FS#8363 - Charger configuration for Sansa e200/c200
Opened by Bertrik Sikken (bertrik) - Sunday, 23 December 2007, 14:43 GMT
Last edited by Michael Sevakis (MikeS) - Sunday, 11 January 2009, 10:20 GMT
This is a proof-of-concept patch that demonstrates fast charging for the sansa e200 and c200. It has only been tested on a sansa e200.
The main thing that this patch does, is to configure the built-in hardware charge controller with sensible defaults for the max. charging current and max. charging voltage (previously it was not configured at all). It causes the battery to be charged with a current of max. 300 mA and voltage of max. 4.00V (in unconfigured state, these values are 50 mA and 3.90V).
The charge current of 300 mA was chosen a bit arbitrarily, corresponding to a charge rate of 0.40C for the sansa e200 (750 mAh battery) and 0.57C for the sansa c200 (530 mAh battery). The max charge voltage was chosen by looking at the battery voltage of my e200 just after a full charge by the original firmware, in my case this was just below 4.00V.
Secondly, this patch changes the ADC channel for reading the battery voltage. Currently, ADC channel "ADC_BVDD" is used, however reading from this channel gives way too high voltages while charging (often 0.5V too high). ADC channel "ADC_RTCSUP" seems to give a much more reliable reading. The measured value from this channel also coincides nearly perfectly which the configured max. charge voltage during the end of the charge, as shown in the attached image.
Finally, this patch adds a line in the "View I/O ports" debug menu to monitor the charger configuration and status. This is non-critical but convenient.
Please use this patch on your own risk. Increasing the charge current and/or the charge voltage may be harmful to your battery (for example reduced number of charge cycles). For technical info on safely charging lithium battery, see for example:
Sunday, 11 January 2009, 10:20 GMT
Reason for closing: Accepted
Additional comments about closing: There's really nothing more that could possibly be done with it at the moment. Works to my satisfaction.