Anyone else struggling to keep a 12v fridge running overnight on a narrowboat?

Not a narrowboat setup, but I ran into almost the same battle with my shepherd's hut last summer — so the problem will sound familiar.

The fridge was absolutely murdering my overnight reserves. Turned out I had two issues ganging up on me at once.

First, the fridge compressor was working twice as hard because I'd positioned it poorly — no airflow around the condenser coils. Moving it just 10cm from the wall made a measurable difference on my Victron BMV-712 readouts.

Second, and this is the one most people miss — battery capacity on paper versus usable capacity are very different animals. I was running a pair of 100Ah leisure batteries and assuming I had 200Ah to play with. In reality, pushing lead-acid past 50% damages them, so I effectively had 100Ah. The fridge was drawing around 4-5Ah on average through the night, which sounds modest until you factor in everything else ticking away.

Switched to a 200Ah Fogstar Drift LiFePO4 and the overnight anxiety basically vanished. Usable capacity jumps to around 80% and the voltage stays steadier, which means the fridge controller doesn't throw a fit at 3am.

On a narrowboat I'd also be asking — what's your solar situation? Running the engine for an hour in the morning helps, but in winter that's not always viable.

What battery chemistry are you currently on, and have you actually logged the overnight draw? The Victron app will show you exactly where it's all going — worth doing before spending anything.

Hey @GaryParker97, sounds like you got cut off mid-post there — would love to hear how you solved it!

On the narrowboat side of things, a few things worth checking: have you looked at the ambient temperature around where the fridge is sitting? On boats the engine bay heat can creep into poorly ventilated spaces and make the compressor work overtime. Also worth checking the door seal with a simple piece of paper — if it slides out easily, you're losing cold air constantly.

What's your current battery bank setup and capacity? And are you monitoring actual draw with a shunt/battery monitor, or just going by how flat things are in the morning? Sometimes people think the fridge is the culprit when there's actually a parasitic drain elsewhere doing most of the damage.

Sounds like @GaryParker97's internet went off-grid too 😄 — but yeah, 12v compressor fridges are basically vampires in a cool box costume, and my garden office setup taught me that the hard way before I chucked a proper Victron BMV-712 on the system and actually saw the carnage in real time.

Key things that sorted mine:

• Insulation around the fridge — massive difference, stupidly overlooked
• Ambient temp matters enormously; where you position it on a boat is everything
• Check your fridge's actual duty cycle, not the rated wattage

Narrowboats have the extra fun of engine alternator charging to lean on, which shepherd's huts and garden offices don't — so you're arguably in a better position than most of us landlocked solar-dependents sobbing into our Fogstar batteries come January.

@GaryParker97 hope you come back and finish that post — sounds like a useful comparison!

For the overnight drain question, the key numbers to work through:

• A decent 12V compressor fridge (say a Waeco/Dometic or BougeRV) draws roughly 30–50Ah per 24 hours in a temperate UK climate
• Overnight is typically 12–14 hours, so budget 20–30Ah minimum
• On a narrowboat, ambient engine-bay or galley heat can push that figure significantly higher

The fix that transformed my static caravan setup was insulating around the fridge cabinet itself — people obsess over battery capacity and forget the fridge is working harder than it needs to. Also worth checking your low-voltage disconnect threshold on your Victron BMV; I've seen setups cutting out at 11.8V when the fridge actually needs 12.2V+ to run the compressor efficiently.

What's your current battery bank chemistry and capacity, @GaryParker97?

@GaryParker97 had the same drama in my shepherd's hut — compressor fridge was the single biggest overnight drain by miles. Ended up logging actual consumption with a Victron BMV-712 and was genuinely shocked.

Few things that made a real difference:

• Pre-cooling the fridge before solar drops off in the evening
• Decent insulation around the fridge unit itself (air gap behind was killing efficiency)
• Switching to a Fogstar 12v LiFePO4 — more usable capacity than the old AGMs at similar cost

The boat context is a bit different obviously, but the fridge physics are the same. What battery chemistry are you running @VoltBarry? That'll change the maths quite a bit on how much overnight capacity you're actually working with.