There is no universally right answer, and anyone who gives you one is selling something. What follows is the set of trade-offs that actually decide it.
Where DIY genuinely wins
Cost per kilowatt-hour. Cells, a charge controller and an inverter bought separately will almost always beat a packaged unit on capacity for the money. If your requirement is large — say several kilowatt-hours that never leave the trailer — that gap grows.
Serviceability. When one part of a component system dies, you replace that part. When a sealed station develops a fault you send the whole thing away. For full-timers a long way from a service centre, that matters more than the purchase price.
Fit. A built system goes where you have room: cells under a bed, inverter near the panel, shunt on the negative. A station is a box that has to sit somewhere, and it takes up floor space that is already spoken for in most rigs.
Where the packaged unit wins
Time and risk. The station arrives working. No cable sizing, no fuse selection, no BMS configuration, no wondering whether your crimps will pass an insurance inspection after a fire.
One warranty. If a DIY system misbehaves, the battery vendor, the inverter vendor and the controller vendor each have a theory about whose fault it is. A station has one support number.
Portability. No built-in system will ever run a job site, a tailgate or your home fridge in an outage. If that flexibility is worth anything to you, it belongs on the scale.
The middle option people miss
A modular fixed system is neither DIY nor a portable box. The BLUETTI RV5 is our listing's 5-in-1 hub — it replaces the converter, inverter, transfer switch, solar controller and DC-DC charger with one unit at 5,000W and 120V on a 48V architecture — paired with the stackable B4810 battery, listed at 51.2V and 100Ah, 5,120Wh, with closed-loop CAN communication so the hub manages the pack directly. You get a permanently wired system without designing the balance of system yourself.
Going the other way, if you want a true component build we stock the Victron kits and drop-in lithium such as the B1232, listed at 12.8V and 314Ah with an IP65 enclosure, Bluetooth monitoring and scaling up to four in series or twenty-four in parallel.
How to choose in one line
If the answer to "does this need to be wired in permanently and grow over years?" is yes, build it or use a modular fixed system. If the answer to "do I want power working this weekend, and somewhere other than the rig?" is yes, buy the station. If both are yes, the station first and the fixed system later is a legitimate order — nothing is wasted.
RV Parts Giant is in Upland, California; we are an authorised Victron dealer and our BLUETTI stock ships direct from Bluetti's US warehouse.