While this question pertains to smartphone , it is being asked from purely an electrical engineering view (My electrical knowledge is very basic)
Trying to understand if charging a cell phone and using it is recommended or not, I came across this Charging Li Ion battery
Quoting extracts (emphasis mine)
portable devices sit in a charge cradle in the on position. The current drawn through the device is called the parasitic load and can distort the charge cycle. Battery manufacturers advise against parasitic loads while charging because it induces mini-cycles, but this cannot always be avoided...."
A portable device should be turned off during charge. This allows the battery to reach the set voltage threshold and current saturation point unhindered. A parasitic load confuses the charger by depressing the battery voltage and preventing the current in the saturation stage to drop low by drawing a leakage current. A battery may be fully charged, but the prevailing conditions will prompt a continued charge, causing stress."
I wanted to verify this by testing to the extent possible with limited means. I ran two tests.
For measurement of voltage/Current used an app 3C Toolbox, which gives measurement at every 1% change in both tabular and graph form
First test was normal charging in air plane mode. Had to keep the phone on to run the app
Second test, was to charge the phone while simulating usage. Instead of actual usage, kept screen display on at 50% brightness to simulate usage load, since this would give a steady load and had read elsewhere that this would approximate a 2G data download load
Test results for voltage and current are pasted below. The first graph on the left side is of first test and next is of second test (pale gold line at bottom shows screen on status)
Charging Time. Identical in both cases -121 minutes
I have edited the question, making it more focused to validate my interpretations of the results of test. In this context :
a) I fully agree that this is not a rigorous scientific experiment
b). Battery University talks of effects observed while charging with device on. Here the comparison from my tests, is not between charging while device switched "off" and "on". It is a comparison between charging while the device is on with " less " load and " more" load (device on with screen "off " and device on with screen "on at 50% brightness")
Having made these points, I believe that these tests offer indicative trends and is reasonable to compare with Battery University and draw conclusions
- Voltage. This offers the most striking contrast.
a). While the time taken to reach maximum voltage and voltage levels are nearly same, the voltage graph shows steep ramp up compared to the first. This means that the topping up of charge is gradual in the first case, since more time is spent at various voltages. This translates to longer battery life per cycle (assuming equal discharge conditions applied to both cases).
b). Battery University says
A parasitic load confuses the charger by depressing the battery voltage....,
this can be observed in the second case more prominently and confirms the behaviour
a). The current graph in the second graph, exhibits a pronounced saw tooth shape before it drops off. This corresponds to mini cycles caused by parasitic load as mentioned by Battery University
The current drawn through the device is called the parasitic load and can distort the charge cycle. Battery manufacturers advise against parasitic loads while charging because it induces mini-cycles, ....
b). Further, Battery University statement below cannot be established, since in both cases, the battery is being charged while in " on" condition and measured drop is nearly the same when you compare the maximum and minimum
A parasitic load confuses the charger by depressing the battery voltage and preventing the current in the saturation stage to drop low by drawing a leakage current.
Temperature. The battery temperature in second case is marginally higher by 2°C and while it is not significant, it can be argued that it is not desirable for battery, since increased internal temperature while charging leads to more internal stress.
Charging Time. Same in both cases and the charger having a limited capability to supply voltage or current, Would imply that there has to be a trade-off between quality of charging with more load, as is evident from the graphs above
Inferences above are in line with Battery University and consequently one can conclude that charging battery, while device is switched "on "or "in use" is NOT a good practice. This is further supplemented by best practices shared and amplified by @ericnutsch (thanks) here.
Seeking anwers for confirmation or negation of conclusion highlighted above (backed by technical sources and citations). Additional inputs on charging methodology implemented by major OEM cell manufacturers to cater for "charge while in use", would be appreciated
Please ask if any other information can be provided apart from above and cell phone is Honor 6, with 3100 mAh battery.OEM wall charger of 2A used