When dealing with rechargeable batteries, one faces two voltage limits: over-charge limit, over-discharge limit. When it comes to charging, most battery charging ICs out in the market will deal with it and frankly, I haven’t yet ran into a situation where I need to delicately control the voltage limit when the charging should stop. The battery charging ICs has a few variants when it comes to overcharge limits: 4V, 4.1V, 4.2V are some examples that I’ve seen in the datasheets.
However, when it comes to over-discharge protection the limits are set very low: 2.7V or 3V. Even these protections are only supported in not just “battery charging” chips but in “battery management” chips which tend to be much more expensive. However, what if you want to cut off battery power when the battery voltage gets lower than a voltage limit that is higher than the over-discharge cut-off voltage supported by the battery management chips? Continue reading “battery overdischarge protection circuit”