The issue with multiple charge controllers, is getting them to recognise when the batteries are charged. As they can finished charging and switch to float mode, then see the other charger's voltage still present on the battery assume it's a fault and disable themselves.
Another issue is limiting the charge current, do you set each charge controller to a fraction of what the batteries needs, then lose power if some cells output less ?
What you really need is either a master/slave capable charge controller, or some sort of bigger device with multiple inputs.
I have no idea as to what is available that is suitable.
To be honest, the extra weight of the big inductors required for MPPT could make it pointless in a solar car, especially with multiple inputs. As the extra weight could cancel the extra power gained.
I'd suggest having a talk with
electrodacusand look at his project.
https://www.eevblog.com/forum/oshw/solar-bms-a-solar-charge-controller-for-lifepo4/It's not 48V though, but I'm sure he can give you some more expert advice.