Charging 18650 Batteries in Bluetooth Speaker Conversion with TDA7492P Amplifier

Hello !
I am a beginner electronics and I am converting old speakers from home cinema into bluetooth columns, which will be powered by four 18650 batteries connected in a basket. With a basket tip 5.5 / 2.1mm dc jack will be connected to the amplifier TDA7492P. My question is: how do I charge them when they are discharged? Is there a charger with a 5.5 / 2.1mm jack input?
I count on help and understanding
Greetings !

Buy any charger suitable for your "batteries", tips 5.5 / 2.1 cost from 20/50 pennies in electronic is there any problem to replace the tip?

I count on help and UNDERSTANDING.
Thank you for your help

Loading them as it goes without so-called Balancer is on average a good idea, because I assume that all 4 cells are connected in series.
So if you do not want to remove them for charging, each of the cells should have its own protection system against voltage increase above its catalog max - that is, the final charging voltage.
In practice, there are no perfectly the same batteries - despite the fact that the labels have identical and even the same production series. Of these four, one may have a 10% smaller capacity and another, e.g. 15% larger, and you have the risk that those that will charge faster in such a series connection, their voltage will increase beyond the permissible max - which contributes to faster wear of such a battery. In extreme cases, even a big BUM can occur!
Here's some news on the subject:
https://www.elektroda.pl/rtvforum/topic3320005.html#16349997
http://mdiy.pl/bardzo-prosty-balancer-do-ogniw-li-ion/comment-page-1/
https://www.swiatelka.pl/viewtopic.php?t=2757
https://forbot.pl/blog/akumulatory-litowo-polimerowe-li-po-kompendium-cz-2-id417
Or you will look for a charger with 4 independent charging channels, which will treat each cell separately and select the optimal parameters for each - then you will be removing the batteries for charging, or instead of using the jack plug, use a few-balancing pin connector (which will lead out all PLUS and MINUS terminals) of each battery on the outside of the device) and use the internal balancer of the charger - some chargers have this with a connector.