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HTC kernel #15 v7 enables trickle charging of EVO 4G battery [Updated]


Soon after the HTC EVO 4G was released in June 2010, we learned that the reason the battery level takes a significant dive soon after being unplugged from its charger (especially after being charged overnight) is that it doesn't trickle charge. So once the battery shows a 100% full charge, the charger turns off and your EVO drains while being plugged in. A popular workaround, usually after a one-time only calibration, has been to unplug the EVO after it's been sitting at 100% for a while, plug it back in until it reaches 100% again, and then immediately unplug it. While this method isn't difficult to do, it's inconvenient and something that we shouldn't have to deal with at all.

And you don't have to if your EVO is rooted.

One of the many benefits of rooting is the ability to flash a new kernel. And wouldn't you know it, ms79723's HTC kernel #15 v7 (based on netarchy's 4.2.1 kernel) prevents your charger from turning off, enables trickle charging via AC and USB power, and is available for flashing (tutorial here) right now. It allows standard and extended capacity batteries to be charged to their maximum capacities without damage, and there are separate versions for use with either Sense or AOSP ROMs. See important update below.

I've been using the latest version of the Sense kernel on SteelROM RevI.2 for about a week now and am consistently able to unplug my EVO and keep the charge at 100% for several hours of idling, which is something I could never do before. Last night, I unplugged it before I went to bed, leaving 3G and WiFi on like I always do, and when I woke up 8 hours later, the battery was at 99%!

Find the version of this amazing kernel for your ROM type (Sense or AOSP) at the link below.

[xda-developers] Thanks, raul & Mitchell!

Update: As several commenters have pointed out below, there is a good deal of controversy surrounding trickle charging. Some have had great success with it (like me), while others wouldn't touch this kind of kernel with a 10-foot-pole due to reports of smoking and damaged batteries. The topic is even more polarizing than task killers! One of G&E's guest contributors will be posting a pros and cons piece on the matter of trickle charging soon. In the meantime, please refer to the links in the comments to read about the potential dangers of using this and similar kernels.

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Jenn K. Lee

Jenn K. Lee is the founder of Pocketables. She loves gadgets the way most women love shoes and purses. The pieces in her tech wardrobe that go with everything are currently the Samsung Galaxy Note II, Sony Tablet P, and Nexus 7, but there are still a couple of vintage UMPCs/MIDs in the back of her closet.

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39 thoughts on “HTC kernel #15 v7 enables trickle charging of EVO 4G battery [Updated]

  • If you are referring to a SBC trickle charge kernel, you need to give full disclosure on the controversy surrounding them. These kernels certainly improve battery life in the short term, but there are huge questions about the long term negative impact on the life of the batteries. There are several people reporting that SBC kernels fried batteries and I happen to have been one of them. There is even one person whose battery started smoking. It would be very irresponsible for you to not mention these supposed risks as you endorse these kernels.

    I am no electrician, but the recommendation from most of the more educated resources in Evo forums is to stay away from these kernels, at least for now.

  • Try myn’s rls5 rom and the 4.2 more havs sbc kernel v7. It works perfect.The few who have had problems overclocked or underclocked. just use it with juice defender.

  • I agree that the trickle charge method has enough ambiguity around it that a little (maybe a lot) of caution is in order. Lots of people have had great success, some others (like me) got the same or worse battery life, and then there’s a handful of people with smoking batteries as a result (I don’t know if it has been definitively proven the SBC mod was at fault…)

    From my own experience, I tried out several different versions of the SBC mod over about a week or so and I found that while it did *greatly* improve the life of the battery from 100% down to about 90%, the remaining battery fizzled away really quickly. So the overall battery life was about the same or maybe even a little less. So I’ve gone back to non-SBC mod kernels so I can have an even and predictable drain on the battery.

  • typical of G&E to be a day late and also a nickel short. Half reports/news too, since it doesnt update the user on dangers/concerns. Should report on both sides & warn of potential issues, instead of just heaping its praise.

  • Avatar of Skylar

    Poor form G&E!

    The uneducated are going to take your recommendation, install the kernel, and (possibly) ruin their battery.

    You need to disclose the controversy and provide links so people can read up on it / decide which argument they agree with.

    Personally, I’m on board with “trickle charging is bad”… I cannot think of any reason a manufacturer would disable trickle charging unless they believed it to be bad for the equipment.

  • Avatar of Master Rooter

    I love this kernel and think it works great. Is it so bad that a battery will “go bad” after awhile (hello, apple)? Isn’t that the one of two main reason you want replaceable batteries (apple?)?

    Count me IN for using this kernel because I can go out and pay $20 for a new battery in a year and a half when (read: if) the battery goes bad either from natural cause or this kernel.

  • That’s kind of what I was thinking too. You can pick up a replacement HTC battery for $20 on Amazon, and most EVO drivers already have a couple lying around.

  • Couple of arguments for NOT building in trickle charging:

    – Out of million Evo batteries, it takes just one catching on fire to cause millions in losses (tarnished reputation, replacement costs, litigation, etc.)

    – LiPo batteries that are trickle charged to 100% or beyond daily will have its life shortened from typical half life of 3~5 years to 1. Lots of Evo customers will be filing warranty replacement.

    There are people who are using SBC kernels and seeing improved battery life (however many seem to be anecdotal and even placebo), however, it’s a no-brainer business AND engineering decision for a corporation.

    Personally, I don’t use it. No need.

  • I’ve seen significant improvement of my battery life by using Collin_ph Battery Tweak 1 that was offered by Myn’s when I flashed his/her’s rom. I had my BF take his Evo to work after he come home complaining that the charge would only last about an hour or two and behold, he got through the whole day without having to charge his battery. This is after listening to music at work for 8 hours also. I HIGHLY recommend this tweak for ROOTED PHONES as I and everyone else I’ve recommended loves their Evo now and have no complaints…

  • Anyone remember Dell..


    I have owned both and many others and none have burned up on me… So much for research and best interest to the consumers from the manufacturers..

    These Kernels came out at the same time people were buying Ebay batteries for $7. I have been using this for as long as MS started and have not experienced a single problem.

    I charge with good chargers, not the $8 walmart or ebay ones. Maybe that is the difference? I don’t know. But I do know I get awesome battery life with these kernels and will state for the record, you could die when you walk down the street..

    You take a chance with everything you do when you go outside of the manufacturers guidelines, rooting, kerneling, software and recovery changes.

    Hell, looking at above with Dell and Toshiba, people stayed within the guidelines and things still burned up.

  • After the charger port on my original Evo went bad I stopped charging the phone that way. I just use a standalone battery charger and have no problems with immediate drop or anything like that. And i got it for cheap on Ebay. Most people are skeptical of buying cheap batteries and such from ebay and that understandable, but I feel like, for $10 for 2 batteries and a charger, its worth a shot. I’ll admit, the ebay batteries don’t hold a charge as good as the stock one, but the charger works just fine.

  • Does that tweak work with RLS5? Or did you have to install a different kernel? Thanks.

  • There is a reason trickle charging is out the window.
    It’s dangerous and unnecessary. Just plug and unplug the phone for a few minutes in the morning and you are back at 100 from 93-95%. If you drop to 80% overnight, you have a problem with running processes.

    And, I got two extra 1800 mAh batteries for 23 bucks. This isn’t an issue. Not one worth explodifying your phone over.

  • Avatar of Nathan

    Morning routine:
    1. Unplug phone
    2. Turn phone on
    3. Plug phone in
    4. Get ready for my day

    By the time I am ready to leave the phone is 100%. I go all day with moderate to heavy usage and still have over 20% at the end of the day (7am – 11pm).

    ROM: Calkulin’s EViO 2 ROM v1.7.7 (Undervolt 50mV)
    Kernel: ziggy471@buildbox #011011

  • Avatar of Waydaddy

    Morning routine:
    1. Plug in phone, Because its been on the nightstand all night. Unplugged.
    2. Go to work with died battery.

  • Avatar of R32Tony

    Don’t do it. I read on xda that SBC kernels kills batteries.

  • Isn’t the EVO one of the few devices that DON’T trickle charge? Most other phones and gadgets do, AFAIK, even the iPhone does, so I don’t think it’s as bad as some people make it out to be. Just my opinion.

  • Avatar of Drew DeNardo

    I’m sorry, you lost me at the mention of 8 hours of sleep. I could get 8 hours of sleep, too — if I added 3 hours to the day …

  • The facts are a hard thing to knee jerk about, like the shooter last weekend.. everyone up in arms without knowing the details.. typical PC BS.

    Toast implied that the Savage kernel using SBC was the culprit according to the developer of all the incidents. NOT sbc on it’s own.

    People are disgusting creatures… We just witnessed the salem witch hunt all over again. Pathetic.

    Originally Posted by jsseidel1 View Post

    he (TOAST)stated that apparently all of the fried battery posts people have targeted savage as the kernel… which is funny because all other kernels out there that had SBC… were using the exact same mod as us.. anyway its a mute point.

    I’ll talk with the guys tonight and we’ll let you all know… another thing toast said was “users come to xda trusting the devs and what they are doing to not brick break or burn there phone”(no verbatim) This is true… i just personally cant see the harm… i mean maybe it wears at your battery, but over heat it or over charge it no way.. i see clear evidence on my battery monitor that when it hit 100% there is no more positive mA therefore not charging. My temp is actually lower since SBC came about… so its not even warm…

    I dunno. but the point is dead, we’ll let you guys know later.

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  • Every pundit came out with their own.. “Look at me” post and blamed everything and everyone without researching the facts.

    It was a sad day at XDA and I am not so sure I look at the community the same. Weak knee Nancy girls.

    And you call yourselves Developers.. Pfft!

  • Myn’s rls5 rom plus the netarchy kernel = ridiculous battery life on 3g. The meter stays flat unless you are actively using the phone. 4G still eats the battery like crazy (and continues to do so until a reset, even if turned off).

  • I just installed RLS5 as myn’s didn’t report any conflicts with the new update…you should be all good to go

  • Avatar of MildlyDisturbed

    I’m running a Seido Innocell 3500 (whatever the extended one is) and running SBC/trickle charge. Getting an average of an hour shorter charge time and when it hits 100% I have a smother drop to 90%.

    I will update if my battery explodes or even heats up. Netarchy/Sprint Lovers.

    At the moment it’s worth it to me

  • Avatar of MildlyDisturbed

    It’s pretty crazy how many people in and android forums are electrical engineers who say that you have to expect the chips in the batteries to fail and handle it on the phone side…

    I think the thing is it’s a slight risk, like rooting your phone, and if I could have a good battery for a year as opposed to a bleh battery for 3, think I’ll accept the trade off and keep paying attention to the contacts and health of it.

    waiting for my national headline about the phone blowing up in my hands.

  • I am having great battery life with SBC kernals. Electrical Engineers buzz away!

  • Avatar of Brian Williams

    I guess this comment comes from a place of some ignorance.

    How can a lithium ion battery not be designed to trickled charge? I know that almost all rechargable devices trickle charge and they’re lithium ion batteries?

    I guess I don’t get it. Is is possible that these are isolated incidents like the iphone batteries at one time?

  • Avatar of Henry H

    Thank You Jen. I’ve been desperately looking for something like this. It’s working perfectly. Exactly what I needed.

  • Yupperoni.

    As I noted in a comment to a later post, *all* rechargeable LiIon battery packs have charge controller chips in them, specific to the cells in that pack — possibly the *exact* cells, but certainly to the model and rating of the cells, at the very least.

    This whole thing is a tempest in a teapot.

    Note that this has been true for a *long* time, too; 5 years or more at least.


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