Queen Battery QB26650-2500 is a 26650 size 2500mAh 50A LiFePO4 cell which supports up to 125A pulse discharge.
The battery was bought from Queen Battery which is my reliable supplier of genuine cells and tested with ZKETECH EBC-A20 and a self-made battery holder. It's a PC-connected battery tester supporting 4-wire measuring and discharging at up to 20A.
I've used version 3.0 of my battery holder based on 0.5mm thick pure copper terminals
I've followed all the prescriptions of the IEC61960-2003 standard concerning battery's capacity measurement. Before each discharging cycle the battery was charged at standard charge current mentioned in its datasheet to charge end voltage. Before each discharging or charging i've held a 1-1.5hr pause. The environment temperature was 25±2°C. To be sure in results i've done each test minimum twice (usually 3-7 times).
Queen Battery QB26650 2500mAh
The heat shrink tube tells us only the model, capacity and nominal voltage.
QB26650-2500 has probably the most detailed datasheet possible. Here are the most important specifications from it (pdf):
Typical capacity: 2500mAh (1C discharge!)
Minimum capacity: 2500mAh (1C discharge!)
Nominal voltage: 3.2V
Charge end voltage: 3.65V
Charge cut-off current: 50mA / 0.02C (100mA used)
Charge temperature: 0–45°C
Standard charge current:
0–15°C: 0.75A / 0.3C
15–25°C: 1.25A / 0.5C
25–45°C: 2.5A / 1C
Fast charge current:
0–15°C: 1.25A / 0.5C
15–25°C: 2.5A / 1C
25–45°C: 5A / 2C
Fierce charge current:
0–15°C: prohibited
15–25°C: 5A / 2C (SOC≤40%, charge time <10min)
25–45°C: 12.5A / 5C (SOC≤40%, charge time <5min)
Discharge cut-off voltage: 2.0V
Discharge temperature: -20–60°C
Max continuous discharge current: 50A / 20C
Max long pulse discharge: 75A / 30C for ≤60sec if cell's temperature ≤60°C
Max short pulse discharge: 125A / 50C for <10sec if SOC≥50% and <3sec if SOC<50% (cell's temperature ≤60°C)
AC impedance at 1KHz: ≤6mΩ at 50% SOC
Weight: 86g
Cycle life: аfter 2000 cycles at 2.5A charge/2.5A discharge (1C/1C) the capacity should be ≥2000mAh (80% of initial capacity).
DC IR at 2500mA in fully charged condition was 6.0±1.2mΩ (measured using EB Tester Software's Resistance test feature).
Measured dimensions: 26.6mm (diameter) × 65.1mm (length).
Measured weight: 84.93g.
Queen Battery QB26650-2500 capacity test results (I've done each test 6 times).
Surpriseee))) In fact it's a 2700mAh cell, not a 2500mAh one. Just look at the results - even at 20A discharge it remains above 2550mAh! The curves also look excellent! Nothing to add...
Comparison with A123 Systems ANR26650M1B
More than a year ago i tested and compared A123 Systems ANR26650M1B Grade A and Grade B cells using v.2.0 of my battery holder. It's a long time i'm using v.3.0 so it wouldn't be 100% fair to compare tests done using different holders, so i decided to re-test A123 cells in v.3.0 holder at 20A discharge. I did each test 4 times for each cell and here we are:
Just look at those numbers! How close they are! ANR26650M1B Grade B has the highest capacity and QB26650-2500 has the lowest but the difference is only 30mAh!
The picture changes when we look at the energy - QB is the best and ANR26650M1B Grade A is the worst. The difference between them is as low as 138mWh!
Let's forget about numbers and look at the curves. ANR26650M1B's curves are good as they should be, but look at QB's curve. It's even better! It doesn't go below 3.0V most of the time (approx 65%) while A123 Systems' cells fall below it relatively quickly. I started to go into numbers again... Well, i just like the QB's curve more))
Now let's look at this comparison table
A123 Systems' cells are winners in capacity and max continuous discharge rate while QB26650 takes the gold in energy and max pulse discharge rate. They all can be discharged down to 2.0V which is very good because most of LiFePO4 cells are limited by 2.5V.
Also Queen Battery's charge end voltage is standard 3.65V which means that it's compatible with the majority of BMS boards on the market.
Verdict
This was the most surprising test for me so far... I didn't expect such a brilliant performance from a Chinese cell... It's rated at 2500mAh but it's a 2700mAh cell! ANR26650M1B was considered as the best and out-of-comparison LiFePO4 cell by me until now... Well, each cell has its pros and cons mentioned in the table above so the choice is not obvious. The good news is that A123 Systems' cell has got a strong competitor with a lower price tag (send an email to QB, don't ask me, i'm not selling them).
Here is the video version of this review:
Check out my YouTube channel for batteries, chargers and other stuff reviews.
The battery was bought from Queen Battery which is my reliable supplier of genuine cells and tested with ZKETECH EBC-A20 and a self-made battery holder. It's a PC-connected battery tester supporting 4-wire measuring and discharging at up to 20A.
I've used version 3.0 of my battery holder based on 0.5mm thick pure copper terminals
I've followed all the prescriptions of the IEC61960-2003 standard concerning battery's capacity measurement. Before each discharging cycle the battery was charged at standard charge current mentioned in its datasheet to charge end voltage. Before each discharging or charging i've held a 1-1.5hr pause. The environment temperature was 25±2°C. To be sure in results i've done each test minimum twice (usually 3-7 times).
Queen Battery QB26650 2500mAh
The heat shrink tube tells us only the model, capacity and nominal voltage.
QB26650-2500 has probably the most detailed datasheet possible. Here are the most important specifications from it (pdf):
Typical capacity: 2500mAh (1C discharge!)
Minimum capacity: 2500mAh (1C discharge!)
Nominal voltage: 3.2V
Charge end voltage: 3.65V
Charge cut-off current: 50mA / 0.02C (100mA used)
Charge temperature: 0–45°C
Standard charge current:
0–15°C: 0.75A / 0.3C
15–25°C: 1.25A / 0.5C
25–45°C: 2.5A / 1C
Fast charge current:
0–15°C: 1.25A / 0.5C
15–25°C: 2.5A / 1C
25–45°C: 5A / 2C
Fierce charge current:
0–15°C: prohibited
15–25°C: 5A / 2C (SOC≤40%, charge time <10min)
25–45°C: 12.5A / 5C (SOC≤40%, charge time <5min)
Discharge cut-off voltage: 2.0V
Discharge temperature: -20–60°C
Max continuous discharge current: 50A / 20C
Max long pulse discharge: 75A / 30C for ≤60sec if cell's temperature ≤60°C
Max short pulse discharge: 125A / 50C for <10sec if SOC≥50% and <3sec if SOC<50% (cell's temperature ≤60°C)
AC impedance at 1KHz: ≤6mΩ at 50% SOC
Weight: 86g
Cycle life: аfter 2000 cycles at 2.5A charge/2.5A discharge (1C/1C) the capacity should be ≥2000mAh (80% of initial capacity).
DC IR at 2500mA in fully charged condition was 6.0±1.2mΩ (measured using EB Tester Software's Resistance test feature).
Measured dimensions: 26.6mm (diameter) × 65.1mm (length).
Measured weight: 84.93g.
Queen Battery QB26650-2500 capacity test results (I've done each test 6 times).
Comparison with A123 Systems ANR26650M1B
More than a year ago i tested and compared A123 Systems ANR26650M1B Grade A and Grade B cells using v.2.0 of my battery holder. It's a long time i'm using v.3.0 so it wouldn't be 100% fair to compare tests done using different holders, so i decided to re-test A123 cells in v.3.0 holder at 20A discharge. I did each test 4 times for each cell and here we are:
The picture changes when we look at the energy - QB is the best and ANR26650M1B Grade A is the worst. The difference between them is as low as 138mWh!
Let's forget about numbers and look at the curves. ANR26650M1B's curves are good as they should be, but look at QB's curve. It's even better! It doesn't go below 3.0V most of the time (approx 65%) while A123 Systems' cells fall below it relatively quickly. I started to go into numbers again... Well, i just like the QB's curve more))
Now let's look at this comparison table
Also Queen Battery's charge end voltage is standard 3.65V which means that it's compatible with the majority of BMS boards on the market.
Verdict
This was the most surprising test for me so far... I didn't expect such a brilliant performance from a Chinese cell... It's rated at 2500mAh but it's a 2700mAh cell! ANR26650M1B was considered as the best and out-of-comparison LiFePO4 cell by me until now... Well, each cell has its pros and cons mentioned in the table above so the choice is not obvious. The good news is that A123 Systems' cell has got a strong competitor with a lower price tag (send an email to QB, don't ask me, i'm not selling them).
Here is the video version of this review:
Check out my YouTube channel for batteries, chargers and other stuff reviews.