Monday, Apr 27, 2009 at 10:22
jd you can buy a dedicated 12v charger, with a little honda motor that just outputs regulated 12v.
What you are suggesting will work, but is hugely inefficient. If you look at it like this. Energy is happy being in one medium, say a 12 v battery. To make it change state, like change to 240v then back to 12v, makes it do work and it doesnt like that so it frets a bit and loses some of that energy fretting. It will do it in the end (change its state) but you'll have less energy at the other end due to the fretting.
Same deal with an engine, petrol to motion, lots of fretting, motion to electricity (via an alternator), more fretting, alternator (AC power) to DC power to charge your battery, a little more fretting.
Every time you ask energy to change its state it loses some, and you can see this as heat (as in an engine), or slipping belts (as in an alternator, and in the end you will have less of it.
For my money if I wanted to use the car to charge the camper batteries, I would throw a lead from the alternator to the camper batteries and run the car directly charging the batteries, or setup the batteries so you can pop them in the car when you take a drive, and hook them up to charge that way.
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