Fridge for a cruiser?
QWe have just bought a small motor cruiser, which has a hole for a small fridge and a gas supply. Reading up on safety, we have decided to use a 12v fridge, but are finding it difficult to decide which type (compressor or absorption). Do any 12v models have control thermostats? The ones we have seen so far seem quite expensive. We only have one battery for starting and lighting and we do not want to use 240v. BRYN GOODALL, via email
ATONY REPLIES: I’m afraid that for you any type of electric fridge is impractical because a modern compressor type will demand at least 200Ah of battery capacity (all calculations estimated). All compressor 12v fridges have thermostats but few absorption or Peltier (solid state) coolers do.
The old Electrolux absorption fridges with gas/12/240 volt operation drew about 8 amps when running on 12v and had no 12v thermostat, so using one of those would imply over 700ah of battery capacity for reliable 24-hour operation.
As this is a diesel boat I would have no great worries about fitting a gas fridge. Otherwise, it might be workable if you only turned it on when the engine was running.
The full answer is to do the power audit and charging calculations (you’ll find them at tb-training.co.uk) and improve the charging system with two independent battery banks, so even if you flatten the domestic battery you could still start the engine for recharging. I think a domestic battery bank of 2 x 110 Ah would run a compressor fridge 24/7 with adequate recharging times.