Vapcell P2150A 21700 5000mAh: More Than Just a Battery

I've had all kinds of batteries: standard ones, protected ones, ones with converters, and even ones with built-in chargers. But this is the first time I've come across a battery this unusual.
Inspection, tests, and conclusions.


When I was choosing batteries for testing, I thought these were just ordinary protected batteries with chargers, and that the only difference was their size. But it turned out to be much more interesting: this is a hybrid of a battery, protection circuit, charger, and power bank.

The packaging is familiar, and at this stage everything is just like with other Vapcell batteries.


Specifications from the website Vapcell
Model: INR21700 5000mah 10A
Size: 21.1*70.5mm
Typical Capacity: 5000mAh (0.2C discharge)
Min capacity: 4800mAh (0.2C discharge)
Nominal voltage: 3.60V
Max Continuous Discharge Current: 10A
End-of-charge voltage: 4.20V
End-of-discharge Voltage: 2.5V
Weight: 76g ( Appr)
Internal resistance: 28mΩ ( Appr)（AC 1kHz）
Standard Charge: 1500mA,CCCV 100mA cut-off
Quick Charge Current: 2500mA
Cycle life : 1C discharge / 70% DOD, ≥ 800 cycles


Everything seems pretty standard, but the list of specifications doesn't end there.
Protect plate (PCB) Specification:
Over charge protection voltage: 4.25+0.1/-0v
Over discharge protection voltage ：2.50+0/-0.1V
Over current protection current: 12~18A

USB Type-C Interface Specification:
USB charge model : CC CV
USB input power : 5.0v ,≥1.0A
USB end-of-charge voltage : 4.20V
USB CC mode charge current: 1000mA
USB CV mode charge current :100mA
USB output : 5.0v ,max 1.5A

The batteries have a protruding positive terminal with a hole, behind which there's a two-color LED. The USB port is also next to the positive terminal, but instead of the usual microUSB found on products like this, it's the more modern USB-C, which is definitely more interesting.
The label also lists all the necessary specifications for both the battery itself and its input/output.


Dimensions and weight.
Yes, the battery's length is a real pain. Very few chargers can fit a battery longer than 76mm. The built-in charger is convenient, of course, but when charging externally, the charge current can reach 2.5A.


Interestingly, the charge current turned out to be about 1.5A, even though both the description and the batteries themselves specify only 1A.
The batteries were initially charged to about 40%. In the “normalization” cycle, I measured 4834 and 4857mAh.


As is often the case, two charging modes are specified: normal, at 1.5A, and fast, at 2.5A.
The normal mode is gentler, of course, but taking almost four hours to charge a battery is a bit much. The built-in charger will take about the same amount of time.


The fast mode is harder on the battery, but it cuts an hour off the charging time, bringing it down to just 2 hours and 38 minutes. The charging time is partly increased by the protection circuit in the battery, and there's nothing we can do about that.


As a preliminary test of the protection circuit, I connected the battery to an EBC-A10H tester, but its 10A output wasn't enough to overload the battery.


All right, let's connect it to a more powerful load and run an automatic test.
The cutoff occurred at a current of about 14A, which is well within the specified range -
Over current protection current: 12~18A


The second sample produced similar results, but it's worth noting that the trip current depends on the state of charge and temperature.


The description also specified:
Over discharge protection voltage ：2.50+0/-0.1V

I set the discharge current to 0.2C and checked the voltage at which the protection circuit disconnects the cell.
I got about 2.411 volts, which is within the specified range. As the load current increases, the trip threshold will rise. This refers to the voltage at the battery terminals, not the external ones.


Capacity measurements.
I tested the first unit at 0.2, 0.5, 1, and 2C, as well as 12.5 A.
The result was 4735 mAh, or 17.25 Wh, noticeably below the claimed capacity. The battery also failed a prolonged test at 12.5 A: its protection kicked in. To be fair, though, nobody promised that much—the stated maximum is 10 A.


As expected, at a high load current the hottest spot is around the protection board; near the connector, the temperature reaches 85 degrees.
Below are the temperatures at the end of the tests at 1C, 2C, and 12.5 A.


When testing the second battery, I set the maximum current to 11.5 A instead of 12.5 A, and it almost completed the test at that load. I think that if the room had been a little cooler, the protection would have let it finish.


The second one performed almost identically, except that at 11.5 A its temperature was not much different from the test at 10 A.


The consistency of the characteristics is very good. I suspect it uses branded cells.


The built-in charger has three modes:
1. If the battery is deeply discharged, it starts by charging at a low current.
2. Once a certain voltage is reached, normal charging starts at 1.5 A.
3. When the battery is fully charged, charging stops. The photo shows the tester's own power consumption.

The LED flashes red while charging and turns blue when charging is complete. Sometimes it flashed red and blue, though, and I never quite figured out the indicator's full logic.

Apparently, it uses a bidirectional voltage converter, so we get up to 1.5 A output and up to 1.5 A charging current. Since it's a converter, the current in the battery circuit is even higher.
This is also supported by the fact that during charging the tester measured only 4105 mAh and almost 20 Wh, while the tests above showed that the battery actually has a capacity of over 4700 mAh.


The temperature at the top of the battery during charging stays below 50 degrees.


The power bank is primitive, of course, but it does have an auto mode: the output shuts off under a light load.
It also has some kind of low-battery indication. Before shutting off, it flashes red, but once again, parts of the indicator's behavior remain a mystery to me.
When checking the protocols, it somehow reported support for Huawei and, even more strangely, Power Delivery. But there was nothing interesting in the listed modes.


The output voltage is quite stable, varying by about 30–40 mV across the full load range. It is also slightly on the high side, which is normal.
If the current exceeds 1.6 A, the voltage starts to drop; as the load current increases further, the output shuts off.


Ripple is moderate. Below are the oscilloscope traces with no load and at 0.5, 1, and 1.5 A, though it could be a little lower at maximum current.


When the power bank entered “sleep” mode, you can see it periodically applying a small voltage to the output to check for a load.


I tested power bank mode at 1.5 and 1 A on the first unit, and at 1.5 A on the second.
The output delivered 2830–2890 mAh and 14.5–14.8 Wh in almost every mode. In addition, the output voltage was 5.14 V at 1 A and slightly lower, 5.10 V, at 1.5 A.
In any case, with a battery capacity of 16.6 Wh, power bank mode delivers 14.5 Wh, for an efficiency of about 87%. In my opinion, that's pretty good for such a compact device.


For an experiment that approximates real-world use, let's take a smartphone and connect it to the battery's output.
The battery was fully charged to start with, and the smartphone was at 30%.
This smartphone can draw up to 2 A of charging current when powered from 5 V. But since the power bank's voltage dropped slightly under load, the charging current dropped too—to 1.6 A in this case. The output stayed on, and the battery kept charging.
A couple of hours later, the smartphone was fully charged and the current had dropped to 350 mA. Yes, I should have connected a fully discharged phone, but somehow I thought the power bank would run out first.

So, in my particular example, the power bank charged the smartphone from 30% to 100%, delivering 2738 mAh out of its 2890 mAh, i.e. almost completely discharged.

I also found that the LED glows blue when the battery charge is above 50%, red when it is below 50%, and flashes when about 5–7% remains.



During operation, the top of the battery warmed up to about 54–55 degrees, and stayed at that temperature almost the entire time until the current started to drop. The positive contact was noticeably hot.


Everything would be great if it weren't for one catch. I noticed it earlier while testing with a smartphone, but first I'll show you another example.
1. Take two batteries, connect them with a cable, and see what happens.
2. Battery 1 charges the battery connected to it, battery 2. All clear and logical.
3. But now everything has reversed: battery 2 has started charging battery 1.


A little more detail. Here I've connected the USB tester to a separate power supply so it won't reboot when the power is interrupted.
1. Set up the same two batteries, cable, and USB tester. Battery 1 (at the bottom) is fully charged, while battery 2 (at the top) is completely discharged.
2. Current flows from battery 1 to battery 2, charging it.
3. But then battery 1 is completely discharged, having transferred all its energy to battery 2, and the current starts flowing in the opposite direction.
4. Yes, that's right: the batteries have now switched places.

It all happens very simply. Once a battery is fully discharged, its output is switched off. Since the output is completely disconnected, the electronics in the second battery think a load has been connected and supply voltage to the output. The first battery now has voltage at its input, so its electronics think a charger has been connected and start charging.

The catch is that quite a few phones use their USB port not only as an input for charging and connecting to a PC, but also as an OTG output, supplying power to connected devices.
I think you get the idea now: once the battery is fully discharged while charging a smartphone, for example, it will start charging from the smartphone :)

Of course, this only happens with devices that have a universal USB port, like the battery being reviewed here. But keep this in mind, or you could connect a smartphone and end up with two discharged devices.


During this test, I measured a maximum temperature of almost 60 degrees, even though the output current was only 1.46 A. Perhaps that was because the battery was already almost discharged.


I measured the battery's internal resistance when it arrived and again after it had "settled in." In my opinion, it's relatively low, which is very good.


At the end, I wanted to compare it with other 21700 batteries rated at 5000 mAh. I hadn't even realized I'd tested so many of them.
The results are for a current of 0.2C, with additional results at 1C for the battery being reviewed and the Samsung 48X, which I consider the closest match.



Conclusions.
I could really only find two things to criticize: the capacity is 4700 mAh instead of the claimed 5000, and the batteries are so long that they won't fit in many chargers. For example, the Vapcell S4 can charge batteries of this size, but they simply wouldn't fit in my old Nitecore i2.

Of course, this is a very niche battery. I can't think of a use case off the top of my head, but it's definitely unusual. In some ways, it's even more convenient than some power banks. For example, I have a basic Ugreen power bank with a real capacity of 10 Ah. It weighs 234 grams, while a pair of the batteries reviewed here would have a comparable capacity but weigh just 150 grams in total!

Essentially, Vapcell has made an updated and significantly improved version of a basic power bank built around a single 18650 cell. I think many people still remember those. At the same time, this battery can also be used as a regular battery with load currents up to 10–11 A.

In short, I think these batteries are interesting and could be useful in some situations, but remember the quirks of using them with devices that have a universal port.

That's all for now. I hope you found this interesting, and as usual, I'll be happy to answer questions and read your comments.