Solar charger current output to batteries in parallel - is there too much current when one battery is full?

Question

I've read from solar charger manual that you can set the charging current. With one battery that I have (a LiFePO4 48V 50Ah Lithium Iron Phosphate Battery), it has Continuous Charge Current of 50A - so I imagine I set my solar charge module to 50A charge output.

Adding a 2nd battery in parallel, I imagine I would want 100A output though - so both can charge at full speed at the same time. However, it seems wrong because if one battery is fully charged and the other is not - the the uncharged battery would get a 100A of charge current it seems. Am I thinking through this wrong?

Can a battery be charged too fast? Why do solar chargers for batteries say they can change the amp output for charging - is it more for in series batteries, or just faster charge speed batteries?

I apologize in advance my electronics understanding. Thank you for the help.

Answer 1

You cannot put 2 batteries in parallel because there will be some difference on how much they are charged and one of them will sink current instead of providing it which will destroy it.

Answer 2

The weakest cell in an array limits the safe charge rate and capacity. It is possible for two battery to be mismatched then the stronger paths takes more load and eventually wears out to be the same as the weaker one. So setting the max current only makes sense if they are new and matched.