Bugzilla – Bug 16502
resets to new battery condition after power down
Last modified: 2010-09-28 12:56:18 UTC
Created attachment 6948 [details] a piece of battery data log file FW 9023 and msp430 1333 When the unit has powered off due to being idle while running on the battery. When powered up on AC the battery charge state is reset to 800 as if it is a new battery. This results in attempting to recharge an already charged battery which will result in overcharging and finally reduced battery life. Note the charge state in the attached log file excerpt is set to 800 at each of the charging events (charge state 8) These are occurring at 30 minute intervals because these units are operating on a timer for the AC power.
I think it it plausible that some users might run into this situation quite often. I am bouncing this bug off a few other people. Since you are pushing back, Vahid, is it safe to assume this might not be the easiest bug in the world to fix?
additional behavior as a result of this bug. Because the charge value is reset when ever a unit is rebooted, if a unit is operated on battery until the charge value decrements to say 1750 (7/8 charged played for an hour), then when the the unit is turned on the charge state is reset to 800 (1/3 charge). The user will be expecting another 5 hours or so of play time before getting a "low battery please recharge warning", they will instead only get 2 hours. Also if they play their unit until the battery is almost flat (charge value 20) then turn the unit off if they turn it back on it will reset to a charge value 800 and the user will think they have more play time than what is actually available.
Okay so in summary, we have three issues here: 1) The possibility of overcharging leading to battery damage 2) Incorrect battery level display after unit is rebooted while on battery 3) The fact that the firmware battery algorithm is part of the Logitech-standard three-layers-of-safety for battery charging. If there is a known bug in the battery algorithm in the device firmware, then we are not living up to the established Logitech battery safety standard. This bug needs to be fixed before we can release this firmware to end users.
Reference document WWP-751183
The main reason for this type of bugs related to battery is the fact that once the iMX25 is powered off the MSP430 cannot access the Battery/Charger information. This means either we have to suppose that after power up we are dealing with a new Battery or the original battery. Before Maurice's change in 9009 build we assume that the Battery stays the same. With his changes we reset the charger, which means we assume it is treated like a new battery. I will change the code to assume the battery is the original one. We have to come up with some sort of documentation to facilitate the users swapping of the Battery if necessary.
What has happened in the past vs new battery old battery. If the unit is booted up without battery and then a battery is added it has been treated as a new battery. If the unit is has had a battery and is booted up with a battery it assumes an old battery. To reset to a new battery it was necessary to boot up without battery, then when a battery was added it was treated as an new battery. I hope the fix is as simple as the proposed as this charger setting.