PowerCore+ capacity

#1

Hello daer folks,

I have the PowerCore+ 26800 battery.
I use the 30W PD charger to charge and I have been happy with it.
It is 1 year old and I used to get a loot of juice out of it when traveling. Otherwise when at home I use rather frequent and usually start charging it when it gets to 20-30% and charge up until 80-90%. Generally I try to keep an eye on the normal use manners to prolong it’s useful life.
However recently it started discharging rather quickly.
I got a USB tester to test what I can get of it and to my surprise - it is way less than stated.
The bank is rated at 26800mAh and 96.48Wh.
During discharging the tester showed 15000mAh, but the Wh capacity showed at 80Wh.
So - my question is - is this normal?
And my second question is - the stated 268000mAh capacity is related to the 96.48Wh, but what voltage is used to get that conversion.
Because looking on the mAh it is obvious this is a very short of what is stated (only 56%), but looking at the Wh it is much more (83%) which I could live with since sometimes it is possible to lose 15% of capacity over a year.
However my concern is that the battery is draining noticeably quicker than before.

I will do a charge cycle measurement just to check how much it will pump in and will post the results, but was curious what you guys think.

Thanks.

Stay safe.

#2

You sound a very savvy person so I don’t mean to offend by asking questions of what you don’t mention.

Are you measuring with the USB meter the Wh or just the Ah and inferring from an assumed Voltage or measuring the Voltage also?

You see the cells are (I assume) 3.6V so 26800mAh is becomes 96.48Wh.

When you metered, what voltage were you seeing? e.g. if you were 5V then 96.48Wh/5*3.6 = 69.47W when measured at 5V. So how was 80Wh measured?

I’d expect in 90%-95% efficiency, Voltage dependent, dropping slightly as product ages, as efficiency lowers the difference between the cell voltage and the output voltage. I don’t know how they wired the 6 cells, probably for the PD it’s 3 cells in parallel then in series. So the cells are 10.8V. So the best efficiency would be somewhere around 12V. The greater the difference from 12V, the lower the efficiency.

mAh is not a fair way to measure, as it’s usually at 3.7V vs output typically 5V so you immediately have in a perfect (impossible) cell give an apparent 26% loss, it is not an actual loss as you’re measuring the wrong thing.

So in summary, you only mention mAh , Wh but never V.

I would expect some loss of capacity over time, more so if the Powercore is stored other than room temperature.

#3

Hello and thanks for your quick reply.
No offend taken :slight_smile:
I am measuring with a USB meter that tracks in real time current, voltage, capacity and Wh.
That being said I presume it calculates the Wh by taking the voltage it currently reads which was ~5V.

I will try also charging the battery with the same USB meter so I can see what I will be able to pump in.

Thank you.

#4

It should integrate the V with Ah to make an accurate Wh.

Almost never 5V, it’s more often in the 4.4V region which is good enough to work as USB, that is more efficient as the phones usually 3.7V so you have the step-up from the Powercore cells to 4.4V then in the phone a step down to 3.7V.

I’d expect about 10% loss of Wh due to conversion efficiency, then that slowly drop off over time, faster if used more or if not used and stored at room temperature. You’ll lose 10% going in, 10% coming out and your device will lose it’s own, particularly if it’s being used while charged.

If it is more than that then it could be a warranty issue.

I avoid bigger and faster Powercore, aiming for just big enough and just powerful enough to function, and if I need more capacity then carry two. Works out lowest cost longer term.

#5

Thanks.

I will follow your advise.
I will not bother myself with warranty and will get the smaller one (20000) soon.

All the best and take care.

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