Charge safely sealed battery pack

hi everyone, im new to this community and iv been learning a lot of stuff since iv been reading your posts.

im planning to build my e board soon this and i thought about the process of charging the battery pack seems a little bit risky:

im going to use 2 zippy 3s 8000mah in series. i saw a few builds that use the xt90-s loop plug to avoid the spark and get the off switch on the way. so heres my first question, what will happen if ill plug the charger to the charge port while the loop plug is still connected? i think that its not very good idea to discharge and chrage the batteris at the same time but i dont know what the consequences will be. thats why i thought about this scheme:

and now i have a few more questions: will i avoid the spark when turning on ? does the 3 way dpdt/3pdt require a specific switch or every other switch will work?

thanks in advance!

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Usually the loop key is used as a switch as well, like an ignition key. You don’ need the switch to have onboard charging, there’s a few useul diagrams in the “Pretty Diagram” thread:

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the purpose of the switch is to make sure that when you plug the charger , you can be 100% sure that the battery isnt dischargning

Don’t use a switch. Just use an XT90 as a kill switch. If you use a switch it will need to be able to handle high currents for charging/discharging. It will also need to have antispark capabilities otherwise after a couple months the contacts inside will be black and provide poor contact.

Just use the XT90 kill loop as your security.