Tips on using power on a boat

Tips on the more efficient use of power on a boat

Mobile Solar Chargers Ltd has specialised in providing portable power for the past 8 years. During this time we have powered a number of  Expeditions/Trips across the Arctic/Antarctic/Atlantic etc and have gleaned some ‘best practice’ when using power off-grid. I hope some of the following tips may be of use and perhaps reduce the number of times you need mains hook-up or to run the engine for recharging.

Redundant 5v System

A separate system for charging all your 5v USB devices (phones/tablets/Bluetooth) rather than your in house 12v batteries can significantly reduce the 12v battery use. For example, a few power banks (10Ah) and a portable 13W/20W (to be effective in cloudy conditions) folding solar panel could keep all your 5v kit charged indefinitely, and give the flexibility of portable power when not in the cabin, i.e. cockpit/roof/away. The other benefit is that power banks can also be charged at home/car and whenever you are running the engine.

Tablet versus Laptop

If it is not work-related (power/software etc) generally a modern Tablet can replace a Laptop. There are significant differences in how they use power. A laptop will generally need 12-19v for a 15Ah + battery to last for around 3 hours, a Tablet needs only 5v for a 5Ah + battery for 8 + hours and does not need the boat electrics for recharging, as above.  If you have cloud synching (Dropbox/iCloud/Google drive etc) you can switch between the more efficient Tablet and the Laptop as you need depending on available power. The other negative for the Laptop is that unless you have a DC (12v) charging lead to charge via boat 12v, you will need an inverter to get 240AC. An inverter will take power from 12v (battery) up to 240v to go back to the 12v your Laptop requires, a significant waste of power in the process. An option is to use a ‘redundant system’ of an Inverter Power Bank which can be recharged from the boat/solar but does not use your boat batteries.

Cold Box versus Fridge

Of all the equipment on a boat, a fridge can be the most power-hungry, either gas or 12v. Air to liquid (milk/beer/wine) cooling is inefficient, liquid to liquid much more efficient, i.e. a bucket of water (even better a cool box with water) will cool liquids much quicker, even if then placed in a fridge once dropped from room temperature.

On a liveaboard, the number of times you need to run the engine/refuel/re-gas can be significantly reduced with a mix of the above and obviously some solar on the roof to go directly into batteries. If feasible a black header tank to pre-heat water a few degrees will also mean less gas for water heating, or even better a thermal solar panel.