Measure your battery capacity and % rundown

More than a year ago - and now I finally did the mortscript I was talking about in my first post related to battery issues. Please lookup the related thread I started at xda-developers. Since I have no E72 any more but noticed the crappy battery levels back that time, I am interested to see the results. So if anyone cares to measure it, please contact me at xda-developers. Full lit display should draw 150mA (see my previous posts) so with a battery of roughly 900mAh it should be empty in 6 hours - check it out.

Replacement batteries, compatibles + offers

While not really needing it now (I have yet to observe real-life behavior of the battery when I will use the device on a daily base) - it is still good to know the options you have :-)
So checking the various ebay offers, it seems that the following BenQ models share the same battery: C31, S81, E81 and E72 (Kyocera E4000). At time of writing the following ebay shop delivers the best price.

Steer your charging options

[updated 20090105, see below]
I remember that for the HTC Tornado there was a setting to disable USB charging - to allow the battery to continue discharging while connected via USB (useful or not is another topic - see further down). As long as the device is switched on, the USB and Battery drivers of the Windows Mobile operating system have control of the charging functions. When switched off, the "hardwired" functionality of the BootROM code takes over. The following only affects the options while the OS is active.

My search in the extracted modules for registry options has revealed in the usbotg.dll the elements:

• USBChargeEnable
  
• USBForceCharge
• ACCurrent
• USBCurrent
  

They are all not present by default and need to be created (only if necessary) as "DWORD" values in the registry path HKLM\Drivers\BuiltIn\UsbOtg.

As written further down, my (refurbished) device was delivered with a non BenQ charger (a Blackberry with exchangeable plugs) - so I continue to use my old HTC Tornado charger which also connects via miniUSB. The systematic (lengthy) investigation has shown the following logic for the registry variables above:

1. none present: device charges from any source (just like when switched off)
2. Charging via USB connection cannot be disabled without also disabling the HTC AC Adapter (USBForceCharge = 0 disables both), but
   
3. charging via HTC AC Adapter can be disabled, still with USB charging possible (set USBChargeEnable = 1; if you want it the other way round - it will not work, I have tried all options)
   
4. Charging via Blackberry AC Adapter can be configured independently of the USB Charging (and follows an understandable logic), I suspect the same will also apply for the normal BenQ/Kyocera AC Adapter.
   
   • ACCurrent = 0 disables the charge via the (BB) AC-Adapter
   • USBCurrent = 0 disables the charge via the USB cable of the linked PC

I have created a table with all options I tried out but It is not usefull to post it here. If you can confirm my assumptions about the BenQ Charger would be helpful.

Now the question "is it useful to discharge the battery (completely) before charging again"? After consulting many resources around the web I strongly believe "no". When busy with the batterylevel problems of the device I have collected some links - make your own decision, see here: 1, 2, 3

I know that some are keen to get hold of the Flash animated homescreen that is present in the Asian ROMs (and I suspect that most parts can be extracted from an available - yet incomplete - dump) but mind that everything that happens automatically on your device will need the CPU and battery. So I recommend reading this article at wmexperts.com.

[updated 20090105:]
After running down the battery completly, I have discovered that the charging current (get it from HKLM\System\State\Battery "ChargingCurrent" value while charging) is limited to roughly 450mA when connected via USB (also for the HTC Charger) - the USB standards allows a maximum of only 500mA anyhow. When connected to an AC Adapter (that is recognized by the system as such - e.g. my Blackberry AC Adapter) then the current draw is higher - I have seen 650mA when the battery was recovering from "emergency switch off".

The lowest voltage until which the battery is used in the E72 is very low compared to my HTC. The E72 uses the battery down to 3.356 V, while the HTC switches off already at 3.570. This may sound like big difference, but it is not in terms of capacity when you look at the discharge curve for LiIon rechargeable batteries. The battery resources I have seen on the web (see links further up) usually recommend not to use a battery below 3.6V to preserve a good lifetime.

Power Drain

The E72 battery driver functions do not deliver drain and temperature, but the backup battery voltage is reported. The measured drain (amperemeter) is (rough values):

• 60 mA display visible - no keyboard lights
  
• 90 mA lowest Light - with keyboard lights
  
• 110 mA more
• 120 mA normal
• 130 mA high
• 150 mA highest
• BT creates peaks ~ 10 mA on top roughly once per second
• WiFi creates peaks ~60 mA similar rate as above
• power off still drains the battery to charge the backup battery but only a few µA (micro Ampere)

The crappy Battery levels on the BenQ E72

Did you notice that some report a bad battery life for this device? I did as well and there are several reasons possible for that - the most important one imho is the crappy battery level indication on the device (at least on mine - the BT-Fusion branded Version):

If you watch the Battery-Level in Windows, it reaches 100% already with a battery voltage of only 39xx mV - far less than a fully charged battery. Always watch for the green LED to indicate a full charge - this comes at 42xx mV as it should be.

This problem applies as well for the dis-charge: Any battery voltage above 3906 mV is reported as 100%. So you think the battery lasts forever - just to give you a bad surprise below that voltage. The Tornado is way below 80% here...

I still hope that this is due to a crappy battery.dll which may be a special version for the BT-Fusion device. In its intended use, it will eat more power than a normal device as it will scan for WIFI to connect a VOIP call via Internet if possible.

If you want to contribute your observations for a non BT-Fusion device - you can get the Voltage and Charge Percentage from the registry anytime at: HKLM\System\State\ or simply use the well known CeleTask option "Power Status".

If you know of a working(!) Batterymonitor that logs data to a file please tell me. My current idea is to create a MortScript that polls the registry and writes data to a file - yet no time to do that actually.

Edit 20090104:
In the meantime I have seen that the charge-level may not only depend on the batteryvoltage alone - see especially this link. When scanning the extracted files from the ROM dump, I have also found a huge bunch of possible registry entries in the battery.dll module. I will not try to debug their influence, so my only hope is that some other ROM contains a better charge-level calculation.