Anyone else struggling to keep a 12v compressor fridge running overnight on a single leisure battery?

Had this exact problem when I first set up my motorhome. Single 110Ah AGM was absolutely hammered by morning — fridge cycling all night just destroys your capacity.

Few things that made a real difference for me:

• Pre-cooling the fridge before you disconnect from hookup. Don't ask it to pull warm air down overnight.
• Ambient temp matters massively. Parked in full sun all day the compressor works twice as hard.
• Insulation around the fridge if it's in a poorly ventilated cabinet — some vans are shocking for this.

Eventually I just accepted one battery wasn't enough and went to a 200Ah Fogstar Drift LiFePO4. Night and day difference. Lithium handles the compressor spikes better and you can actually use most of the capacity without worrying about damaging it like you would with AGM.

If you're not ready to upgrade batteries yet, a small solar panel even 100w through a Victron SmartSolar controller will top you up enough to extend things considerably — especially spring through autumn in the UK.

What fridge are you running? Some of the cheaper compressor units are genuinely inefficient compared to something like an Indel B or Dometic. That could be part of your problem before you even look at the battery side.

@StormyViking — been there with my van conversion, and the thing that finally clicked for me was tracking when the fridge was working hardest.

Turns out, if the fridge is warm when you start your evening (loaded with room-temperature food and drinks), it's doing massive work for the first 3-4 hours before settling into gentle cycling. That initial loading phase was quietly murdering my overnight reserves.

Now I pre-cool everything at home before loading. Combined with swapping to a Fogstar Drift 100Ah LiFePO4, the difference was extraordinary — usable capacity basically doubled overnight, and the fridge's compressor actually runs more efficiently drawing from lithium's flatter voltage curve.

One 100Ah lithium genuinely outperforms two 110Ah AGMs for this exact use case. The science is just in your favour.

Worth noting — a 110Ah AGM isn't actually 110Ah usable. You're realistically looking at 50-55Ah before you risk damaging it (50% DoD rule for AGM). So the maths already don't work before the fridge even kicks in.

Swap to lithium and that same physical size battery gives you ~90Ah usable. Fogstar Drift 100Ah is the go-to for the price point if you're on a budget.

Also — what's the fridge's average draw? Most people quote peak compressor start current but the average over 24hrs is what actually matters for overnight planning. Typically 2-4Ah per hour depending on ambient temp and thermostat setting.

Sort the usable capacity problem first, then worry about solar or split charging.

@GlenDoug is absolutely right about that AGM ceiling, and it catches so many people out.

On my narrowboat I made the mistake of running a single 120Ah AGM through a whole Midlands winter before I understood the numbers properly. Fridge compressors are particularly brutal because they pull a sharp spike on startup — sometimes 3-4× the running current — and if your battery's already depleted, that spike voltage-drops everything.

What transformed my setup was moving to a proper battery monitor (Victron BMV-712) rather than guessing by voltage alone. Voltage under load tells you almost nothing useful. Actual amp-hour counting changed everything.

Second boat now runs two 100Ah Fogstar Drift lithium in parallel — fridge runs three nights comfortably without solar input. The lithium discharge curve stays flatter too, so the compressor starts reliably right down to 20% capacity.

One battery for a compressor fridge is genuinely undersized for overnight use.

@GlenDoug and @RetiredNurse have nailed the AGM issue, so I'll add a different angle.

When I switched my van build from AGM to a Fogstar Drift 100Ah LiFePO4, the usable capacity jump was transformative — but the real revelation was pairing it with a Victron BMV-712 battery monitor.

Suddenly I could see exactly what my Alpicool compressor was actually drawing across a full night's cycle. Turned out the fridge was spiking nearly 8A on startup, then settling around 2.5A average. That data completely changed how I sized my second battery.

The startup spike is what kills AGM banks quietly — repeated high-current draws over months accelerate sulphation before you even notice capacity loss.

If you're committed to a single battery solution, at minimum get a proper monitor on there before throwing money at extra capacity. Know your actual numbers first.