[GUIDE] Undervolting, The Right Way

It seems alot of people dont know the proper way to undervolt their phones, so I'm gonna try to help out! This is my first attempt at a guide, and i tend to ramble so just tell me if it makes no ****-for-sense

Undervolting is great, it allows us to change the voltage in our phones while we use it! this can really increase battery life and reduce heat in the phone. but if its not done right, it causes many more problems than it fixes.


But after its all done it should work much better

To start off, too much or too little voltage in the phone causes any number of things including:

• Reboots (Screen Off and Screen On)
• Lagging
• Phone Overheating (Hot to the touch)
• Reduced Battery Life (this includes the phone using more power, as well as reducing the battery's ability to hold a charge)
• 'Strange' issues with things shutting off/not working (WIFI, Bluetooth, your favorite app, ect...)
• Many other 'weird' things

If you are having any of the above issues, and you are using a custom kernel, they may be caused by inproper undervolting.
THIS CAN BE THE CASE EVEN IF YOU HAVE NOT DONE ANY UNDERVOLTING YOURSELF!!!
Most custom kernels have undervolting build into them, and even 'stock voltage' versions allow overclocking, and those frequencies have no 'safe' voltage associated with them.



*this assumes you have no idea where to start, if you have some past experience, USE IT!!!*

First, Undervolting a phone the right way is not a quick job, like most things in life the more time you put into it the better your end result will be. For me i like to take an ENTIRE WEEK OR MORE to get all my settings down right. whenever you decide to do this, expect any and all of the issues i listed above to happen while you are trying to find the right settings.


Disable all overclocking, undervolting, AND PROFILES on the ROM, you need to get the stock speeds working before you try to push the phone to its limit.

This will be your baseline. Use the phone like you normally do, text, call, surf the web, even let it sit in your pocket for a while. Do this for as long as you need to to be sure that everything is stable.

If you have any issues during this stage. STOP! add +25mv to every frequency across the board and start over. Do this up to 3 times if necessary, if after you have added +75mv to your stock voltage and you are still having issues, it is most likely something else in the rom causing the issue (rogue app, wrong kernel version, phone was dropped in the toilet too many times...) try to fix that first, or just try to ignore the issue, its up to you.

Otherwise, if everything is stable, Continue to step 2!

Lower all of the voltages by -25mv across the board. (If your phone needed any voltage added over stock to be stable, skip this step.)

This is where you begin testing the waters. Once again use the phone like normal, including some screen off time, as well as some CPU intensive tasks (playing music while websurfing, gaming, ect.)

If your phone is still stable after a good amount of time, then do it again. Your looking for the moment when things start to go wrong.

When you notice your first random reboot, or you start to feel the phone getting hot, or not responding STOP! you found the limit of your phone. Go back to the last working voltages you have and use them for step 3.

The more time you spend at this step the better your overall result will be! if you dont get any symptoms in an hour, they might show up later in the day, or overnight. Just take your time and have some patience.

Now that you have a stable working phone. you can start lowering voltages one by one!

Starting with the lowest frequency, lower the voltage by -25mv.

Run this for a while, until you feel it is stable. Then move to the next highest voltage and do the same.

*If you have any issues, undo ONLY that frequency!!! Write down that frequency somewhere. you are done with it! you know that frequency is stable, and you shouldn't need to touch it again!!!

Keep doing this till you get to your stock maximum frequency, then continue to step 4!

*NOTE:* if any 2 voltages have more than a 100mv difference (125mv difference on Morfic's Kernels) between them, you need to raise the others around it to be equal or less than that. For exampe:

if at 1ghz, the phone is at 1000mv and at 1.2ghz the phone is at 1150mv. the higher one needs to be lowered (set 1.2ghz to 1125mv). if that is not stable for you then you must raise the lower one higher (set 1ghz to 1025mv).


At this point you should have a completely stable phone with no overclocking, grats! Now you get to start raising the frequency.

starting with the next highest frequency, set it to its stock voltage. if this is more than 100mv (125mv for Morfic's kernels) more than the previous frequency, set it to 100mv (125 for morfic) more than that.

run this until it is stable, and keep reducing it as much as you feel until you find instability. set it one step higher and move on to the next highest frequency.

if, after setting the voltage to 100mv (or 125mv) more than the last one, it is not stable, you need to raise the lower frequency's voltage up. sometimes this can cause a chain reaction that makes you raise 3, 4, or even all of the other frequencies up, if this happens you need to decide if that frequency is worth it to raise all the other frequencies to the next level.

If all is running good, proceed to step 5!


(this step is optional, its just something i do to help with stability)

Now that you have a fully overclocked phone that is running as low of a frequency as it can safely, raise all of the voltages up by +25mv!

yes yes, i know, it sounds retarted to just undo that hard work and all that time you just put into finding the perfect voltages, but just hear me out.

Even if you spent a week on each step, did everything perfectly and tested everything you ever do on your phone and it is all completely stable. one day you are going to do something that will push the phone, which is running at its limit. so by adding 25mv to everything you are giving yourself some insurance. you may loose some battery life (i honestly don't ever notice a change with only 25mv) but when your phone alarm goes off in the morning to get you up for class, or you get that call you got that job you wanted, just be happy its not frozen on the table, or black screened in your pocket.



There you go! you should now have a stable phone with great battery life, and now you can stop bugging the devs about 'that strange reboot that is still there' or 'how every time you use his kernel you get black screens'







If your having issues with your phone and you think its related to UV, and your much too busy/lazy/cool to read the above, try this: (Results will most likely be worse...)

Set (all of) your lowest voltages to 775mv (or 750 if you think your phone can do it)
Set your 1ghz voltage around 1000mv (give or take 50-100mv)
Set the highest speed to no more than 100mv below its stock seting.
Set the rest of all the speeds below 1ghz on a line between it and the lowest, and after 1ghz on a line between it and the highest. ex(From Morfic's T15 Kernel):



Post any questions or feedback you have, ill try to answer it as best i can!

imoumni said:

This is done using setcpu?

Sent from my LG-P999 using XDA

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Any CPU managing app. I use CPU Master but there's lots more options out there. I don't use SetCPU because it took nearly a year to update.

Sent from my amazing LG G2x running Bionix Reloaded v1.4

I'm assuming the whole difference of more than 100mV is a bad thing is due to something similar with overclocking PCs where if vdroop is active the voltages climb and fall is too fast causing it to freeze up. If I'm right about that then I might have a problem overclocking mine. Currently I am running stable with the following.

Mhz - mV
216 - 375
432 - 450
594 - 550
750 - 650
1000 - 825(becomes unstable at 800)

Anything after 1000 becomes super unstable unless I give it 1175mV or more but even then it is very unstable leaving me to believe its due to something similar to vdroop. I honestly don't mind staying at 1Ghz but if possible I would like to get a stable overclock at 1200Mhz.[/QUOTE]



Nice, I'm running PA 12 with Harsh's OC kernel, currently mine numbers are:

Mhz- mV
216 - 565
324 - 630
655 - 730
816 - 830
1015 - 920
1100 - 955
1216 - 1055
1408 - 1105

The way I did mine was using SetCpu to manually set clock between each Mhz range, then see how low I could push the high and low of that range before freezing. After that I smoothed them out to make sure they didn't have more than 100mV difference (except for the 1015-816 range but so far it's a start). Now I start just using and see how stable it is over time. I'm also using Seeder, and occasionally I use a task killer just make sure my ram is being used well but very rarely do I kill apps. I just flashed this rom a couple days ago so battery still needs to go through a few more cycles at the clock rates and voltages before it's used to it, but so far no overheating (Have an underclock profile set just in case it does). This is why I will never buy an Iphone, can't really do this much with apple and you can't pop the battery in an emergency.

This is done using setcpu?

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Click to collapse

It can be done with any app that works with this phone.
I use an app called "System Tuner Pro" because it allows you to add voltage from stock settings (my phone seems to like a minimum voltage of 775 vs the 750 that most kernels start with) and im not sure any more but i think its free...

r4d14n7 said:

My only question: I understand what you're saying, but I think your example may be incorrect. 1200mV - 1000mV = 200mV difference, so you would need to change one or the other by 75 to 100mV, right?

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thanks, yeah thats what i meant to say

All Fixed

Truly a great guide. I agree mostly with the last part, my alarm stopped ringing two days in a row, so I added 25 mv across the board, and it works perfectly. Thank you on behalf of the community, everyone will appreciate this guide for sure.