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Rockbox mail archiveSubject: YACQ (Yet Another Charging Question)YACQ (Yet Another Charging Question)
From: Johan Vromans <jvromans_at_squirrel.nl>
Date: Wed, 17 Sep 2003 19:29:07 +0200 Two observations (for AJBR20): While the recorder is connected to the charger and the battery voltage steadily increases, the charge percentage first takes a dive before it also starts increasing. Also, when I remove the charger when it's at, say, 60% and re-insert it, the charging screen suddenly shows it's fully charged. An attempt to explain this: Internally, rockbox makes use of two tables to map battery voltages to percentages[1]. One for normal operation, and one while charging. The difference is that while charging, the voltage is much higher than its real (not-charging) value. For example, a voltage of 5.2V indicates about 80% charge, but while charging it corresponds to only 10% charge. Likewise, 80% during charge requires 5.8V. So, when the batteries are filled to 80% (5.2V), putting in the charger will cause the battery voltage to increase slowly and steadily. Meanwhile, Rockbox has switched its voltage_to_percent table to the charging variant, and the charge status would suddenly drop to 10% -- but there's a (Rockbox imposed) limit on the amount that the charge status can change (not more than 1% per minute). So what you see when looking closely to the charging screen is that the voltage is rising while the percentage slowly drops. I've seen it dropping as low as 9% before the rising voltage could catch up and it started increasing. Slowly, since there's still the 1% per minute maximum allowed change. This explains that, while the recorder is connected to the charger and the battery voltage steadily increases, the charge percentage first takes a dive before increasing. When I remove the charger when the voltage is, say, 5.7V (60% while charging), and re-insert it, the charging screen suddenly shows it's fully charged because Rockbox first looks at the voltage using the normal mapping table, that says that 5.7V is well exceeding 100% charge) Are these observations and explanations correct? -- Johan [1] see firmware/powermgt.c, table percent_to_volt_decharge (line 79 in my version), and table percent_to_volt_charge (line 121). Received on 2003-09-17 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |