Replace converter with 24v PS and Solar Controller

That voltage is usually reserved for equalization.

Has the amps but seems complicated, unless you already have the power supply and TS-45. A smart charger might be cheaper. With that high of voltage for the batteries most be Interstates.

OP, could you post a link to the charging instructions for your batteries? That's very interesting if they need 15.3v.

X2 where did it say to charge at 15.3
I have four Sams gc 2 and an industrial equipment/cart charger (Quick charger brand)that will do a 15.2 volt top charge. When I was running on generator only last year I would sometimes let it go to that voltage but usually only 14.8 or so. Generator times were short and water use went up. They bubble too aggressively.

Another upgrade that I did was add a Progressive Dynamics converter that goes to 14.4. That works much better than the 13.6 model. If you go solar with voltage adjustment you may do 14.6 or 14.8 with no problem and some controllers allow equalization.

https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.interstatedealers.com/pdf/201535.pdf&ved=0ahUKEwjRo--M-dzKAhUO7GMKHcLoCUwQFgg9MAQ&usg=AFQjCNFSKnh1sijmuAK1C2lAUAJGoPzLOA&sig2=tPB0q_bArQhiC_3EilPpPg

This is weird. Too bad you didn't know this before buying them.

Oh OK, so they are interstate.

The TS-45 has no DC to DC voltage converting circuitry in it like an MPPT control would. A power supply does not behave like a solar panel.
You can call Morningstar and ask them but I don't think it will work.
I recently replied in your first thread. I think your best bet is to purchase a good, programmable charger or inverter/charger. They do exist. There's no reason to cobble together devices that weren't designed for this purpose as an experiment.

They will reach full charge at a lower voltage it will just take longer. The some what lesser charge rate might actually be better for along life. When in doubt call an Interstate engineer.

I find it odd that the absorption charge is so close to the equalization charge. You will be equalizing at every charge cycle. And you will have to isolate the battery bank from your rig every time you charge.

A longer absorption charge at 14.8V and equalize more often, say once a month depending on how you use them, may be in your future.