Serious bug in BC100 Lithium Ion charger reference firmware

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Just noticed this morning, slipping ammeter probes between the battery and spring to measure charging current to a 1200mah cell raised the charging voltage enough to switch from constant current charging to constant voltage charging. THERE IS NO CURRENT LIMITING IN CONSTANT VOLTAGE CHARGING! After taking the ammeter out, the charge current went from 700ma to 1.6 amps, limited only by the 4.2 volt clamp. Such overcurrents could potentially be triggered by bad contacts or jostling the battery or case.

One fix is to switch back to CC state in chargefunc.c if bulk charge current is exceeded.

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If you have an idea for a patch (or just want to report the bug), you can send an email to avr@atmel.com and open a ticket. Atmel asked Martin and I to make a GCC port of their IAR firmwire. I'll be glad to incorporate a patch for the behavior, but to keep the GCC port compatible with Atmel's published firmware, it'd be nice for Atmel's BC100 engineers to publish what they think is a good fix and I'll follow their lead.

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It sounds to me like this is a hardware problem, rather than a software one. The battery-charger firmware should be looking at a wire coming back from the cell(s), and through which no charging current flows, to see what the battery voltage is.

If one wanted to measure the charging current, do that by tapping into whatever separate line DOES carry the charging current