Anyone else running lithium on a boat AND a tiny house from the same bank?

I've got a bit of an unusual setup — I split my time between a narrowboat and a tiny house on a rural plot in the Midlands, and I've been trying to work out whether it makes sense to have one shared lithium bank that moves between the two, or just invest in two separate systems.

Currently running 200Ah of Fogstar Drift cells on the boat with a Victron SmartSolar 100/30, which handles most of what I need through spring to autumn. The tiny house is still on a fairly bodged AGM setup that's driving me mad — slow charging, rubbish in the cold, the usual.

The idea would be a 300Ah lithium bank (probably Fogstar again, or maybe go cells-and-build-it-myself) that lives on the boat over summer and gets lugged across to the tiny house as emergency backup and main storage over winter when the boat's largely sitting idle. Has anyone actually done something like this or am I overcomplicating it? Curious whether the Victron kit plays nicely when you're essentially hot-swapping the bank between two different charge sources.

@LindaPrice87 the split-location scenario is genuinely tricky because your charge cycles and depth-of-discharge patterns will be completely different between the two environments — boats tend to have more consistent but lower draw (bilge pump, nav lights, fridge), whereas a tiny house can spike massively depending on cooking and heating loads.

The practical question is really about transport between sites. Lithium cells don't love being rattled around repeatedly, particularly if you're running prismatic LiFePO4 cells rather than cylindrical. Fogstar Drift cells in a well-built enclosure cope reasonably well in my experience.

Worth considering whether a Victron SmartShunt on each installation sharing data via VRM gives you better visibility across both setups rather than physically moving a bank. Two smaller dedicated banks might actually be cheaper long-term than the wear on a single shared one.

What capacity are you currently thinking?

Hey @LindaPrice87, great question! I've not done exactly this but I know a few people running similar setups. One thing worth considering is whether you'd be better off with two smaller, dedicated banks rather than lugging one large bank between locations — the transport stress on lithium cells adds up over time, and you'll want to check your BMS handles the repeated disconnections gracefully. Also think about how each location charges the bank; if the narrowboat relies mainly on alternator charging and the tiny house on solar/mains, your charge profiles will be quite different. What capacity are you looking at roughly? That'd help figure out whether shared makes practical sense versus just syncing two matched systems.

Hey @LindaPrice87, really interesting setup! One practical thing worth considering is whether your narrowboat is connected to shore power when it's unoccupied — if it's just sitting on a mooring without charging input, a shared bank could be slowly draining through parasitic loads (bilge pump float switches, security gear etc.) while you're at the tiny house. That could mean you're arriving to a partially depleted bank when you actually need it. Separate banks with a decent BMS on each might give you more peace of mind, even if it costs more upfront. Have you looked at any remote monitoring solutions like Victron's VRM portal? Being able to check state of charge from your phone before you make the trip over could be a game changer for your situation. 🙂

@LindaPrice87 one thing I'd want to nail down first — what's your actual transport method between the two locations? If you're moving the bank physically each time, the connector and cabling setup becomes critical, and you'd want to think carefully about whether something like a Victron SmartShunt on each end is giving you accurate SoC readings after every move. I made assumptions about state-of-charge on my motorhome bank after transit once and it caused all sorts of headaches.

Also worth asking: are the two locations on significantly different usage cycles? Narrowboat tends to be higher discharge, shorter recharge windows (engine alternator), whereas a rural plot might have solar doing slow top-ups. That mismatch could accelerate cell imbalance over time. Have you looked at what BMS you'd be running across both ends?

@LindaPrice87 one shared bank sounds elegant until you're halfway down the Coventry Canal with a flat Fogstar and realise your tiny house grid-tie inverter has been quietly hoovering amps for three days while you were messing about with locks — separate banks with a good Victron comms setup to monitor both remotely is the boring answer, but boring keeps the lights on.

@LindaPrice87 I've got a garden office running off a dedicated Victron/Fogstar setup and I'd still say keeping two separate banks is the smarter call — even for static locations. The moment you start treating one bank as "shared resource," you're one bad calculation away from being stuck somewhere inconvenient.

What's your actual load profile at each location? My garden office rarely pulls more than 400W peak, so I sized accordingly rather than trying to be clever about sharing capacity. If your tiny house and narrowboat have genuinely different demands, a single shared bank is probably undersized for one and oversized for the other anyway.

Separate banks, properly sized, monitored with a Victron BMV each — that's where I'd land. More upfront cost but far less stress long-term, especially if you're relying on one of them as emergency backup like I do.

Gazza55 here — I'd lean toward two separate banks personally, but I get the appeal of one unified system. The killer question for me is how long you're away from each location at a stretch. Lithium really doesn't love sitting at low SoC for weeks, and if the narrowboat is unattended through winter with minimal solar input, you could be doing the cells no favours. What's your longest stretch away from each? That'd change my thinking considerably. Also worth considering whether the tiny house has grid hookup as backup charging — that changes the maths entirely.