I used a TOMO Power Bank V8-4bay, with 4 3400mAh panasonics.
All 4 panasonics were fully charged and rested for 24 hours, bringing them all to 4.10v
I was testing how many times I could charge a 2300mAh lipo battery of an Alcatel Idol 4.
So I brought the phone down to 50% and charged it with the powerbank to 100, then drained the phone to 50 etc.
I could do this 5 times and the 6th charge went from 50% to 65% and the powerbank turned it self off.
I checked the 18650’s under load and they all cut off at a nice 3.0v.
The constant drain for charging the phone was 1.3A at 50% to 0,50A nearing the 100%.
Beeing able to charge a 2300mAh 5 times from 50% to 100% is nice, but shouldn’t it be more like 10 times of even higher?
Also during this time the screen of the phone was off and I also turned off the green screen of the tomo.
I did the 50% to 100% test because draining the phone below 20% and charging it to 100% would ask an even higher amperage of the 3400’s, draining them even faster.
Edit: I did test the 4 3400mAh panasonics 2 days before and they all had atleast 3200mAh a piece.
Are you charging the phone using USB?
If so, there is your problem.
The powerbank steps up the voltage to the 5V for USB, probably via a very inefficient boost converter.
Charging through usb requires 5v, so the pack has to boost the v to that, then the phone brings it back down to 4.2v, plus the resistance in the cable, this all takes power, especially the boost part, that is where your ‘missing’ power has gone.
Don’t worry about it, its a fact of life we all have to live with when using power packs to charge with.
Yes with USB, with 5.04V…hmmm.
Right so it is 3200mAh with 3.7V against 5V which would make the 3200mAh actually… uhm like 2050mAh when using 5V right?
Yea a few factors.
Efficiency wise maybe you will get 80% of the full batteries capacity. You get loses from every thing including the USB cable.
Also things like the NCR18650b you need to drain to 2.5v for full capacity.
I have fast charging usb cables, but they are longer like 20cm would they be better?
The cable used in my test and the fast charging cable both deliver the same amperage with the tomo and my phone.
