Some people I know say that replacing the battery helped their smart phone improve its decreased speed resulting of two years of use.

My initial guess is that this would not have any influence because the speed is mostly about the phone's processor and built-in memory.

But then I got to wonder if I'm mistaken. Maybe if the battery is old, it does not deliver sufficient power and forces the processor, and thus the whole system, to work slower. Or maybe even, that the smart phones switch to "economy mode" (does that even exist in a smart phone?) when it detects that the power delivery is not sufficient.

Any thoughts? Thanks


closed as off-topic by PeterJ, Andy aka, Daniel Grillo, Null, nidhin Jan 4 '16 at 7:39

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  • \$\begingroup\$ Sometimes a phone runs slow because its memory has silted up with leftover junk and needs to be dredged. That means power-cycling it; removing and replacing the battery is one way to do that. \$\endgroup\$ – Pete Becker Dec 26 '15 at 14:12
  • \$\begingroup\$ This seems most unlikely. Mainly, I can't think of any mechanism that would cause this. A processor may slow down due to over-heating, but I wouldn't think the heating contribution of the discharging battery would be significant enough to trigger this effect. (The processor and power conversion circuitry are probably the main heat sources). \$\endgroup\$ – mkeith Dec 26 '15 at 19:49

First of all, a phone would not just run slower like an old cassette tape deck. Either it has sufficient power to run, or it has dropouts - though mobiles switch off before dropouts occur.

My Android Phone can switch to some kind of "economy mode" either manually or automatically when battery charge falls below a given threshold.

This mode includes dimmer display, shorter display-on time and reduced background functionality (i.e. processes running in the background like position tracker, messenger, email, ...)

However, the phone notifies me about this, and I'm not aware of any phone that would switch to "eco mode" silently just because the battery is worn out. Also, many phones even don't know if their battery is worn.

A new battery will help if the time the old one lasts until charging is required has decreased a lot.

The main reason for a slow phone is that the old phone seems slow compared to new phones with faster hardware. Also, apps tend to need more and more resources from version to version, so a current version may run slower than an old one. Plus, all the stuff you installed over time may slow down the phone.


The cell phone would have no way of knowing the battery is old. When battery's age they just hold less of a charge. From what I understand as a battery dies they produce slightly less voltage. The battery is effectively "dead" when its output voltage is less then the rated voltage of the smart phone. This shouldn't have any effect on performance. However if the phone is placed in some sort of power saving mode Its possible for the CPU's oscillator frequency to decrease in order to save power which would defiantly effect performance But I think that power saving feature is Mostly just in laptops


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