[EVO 4G Android Development] mikeyxda:
I feel like this is something I should have been able to find in the thread search but I can't find an answer. Does the kernel that comes with Deck's ROMs have SBC or not: I mean if you just flash the ROM and don't put any separate kernel in? Having installed a battery monitor that logs voltage and mA, here's what I found:

With Deck's 1.2v and logging battery stats every 5 min, the battery charges up to 4200mV and during the charge up to 4200, I see positive mA due to the charging. Then once it hits 4200mV, I see negative mA which would indicate the battery is draining... but as soon as the voltage hits 4199mV, it charges again (I see positive mA on the current being "used") and brings it back up to 4200mV. That seems like it's SBC: it's not letting the voltage drop below the fully charged 4.2v. Am I right?

I've read that the stock HTC (unrooted) ROM lets the battery drain down to 90% before it charges back up to 100% so at any random time when you remove the phone from the charger, you'd get an instant drop anywhere from 90% to 100%.

Now... with the Savaged Zen kernel which I know is SBC installed over 1.2v, the charging characteristics are a little different: it shows positive mA current (charging) all the time. But the voltage only gets to maybe 4203mV and the current is about 3 mA which would equate to a very slow trickle charge.

So given the battery log, here's what it appears is happening:

Deck's 1.2v kernel: Doesn't trickle charge but as soon as it notices the voltage drop below the full 4.2v after the charge is initially complete, it applies a charge thereby eliminating the potential 10% immediate drop off the charger. This results in frequent cycling of draining/charging/draining/charging about every 20 to 30 minutes but since only the very top of the full-voltage window is being used, you don't ever get a major drop when pulled off the charger.

Savaged Zen kernel: Trickle charges a few mA even after a full charge so that the battery is never being drained. This results in a full 100% charge every time you take the phone off the charger but could cause at least some overcharging which, while it might reduce battery life, has the fortunate side effect of your phone sitting at 100% for up to a few hours before the percentage ever goes down.

Or in short:

HTC stock ROM: keeps charging/discharging between 4.0 and 4.2v (90% and 100%) and wherever it happens to be in that cycle when you take the phone off the charger is where it drops to when you unplug it: could be 100%, could be 90%, could be 94%, etc.

Deck's 1.2v: Keeps charging/discharging between about 4.198 and 4.2v, ensuring that it is always 100% when you unplug the charger because anything over about 4.15v is considered 100%.

Savaged Zen w/1.2v: Keeps trickle charging all the time and the voltage will always be (on my phone) 4.203v (100%).

So... do I have it right?

If so, then the question becomes, is it better to do what Deck's kernel does (cycling between charge/discharge every 20-30 minutes) or what Savaged Zen does (trickle charging at a very low current so no discharge ever occurs). I know this last question will prompt another "not this sh*t again" banner, but inquiry minds want to know. :p The usual (probably ni-cd and not Li-ion though) theory is that anything would have to be better than the continuous 10% discharge/recharge cycle because a battery is only good for so many cycles and even a partial discharge (bumping between 90 and 100% like stock) counts as a partial cycle. So I'd think either Deck's kernel or something like Savaged Zen would be better since it is basically preventing the partial discharges. OK, now flame suit on and I know there are different "camps" on this... just wondering which camp has the lead at 8:35pm eastern on June 5. :D

Mike