This is why your battery drops 10-15% in the first 20 minutes.

[xorbe]

@SPL15 - Yes, we are saying the same thing, my wording was misleading, I know that the tail charge is at 4.2v until conditions are met, I sort of generalized a bit too much. My point was that current will not flow forever @ 4.2v, it will stop eventually.

@minsc - my cable failure prevented me from concluding anything. I really want to measure the mA draw on the battery. All I can report is that my battery is 4.2v in the morning, and not drained.

A lithium does NOT stick around 4.2v ("100%") for long under any sort of load ... I think these battery indicator apps and their % numbers are misleading people. The older the battery gets, the stronger this effect is going to appear.

I went to bed with the phone at 40% last night (out of town, no charger), and it was at 25% in the morning.

 

[eagle63]

@xorbe
Ok, gotcha. I'm an RC guy too (planes) and I used to have a decent battery conditioner with a voltimeter on it, but I can't seem to find it right now. I have a Kill-A-watt too, but as you mentioned I don't think that's sensitive enough to conclusively prove anything.

As an update, I am able to re-create this problem consistently. When I unplug the Evo in the morning after an overnight charge, I can literally watch the battery level drop from 100 down to 91 or 92 in about 2 minutes or less. If I recharge and then pull it off the charger once the light turns green, it will stick at 100 for a long time.

One experiment I did try yesterday: in the morning (after an overnight charge) I kept the Evo plugged in, and then fired up Pandora and let that stream music for about an hour. THEN I pulled it off the charger and observed the battery level. I expected it to drop like a rock to around 80% (or worse), but it didn't - it only dropped to around 97%. So maybe during the course of the Pandora playing, it DID cross some magic threshold and start charging up again?

 

[PookiePrancer]

Has anyone considered manufacturing/quality deviations even in "new" batteries? There are SO many factors that affect battery life it's not even funny.

As for the theory behind this thread: I don't buy it. First of all, expecting a phone to stay at 100% after unplugging it is just a tad unrealistic. By design, AS SOON AS you unplug your phone, it is running off the battery. The battery CANNOT remain at 100% when it is being used, it MUST drop from 100% as soon as you unplug it. If your Evo behaves like mine, the lock screen flashes on as soon as you unplug it (wham, you just used the battery), and the radios are working round-the-clock anyway, so they switch to battery power immediately. If you're seeing drops of 10-20% within a half hour of unplugging, I'd look more at what services/apps/widgets you're using, and the strength of your 3G/4G/wi-fi signals (this, more than anything, will SUCK the life out of your battery). Also, I can't stress enough the difference in new battery quality, even OEM, I've experienced; it's unreasonable to expect 100% flawless batteries running off any production line, and you may have gotten a sub-par one.

When charging is complete, the phone (like almost every other phone/laptop/gadget) will run from ac power, and yes, the battery will stop charging. As the topped-off battery begins to lose its charge, it will reach a threshold at which point it will "trickle" charge to stay "topped off." Unlike some laptops, unfortunately, the battery must stay in the device to complete the charging/power circuit.

I get excellent battery life from my Evo (except in low-signal areas which are mercifully few); the only time I didn't was when I had installed Knockout 2. For some reason, that game kept running even after being "killed" and it just pummeled my battery life.

The results I've read from some here are interesting, but I suggest going further (I'll try this as well and hope I don't eat my words):

Charge your Evo to 100%. When it's fully charged, keep it connected to the charger, and start using the cowpies out of it. Movies, 3D games, music streaming.... If this thread's theory is correct, your Evo should eventually go dead even while it's been on its charger (because the charger stopped working once the battery reached 100%, right?)

 

[Jerzyiroc]

It's not the battery. I charge the OEM through an external battery wall charger. 2x 1500mAh battery + dock charger for Sprint HTC Evo 4G - eBay (item 250641711190 end time Jul-29-10 01:08:58 PDT)

Previously I would charge the phone through the supplied HTC charger. When I would unplug it from an overnight charge the battery would quickly drop well over 10% within only a few minutes then sort of level off. I would get about 12 hours or so. Charging the OEM battery through that external battery charger from that link above has drastically changed the battery life. I'm getting close to 20 hours of battery life now with the same usage as before. When I put the battery in after a full charge I can browse the web, tweet, check facebook, engadget, huffington post all for close to 10 minutes before it even drop to 99%. So your theory that it can't stay at 100% is wrong. And your theory that it's gotta be service/apps/widget are also wrong. And just for the record, a tech I spoke to from HTC last night even said he has the same problem and he agrees that it's a trickle charging problem. The problem he said is more than likely software related than hardware related because there would be other symptoms along with a trickle charging issue, but he didn't say exactly what. Further proof of this is a lot of people are reporting better battery life when they root and install custom roms. And it wont go dead, the issue it the charger wont KEEP it at a full charge, but it will keep it at its nominal charge. I used to think it just ran off the battery but after a convo with Darth Mo and further research I'm agreeing with the not keeping it charged as opposed to it running off the battery. Either way you're wrong.

 

[Caitlyn McKenzie]

Why are we at page 11 for this discussion? This is simple established fact.

For those seeing "unusual" results from external battery chargers, you're neglecting the true cause. It's not the charger, its the fact that the battery isn't being used. If you charge your phone to 100% and turn it off, it'll have the exact same effect.

 

[Jerzyiroc]

Why are we at page 11 for this discussion? This is simple established fact.

For those seeing "unusual" results from external battery chargers, you're neglecting the true cause. It's not the charger, its the fact that the battery isn't being used. If you charge your phone to 100% and turn it off, it'll have the exact same effect.

Not understanding your point... Nobody ever said, or at least I didn't, that it was the charger. I'm using an external battery charger because THAT charger is giving the battery a trickle charge as opposed to the phone. And I've tried the turning the phone off theory and while obviously the phone isn't on to discharge any battery after it's charged, the battery still gets a better charge and lasts longer when I charge it thru the wall charger. I"m not seeing "unusual" results from using a battery charger. I'm actually seeing what should be normal results if the phone actually charged properly. Bottom line is the Evo doesn't trickle charge. It doesn't keep a full charge after it's been charged and the phone isn't realizing it either which is why it'll say 100% still even though it's not.

 

[Caitlyn McKenzie]

Incorrect thinking. If it didn't keep it charged, it would eventually die while on the charger. At worst all the evo does is avoid overcharging, something your external charger likely doesn't. Also, this is not called trickle charging. A trickle charge is simply a show charge as the battery is close to fully charged.

 

[Jerzyiroc]

Actually it's very correct thinking. You obviously didn't read what I wrote. It's not letting it keep a FULL charge like every other lithium powered device made. Instead it lets it drop to it's "nominal charge" which is why it doesn't actually die but loses power. And yes it is preventing an overcharge on my charger just like every other lithium charger. There are regulators to prevent overcharging in lithium chargers. Technically it's called a "floating charge". Floating charge actually trickle charges but has regulators to prevent overcharging, hence the name floating. The Evo doesn't keep a full charge.

 

[Caitlyn McKenzie]

Actually it's very correct thinking. You obviously didn't read what I wrote. It's not letting it keep a FULL charge like every other lithium powered device made. Instead it lets it drop to it's "nominal charge" which is why it doesn't actually die but loses power. And yes it is preventing an overcharge on my charger just like every other lithium charger. There are regulators to prevent overcharging in lithium chargers. Technically it's called a "floating charge". Floating charge actually trickle charges but has regulators to prevent overcharging, hence the name floating. The Evo doesn't keep a full charge.

No device keeps a full charge. Go take your laptop, charge it to 100%, unplug it, drain it to 96%, and plug it back in. It won't even charge (especially noticeable on macs).

 

[Jerzyiroc]

Sigh... totally missing my point but w/e i give up.

Btw, just plugged my laptop with 97% battery and it charged to 100%... just saying..

 

[Caitlyn McKenzie]

Sigh... totally missing my point but w/e i give up.

Btw, just plugged my laptop with 97% battery and it charged to 100%... just saying..

Macbooks will actually show you. Others may not, just like the EVO. But you never even noticed it on your laptop

 

[Jerzyiroc]

My laptop has a meter on the bottom right. When i read what you put I checked the level and it was at 97%... I plugged the charger back in and it then charged it to 100%...

And I've NEVER had an issue with my battery on my laptop. The level drops at a normal pace. Not 10-15% within a few minutes then levels out like the Evo. As a matter of fact it's still at 100%....

 

[Caitlyn McKenzie]

I've never had issues with my EVO either. Also, you misunderstood what I said about it reporting the wrong levels.

 

[Predator-1]

Instead of all this speculation, has anyone bothered to contact HTC about how the Evo handles charging? I think the OP has an interesting and almost believable point but until we hear from the actual makers of the device, it's all speculation and theory...

 

[Jerzyiroc]

Lol I'm throwing in the towel dude. We're going in circles here. Bottom line is my Evo isn't doing what my Hero did, and that's hold a full charge. My Hero's battery NEVER dropped the way my Evo does the first 10 or so minutes. Not even close. And I've charged the Hero battery on the wall charger and I've gotten the same exact battery life as I would with it charging with the HTC charger. If your phone isn't doing it. Well good for you. You're lucky. Unfortunately myself and other aren't so lucky.

 

[RayStinkle]

I don't understad why you guys are saying the evo does not trickle charge. When you plug in your phone and charge to 100%, and then leave the phone plugged in and use it for like 45 min, are you saying that the battery will start to drop even while staying plugged in? Cause my nexus does not work like that. Once it hits 100% I keep using it for browsing or games, and it never drops down from 100% even using it for hours while plugged in. The evo does not do this as well?

 

[Jerzyiroc]

Instead of all this speculation, has anyone bothered to contact HTC about how the Evo handles charging? I think the OP has an interesting and almost believable point but until we hear from the actual makers of the device, it's all speculation and theory...

Yes I have. Last night. The tech said he's noticed the SAME problem with HIS personal Evo. He also agreed that it's a trickle charge/floating charge problem where it's not letting it keep a full charge like it's supposed to. He said it's probably a software issue because there would be other issues as well if it wasn't able to trickle charge because of a hardware defect. That makes sense considering the dramatic increased battery life some people are getting when they root and install custom roms... He actually mentioned that the Froyo update would almost definitely fix the problem but that he knows of there is no HTC update for this problem..

 

[Jerzyiroc]

I don't understad why you guys are saying the evo does not trickle charge. When you plug in your phone and charge to 100%, and then leave the phone plugged in and use it for like 45 min, are you saying that the battery will start to drop even while staying plugged in? Cause my nexus does not work like that. Once it hits 100% I keep using it for browsing or games, and it never drops down from 100% even using it for hours while plugged in. The evo does not do this as well?

The problem is it wont show the battery level dropping. But once you unplug it the battery level will drop 10+% within a few minutes. that's not normal. The fact that even though the battery level IS actually dropping even if it's still plugged in but not SHOWING is one of the reasons the tech said it has to be a software issue and not a hardware issue. I can have my Evo plugged in and fart away with it after it's 100%. But once I unplug it it'll drop from 100% to less than 90% within minutes. It's NOT supposed to do that. And the fact that NO other phone, like my Hero for example, does that it's FURTHER proof that there is a bug in the Evo that's not letting HOLD a FULL charge. Vincent is right that a lithium charger wont actually keep it at 100% all the time, it lets it drop a little and go up a little. It's called a floating charge. BUT it's not supposed to let it drop more than a few tenths of a volt. The Evo is dropping way less than that THEN it'll hold that charge. Which is why you dont hear anyone say it dropped to 70 something %. You'll only hear people say it'll drop at worse somewhere in the mid-high 80's because it wont hold a full charge, but it'll hold it at it's nominal range. What that voltage is I don't know but maybe that's the issue. Maybe the bug is the "nominal charge" is set too low. I don't know. I'm not an expert in batteries but I am knowledgeable in how it works. And the fact that a TECH FROM HTC agreed and mirrored EVERYTHING I've been saying only solidifies my point.

 

[Predator-1]

Yes I have. Last night. The tech said he's noticed the SAME problem with HIS personal Evo. He also agreed that it's a trickle charge/floating charge problem where it's not letting it keep a full charge like it's supposed to. He said it's probably a software issue because there would be other issues as well if it wasn't able to trickle charge because of a hardware defect. That makes sense considering the dramatic increased battery life some people are getting when they root and install custom roms... He actually mentioned that the Froyo update would almost definitely fix the problem but that he knows of there is no HTC update for this problem..

Good info... Bring on Froyo!!!

 

[meyerweb#CB]

I don't know if the trickle charge issue is real or not. Either way, though, I think battery life even for the first 15%, has far more to do with what you do with the device than how it's charged.

I spent most of today working in my garage, with the phone sitting in the house. I was out and about, with the phone, for a couple of hours in the morning, the rest of the day it's been connect via WiFi. No calls, a few emails, that's about it.

The phone charged on AC all night, this morning I unplugged it and walked away with it. No turning it off, plugging it back in, or anything else. After 7 hours, I still showed 85% battery. Right now, at 9 hours, I'm at 81%.

I think what you do with the phone has far more impact on the first 10 to 15% drop in battery than how you charge it.