OP if you have EC3/IC3 plugs and JST plugs, solder up an adapter.

The adapter you need is part number: SPMXCA310, but this from amazon will work just as well: https://www.amazon.com/BDHI-2pairs-Female-Adapter-B169-2/dp/B095LX46R5/

Personally, I would buy this: https://www.amazon.com/dp/B06XD8PBXT

and change the banana plug to this: https://www.amazon.com/Spektrum-IC3-Battery-Connector-SPMXCA302/

That way next time you have a weird battery to charge you are covered.