Overcharge, overput, which should be changed according to the material of the battery, this seems simple, but to the details, there is experience and knowledge.
Overcharge protection, in our previous single battery protection voltage will be 50~150mV higher than the full battery voltage. But power batteries are different. If you want to extend battery life, your protection voltage is the full battery voltage, or even lower than that. For example, the manganese lithium battery can choose 4.18V~4.2V. Because it is a multi-series number, the life capacity of the whole battery pack is mainly based on the lowest capacity of the battery, the small capacity is always in the high current and high voltage work, so the attenuation is accelerated. And large capacity each time is light charge light release, natural attenuation is much slower. In order to make the battery of small capacity also lightly charge and discharge, so overcharge protection voltage point should not be selected too high. This protection delay can be up to 1S, to prevent the impact of the pulse to protect.
Overdischarge protection is also related to the material of the battery, such as manganese lithium battery generally selected in 2.8V~3.0V. Try to keep it a little higher than the overvoltage of a single cell. Because, in the domestic production of batteries, battery voltage is lower than 3.3V, the discharge characteristics of each battery is completely different, so it is advance protection of the battery, so the life of the battery is a good protection.
The overall point is to try to make each battery work in light charge light down work, must be on the battery life is a help.
Overdischarge protection delay time, it should be changed according to the different load, such as power tools, his starting current is generally above 10C, so it will pull the battery voltage to the overdischarge voltage point in a short time to protect. You can't get the battery to work at this point. That's the thing to notice.