USB meter to test the mah capacity of a powercore speed

Hey guys,

Would to ask you something. Did anyone try to measure the total capacity of your powerspeed upgrade or the powercore 20100 to see what the max output (mah) and what’s the estimated full capcity of your power bank? I noticed that of the 2 powercore I purchased recently, they have a variance of 1000mah when charged to full.

Lithium ion batteries start to lose capacity as soon as they come off the assembly line, so it’s normal for it to be a little under the rated amount. However, I can’t say if 1000 mah under is normal. How long have you had these powercores?

Say no more than 2 weeks ago. My hypothesis aligns with yours as the powercore 20100 seems to suffer, which I could only speculate that it might be a older bunch… then again, it could be faulty.

You have to account for power loss due to conversion and efficiency rate. The best batteries have about 90 percent efficiency, so Power bank real capacity = claimed power bank capacity * battery efficiency
So in this case a 20100 mah is realistically 18,090 mah

You can also measure the exact amount with the use of a Drok meter. Fully discharge the battery, plug in the meter and measure the amps at the beginning of the charge and also note the amps at the end, you will also have the time it took to charge it fully. Take the first two numbers and average them out and multiply that by the time it took to fully charge the batterypack and that will give you the exact battery capacity

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Elmo, you are correct that due to heat dissipation and transfer loss, i should expect a performance of roughly 14000mAh (20k*.7), which is performing on both the PowerCore 20100 and the PowerCore Speed Upgrade 20k. The problem is that on my PowerCore 20100, i can achieve 13,459 while my PowerCore Speed is between 14875- 15984mAh. Therefore, my question is whether this is normal as PowerCore 20100 is an older generation and perhaps its been sitting in the inventory for a longer period.

I will take a look at the Drok Meter, thanks for the suggestion!

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Each cable is also different and cables age too

Hi @dragonjiang2002,

Thank you for contacting Anker via the community.

We usually do not suggest customer measure the capacity or output via the USB meter unless a qualified professional equipment is tested.

To verify whether the battery outputs its rated specs, we can test it to charge a device/phone and see how long it takes to charge.

Generally speaking, the battery is normally capable of a 60%-70% charge transfer of its capacity depending on the internal resistance of the USB cable.

Approximately 30-40% of the battery capacity is unable to be used because of efficiency problems that affect all electronics devices. These include power lost from circuit heat and voltage conversions from the battery, the charging cable and your device.

For more details on the transferring rate of external batteries, you can refer to below link:

To calculate roughly how many times the battery should charge your device you can use this formula:

(Capacity of the portable charger *0.6~0.7) / Capacity of your device = Number of possible charges

If you have any problems with your PowerCore 20100, please contact us via

Wish you have a nice weekend!

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