Potentially fake Panasonic 18650 3400mAh protected

[vex_zg]

I know what protection is and how it looks like. The cells are protected.

Why do you say they don’t need protection? The protection is usually for overcurrent, overcharge and overdischarge.

[Default_Username]

Just to clarify: have you tested another battery in you charger setup? Have you verified that contact/wire resistance is not to blame?

[vex_zg]

@Default Username

Just to clarify: have you tested another battery in you charger setup? Have you verified that contact/wire resistance is not to blame?

I have been using the charger (Skyrc imax b8+) for some two years with lipos and lions (trustfire, sony), as far as I remember it always worked fine with higher currents, and termination voltages were correct.

I could charge and discharge RC lipos with high currents, don’t remember so much about high current and lions, but I will verify it again now with same setup and different batteries.

[chris_n26]

@ vex_zg

What is the cut off voltage of the charger? Did you record the resting voltage after discharging?

I’ve got a few ncr18650b’s and discharging to 2.8v @1a gives me a capacity of 3200mah and a resting voltage of 3.2. It could be that the protection circuit is cutting off too soon, or that the charger is triggering an early cut off.

[vex_zg]

4.2 termination voltage for charging, 3.0 for discharging.
Didn’t record rest voltage.

Update: made new connection wires with 12awg wire pressed against terminals with vice. So far big difference with max charge and discharge currents. Will post details in some 24h.

[leaftye]

@vex_zg

Way forward: I looked at how HKJ does the tests, this it how I plan to do another round of tests: - ensure good contact with the battery terminals using plenty of stripped copper high gauge wire and a vice to provide connection force

Be careful about applying too much pressure. The positive contact of the NCR18650B is very easy to crush.

[vex_zg]

@leaftye

@vex_zg

Way forward: I looked at how HKJ does the tests, this it how I plan to do another round of tests: - ensure good contact with the battery terminals using plenty of stripped copper high gauge wire and a vice to provide connection force

Be careful about applying too much pressure. The positive contact of the NCR18650B is very easy to crush.

didn’t think of it. But it was tricky to hold it in place, the battery slides away once you start applying pressure, so I didn’t crush it. Also used some soft material as pressure buffer. Posting pic and results tomorrow after some test runs.

[vex_zg]

upgraded the rig, and ran some more measurements:
summary: some improvements, but 0.5A discharge is still 3066, lower than any other NCR1850B test I’ve seen.

Rig update:

- made new charging cables with 12AWG wire, silicone insulated from hobbyking, solered and screw-pressed into connectors. Can’t get much better connection than that.

• Press-fitted the stripped wires directly to battery terminals using a vice

Measurements:

- measured for voltage drop on charging terminals - at 5A discharge I get 0.006V votage drop in the 12AWG terminals

- during 5A discharge: measured input voltage to compare what multimeter sees against what the charger detects: at 5A discharge multimeter sees the battery with 0.3V higher voltage than the charger sees it. This equates to the charger’s current meter having it’s own internal resistance of 60mOhm. This could partially account for much lower capacicity at higher current discharges because of premature termination, but the 0.5A discharge capacity is still much less than it should be.

- Used calibrated fluke multimeter to check if charging current and termination voltage of the charger are correct, charger reports cca 1.5% lesser current than multimeter, and cca 0.03V higher voltage than multimeter. Don’t find this significant.

- mystery: charged and discharged capacities mismatch, measured charged always lower than measured discharged.

Notes:

- With new connection wires can charge and discharge at much higher currents

• Discharged capacity still much lower than it should be at all currents

This is how I cycled the battery, sequentially:
Step 1: Discharge
Current: 3.4A (1C)
Discharged capacity: 2260mAh

Step 2: Charge
Current: 1A
Charged capacity: 1893mAh (I can’t think of a technical reason why the charged capacity is lower than the just previously discharged???)

Step 3: Discharge
Current: 2A
Discharged capacity: 2774 mAh (Again, higher than the just charged capacity)

Step 4: Charge
current: 1A
charged capacity: 2473mAh (lower than the previous discharge)

Step 4: Discharge
Current: 0.5A
Discharged capacity: 3066mAh (higher than previous charge)

Rig pictures:

[chris_n26]

Kudos on getting a charging rig up, might do that someday when I get a good hobby charger. Have you considered using a smart charger like the opus bt-c3100?

It does look like improving your charge/discharge rig you’ve actually reduced the resistance between charger and battery and so increased the accuracy of the readings. However as it is still a far cry from what an ncr18605b should be I think the problem is within the cell itself. I don’t think they’re fake, the capacities are close to the real deal. The only thing I can think of is there’s something wrong with the protection circuit, either the circuit adds too much internal resistance due to a shoddy part or the way the connections are welded was done poorly. If you wanted to be 100% sure and were willing to sacrifice a cell, just remove the protection and run capacity tests.

[Dru_dragon]

@vex_zg

On 2A discharge the voltage drop is so high that I get like 40mAh out before it drops below 3.0V.

This quote along with your strange charging numbers has me thinking that you have a bad protection circuit with higher then normal resistance. Are you able to measure the internal resistance?

If these cells are new then I would run a few cycles and see if the capacity improves. Is there a date code on these batteries? Before accusing the company of fakes I would run a lower charge rate, so termination voltage is within spec and a 0.1A discharge down to 2.8v.

Your numbers don’t add up, worse comes to worse I would rip the protection off and file a claim for a partial refund. Quote the datasheet for comparison.

[vex_zg]

Thanks for the datasheet link. Filed for partial refund.

edit: and I am using a smart charger, Imax B8+

[Default_Username]

Would you happen to have a different 18650 lying around that you could test with?

[vex_zg]

@Default Username

Would you happen to have a different 18650 lying around that you could test with?

yep, just doing test runs with a 2 years old sanyo 2600mAh protected

first discharge: 2223mAh @ 3.4A
will take a day to run all tests again on Sanyo

[Calmaja]

NCR 18650B cut off at 2.5V, if you discharge up to 3.0V still have some capacity left.
This is the datasheet
Can use HKJ’s comparator to get figure if cut off at 2.8V.

[vex_zg]

@Calmaja

NCR 18650B cut off at 2.5V, if you discharge up to 3.0V still have some capacity left.
This is the datasheet
Can use HKJ’s comparator to get figure if cut off at 2.8V.

Thanks, but already took into account what discharge of protected cell to 3.0V should be, my cell is still getting lower capacity than it should.

[Halo]

You may be able to test the battery directly, bypass the protection, without actually removing the protection. If you can lift up the pcb enough to get to the battery negative. Fasttech has new 18650 clear shrinkwrap.

[leaftye]

@Halo...

You may be able to test the battery directly, bypass the protection, without actually removing the protection. If you can lift up the pcb enough to get to the battery negative. Fasttech has new 18650 clear shrinkwrap.

If you're removing the shrink, you don't need to lift up the protection because the body is negative.

[vex_zg]

@leaftye

@Halo…

You may be able to test the battery directly, bypass the protection, without actually removing the protection. If you can lift up the pcb enough to get to the battery negative. Fasttech has new 18650 clear shrinkwrap.

If you’re removing the shrink, you don’t need to lift up the protection because the body is negative.

good tip, didn’t think of that. When I finish this round of tests with Sanyo 2600mAh, I’ll try going bypassing protection.

[Halo]

@leaftye

If you’re removing the shrink, you don’t need to lift up the protection because the body is negative.

I mean removing only the clear shrink.

[vex_zg]

@Halo…

@leaftye

If you’re removing the shrink, you don’t need to lift up the protection because the body is negative.

I mean removing only the clear shrink.

yes, I know what you meant