Hello I am looking for assistance in selecting components and creating a parts list for a power system utilising a Fogstar 48V 125A battery. My goal is to step down the 48V DC battery power to both 24V and 12V using the following units:
- 48V to 24V: Victron Orion-Tr 48/24-16A Isolated DC-DC Converter (to power a National Luna Fridge and charge a Grecell T-1000 power station).
- 48V to 12V: Victron Orion-Tr Smart 48/12-30A Isolated DC-DC (to power lights and provide emergency vehicle battery charging).
While I plan to add an inverter in the future, my current focus is solely on the DC-DC step-down setup. I currently have the Fogstar battery and a Mean Well NPB-450-48 charger.
Can anybody advise on the following:
1. Connectors: Between the battery and converters, would you recommend XT90 or blue 48V Anderson plugs?
2. Protection: I assume I will need a battery cut-off switch and MRBF fuses. Could you specify the correct sizes and any other necessary safety components?
3. Wiring: What gauge of wire is required for battery to converters (16mm 6awg) and DC converters to peripherals?
4. Distribution: Would this require adding a Victron distribution box or a SmartShunt now, or should I wait until I expand the system?
I intend to charge the battery via campsite hookups during an upcoming trip to Iceland in April. I would greatly appreciate it if you could help me compile these items into a final purchase list. I want to make the Fogstar initialy a safe basic DC step down bank to eventualy build into a full ssytem with inverter. Any help input verymuch appreciated.
Why connectors at all. Any additional connection or crimp is not only another point of failure but also added resistance. Theres plenty of threads here about loose connections and how hot they got.
If you want them for mobility, yeah ok, but still, as i understood the system will be built into a vehicle, so you wont go around carrying your 48V battery from place to place. You install it once, and then it stays there.
Also keep in mind the connectors cycle rating, as with age and wear, its contact resistance will rise. XT90s for example are rated at 1000 cycles, which might seem a lot, but its only about three years of daily unplugging. Also that number is not guaranteed, dirt and grime most often dont help.
Personally i think a cutoff is optional, i rarely use one. The amount of times that i really need to completely power down something are so infrequent that i can just as easy pull the main fuse.
Fuses are always a good idea, but keep in mind the potentially very high short circuit currents involved with LiFePo. megaOTO and MRBF are generally rated for 2kA, but therres also plenty of threads which discuss the pros and cons of different fuse types.
As for sizes, you know the load, for example 48/24-16 Orion, which means 16A output at 24V, so it will pull a max of 8A at 48V on the input. 8A may be hard to find, but a 10A fuse would be fine.
From there you then need to determine the cable length, and both the fuse rating and the cable length will give you the necessary cable gauge.
Good resources for more info are victrons wiring unlimited book as well as the victron toolkit app which you can use to calculate voltage drop
You can of course use a lynx distributor, but i personally think they are a bit overengineered for small systems. I like to use the iMaxx HMD4-MG1 fuse holder, it offers a spot for a megaOTO main/inverter fuse and four midiOTO for other devices