Ya’ know, over the years I’ve always left the battery in the cars hooked up using a battery tender/trickle charger. BUT, on these cars I’m going to disconnect both positive and negative cables, then hook up my trickle charger. If it’s not convenient to do it this way, then remove the battery, hooking it up to your trickle charger/battery tender.

In your case, I would just pull that battery that your replacing, waiting to spring for replacing.

Others here will chime in for sure.

Regards,