Question removable battery lithium

Please help me find a good universal charger/discharger for my BM20 and BP-5L batteries

???

There is no such thing as a GOOD universal charger designed for such batteries.
Universal chargers, unless they have different connections with different internal settings for different batteries, or are programmable, are a compromise. They cannot be anything else.

Good chargers are such as the drone battery chargers discussed earlier, or like the Opus 3100 etc., but YOU need to make or modify the connector adapter to use such things with the battery types you have, as they are obscure and/or obsolete.

There is no point keep asking for something that does not exist.

Is it true or false that long-term storage of Li-Po batteries at a certain voltage brings benefits for self-discharge? what is the best voltage?

I need to find some Li-Po battery charger and discharger to keep my batteries at the proper voltage but I don't know the best option because I don't have the smartphone

Check the charger in post #11. The one I purchased, the plug did not meet US specifications for thickness, thus they fall out of the socket.

I could not get the point across.

actually i charged my Li-Po batteries for 3,85v this voltage is good for long term storage or better i reduce for 3,6 or 3,7v?

I need to find some Li-Po battery charger and discharger to keep my batteries at the proper voltage but I don't know the best option because I don't have the smartphone