# Regulating Cell Phone Charging

#### MrAl

Joined Jun 17, 2014
8,257
Hi,

I was thinking about maybe creating a cell phone charging 'regulator' to regulate the amount of charge that gets to the cell phone arther than just let it charge and charge or charge up to 100 percent and then disconnect manually.

Here is the thought that goes behind this.
First, i find that even if i dont use my phone i have to charge it every day or two. It does not need a full charge at those times so it is not too bad, but still day after day repeatedly charging and discharging it's going to kill the battery sooner than later.

So the idea is to regulate the charge (Ampere Hours) that gets to the phone so it mainly only powers the background tasks while the phone is mostly inactive but not powered off completely. This would be similar to maintaining a battery when it has some self discharge where you dont want to charge it just keep it topped off.
The ideal charge state is probably around 85 percent, so the regulator would have to supply just enough current to maintain the background tasks while not actually charging the battery anymore and NOT forcing it up to 100 percent charge which is not a good idea for long term.

I am thinking maybe even a series resistor might do the trick, although it would not be at the perfect level it might get close enough. So the cord would have to be broken and a series resistor of some value inserted in series with the power input to the phone. I guess a more advanced method might be to regulate the input to some voltage level like 4.5v instead of 5.0v or maybe regulate to 20ma (with included top voltage regulation) or something rather than 450ma which would be a normal charge current.

#### Irving

Joined Jan 30, 2016
1,549
Why do you think charging it every day will kill the battery? That was true of earlier chemistries (NiMH, NiCAD) but isn't true for LiPo. Its true that LiPo prefers not to be stored at 100%, it likes to be between 30% and 70% SoC. So simply dont charge it until it gets to 30%. However, there is no easy way to control SoC during charging. Reducing the voltage will simply stop it charging, and the internal charger circuit fixes the charge rate at some constant current based on the USB connection (standard v fast charging). Putting anything in the loop to try and reduce the charge current is likely just to cause the internal charge regulation to simply shut down and refuse to charge, probably with some 'problem with cable' charging error message.

Once the phone reaches 100% charge it will stop charging and the internal components usually run off the charger leaving the battery fully charged for when you disconnect it...

#### MrAl

Joined Jun 17, 2014
8,257
Why do you think charging it every day will kill the battery? That was true of earlier chemistries (NiMH, NiCAD) but isn't true for LiPo. Its true that LiPo prefers not to be stored at 100%, it likes to be between 30% and 70% SoC. So simply dont charge it until it gets to 30%. However, there is no easy way to control SoC during charging. Reducing the voltage will simply stop it charging, and the internal charger circuit fixes the charge rate at some constant current based on the USB connection (standard v fast charging). Putting anything in the loop to try and reduce the charge current is likely just to cause the internal charge regulation to simply shut down and refuse to charge, probably with some 'problem with cable' charging error message.

Once the phone reaches 100% charge it will stop charging and the internal components usually run off the charger leaving the battery fully charged for when you disconnect it...

In my experience charging at 100 percent indefinitely is bad for the battery. I did that for a year or so and the last battery i replaced was bulging badly.
Since then i realized that this Li-ion battery (not lipo) is just like any other Li-ion battery so 85 percent charge would be good.

When i charge with a short USB cable the charge current is 444ma.
When i use a longer 10 foot cable the charge goes down to about 330ma.
So i think there is a way to control it although i havent tried anything yet (like with a power pot or voltage regulator or something).

I could time the charge, but then i have to keep setting the timer every time i charge.

I think the OS should allow a way to charge up to some predetermined level and then cut out. That way we could set it to 50 percent, 70 percent, 86 percent or 100 percent or some other level.
To install that kind of circuit though i would have to wire up to the battery itself and monitor the charge and turn off at the right level.

But you gave me another idea. I could use a timer inline with the USB charger. That way i could set that permanently to maybe 1/2 hour. After that it would turn off. Maybe i simple way to change the time with say a 10k pot or something. Sound like an Arduino project right?
I think i would want to keep it simpler though, just a 555 maybe or two 555's or something simple like that. I wouldnt want an entire controller board hooked up to this thing, although maybe a Microchip controller chip, 8 pinner, with a simple algorithm. I'll have to give this some more thought, but any ideas are appreciated.

#### Dodgydave

Joined Jun 22, 2012
9,956
The phone already does this for you, why do you want to re-invent the wheel !!

#### MrAl

Joined Jun 17, 2014
8,257
The phone already does this for you, why do you want to re-invent the wheel !!
Hi,

I dont think you understand the situation.

First, the phone only cuts off the charging when the battery reaches 100 percent charge. I want it to cut off when it reaches 85 percent charge and hopefully then just provide enough current to run the background tasks that run when the phone screen is off but the phone is not powered completely off.

If that background powering is not possible then at least have it cut off completely at 85 percent with no powering at all after that and another charge cycle only initiated after the user chooses by pressing a button maybe or maybe after a certain time like 12 to 24 hours.

What i have to do now if i want a top 85 percent charge is i have to connect it and let it charge, then unplug it. Then the next day, same thing...plug it in, let it charge, then unplug it. This is true even if i go all the way to 100 percent though. But day after day after day of this action seems silly when in today's world we have everything automated for us. I should be able to leave it plugged in indefinitely and have it only go to 85 percent.
The only time i really have to disconnect is when i go out, and i have been going out much less now due to the virus problems.

But thank you for the reply as you just made me think of something else too now. That is, the battery current draw (or rather the USB port input current) drops significantly as the battery charges. I may be able to monitor the input current and cut out with a relay or transistor when the current gets to a certain low level. I'll have to check this soon. If this works, even if it goes to 90 percent instead of 85 percent i think i would be happy with it. Then i could leave it plugged in all the time. It would turn back on after a certain time limit like 12 to 24 hours.

I am home and bored anyway

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#### Alec_t

Joined Sep 17, 2013
12,089
Have you considered a charging limit app, such as this ? It does require root access on an Android phone though.

#### BobTPH

Joined Jun 5, 2013
3,332
If you have an iPhone, go to settings - battery- battery health and turn on Optimize battery charging.

If you don’t have an iPhone, why don’t you?

Bob

#### MrAl

Joined Jun 17, 2014
8,257
Have you considered a charging limit app, such as this ? It does require root access on an Android phone though.
Hi,

Thanks for the idea.

I doubt my phone will work with that. I dont have root access and i am not sure i want to. Maybe some day though.

#### MrAl

Joined Jun 17, 2014
8,257
If you have an iPhone, go to settings - battery- battery health and turn on Optimize battery charging.

If you don’t have an iPhone, why don’t you?

Bob
Hi,

No i do not have an iPricedWayTooHigh (ha ha) phone.
I cant see buying a USD $900 phone and then dropping it or having it go out for some reason then having to buy another one. I would like to have the OLED display though i miss that. The cheaper versions are not as good. Also, if the battery is non user replaceable then it would cost a lot to have the battery replaced. Not sure i feel like paying for that either. What are your reasons for buying one, assuming you did? I like to hear about pros and cons. Is the battery easily replaceable? Last edited: #### BobTPH Joined Jun 5, 2013 3,332 The cheaper versions are as good. I’ve just pointed out one reason they are not as good. I’m going on my fifth year with my SE, which comes to$120 per year or $10 per montth. Bob Thread Starter #### MrAl Joined Jun 17, 2014 8,257 I’ve just pointed out one reason they are not as good. I’m going on my fifth year with my SE, which comes to$120 per year or \$10 per montth.

Bob
Sorry, i meant to say that the cheaper versions are NOT as good. Miss typed it.

The way i read is was that the cheaper versions dont have the OLED screens and have knocked down software. But the screen is the most important thing for me i would want the OLED type if i was going to go for one in the first place.

I know other people too who swear by their iPhones.

#### atferrari

Joined Jan 6, 2004
4,331

In my experience charging at 100 percent indefinitely is bad for the battery. I did that for a year or so and the last battery i replaced was bulging badly.
.
Hola MrAl,

I have been doing exactly that for more than four years now to my Galaxy J7 (original battery). I leave it connected until going out no matter when it reached 100% level (most likely during night). Battery looks healthy.

Around one year ago I noticed a sensible reduction in the duration (maybe from 2 days to just 1) but since then, until now, in average is keeping the same, quite consistently. My usage profile is notoriously the same, whether at home and before when at work in the field.

#### MrAl

Joined Jun 17, 2014
8,257
Hola MrAl,

I have been doing exactly that for more than four years now to my Galaxy J7 (original battery). I leave it connected until going out no matter when it reached 100% level (most likely during night). Battery looks healthy.

Around one year ago I noticed a sensible reduction in the duration (maybe from 2 days to just 1) but since then, until now, in average is keeping the same, quite consistently. My usage profile is notoriously the same, whether at home and before when at work in the field.
Hi,

Oh that's great. I guess my phone isnt as good. It was just 100 dollars USD back several years ago. It may have been a less than great battery too who knows. But i have the new battery in there now.

Yeah i used to do that too. Kept it on charge for at least a couple years but before that i used to turn it off when i wasnt using it so it is a little surprising that the battery got that bad. I checked the charge current and it does go down very low after the charge reaches 100 percent, so maybe ithat wasnt the problem after all. Maybe just a crappy battery. It was the one that came with the phone.

But i know for a fact that charging it to 100 percent 'wares' the battery out faster, but i think it is a matter of 4 years vs 5 years so maybe most people wont care.

But there is something to be said about leaving it at 100 percent and still 'charging'. If the phone is getting the power for the background tasks then it seems that would mean the battery does not run down. so it seems we would save charge cycles which is known to cause battery ageing.

Thanks for the info.

#### MrAl

Joined Jun 17, 2014
8,257
@atferrari

After considering your reply again i think i might try doing the 100 percent 24/7 charge routine again. I could have just had a bad battery to begin with, the one that came with the phone.
Also, when i monitor the charge current when it reaches 100 percent on the phone it makes a low level tone, and the current stays at around 590ma (using the actual phone charger that i had been using before going to using the USB port on the PC computer), but then it gradually drops to 2ma and 1ma of that is for the LED at the end of the USB cable used to charge the phone, so the charge current or should i say the current going into the phone is about 1ma. So i tend to believe that the charge current itself is down to zero. If i start the screen up it draws over 200ma again. So that 1ma is probably correct.

My only guess now is that the input current to the phone is so low that the background tasks are operating off of the battery not off of the input current, but i cant prove this yet. I will have to monitor the input current over longer time periods to see if it goes up, goes back down, goes back up, etc., or just stays solid at 1ma. That way i could tell if the battery is draining and charging, draining and charging, etc., or just staying at one charge level (100 percent) while the 1ma powers the background stuff.

Right now it is at about 250ma, down from 590ma and it only took about 10 minutes to get that much lower. So once it gets back down to 2ma (1ma actual) i'll start looking at it every 1/2 hour or something.
I am not that worried about the battery life as much as i am about the battery bulging. I just hope that does not happen again.
I can also see why those Samsung phones caught fire. Those batteries can bulge pretty badly where they swell at least 20 percent outward. If they are constrained something has got to give.

I'll post more when i do more measurements. Until then any other ideas will be appreciated.

Interesting the text change size on me for some reason. Somehow it started out very large in this post then got smaller.

#### atferrari

Joined Jan 6, 2004
4,331
@atferrari
Interesting the text change size on me for some reason. Somehow it started out very large in this post then got smaller.
Probably in sync with your charging rate: 590 mA >> bold - 200 mA: normal font - 1mA >> OFF.

There is a variety of applications measuring your consumption (at least for Android) but I believe they cannot distinguish so finely what you are interested on, considering that to read the info, screen should be running full on. Not sure if any of them could have kind of a record for different items that you could verify at a later moment.

I downloaded one that other than warning me, from time to time, that Galaxy store was using the battery, did nothing of any use to me.

#### MrAl

Joined Jun 17, 2014
8,257
Probably in sync with your charging rate: 590 mA >> bold - 200 mA: normal font - 1mA >> OFF.

There is a variety of applications measuring your consumption (at least for Android) but I believe they cannot distinguish so finely what you are interested on, considering that to read the info, screen should be running full on. Not sure if any of them could have kind of a record for different items that you could verify at a later moment.

I downloaded one that other than warning me, from time to time, that Galaxy store was using the battery, did nothing of any use to me.
Hi,

I have a screen in Settings that tells me what the distribution of power is for all the apps including the screen. For example, it will show how much was used on Playstore.
If i use the phone more with the screen on the "Screen" value will be higher.

#### atferrari

Joined Jan 6, 2004
4,331
Hi,

I have a screen in Settings that tells me what the distribution of power is for all the apps including the screen. For example, it will show how much was used on Playstore.
If i use the phone more with the screen on the "Screen" value will be higher.
Not Android, I guess.

Long ago, I decided to disable maybe 80% of the apps coming installed (Samsung & Galaxy). Activity reduced notoriously.

#### MrAl

Joined Jun 17, 2014
8,257
Not Android, I guess.

Long ago, I decided to disable maybe 80% of the apps coming installed (Samsung & Galaxy). Activity reduced notoriously.
Hi,

No actually it is version 4.0 Android, a pretty old version now. I would think anything after that would have this in the settings.
It is under:
Settings/Battery/Battery Usage

IT gives the usage in percent for each thing.
,