Test/review of EnerPower VC+ 18650 3450mAh (Purple)

Batteries and Chargers Rechargeable Batteries
1

EnerPower VC+ 18650 3450mAh (Purple)







Official specifications:

  • Recommended maximum current: 12-14A

  • Nominal Capacity: 3500mAh

  • Minimum Capacity: 3400mAh

  • Nominal voltage: 3.635V

  • Standard charge: 0.5C (1700mA) 4.2V, cut-off 50mA

  • Max. charge voltage: 4.2V +/- 0.05V

  • Max. charge current: 1C (3400mA)

  • Standard discharge: 0.2C (680mA), cut-off 2.5V

  • Max. discharge current: 10A

  • Weight: Max. 49.0g

  • Cycle life : 400 cycles, charge 1.5A, discharge 4A (80%)

  • Operating temperature: Charge: 0° ~ 45°C, Discharge: –20°C ~ 60°C

  • Storage temperature: 1 month: –20°C ~ 60°C, 3 months: –20°C ~ 45°C, 1 year: –20°C ~ 20°C




These cells are a test of a high performance protection, it has lower resistance and can handle higher current than usual protections.











The discharge chart shows a very good cell and the new protetion means less voltage drop due to protection, but the protection trips at way to high current.



The rated 10A is handleded within the allowable temperature



But at 15A the temperature gets too high and I stop the test.



At 20A the discharge stops because the output voltage drops below 2.8V















Conclusion

It is nice with a lower voltage drop on the protection, but the protection has too high current limit for this cell.



Notes and links

The batteries was supplied by Enerpower for review.

How is the test done and how to read the charts
How is a protected LiIon battery constructed
More about button top and flat top batteries
Compare to 18650 and other batteries
2

Thanks!

I don’t understand the conclusion, sorry
Too high current limit for this cell? You mean it should trip at lower current to avoid the cell getting too hot and damage internally?

3

Exactly, the current limit trips above 20A and this cell cannot really deliver 20A.
Compare to the other VC cell I have tested where this current limit works fine: Test/review of EnerPower VC+ 18650 3000mAh (Purple)

4

Apart from what the manufacturer states what the max current is, how do you determine what the limit is? I suspect a lot of voltage sag and reduced capacity are indicators that the limit is reached, but these occurrences themselves are not the real reason I think; one may think so what if you have a lot of voltage sag. Is it temperature? If a certain temperature (usually around 70 or 80 degrees C) is reached at high amps then test is terminated due to safety?

5

I know the current limit from the other VC cell I tested (Enerpower has told me they uses the same protection circuit), in this test I did not trig over current limit.
I terminate at high temperature, as I did with the 15A test.

6

Interesting. So the protection circuit for this cell (rated 10A) is the same as that of the 30Q cell (rated 15A) you tested recently, if I read this correctly? I do assume (maybe wrongfully, let’s hope not) Enerpower did this as these cells are prototypes. I mean it does not make sense for them to put a 20A protection limit on a 10A rated cell…

7

As I wrote at the start of the review this is testing of the new protection, I do not believe he will sell this battery with this protection.
But it is interesting to see what an improved protection can do for the output voltage.

8

Right, clear! Thanks!

9

Well, after peeking at some li-ion protection ICs it seems the discharge overcurrent detection voltage is ≈150mV, even for 1S configurations. Along with the MOSFET's resistance/conductance, this gives out the maximum amps trip point. This means lowering the MOSFET resistance increases protection efficiency (less voltage drop and energy losses), but can also mean the overcurrent trip point can get quite high.

Since I'm only really interested in low voltage protection (over-discharge), to me this is nice: less losses. For my 2S AA Ni-MH hairclipper total conversion I have a 15A continuous BMS in the mail LoL!

Cheers ^:)