This guest post was written by Joseph Davenport.
One of the hot-button issues concerning the HTC EVO 4G is the safety and value of trickle charging and the use of kernels that supposedly enable it.
In layman's terms, under normal charging your EVO charges to 100% and then the internal charger shuts off, forcing your phone to run off the battery instead of using power from the outlet or USB port on your computer. When you have a trickle charging (aka SBC) kernel, your charger stays on, continually feeding your battery a small charge after it hits 100%. This keeps your battery at 100%, instead of your EVO running off the battery and losing charge.
Although this sounds great, some believe that things that sound "too good to be true" usually are. So let's briefly discuss the two sides of the trickle charging argument.
One the one hand, you have a fully charged battery. This should be kind of obvious, but the reason that you want to trickle charge is that you'll have a battery that doesn't display the false 100% charge. Instead, you have a battery that is running at an actual 100% charge, which will extend your battery life.
On the other hand, you might turn your phone into a grenade. As some of the commenters in the previous trickle charging kernel post have pointed out, trickle charging is seen by some as being dangerous and at the very least potentially damaging to your battery.
So, you have the two schools of thought: those who feel trickle charging is the greatest thing since sliced bread, and those who think it’s the most dangerous thing you can do with your EVO other than attempt to eat it. But who is right?
Everyone is.
In the end, you just have to feel comfortable about what you’re putting onto your EVO. Every person has their own threshold of risk that they are comfortable with. It’s the reason that there are some people who root their EVOs and flash everything under the sun (thanks, Nandroid!) and some who keep their EVOs bone stock.
I have used luisrcastillo and jsseidel's Savage kernel in the past on my own EVO (hardware 0002, CyanogenMod 6.1.2) with no ill effects. On the contrary, my EVO's battery life extended by at least a couple hours. I charge every night, so I'm not sure exactly how long. All I know is that every time I went to bed, my EVO showed in the green. Note: It seems that the Savage devs have pulled SBC off of their kernel for the time being, probably because of the mixed feelings about it. The versions (1.5.2 and 1.6) that I used, however both had SBC.
If you're still on the fence about what to think of trickle charging kernels on your EVO, then check out what was posted to the XDA Developers Blog the other day. Evidently, our EVOs were shipped with a hardware failsafe against overcharging past the battery's safety limits. You cannot remove or change the failsafe with a kernel. A quote from the author, egzthunder1:
"So, to all of you who assumed that the SBC kernels could indeed override this, as there is a hardware protection in place, the device cannot be overcharged or rather charged past its safety limits."
So with all that being said, SBC kernels, while controversial, are most likely safe.
There are always going to be isolated incidents where EVOs start to malfunction, but what we don’t know right now is the specific cocktail of circumstances.
But here’s some quick, one-hit advice if you’re going to use an SBC kernel: Don’t overclock your processor past 1.1Ghz. As we all know, SBC puts a strain on the battery, more stress than HTC originally intended to have put on it. Overclocking the processor unreasonably just adds to the strain.
Whatever you decide to do, please study up on it and make sure you know the risks.
This guest post was written by Joseph Davenport (J.D.), editor-in-chief of The Tech Councillor.




















Yeah i’m good with the stock battery and charging setup… I just recently got 2 extra batteries from amazon and a travel charger for them, I barely even watch my battery percentage anymore I just wait for the “connect your charger warning” and go grab another battery. Though it is kinda annoying that I need to power off the phone then power it back up for a battery swap it is nicer then being tied to an outlet like most I users
Well according to XDA dev willy900wonka is that the trickle charge is not at all possible on the EVO due to hardware constraints. See link below for full trickle charge myth with pictures (from XDA forum)! What is really odd is that I too have had seemly good performance from trickle charging on my Evo so I’m not sure if this is 100% accurate? Every couple of battery charge cycles I trickle charge my evo battery by waiting till the green “finish charge light” appears and then pulling the a/c cord and plugging it back in to get another 1-2 minute charge. I’ll sometimes sit there for at least 10 cycles trying to get every last drop of battery I can!
http://forum.xda-developers.com/showthread.php?t=906144
Article on AndroidPolice.com:
http://www.androidpolice.com/2011/01/13/makes-sense-htc-evo-4g-batteries-have-overcharge-protection-chip-inside/
This was a very responsible and informative post. Thanks!
I believe there is a difference between trickle charging and over-charging. Trickle charging is simply putting a small amount of energy into the battery to ensure that it stays at 100% instead of the internal charger shutting off and allowing the phone to run down while still on the plug-in charger.
Over-charging is overloading the battery. I believe I read somewhere on XDA-Devs that damage occurs at a certain voltage, and the SBC kernels in question don’t hit that voltage.
http://tinyurl.com/4kl6rms
Good article. Definitely provides both perspectives. What would be real nice is to see an actual innovation in the battery technology itself so that we would get longer lasting batteries to start with.
All this debate over trickle charging is kind of amazing to me. There are countless different types of cell phones out there, and most of them trickle charge and have batteries very similar to those in our EVO.
Whats actually surprising to me, is that the EVO doesn’t trickle charge and that so many people think its dangerous to do so.
Will it cut the lifespan of the battery? Maybe. I’ve not seen proof of that but even if it did its a non issue. The lifespan of the battery, even if it were cut in half by trickle charging still far exceeds how long we will be using it. Most people are probably going to switch to a new phone in 2 years tops.
LOL. I love it when people do that.
RE: “But here’s some quick, one-hit advice if you’re going to use an SBC kernel: Don’t overclock your processor past 1.1Ghz.”
————————————-
I followed yesterday post of “Using SetCPU to boost battery life on rooted HTC EVO” to configure my CPU.
I mirrored the picture’s setting of 1113600 max
Is this a safe setting to keep it at without putting too much strain on the battery? I have Kernel 2.6.32.27-SBC-net4.2.2.more-havs
You’ll probably be fine. I only put that because the Savage kernel that I was running would allow you to overclock pretty far past 1.113Ghz. For me, Savage was stable with great battery life between 1.075Ghz and 1.113Ghz.
However, the one time that I did try to overclock past 1.113 on Savage, my EVO locked up and I had to pull the battery to fix it.
(Remember, neither Jenn nor myself are responsible if your phone explodes, bricks, etc.)
Just like “Joseph Davenport (J.D.)” said, there’s a difference between trickle charge a battery and overcharge it.
I think a big part of the problem is the super cheap batteries lots of ppl are using (including me).
For example my evo runs on a generic 3,500mAh which never reports it’s temperature to the phone, and also doesn’t seem to have a hardware protection against overcharging (an EE did some tests, and apparently the batt didn’t cut off current even after almost reaching 4.3v)
So the risk with this battery is high, ¿do i use kernel with tricke charge? YES, i choose to use it because:
* The kernel i use never lets the battery past 4.2v
* I get around 30-40% more juice than standard kernel
* The battery temperature never exceeds 30ºC during charge periods
So, my friend tells me that the risk would come only if the voltage would reach too high (fortunatelly he helped me test it too with some equipment so we didnt have to rely only on the phone’s reported value) and also heavy use while charging is not recommended either, because like Jenn K. Lee said: it puts a high strain to the battery.
Sorry for the long post, im at work and have lots of free time ^^
* I get around 30-40% more juice than standard kernel
Are you saying standard kernels only charge the battery to ~70% capacity?
I’m running Netarchy 4.3.1 BFS SBC HAVS with no CPU management, Ultimatejuice (with no cpu). I took my phone off the charger today at ~8am, did not use it. At 2:30 I looked at the phone and it had just hit 99%.
Juiceplotter shows a nice flat line… I will say though, I notice the top 10% of the battery seems to be weak… load above 90 drains faster (and I have calibrated the thing all to hell)… but a good kernel, a full battery, that’s a recipe for a good experience.
Even if the battery fries in a year instead of 3, I’m getting ~2 hours additional per day, or 720 hours / 1 solid month of additional battery.
Or it could explode…
Well i don’t have rock solid proof since my usage vary a lot, but after the trickle charge kernel there’s a really significant boost for me, i even dare to say again i get 30-40% more, specially in the most demanding situation i put my phone when road tripping:
* Mobile Data always on with ebuddy connected
* GPS Tracking the whole time with ‘My Tracks’ (awesome apk!)
* Music playing volume at 90% the whole time too
* Some random guy toying with my phone while i’m driving
After 2 hours of this the battery drops from 100% to 88-75%, while the usual was a bit bellow 60% (same battery)
I love the fact that when on light use, after some days i think “when was the last time i charged my evo?”.
My only regreet now is all the money i spent on travel and emergency chargers, now i don’t need them at all haha.
So, if the battery ever dies i think it was totally worth it, it was so cheap (UNLESS THE PHONE BLOWS UP TOO, THEN I’LL CRY HAHA).
Oh !
Also the charging takes more time, with SBC kernel it takes twice the time to charge: after it reachs 100%, it continues to charge until the battery reaches solid 4.2V so my guess is that the battery wasn’t being fully charged with ‘normal’ kernel.
Again… sorry for long post… lots of freetime nowadays =3
sbc made my battery about as useful as… well lets just say it reboots every 20 minutes whether i am using it or not, even in recovery mode.
Oh i don’t want to flood the topic but i just did some research based on awesome link Knarf posted (im SO gonna use it with my lazy friends from now on haha).
So for lithium-ion batterys tricke charge IS harmfull because:
* Battery is charged with a small current very close to it’s self-discharging rate.
(Quote: “lithium-ion is unable to absorb overcharge. A continuous trickle charge above 4.05V/cell would causes plating of metallic lithium that could lead to instabilities and compromise safety”
So, in my opinion this kernel is potentially dangerous IF you leave the phone connected too much time after the battery has reached full capacity.
This is how mine behaves:
1) It will charge the battery at normal rates. +500-600mAh when it reaches “fake 100%” (around 4.100v) and +300mAh when VERY close to 4.2v)
2) When it reaches 4.2v (100%) it will begin trickle charging (+10-20mAh)
So if at this point you disconnect the phone it would mean it’s safer right? I will try to do that now xD.
Still… Awesome battery life !
So, the SBC kernel does behave normally until it reaches 100%, that’s when -i think- we should disconnect the phone:
http://batteryuniversity.com/index.php/learn/article/charging_lithium_ion_batteries
Long post, lots of free time ! (im sorry again *bows*)
I think that has more to do with your rom/kernel combination than SBC in and of itself.
So basically, if you trickle charge and your just paid off home gets burnt down, don’t go suing HTC.
Yeah that’s why i use the word ‘choose’ in my previous posts.
1st of all, us ppl who CHOOSE to root our phones are all aware that we are losing the guaranty of the device.
Then, if we choose to modify the device’s kernel through other’s ppl work, its our decition.
If the hardware fails it’s all my fault, not htc’s.
Sony, Nintendo and Microsoft say modifying their consoles is potentially dangerous and may cause malfunction that could lead to hazardous results and yet there isn’t a storm of people whining at Users who choose to use such modifications.
I personally hate that developers are so great that they have managed to make the gain-root process so easy, so easy that lots (of course not all) of people are like:
1) connect phone to pc
2) run program, click “begin process”
3) you are root !
4) begin flashing stuff
4) If Doesn’t work as expected, go QQ at the forums and treat developers like trash
I do miss the times when this stuff was difficult so there were no n00bs involved.
PS Excuse my english, not my native language, also this is my last post in this thread, dont’ want to flood this awesome site.
I just wish that they had put in a larger battery. I don’t really care if it gets thinner at the edges. I think the thicker edges would be worth the extra power.
(No, I don’t want some janky, pop-out extended battery!)
Is it really all that bad?
http://www.apple.com/batteries/
Well, y’know, I spent 4 years working with people who make a living in the battery business; they’ve been rebuilding battery packs almost as long as my girlfriend’s been alive.
And they don’t rebuild LiIon rechargeable packs at *all*.
And the reason why is that inside each such rechargeable pack is a little chip called a “charge controller”. It cuts off drain to the battery when the pack reaches its minimum safe voltage, limits current draw, and makes sure that the cells are never charged too fast, or too high — a LiIon battery charger has *no smarts in it at all*: it’s a power source.
The charge controller in the pack does it all.
So anyone who tells you that there are any smarts in an Evo to protect the battery pack *who cannot show you technical documentation to back it up* (schematics, chip data sheets, and the like) almost certainly doesn’t have the first clue what they’re talking about.
And certainly it should be safe to trickle charge the battery pack.
Forgive me, the money shot there is “and that charge controller chip is custom to each set of cells”; this is clearly the important part.
My apologies for leaving it out.
Couldn’t you just turn youre phone off when you charge?
Turn….off….phone?! What is this thing of which you speak?!?