I'm a little confused about your battery wiring. What you want is two parallel banks of two 12V batteries in series (for 24V); I'm not sure that's what you've got here in the diagram.
Make sure you use sufficiently sized cables for your batteries (triple-aught, I think) in the series connections. I would recommend a battery switch on the positive leads to each bank so that you can disable one for maintenance while still having power from the other one. Also a fuse on the positive leads. You'll have to check the rated amperage of your motors and maximum draw of your batteries to determine the appropriate size fuse. Probably around 200A.
I don't like the 4x AC charger when you're using a parallel/series layout -- I would use a 1x charger and run it to your battery switch. The AC charge controller should also be appropriately sized for your batteries. If you have these four batteries in parallel banks of series batteries setup, then you'll have 490Ah @ 24VDC. Somewhere between 5% and 20% of your batteries' rated amp-hours will both charge in a reasonable amount of time and also prevent overheating. So for your 490Ah, you want a DC output of between 24.5A and 98A @24VDC.
If the charge controller can handle it, you should put your solar panels in series for greater voltage (less loss) between your panels and your charge controller. If the panels are 12V, then in series they'd be 24V. If they are 24V, then in series they'd be 48V. The higher the voltage, the less loss you will have over the same sized wire.
If you have the room and the cash, I would scale up the PV panels and charge controller. 100W isn't going to do much to charge your batteries. I would think about 2x 200W panels and an Outback Flexmax 60
. That charge controller will be robust, provide system status, enable equalization of batteries, and provide plenty of room for future expansion if desired.
The Samlex is a good choice for DC-DC converter. I've been using a SDC-60 on my house and it works great. BTW, the 30A rating is on the output, so 30A x 12V is 360W. That's not a huge amount of power. If you need more than 360W, consider upgrading to the SDC-60
Here's my recommended setup:
BTW, in this configuration, you can actually shut off both battery banks entirely and still power your DC loads from the IOTA, which acts as a DC power source in addition to a charger, while on shore power. However, you would be limited to the 40A output (80A @12VDC -- more than the SDC-60 can put out anyway). That said, it would be best to have batteries connected whenever possible.
One more consideration... if your motors use approximately 100A (2400W), then you'll have just over 2 hours of run time before the batteries are discharged 50%, which is about as far as you want to take them. In an emergency, you could of course get more, but you might damage or shorten the life of your batteries. Putting an automatic cutoff or at least a low-voltage alarm in the system would be a good idea. If you need more run-time than that, consider adding a third bank of 2 batteries or increase the size of these four batteries.