Ask PYS: Power

Bill, on Nov 23, 2011 asked:

I can't seem to decide on a 12V or a 24V battery for my bow thruster install. I don't understand why I'd choose one over the other - I know it's the same idea as for a windlass but why choose 24V? I know current draw is half in series and I want to the load on the batteries to be low, but I need two batteries anyway to make 24V. So if I use two batteries for 12V and put them in parallel, I'll get double the capacity. The thrust is the same and some people were saying a 24V motor is smaller but the overall dimensions are the exact same. What should I do?

Hi Bill,

Going with a 24V thruster allows someone to reduce their wiring requirements by half. Power = Current x Voltage. Therefore, if you have more voltage, you need less current to power something. The higher the current, the bigger the wire needed. This means that if you go with 12V you will need to use bigger wires than with 24V. Larger wire is more expensive and could pose installation difficulties, costing you more in labour as well. In your case this is NOT so important since you are installing a battery bank adjacent to the thrusters (which means you only need a short piece of wire). Just make sure your wiring (most likely to be 4/0) can accommodate the enormously large amp draw at 12 volts required to power the thruster.