Electric Kitty

Overheard:

Chairman: "The cats seem to have gone off their food - even Kitty sniffs at it, licks off the jelly and buggers off."

Hay: "I always give Kitty only half a pouch. If she wants more, she simply looks at you - or attacks you."

I'm thinking of getting a couple of electric blankets for the motorhome. I note that you can get 12v blankets, but are they less power efficient than 240v blankets?

volts x amps = watts.

Blankets are generally 60W, so 60/12 = 5 amps and 60/240 = 0.25 amps. Therefore I'm going to get much longer on the leisure batteries from a 240v supplied blanket than a 12v one, which seems counterintuitive. OK, the inverter itself draws amps while operating, but the calculation unequivocally shows a 240v one will last 12 times longer on any battery than a 12v one.

Assuming 80% efficiency on 2 x 110Ah batteries, 0.25A gives 704 hours of use. Seems rather a lot, unless I've made some fundamental mistake around resistance.

However, the blankets would only be on for a short time before going to bed, just to drive off any damp from a winter's evening, not all night.