Task which allows charge until it reaches a given battery percentage?

I would like to use an old Android phone as a testing server. So it has to be connected 24/7 to its wall charger. To not ruin the battery (although I read it will not happen) I was thinking about a task which allows the charge within a given percentage: (40%<X<80%, assuming X is the battery percentage) it has to allow charge only when it reaches 40%, stops at 80% and charges again when it drops down to 40%. Is it even possible? Thank you!

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