. I have been trying to charge LiPo 3.7 V) salvaged laptop batteries with two different Chinese "smart" chargers, but they assume that the max battery voltage is 3.7 volts and cannot charge it more! They also use a small current, of about 50 mA. I have been charging 18650 Li batteries normally, but only LiPo (not LiFePo) batteries seem to be in error.

How do they measure batteries and determine the type? I could not find any info on Google, so if anyone has an idea i would be glad to hear it.
Thanks a lot.

[Brexei]

Well, it appears to be a difficult question...

Today i tried to charge the battery using a TP4056 ebay charger and it charges normally up to 4.2 volts. No heating at all, so probably it was not a 3.75 volt battery, as the 'smart' charger suggested.

Originally it was charged to 3.7v, and i continued from there on.

[mvs]

Now, i would like to ask if anyone has an idea on how "smart" chargers identify lithium battery types.

They measure actual voltage and internal resistance of the battery. High capacity 18650 do have higher internal resistance, then high current capable LiFePo4 or LiPo cells.

[mikerj]

3.7v is the average voltage for most lithium cobalt cells (voltage varies 3.0v-4.2v over the full state of charge), and the cells are often described as 3.7v parts.  I'm not aware of a lithium chemistry with a 3.7v maximum voltage, though lithium iron phosphate is close at 3.6v.  Do you have a link to the chargers you were using?

[Bud]

I reviewed one here, it charges Li-Ion  to 4.2V

https://www.eevblog.com/forum/reviews/xtar-vc4s-universal-battery-charger/

[Brexei]

I have a Liitokala Lii-202 charger bought from ebay and another one (also from ebay) that i cannot remember the model right now. They both recognize my flat salvaged laptop batteries as LiFePo and charge them up to 3.7 volts. So, i guess it is because these batteries have a lower than normal resistance and the charger is tricked to believe they are LiFePo ones...

Anyway, i charged them up to 4.15 volts and they seem to be fine after 8 years!!!!

I reviewed one here, it charges Li-Ion  to 4.2V

https://www.eevblog.com/forum/reviews/xtar-vc4s-universal-battery-charger/

Nice review and very interesting charger. I did not know it existed. Otherwise i would have bought it. I like the display and the visual representation of charging voltage, resistance, capacity and other info.

[mikerj]

I'm not aware of any chargers that can automatically determine lithium battery chemistry, seems like a recipe for disaster.  The Liitokala Lii-202 clearly has a mode setting button to select chemistry type, though it may default to LiFePo as a safety measure if the correct chemistry is not selected.

[David Hess]

The smart chargers I have seen can automatically detect the difference between NiMH and Lithium but must be explicitly configured for which lithium chemistry is present.

[Brexei]

The Liitokala Lii-202 clearly has a mode setting button to select chemistry type, though it may default to LiFePo as a safety measure if the correct chemistry is not selected.

It only has a single button for current selection but it will not let me choose the voltage of the battery. Maybe i will have to do a search for this again...

[kjr18]

The Liitokala Lii-202 clearly has a mode setting button to select chemistry type, though it may default to LiFePo as a safety measure if the correct chemistry is not selected.

It only has a single button for current selection but it will not let me choose the voltage of the battery. Maybe i will have to do a search for this again...

From this review

The user interface is a couple of leds and a single button.
A fast press on the button will select battery type, when a battery has just been put into a slot.
A long press (2 seconds) will change current at any time

So yeah, you can change battery chemistry on it.

[Brexei]

Oooooh i feel sooo stupid for not checking this out!
It really works and i can choose the battery type.
Thanks a lot.