Thank you. I’ll update the post.
Charging is done by voltage levels. The max_capacity is used for estimation of the remaining battery power. I wouldn’t use deep discharged batteries too if there is concern of fire. The most laptop batteries (if not all) are disabled by a blown up, non resettable, security fuse when one of the cells is below the minimum voltage level (around 2V-2.5V.) Yes you are right, it might be potentially dangerous changing batteries to out of specification types 
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