Good and EVOSoftware UpdatesTips & Deals

Kernel included in latest HTC EVO 4G OTA update supports trickle charging

No, I couldn't possibly have another biteEarlier this year, the big hot-button topics were about the potential dangers of trickle charging and what SBC (superior battery charging) kernels could do to your HTC EVO 4G and battery. There was debate on whether it even could be done due to hardware constraints, and pictures of exploded batteries along with first- through third-hand tales of woe.

Some of this consternation was due to one specific ROM and kernel combo overcharging, pushing batteries past the breaking point. Some was due to some extremely cheap batteries that were just ready to die, and some incidents were just random.

But the realm of trickle charging the EVO 4G was left solidly in the hands of the root world, even though most other manufactured phones supported it. Root got the benefits of another hour or two of battery life, while the unrooted world got a phone that reported 100% charge on the charger, then 10 minutes later dropped 10-15% because the battery was not charged.

G&E reader Howard in Central Florida recently wrote in to ask if anyone else had noticed that the kernel included in the latest OTA, htc-kernel@and18-2#1, "turned on" trickle charging. I did some Google searching and found many custom kernels that had been modified to support trickle charging, but found nothing about the stock HTC kernel officially joining the fray.

I unrooted my HTC EVO 4G on Sunday and went back to stock, updated to the current OTA, and ran it overnight using Battery Monitor Widget to keep tabs.

Sure enough, it's trickle charging on my now-stock HTC EVO 4G running a Seido 3500mAh extended battery. Howard's batteries are stock.

It appears when the battery is full that the kernel is still spoon feeding the battery an additional 30-160mAh the entire time it's on the charger, which makes me wonder if this is now considered safe. Is this some plot by HTC to blow up everyone's batteries, or did trickle charging accidentally escape in a test build? Anyone's batteries die or explode after an update recently?

Thanks, Howard! Additional thanks to Jim over at for help in verifying the trickle.

Pocketables does not accept targeted advertising, phony guest posts, paid reviews, etc. Help us keep this way with support on Patreon!
Become a patron at Patreon!

Paul E King

Paul King started with GoodAndEVO in 2011, which merged with Pocketables, and as of 2018 he's evidently the owner. He lives in Nashville, works at a film production company, is married with two kids. Facebook | Twitter | Donate | More posts by Paul | Subscribe to Paul's posts

Avatar of Paul E King

22 thoughts on “Kernel included in latest HTC EVO 4G OTA update supports trickle charging

  • Does this have a significant improvement in battery life?

  • This does not apply to the rooted stock rom, does it?

  • Avatar of nopking

    If it’s got the stock kernel, then yes. Run BMW on it and see

  • Avatar of Libdawg

    Can we download the kernel separate anywhere? I’m running a rooted rom and would like to try this kernel with it.

  • How does BMW confirm if it is being trickle charged?

  • I am figured this was happening but I was told that HTC wouldn’t be caught dead flashing an SBC type of kernel. I noticed that an evo replacement 004 battery lasted much longer than my broken 001.

  • Avatar of Biker1

    The following is a good reading about Li-ion cells.

    I quoted a couple of excerpts from the article, which should be of some interest to the readers:

    “Li-ion cannot absorb overcharge, and when fully charged the charge current must be cut off. A continuous trickle charge would cause plating of metallic lithium, and this could compromise safety. To minimize stress, keep the lithium-ion battery at the 4.20V/cell peak voltage as short a time as possible.”

    “Some lower-cost consumer chargers may use the simplified “charge-and-run” method that charges a lithium-ion battery in one hour or less without going to the Stage 2 saturation charge. “Ready” appears when the battery reaches the voltage threshold at Stage 1. Since the state-of-charge (SoC) at this point is only about 85 percent, the user may complain of short runtime, not knowing that the charger is to blame. Many warranty batteries are being replaced for this reason, and this phenomenon is especially common in the cellular industry.”

  • if capacity is 100% and there’s still a positive charge / it never stops charging and never drops below 100%, you’re trickle charging.

    Just means a trickle of juice is still going into it even though it’s at the peak…

  • Avatar of Biker1

    From the Linked article I’ve attached, it would appear that the stock charger is not going through the Saturation Stage, and the Battery is not reaching Full Charge.
    The ‘Trickle’ Kernel is just enabling the battery to have the saturation step applied to the battery, making up for the Charger’s short comings.
    So the ‘Trickle Charge’ is not Trickling a Fully Charged Battery. If the former is true, than it would appear that this is Not a dangerous condition as it applies to the battery.

    As a side note, the reason why the SE4GT takes so long to charge may be attributed to the device enabling the battery to go thru the Saturation Stage, and not just because the battery is 1800mAh, which some customers attributed the long charging times to. And that would account for the Samsung having pretty good runtimes, considering the specs of the device.

  • I’m not exactly sure what it is doing, I’ve never seen a non-SBC continually apply that much current. Been trying to figure out a way to get a screenshot of the stock rooted 4G, seem to be coming up blanks.

    From 10:58am October 31st till 3pm the battery was at 100% and kept putting in an average of 150mA, at 3am the first negative MA appeared, 5 hours after it reached 100. 1 hour of some + and -, then it kicked right back in and kept trickling a charge of 20-166ma until 5:38am the next day.

  • all I have been able to tell, since my 4G is not hooked up to the network, is taht that initial 8-15% drop is not showing for me…

    However, I have a lower power draw as I don’t have service… not sure how uncommon it is to go half an hour without dropping 1% on wifi.

  • Avatar of biker1

    Making up for the “Device’s” shortcomings, not the Charger’s short comings.
    This is because the charger of a cell phone just supplies the current, and the cellphone’s circuitry determines how the current will charge the battery, in addition to the battery’s internal safeguards.

  • Avatar of biker1

    So after searching for a wifi signal for a half hour, not even a 1% battery voltage drop.
    It’s obvious that the kernel is supplying that ‘saturation charge phase’ to the battery, which the native kernel as it corresponds to the circuitry was not. Or something like that, as I don’t know the technical aspects of the OTA, as it influences the kernel in the devices circuitry as it relates to charging the battery.

    I’m wondering though if the battery indicator is showing a true state of charge, or whether the OTA has made the proper modifications to the indicator?

  • I will test with my wife’s evo tomorrow (charging it on mine, putting the battery in hers) – tad too late for that shenanigans.

    Betting it’s the true state of charge as BMW is showing constant juice intake, and unless they are fooling BMW now… I honestly forgot what I was going to say

  • You know its funny I am running SOS ( (10.31)) and I still see the 6-10% drop, not sure why. My wife on the other hand is running Stock (never been rooted) and she gets a similar drop but is trickle charging for sure. That’s what I sent over to G&E for review when I found it… her immediate drop is about 6% but still way better then 15-20% from no trickle charging overnight.

    I let me phone die completely overnight then charged up again but still see the drop. May try a few other ROMS before I land on one…

  • Download link for the kernel?

  • Avatar of Guitarified

    I second Nick’s emotion…

  • will look later, there as one in kernel manager earlier of stock but it’s not showing now.

  • I know this is a bit late but my stock battery (bought the phone in October 2010) died in Novemeber. I wasn’t aware of an OTA update (must have done it while I was sleeping) or the issues with trickle charging but now that I read this article it makes perfect sense why my battery died. The Sprint tech tried to blame it on ATK and did a factory reset without my permission causing me to have to re-install all of my apps. Plus they had to order the battery causing me to be without a phone for 3 days so needless to say I was not very happy by the time all was said and done. I keep my EVO on the charger for the entire 8 hours that I’m at work so I wonder how long this new battery is going to last if it’s receiving a trickle charge 8 hours a day, 5 days a week plus whatever hours it’s plugged in and fully charged while I’m sleeping at night.


Leave a Reply

Your email address will not be published. Required fields are marked *