Alan McNamara asked:
For some time I have been trying to find an answer to my question; if I charge my mobile devices at home it costs me money (power bills). If I recharge whilst driving, does this cost money?
Well, for a start, it depends if he’s paying for the petrol because basically, that’s what it boils down to. So, when you're driving along, any electrical item you run inside your car, is running off the alternator or the battery, and the battery is recharged using your petrol when you're driving, the alternator uses the petrol when you’re driving. So, when you plug stuff in, there is more drag in a nutshell and your fuel consumption is affected accordingly. However, a mobile phone costs about 50 p to charge over the entire course of the year, so I really wouldn’t worry about it. If he wants to save on his electricity costs, he should probably look at things in his home like his plasma TV perhaps which might be 100 pounds over the course of the year, maybe something like a washer/dryer. The dryer part of a washer/dryer is going to cost many dozens of pounds a year and stuff like that. I think my favourite one is a microwave oven. So, the clock on a microwave oven uses more electricity over the course of his lifetime than cooking food does. So, if you want your microwave oven to cost the least amount of money, don’t use it as a clock. Just turn it on when you want to use it.
You are talking about really trivial amounts of money your mobile phone charger would cost you at the most if left running for a week £0.50 as for charging during driving the most minor variation in driving technique would far exceed in cost the cost incurred in charging. syhprum, Sun, 13th Apr 2014
Yes, taking energy from the electrical system of the car means that the engine has to work harder.
Most countries now have regulations on the minimum efficiency of chargers; these regulations typically require that chargers are at least 85% efficient while active, and consume < 1 Watt when inactive. This basically requires them to shut down when they aren't actively charging.
"(after all, the long-term efficiency of your average motor vehicle is almost precisely 0.00%)."
I believe that you are guys are sarcastically referring to the fact that a car may well end back where it started with an empty tank; even so, the efficiency of a car is not zero in any normal sense at moving around, or charging your phone; it's about 20-30%; the fact that you got to go where you wanted, and were able to talk implies a non zero percentage. wolfekeeper, Mon, 14th Apr 2014
Perhaps you should just fork out the dough for a solar charger. CliffordK, Mon, 14th Apr 2014
Alan McNamara asked the Naked Scientists: If I charge my mobile devices at home it costs me money (power bills). If I recharge whilst driving, does this cost money? Thank you Alan McNamara What do you think? Alan McNamara, Tue, 15th Apr 2014
Can I rephrase the question somewhat - I'm asking not to save money, but just out of curiosity. If I charge an item using the car's battery while the car is running, am I using waste energy? I'm thinking the car's battery probably is capable of outputting more power than the car actually needs (as long as the battery is healthy) - so when I plug into it, I'm not really taking anything from the car. Bored chemist suggests that it will make the engine work harder but I wonder if that's really true. I guess the question really is - does a car battery produce more power than the car needs while the car is running? Alison, Fri, 11th Mar 2016