This is not a thread about best battery tips, etc. And I'm hoping it is not another standard thread about how to calibrate our batteries.
There is a lot of information flying around regarding battery calibration. A lot of it involves draining the battery, plugging it in at certain time, removing the battery, erasing batterystats.bin, etc. etc. etc.
Some feel the batterystats.bin file is key, and others believe it is completely unrelated to how the battery performs--just a log of stats.
How can this be reconciled?
UPDATE: Deleting batterystats.bin to "recalibrate" a battery is total and utter nonsense
http://forum.xda-developers.com/showthread.php?t=1442989
https://plus.google.com/u/0/105051985738280261832/posts/FV3LVtdVxPT
Over on the Nexus One forum, there was/is an extensive discussion, with REAL data gleaned from reading the technical datasheets of the battery itself, and the DS2784 chip within. The key to the Nexus calibration program was the ability to reprogram values on the battery chip.
http://forum.xda-developers.com/showthread.php?t=765609
I don't know if much of anything is going to be the same on the GNex battery, since the N1 was a HTC product. However, if the charging algorithms are all dictated by the Android OS, instead of hardware specific, then it could provide useful precedent. (I am not going to go through all the Samsung forums to look for valid battery calibration threads--if you know of some, for say, the Nexus S or Galaxy S2 (predecessor and comparable cousin, let's call them) please comment).
Here's a primer for all I learned that was used on the Nexus One battery calibration program. Full credit to those fine users who took the reins and made that happen, and to the fine users who continue to provide user support to the newcomers who don't know/refuse to acknowledge the existence of a search function.
My hopes are that this will lead to more rational battery life discussions and maximization for the Galaxy Nexus.
(I am not an engineer, so if any of you out there would like to tighten the language used here, please let me know).
What are the important values in battery/calibration?
1. mV = voltage
2. mAh = milliamp hours, a measure of capacity. This is how much 'juice' your battery has left/stored.
3. mA = milliamps, a measure of current. This is how much 'battery power' your phone is drawing/using at a set time. GPS/bright screen means large mA usage.
Apparently, Samsung (and Motorola phones) do NOT have mA readings in their battery drivers. This poses a problem. Apps that measure current (such as the excellent and free "current widget") cannot give a readout.
How is the battery life % calculated?
Present mAh / "full" capacity mAh (more on "full" later)
When does a phone shut down?
1. When mAh = 0
OR
2. When mV < 3416, which is coded on the battery as the "empty voltage"
Whichever occurs first.
If mAh = 0, then batt % = 0. However if condition 2 occurs, batt % could be anything.
I have found the empty voltage on the GNex to be the same, 3416 mV.
I have found the maximum voltage on the stock GSM battery to be 4197 mV.
Through experimentation, it was found that reprogramming the "empty voltage" down to 3201mv could provide extended battery life. The voltage was found to drop very quickly any lower than that, providing minimal gain afterwards.
What is the full capacity of a battery?
On the N1 battery, it is coded into a chip on the battery itself. This can be reprogrammed with the calibration utility. The stock value was ~1400mah. This is called the Full40 value (the mAh at 40oC). A value called "battery age %" is used to adjust how close the real capacity is to the full, which decreases with use and age. By multiplying (batt age * full40), you get the real assigned capacity.
Some non-OEM batteries, however, had miscoded capacities, usually LOWER than what was advertised. This led to very disappointed users who had purchased extended batteries that lasted no longer than stock, due to wrong mAh coding. (See below how this could be corrected).
Other low-end crappy non-OEM batteries had a crap chip which was coded with nonsensical values. This also led to unreliable battery life. These chips were not reprogrammable.
The very interesting thing is whenever the battery thinks it was completely charged, the mAh becomes SET to this number. mAh is NOT an independent value. Also, you could set it whatever you wanted, whenever you wanted, whether it was accurate or not. % battery left was basically calculated as present mAh / (full40 mAh*batt age). So you could get false values of either too little or too much battery left.
Why does this matter? If that was falsely low, the phone would cut out at 0% battery life, but you would still have usable battery left. If it was falsely high, it would cut out at 10% or whatever, since voltage would hit 3416 faster than mAh hit 0.
How does the battery know/think it is full?
When connected to a charger, the phone draws +mA. It can start around 1000mA (depending on the charger), and drops as the battery becomes more and more charged.
Another coded value, the "minimum charge current," tells the battery when to stop drawing current. This is set at default to +80mA.
Another coded value, the "minimum charge voltage," tells the battery that as long as the voltage is less than this #, it should continue to charge. At default, this is 4099mV.
An important concept is that once the charge amperage drops below minimum charge current (and the voltage is > the minimum charge voltage), the battery thinks it is done. Again, that state becomes 100%. Again, the capacity mAh is SET to the full capacity, no matter what is at that time. The actual mAh doesn't matter--it BECOMES whatever is coded as the (age % * full capacity).
As with other values in the battery chip, minimum charge current can be changed. It can be made to 40mA, or 20mA, or whatever you wish. By doing this, the battery will continue to draw current, and thus charge more and longer, until the minimum charge current is met.
Speaking of charging amperage, this can be an issue when using a non-OEM crap car charger when using your smartphone as a GPS. If the DC adapter is NOT truly giving 1A, the phone will use more current than it is receiving, and the battery will continue to LOSE current despite being hooked to a charger. Upgrade your car DC adapter! They are not all made the same.
How does 'bump' charging relate to all this?
Bump charging is essentially a way to trick the battery to continue charging despite the current draw being < the minimum charge current.
There is a problem with this "full" battery detection method:
If you draw enough current from the battery, while it is charging, after the minimum charge volt is reached, you can PREMATURELY fool the battery into thinking it is done.
Say the charging mA is at +200mA. If you turn on your smartphone, start GPS, turn the lights on, stream Pandora, etc., the mA will easily drop from +200 to a lesser value, negative even. The phone will think the charge is complete, since it is <80ma. THAT state becomes 100%, because the mAh get set to full capacity. Falsely.
However, this should only happen when the charge is ~90% or greater (when mv >4099). So, it may not play a huge significant role in battery time, basically missing out on 10% or so of battery life. Also, at the next recharge cycle, provided you don't fool it again, the mAh will be RESET to the more appropriate designated value.
If mAh can be set to whatever value whenever, how do we get it PROPERLY set/calibrated?
There are 2 times when mAh is automatically set. Upon draining the battery to empty (3416mv by default, 3201 preferably), when the phone shuts down, the mAh will be properly set = 0. This is good. We want mAh = 0 when mV = empty voltage.
The other time is when the battery thinks it's full, when minimum charge current is met--this is often not accurately set, not good.
If we start charging when the battery is empty, the mAh rises as the battery is charged. However, the MAXIMUM mAh needs to be watched. The mAh could be HIGHER than the programmed full mAh. Or far lower. Finding this maximum mAh, and reprogramming the battery accordingly, is the key.
Once again, when the battery hits the minimum charge current, the mAh will either jump up to the set battery capacity value (so the battery will die sooner than expected), or less commonly, drop down.
The goal is to get an accurate mAh capacity of the battery, for the voltage range between min + max, and have this set every time the battery is charged to capacity.
If we know the maximum mAh the battery reaches when charging, provided it started from 0, we want to reprogram the battery so that this value is set each time it completes charge.
There is a "learn mode" on the Nexus battery. Provided this was activated, through a series of very specific events, the battery would give itself a "battery age %". This is used to give the accurate (battery age % * full40) = true capacity. On the Nexus, the default battery age was 94%. So, mAh was set at every full charge to 94% of the full40 capacity. Obviously, this is not true for every battery forever.
Once again, why errors can and do occur:
mAh and mV are not directly linked. If mA falls to 0, or mV is less than the cutoff empty voltage, the phone will shutdown, even if the other value is still sufficient.
1. mAh is falsely high. The battery won't last as long as we think it will. Battery % is falsely high. Phone won't get to 0%.
2. mAh is falsely low. The voltage is adequate, but the mAh isn't correct. The battery % is falsely low. Phone gets to 0% too quickly. Perceived loss of battery life duration.
Why use mAh at all? Seems like mV is the only important thing?
I don't know. Why is mAh capacity important in telling the phone to shutdown? Someone enlighten me.
I think one reason is that voltage can and does fluctuate up. So using this to calculate battery % life would be extremely erratic and confusing.
What does this teach us, overall?
I'd have thought there would be much better technology built into battery calibration. Seriously. This is one big mess of poor design.
This is a bunch of technical mumbo jumbo. How does this help me?
On the N1, you can give yourself more battery life!
1. Set your 'empty voltage' lower
2. Set your minimum charge current lower
3. Calibrate the maximum mAh to a higher value to accomodate the new 'empty voltage' and 'minimum charge current' values
4. Don't play with the phone too much when it is >90% charging or it will prematurely end its charge cycle, give you a falsely higher charge %, resulting in the battery dying before you think it should.
5. Profit.
(On an extended 3200mAh battery from Seideo, after lowering the empty voltage and minimum charge current, I found >3900mAh (!) as my new maximum mAh. That's a heck of a lot of free juice).
On other phones? I'm hoping real programmers here can figure out how to do the same.
So, for the Nexus One, there is ABSOLUTELY NO correlation between battery calibration and the battery stats file. NONE. The values on the battery chip determine everything.
So, please comment on how battery calibration tech has changed over the past 2 Nexus generations. If it has.
ADDENDUM:
RogerPodacter, the xda guru/user who was instrumental in creating the N1 battery calibration app, has been looking into the GNex battery quite intently.
I just stumbled across some useful info about our battery fuel gauge from the sgs2 forum. Basically the result is there is not much we can do with our fuel gauge. But they do talk about how to truly calibrate it. And they discuss the improved version max17042 which is used on tbe sgs2 and has all the bells and whistles.
Heres the topic.
http://forum.xda-developers.com/show....php?t=1312273
Click to expand...
Click to collapse
(If you found this info useful, please click the THANKS button!)
Somebody is looking at this already. That same somebody who made the nexus one battery app. This chip doesnt supply amperage either. After i told him my battery seems to only charge to about 4.15v and that on discharging/charging my voltage is everwhere so it is hard to ascertain how accurate my % is. He finally got a chance to look over some stuff and we both think the nexus only allows charging to 4.15v. And. I think the battery shutdowns at 3.6v this go around. From initial observation he led me to believe everyrhing seems to be fine and we might not be able to do much. He might be able to get 4.2v and 3.4v for the voltage cycle. This is partly my speculation but we did agree that samsung may have done this intentionally for longevity of the battery. We will have to wait and see because he is still tinkering with his phone and deciding how to initially proceed. Might be a few days though. I am getting the extended battery soon so i would like to see what changes there are from the 250mah difference.
Sent from my Galaxy Nexus using xda premium
To gleam is to shine or sparkle... to glean is to learn or become knowledgeable about.
FrayAdjacent said:
To gleam is to shine or sparkle... to glean is to learn or become knowledgeable about.
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..wow, just wow.
To the OP thank you for all this compiled information.
Sent from my Galaxy Nexus using XDA App
FrayAdjacent said:
To gleam is to shine or sparkle... to glean is to learn or become knowledgeable about.
Click to expand...
Click to collapse
I thought the same thing but possible typo. N and m are next to each other. But if op ends up giving us something tangible positively foe the nexus he will have gleamed. Lol.
Sent from my Galaxy Nexus using xda premium
Agggh. I suppose gleam could be appropriate here. But yes, glean was the original intent.
Due to my grammar OCD-ness, it has been edited. =P
@rbiter said:
Somebody is looking at this already. That same somebody who made the nexus one battery app. This chip doesnt supply amperage either. After i told him my battery seems to only charge to about 4.15v and that on discharging/charging my voltage is everwhere so it is hard to ascertain how accurate my % is. He finally got a chance to look over some stuff and we both think the nexus only allows charging to 4.15v. And. I think the battery shutdowns at 3.6v this go around. From initial observation he led me to believe everyrhing seems to be fine and we might not be able to do much. He might be able to get 4.2v and 3.4v for the voltage cycle. This is partly my speculation but we did agree that samsung may have done this intentionally for longevity of the battery. We will have to wait and see because he is still tinkering with his phone and deciding how to initially proceed. Might be a few days though. I am getting the extended battery soon so i would like to see what changes there are from the 250mah difference.
Sent from my Galaxy Nexus using xda premium
Click to expand...
Click to collapse
Great to hear! Is that on this forum or rootzwiki, or a private communication?
I have noticed that shut down is usually at 3.6 or so. I drained it completely one time with multiple reboot attempts, and I got battery monitor widget to log a 3.417 or so that ONE time, but yes, the battery prefers to quit more around 3.6.
Battery monitor widget outputs an 'estimated' mA, but that's the closest thing I could find.
Wow you brought up the nexus one battery project. I was actually the one who re-wrote that battery driver for the n1 linked in the thread in the first post. Then I wrote the apk with dvghl. I even got my altered battery driver officially merged into the cyan kernel repo for the n1.
Anyway my point is that I learned an ENORMOUS amount about how these fuel gauge chips work, specifically the ds2784 chip in the n1. The bad news is our galaxy nexus chip max17040 doesn't have all the cool features that I cracked open on the ds2784 chip. But still worth trying a few things. Specifically I'm curious what the rcomp register does in our battery driver.
Also the other bad news is our galaxy nexus max17040 cannot give current mA readings. It can only be estimated using battery monitor widget for example.
Unfortunately we don't have a learn mode or age register like we did in the n1, so we can't get too deep into the chip like we did in that project. Kinda unfortunate. Seems the max17040 only has about 7 memory registers, where the n1 ds2784 had about 30 or so registers we could hack into and tweak.
RogerP, so good to see you here! Hope my summary gave some hint as to the enormous amount of effort your project took, and the huge leap in battery charging knowledge it provided.
waylo said:
RogerP, so good to see you here! Hope my summary gave some hint as to the enormous amount of effort your project took, and the huge leap in battery charging knowledge it provided.
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Hey man, you did a near perfect job with the write up. That project was a one of a kind opportunity in the sense that the ds2784 chip, and the tech sheet and hacks we did, all lined up to be the perfect storm of what we can learn and do with these batteries. So much knowledge was extracted from that effort.
The bad news is that Samsung phones don't typically use the ds2XXX fuel gauge chips, instead they use max1704X chips. These chips use voltage to determine SOC along with their "secret" algorithm that they don't publish. In the end there isn't as much ability to do anything with our fuel gauge like we did with the n1. There are 7 registers or so, SOC, mode, volt, rcomp, but no current and no mAh. The rcomp is the one I was curious about tweaking.
This weekend I was thinking of setting up Ubuntu build environment and attempting to play arount with this new driver and see if we can learn anything more. I'm sure there are more capable devs who maybe already know about this fuel gauge cause the nexus s and other Samsung phones use similar chip. It'd be another fun project if so!
Thanks OP. Very helpful.
Glad to spread the word!
Don't forget to click the THANKS button if I helped!
thanks!! helps alot more knowledgeable now about batteries
I bought the spare battery kit that comes with an external charger. I run my battery to near empty or empty then swap it out. Do the external chargers behave the same way?
Sent from my Galaxy Nexus using Tapatalk
Very happy to see the same crew from the N1 battery calibration days on the GN. I was pretty disappointed when I got the NS and there was little discussion or attention given to the battery at such a detailed level. By the time I picked up the GN I had mostly accepted that the N1 situation and battery related dev/testing/discussion was unique in that it was both possible to tinker with and we had some dedicated fellas, especially you RP, that were willing/able to tackle the task.
As with the N1 battery testing, I'm all in to test and help whenever possible to break some ground with the GN.
This topic made me reminisce about my old N1, wish I hadn't sold it on eBay. I sold it to a Canadian, cost me a bloody fortune to ship to him bc of restrictions on amount of lithium cells/customs regulations. The guy was probably wondering if he bought it from some nut job when it arrived with like 7 batteries of many different manufacture/capacity and spare battery chargers. I half expect that US/CAN Customs put me on some kind of list when they inspected the shipment.
ellesshoo said:
As with the N1 battery testing, I'm all in to test and help whenever possible to break some ground with the GN.
Click to expand...
Click to collapse
I'd also be willing to contribute to these efforts.
Sent from my Galaxy Nexus using Tapatalk
deekjx said:
I bought the spare battery kit that comes with an external charger. I run my battery to near empty or empty then swap it out. Do the external chargers behave the same way?
Click to expand...
Click to collapse
That's an excellent question I don't know the answer to. I'm not sure what kind of charging algorithm the external chargers would use, except to stop charging once the current reaches a certain low level.
As RogerP described above, most of the GNex battery algorithms are a mystery at this point, with some proprietary methods that won't ever be voluntarily revealed =P.
There is probably not a whole lot that can be done with the nexus battery. Yall gotta remember there was a bugnor bad programming revealed and that is why so much time was devoted to that. Roger already found that the battery stops around 4.15 volts. Changing it 4.2 will not make a big difference here and im sure it is intentional to extend charging cycles.
My grandma beat me down and took my nexus. Sent from a jitterbug with beats by dre.
well i dont think this project is "dead". i still plan to compile a kernel with a few batt driver tweaks and see if we can extract what the "rcomp" register is, what values it contains, and if we can tweak it at all. same with the "mode" register. also if you guys browse the source, there is a different driver called max10742 and it has all the extra options including "age". if only samsung had given us that one.
the other thing i want to do, or someone here could do, is map the voltage readings to the batt percentages. we did this way back in the beginning on the n1, except we mapped percentage vs mAh. but here we dont have mAh readings, only volts. what we can learn from this is if the percentage is calculated precisely from the voltage, how linear the mapping is, or if it's loosely estimated based on their modelgauge algorithm or whatever they call it at maxim.
i think it would be easy to just use battery monitor widget and export a full day's worth of your logs. maybe i'll install it and give it a shot.
I already have weeks of mv vs. batt % if you need that, specifically from battery monitor widget.
Graph 1: All data from the start. 5000 data points.
Graph 2: ~600 data points, starting from after I ran the battery down to 0 completely, plugged in with phone off, and charged to 100%.
Not sure why all the data gives 2 distinctly different patterns. The lower data plots seems more favorable, with higher % at lower mV.
I just got my epic touch the other day, has anyone else noticed that it has trickle charging? If you use battery monitor widget you can see that it has positive ma's all the way down to 2 .
Sent from my SPH-D710 using xda premium
Battery monitor estimates current, and it's not reliable at such low levels.
I came from the evo, on an sbc kernel battery monitor widget is what we used to determine if trickle charging was functioning correctly. The closer you get to a full charge and as the volts raise the positive ma's slowly lower until they reach +1-+2 and then hold constant while connected to the charger. That is exactly what my epic touch running calk's 2.9.2 is doing.
Sent from my SPH-D710 using xda premium
If you look at the mV and milliamp values, you'll see how erratically they jump around while charging. I believe the app uses time and mV to calculate the milliamp value that you see, and without doing any math on my end, I suspect that there exists a large error built into this resulting value.
Windows Mobile 6.x devices seemed to be very accurate in reporting charge/discharge rates. Nothing I've used in Android is as accurate IMO.
If you're interested in this, you should check out the kernel options for this. It's possible to scale maximum charging rates based on a host of factors, including battery temperature and level (trickle charging).
quick99si said:
If you look at the mV and milliamp values, you'll see how erratically they jump around while charging. I believe the app uses time and mV to calculate the milliamp value that you see, and without doing any math on my end, I suspect that there exists a large error built into this resulting value.
Windows Mobile 6.x devices seemed to be very accurate in reporting charge/discharge rates. Nothing I've used in Android is as accurate IMO.
If you're interested in this, you should check out the kernel options for this. It's possible to scale maximum charging rates based on a host of factors, including battery temperature and level (trickle charging).
Click to expand...
Click to collapse
Really? can you post some info on how to do this? I'd be interested with looking at those.
quick99si said:
If you look at the mV and milliamp values, you'll see how erratically they jump around while charging. I believe the app uses time and mV to calculate the milliamp value that you see, and without doing any math on my end, I suspect that there exists a large error built into this resulting value.
Windows Mobile 6.x devices seemed to be very accurate in reporting charge/discharge rates. Nothing I've used in Android is as accurate IMO.
If you're interested in this, you should check out the kernel options for this. It's possible to scale maximum charging rates based on a host of factors, including battery temperature and level (trickle charging).
Click to expand...
Click to collapse
The thing is it's not erratic, it's a steady build in volts, and a very steady even decline in ma's as the battery reaches 100 percent. I never have -ma's while on the charger
I also hold at 100 percent 20 to 30 minutes after taking it off the charger, even while the phone is in use.
Sent from my SPH-D710 using xda premium
I just got one of these extended 3600mAh batteries for my i927, and now i wonder if there is any way to tell the phone/android when/if i am swapping batteries and therefore changing capacity of the battery.
So far, the only thing i found was a way in CWM to reset the battery stats. I now try to train the phone to the new 3600mAh battery, but if i ever should even just temporarily swap it against the older 1800mAh battery, then the stats will get totally screwed up again, right ?
So, any app to maybe store and recall the battery stats ? Then it would be possible to train the phone independendly for each battery, store the stats, and accordingly use the app to recall the battery stats after swapping it.
Thanks
It's not the phone that gets trained, but an IC in the battery itself. Each battery has an embedded processor that tracks current charge levels using a semi-predictive algorithm. That's what the third conductor is for -- it's a one-wire serial connection between the phone and the IC inside the battery. So when you switch batteries, you're also switching the IC that's tracking the battery's charge.
The batterystats.bin on the phone is just statistics tracking for what is using power, how much, and how often. These are the stats you see in Settings -> Battery and have nothing to do with current charge levels, actual or displayed.
tl;dr: It doesn't work that way. Swap your batteries freely and don't worry about it.
Brightness taking the battery?
Is there an app or tweak that will let me turn down the "ambience" on my captivate? I mean, on my old iPod (I know, right ) there was a Cydia app that allowed me to set a certain time for when the brightness would kind of "lower the hue" and made it look kinda like a old style fleurescent light. Kind of amber in color.
In my battery manager, the screen takes up MORE than 50% of my battery life, and I was wondering if there was a way to do that, instead of having to manually turn up the brightness when I need to. It's currently all the way down, and yet STILL ueses a bunch of battery.
Anyone?
I use the Lux app from the app store and it does this. At a certain time it will transition to a warmer color that you set and it also has many settings for light dimming based on a number of factors. You can also set the output to sub zero.
Sent from my SGH-I927 using xda app-developers app