So I’ve had my spark and batteries for a year and they’ve always simultaneously charged but now only two will and one of them labeled B is the one that always doesn’t charge if two others are on the hub. If B is plugged in with one other one or by its self it will charge. My other batteries do not act like this so I’m really confuesed.
Sometimes battery acts as if it is not charging but if you wait about 20 minutes the lights will come on n the battery will charge as normal. Or it is broke. Keep an eye on it.