Li-ion Weird phenomenon

I have this project where I have connected a 3020 LED module which I ripped off from an IKEA JANSJÖ to a tp4056 v2 module which is connected to an old samsung 800mAh phone battery.

I had fully charged the phone battery using the tp4056 module and then started to power the LED to find out how long does it keep powering. I measured the battery voltage at the battery terminals regularly to keep track of the voltage. For the first 10 to 11 hours the battery voltage dropped from 4.18 volts to 3.57 volts. Then I simply tried to test how many amperes does it draw using the 200m function of the multimeter and got a value of 47.2. Suddenly just after I checked the ampere the battery voltage dropped to 2.8volts and the light would no longer turn on.????

I plugged in the USB charger to the tp4056 module and immediately unplugged it and suddenly the battery voltage jumped back to 3.5volts and the LED started to light up.?? 2 hours after that it still keeps o powering and voltage is at 3.5volts.

what the hell is happening? what did I do wrong here? :o

Note: With a USB power doctor the LED module draws 0.06 amps at 5 volts. The LED module seems to have current limiting with two J3 smd transistors and 2 smd resitors of value 100 and 682.

Some LiPo batteries have a protection circuit inside. You might have triggered the inbuild undervoltage protection of the battery while measuring. Leo..

but how did it jump back up to 3.5volts with just 1 sec of charging?

Because undervoltage detectors have hysteresis to prevent chattering on and off for ages.

so how can I know the actual voltage of the battery? it still shows 3.5volts now.

With LiPo/li-ion batteries, voltage is a poor indicator of charge as the difference between fully charged and dangerously discharged is rather small.

Noobian: so how can I know the actual voltage of the battery? it still shows 3.5volts now.

Have you tried recharging it fully ?

pwillard: With LiPo/li-ion batteries, voltage is a poor indicator of charge as the difference between fully charged and dangerously discharged is rather small.

Yeah, but the LED was supposed to stop after 9-10 hours because of it's 0.3W draw and the battery's 2.96WHr rating.

Have you tried recharging it fully ?

I will when the battery runs out of juice. Whats the matter?

LED was supposed to stop after 9-10 hours because of it’s 0.3W draw and the battery’s 2.96WHr rating.

The rating is an approximation of the capacity of a NEW battery. Your battery is not new.

Noobian: Yeah, but the LED was supposed to stop after 9-10 hours because of it's 0.3W draw and the battery's 2.96WHr rating. I will when the battery runs out of juice. Whats the matter?

3.5v is low, taking current until it stops working will destroy a lipo.

There is likely some sort of protection built in though

Boardburner2: 3.5v is low, taking current until it stops working will destroy a lipo.

There is likely some sort of protection built in though

Yes, but even if the battery doesn't have one the tp4056 module has one (DW01-X).

also the battery is very old and it probably doesn't have full capacity.

Then I simply tried to test how many amperes does it draw using the 200m function of the multimeter and got a value of 47.2.

What do you mean by this? You mean you put the meter inline with the LED, or you put the meter directly across the battery?

He read 47 mA so i suspect a an accident with the probes tripped something.

polymorph: What do you mean by this? You mean you put the meter inline with the LED, or you put the meter directly across the battery?

I connected the positive of the battery to the +red probe of the multimeter and connected the positive of the LED to the -Black probe of the multimeter.

Boardburner2: He read 47 mA so i suspect a an accident with the probes tripped something.

or maybe the multimeter is real crappy. I think only the Voltage and resistance part of my multimeter is reliable.

Noobian: I have this project where I have connected a 3020 LED module which I ripped off from an IKEA JANSJÖ to a tp4056 v2 module which is connected to an old samsung 800mAh phone battery.

Important question;

What did you set the charge current to ?

srnet: Important question;

What did you set the charge current to ?

charge current to the Li-Ion cell? it's 200mA

Noobian: charge current to the Li-Ion cell? it's 200mA

Thats about right, for that cell.

Problem with (at least some) of the TP4056 modules is that they come with the charge current set as high as 1A. 'They' expect you to know to change the resistor to limit the current to a safe level for your battery.

And Samsung now knows what happens when you try to charge these type of batteries too fast ..........

srnet: Thats about right, for that cell.

Problem with (at least some) of the TP4056 modules is that they come with the charge current set as high as 1A. 'They' expect you to know to change the resistor to limit the current to a safe level for your battery.

And Samsung now knows what happens when you try to charge these type of batteries too fast ..........

It did come with a 1A charge setting. I had the resistor changed to bring it down to 200mA.

Samsung sure did learn a lesson which they won't forget. :D

Noobian: Yes, but even if the battery doesn't have one the tp4056 module has one (DW01-X).

also the battery is very old and it probably doesn't have full capacity.

If the DW01 trips then connecting the charger resets it so explains one behaviour.

Could just be a worn out battery.

Boardburner2: If the DW01 trips then connecting the charger resets it so explains one behaviour.

Could just be a worn out battery.

But the voltage I measured was directly from the battery terminals and not from the output ones on the module.