Is there a limit to the size of battery I can use with my J35?

There is no limit to the size battery that can be installed alongside your J35.

The more battery capacity you have, the longer it will take to charge.

Battery Capacity	Soft Start	Boost + Bulk-Absorption	Float
≤ 100Ah	6 hours	5 hours	6 hours
150Ah	6 hours	7.5 hours	6 hours
200Ah	6 hours	10 hours	6 hours
250Ah	6 hours	12.5 hours	6 hours
≥ 300Ah	6 hours	15 hours	6 hours