As I replied above, it will not be charging without the engine running and being monitored. The Delta automatically reduces the rate of charge to zero as it approaches 100%.
I'm not sure of the value of fusing each side of the converter. The converter has a variety of built in protections as does the Delta. There is no fuse recommended when I feed it with 40 watts of panels at 10 amps. Why would this be different.
Here are the features of the converter. Note the last item regarding built in protections:
Features:
- 100% full power and stable current output, non-isolated module.
- Waterproof level IP68 and anti-shock protection, Ultra-compact size, lightweight.
- Industry grade DC 12V to DC 48V converter, efficiency up to 95%.
- Die-cast aluminum shell, epoxy potting, cooling by free air convection.
- Protections: Over-current, Over-voltage, Over-temperature, Over-load and Short-circuit, auto-recovery when the device is back to normal operating.
I just have to say that as a disclaimer about proper fusing so you don't burn your car to the ground and blame it on me hehe. Fuses are there to protect the wiring from melting in a dead-short or overcurrent situation.
Back in 1995, I had this 1987 convertible Mustang, where I installed 2 batteries, main one in the front and a gel battery in the rear for some audio amps, and I had only fused the cable-end near the front battery, and a couple years later, the wire grounded-out through the insulation (from the weight of back seat support rail pressing on it when people would sit back there).
So it grounded out one day (friend in the back seat started yelling, 'whoa what's all this smoke coming out of the seat?!'), and the whole 4 AWG wire from under the back seat all the way to the trunk started glowing cherry red, melted all the insulation off, and was trying to start my car on fire (the carpet along the wire was starting to flame up), luckily I remembered I had a Leatherman w/ pliers/cutters on it in the glove box, and was able to quickly go grab it and cut the wire, before the flames got too big, then pat out the flames.
I learned in that particular case, not only did I require the one fuse, but TWO (one on each end), since I had two power sources paralleled, at each end of the car hehe. The fuses protect the wire from dead-shorting, not the just the circuit from device overcurrent.
Fuse protection is used at your own discretion, you will obviously be there to babysit it, since you will disconnect it after use. So it is ultimately up to you