271Ah + 60Ah?

[Aphers]

I'm running a 4S 271Ah bank, built from bare cells and using a 200A JBD BMS. Very happy with it, only thing is, it's a bit smaller than I need. Charging is from solar only, using two MPPTs that top out at about 45A max.
I also have a little Sterling 60Ah drop-in with integral BMS. It's non Bluetooth so a bit of a black box.
What would happen if I hooked it up in parallel with the bigger battery? Should I ensure both are at the same voltage before connecting? Or is it just a really bad idea due to the size difference?

 

[TomC4306]

There's nothing inherently wrong with doing that. Check out these experiments.

 

[TomC4306]

Part 2.

 

[Aphers]

Right I'm going to go ahead with this.
Can somebody double check my plan?
The small battery can only charge at 30A max, so I'm going to install a 30A fuse.
But the whole system can draw up to 200A, so I'm risking that fuse blowing under heavy load. Of course the vast bulk of the current is coming from the bigger 271Ah pack.
Is this going to work, or am I just going to keep blowing that little 30A fuse? I never actually draw the full 200A, but occasionally need around 170A in real life.