[EVO 4G Android Development] frankpreyes:
Here is another post on the SBC trickle charging kernels. I thought it might be helpful to those interested in whether or not to use / continue to use this method of battery charging. I also previously posted questions I asked an engineer responsible for implementing Lithium Ion Polymer batteries in aerospace applications.

http://xdaforums.com/showpost.php?p=9420778&postcount=98

"I've been quietly watching this thread with a little hope and a lot of concern, but now I just have to speak up:

I'm no Dev, but I do have an extensive background in electronics and I began using Lithium-Ion Polymer (LiPo) batteries when they were a brand new (read: experimental) technology. It's people like me who helped determine what works and what doesn't via trial and error and one of the first things we learned was that error can result in some spectacular balls of fire.

Before you dismiss the possibility offhand, go to YouTube and do a search for lipo fire. Then watch some of the videos. Yeah, most of the fires were deliberately triggered and I've done the same thing myself countless times, but what you need to understand is how easy it is to do. LiPo cells have a volatile nature and they don't tolerate abuse or mistakes.

That said, here's what concerns me about the charging mods you folks are discussing: I see lots of evidence that you aren't even considering consequences in your quest for a fix and I see a very real potential for some smoking piles of debris before long. And for what it's worth, here's why:

Everyone seems so focussed on "percent" of charge that you're ignoring the one thing you should be most concerned with: Battery Voltage. I say that because one of the most "sure fire" ways there is to trigger a LiPo fire is charge a cell past 4.2V.

And the thing which scares me the most is the majority of the evidence that I've both experienced myself and read about in these forums leads me to believe that the algorithm in the kernel which calculates percent of charge is broken.

My own Evo is a classic example: It will continue to run for a considerable amount of time after the battery "gauge" shows 0%. Shutdown apparently occurs at 3.5V (which, for all practical purposes, is completely discharged at the low discharge rates a cell phone draws) yet my phone has shown 0% when the battery voltage has been as much as 3680mV (3.68V) as reported by Spare Parts. Now compare that to this discharge graph which is of an HTC OEM 1500mAh battery discharged at 250mA (thanks to batteryboss.org): At 3.68V there is still at least 440mAh of useable energy left in the battery. That's close to 1/3 of the available energy!

My Evo has also shown 100% charge at anywhere between 4110 - 4191mV (4.11 - 4.19V) and like the 0% end of the scale it's inconsistent. Considering that the entire usable voltage range of a LiPo cell is only ~0.7V the inconsistencies are HUGE!

Now is it really wise to base your kernel mods on something that unreliable? And how wise do you think it is to take out a "piece of code that stops the charger"? All I can say is I hope for your family's sake that you're charging your phone in the fireplace or the middle of an empty garage floor.

The bottom line is you folks are trying to navigate the proverbial minefield and you need to proceed with caution. If you don't completely understand what you're doing you shouldn't proceed at all. So carry on if you must, but please be careful people! There can be serious consequences for getting it wrong.

In closing I suppose I should add that my Evo is box-stock 0003, 2.6.32.15, 3.29.651.5 with the OEM 1500mAh battery. I'll also add that I think HTC's mistake was trying to implement a level of battery management sophistication which is completely unnecessary, although the fact that they've apparently stopped using the tried-and-proven system they once did could be the result of patent rights litigation.

Pete"