System on wheels

Been thinking about this a lot lately after seeing a few impressive rack-style builds knocking about online.

On the boat I've gone 24V as well — partly because of what the existing solar charge controllers could handle, and partly because rewiring the whole thing for 48V felt like a winter I didn't want to spend hunched in the bilge. Sometimes the system dictates the voltage rather than the other way round, and that's just reality.

I'm running a Victron Multiplus-II and a couple of Fogstar Drift 200Ah cells at the moment — modest compared to some builds, but she does the job for living aboard through the shoulder seasons.

What I've been mulling over is the idea of building something more modular and portable — essentially a battery stack on a proper frame with the Lynx busbars, fusing, and the MPPT all mounted up neatly behind. Like a self-contained energy cabinet you could wheel into position or even move between vessels.

The heavy cabling is obviously the headache — 150mm² flex is not exactly something you're casually rerouting on a Sunday afternoon.

Has anyone here actually built something along these lines for a boat or a mobile setup? Specifically curious about:

• How you've handled cable management when the whole thing needs to be serviceable
• Whether you've used dynamic ESS in a marine context — seems like it's more of a grid-tied house thing but I could be wrong
• Any UK suppliers worth a mention for the big lugs and busbar gear beyond the usual suspects

Would love to see some photos if anyone's got a tidy build to share.

@ExChippie72 the shepherd's hut I converted runs on 24V and honestly it was the best decision I made from the start. Smaller cable runs matter enormously when you're working in a confined space — even a few centimetres saved adds up when you're routing around curved walls and limited ducting.

One thing worth considering if you're going rack-style: bolt everything to a proper sub-frame before you think about the electrics. I learned that the hard way when my first attempt shifted on an uneven pitch and stressed a busbar connection I hadn't adequately secured.

I used Fogstar Drift cells and a Victron SmartSolar — the integration between the two via VE.Direct is genuinely tidy for a mobile setup. Nothing worse than a nest of adaptors and dongles rattling around when you're on the move.

@ExChippie72 rack builds are brilliant until the boat heels 30° and your carefully torqued busbars decide to audition for abstract sculpture — make sure whatever cells you're using (Fogstar Drift are worth a look for marine use) have a BMS that'll handle the orientation changes and vibration, because a standard JK BMS doesn't care that you're beating into a Force 5 until suddenly it very much does.

@OldSailor 😄 that busbar comment is painfully relatable — I had a terminal work itself loose on my narrowboat after a particularly enthusiastic lock encounter and didn't notice until the BMS threw a fit.

One thing worth flagging for rack builds on any moving platform: torque sealing compound on every connection, not just torque settings. Also seriously consider whether your rack is actually secured to the boat properly, not just sitting there looking pretty. Vibration is sneaky.

On the 24V point — I run Victron kit throughout and the component options at 24V vs 12V are genuinely better. Thinner cable runs, less voltage drop grief. For a narrowboat especially, where cable runs can get long, it makes a real difference.

@ExChippie72 curious whether you've thought about the BMS side of things for a mobile rack build? I'm planning something similar for a garden office and the vibration question keeps nagging at me — even without 30° heeling like @OldSailor mentions, my site isn't exactly smooth ground for a wheeled unit.

Are you running individual cell-level monitoring or just a standard pack BMS? I've been looking at Fogstar Drift cells with a Daly or JK BMS but wondering if the interconnects between cells become the weak point when things get jostled regularly. Anyone had issues with cell-to-cell bus connections working loose over time on a mobile setup?

@HollyGazer BMS for mobile is a different beast entirely. Fixed cabin stuff you can get away with more basic protection but anything on wheels (or water) needs proper comms — I run Victron Lynx Smart BMS on the motorhome and it talks nicely to the Cerbo. Means I can actually see what's happening rather than guessing.

One thing people overlook: vibration kills connections over time. Doesn't matter how good your BMS is if the cell-level sense wires are intermittent. I use ferrite on mine and check everything every few months.

@ExChippie72 the 24V decision makes sense for longer cable runs on a boat anyway — less loss, thinner cable, easier to manage.

@DownsCruiser that's really interesting — what specifically are you looking for in a BMS when it's going to be moving around constantly? I've got a Daly on my boat at the moment and I'm genuinely not sure if I should be worried about vibration affecting it over time.

Also wondering whether a rack-style build would even make sense for a small vessel where every millimetre counts — does anyone here run something like that in a tight space? My tiny house project is tempting me toward a proper rack setup but the boat feels like it needs something more bespoke.

Are there particular BMS units people here rate for mobile/marine applications? I've seen Victron's stuff mentioned a lot but the price jump is significant compared to what I'm currently running.

@RustySkipper good question — from my motorhome experience the vibration tolerance is the big one people overlook. Had a basic BMS on a Fogstar cell build that started throwing spurious low-voltage alarms on rough B-roads, turned out the cell-level sense wire connections were just flexing slightly.

For the narrowboat I'm now looking hard at whether the BMS can handle constant low-level movement too — canal wash, lock turbulence etc. Anyone running a Daly or JK BMS long-term on a boat? Curious whether the JK's internal resistance monitoring gets thrown off by vibration or if it's robust enough for this kind of use.

@AGM_Pro vibration is massive — learnt that the hard way with my garden office setup when I moved it on a trailer. Connections I thought were solid just... weren't.

For mobile BMS I'd also flag cell balancing under load as something to check properly. Static balancing is fine when everything's sitting still but when you're drawing decent amps on the move it's a different story.

I'm running a Daly on my cabin build and it's decent enough for fixed use, but I wouldn't trust it rattling down a B-road personally.