[paulgato]

Having discovered that my mpg rises by almost half a mile per gallon for each amp I reduce my electrical consumption by, I just thought of another mod to reduce electrical consumption.

In most cars I have owned, when the headlight main beam comes on the dipped beam goes off. It's only when pulling on the light control stalk that both come on together momentarily - for signalling.

In my present VW Golf Mk4 TDi (PD) estate car, the dipped headlights stay on all the time the headlight switch is on, even when the high beam (HiD) lights are being used. This uses 110w (or nearly ten amps) that I don't think needs to be used at all. It would be a simple matter to fit a relay in line with the dipped headlight bulbs so that when the high beam is on (2x35=70w) the dipped beam goes off.

Admittedly, I more often use dipped beam than main beam, but it's such a simple and cheap mod, and when I do use main beam it will make about 4mpg improvement to f/e.

Whilst in this vein (and right now this is about extending my driving range without an alternator) I have just ordered some low energy bulbs. So I'll be fitting LED's in place of the regular front side lights and tail lights, as well as rear number plate lights. These are all nominally 5w bulbs at an 80% saving in energy so will save me 40w. (There are two pairs of tail light bulbs.) I also ordered a pair of energy saving H7 headlight bulbs (Phillips Eco Vision) which claim a 20% saving on energy, as well as a doubled lifespan. A guy on t'interweb somewhere has tested the current draw of these and sure enough they put out as much or more light than standard bulbs but use 44w as opposed to the standard 55w. So those should save me another 20w, making a total of 60w saved. I also think it's worth changing all the interior bulbs for LED's, but I'll do that another time.

Frankly, this is small potatoes as far as fuel saved per pound spent goes, but there is the added benefit of vastly improved reliability (and therefore safety) of these low energy bulbs over conventional ones. In the context of designing an alternator-free system, I can expect to save about five amps using these new bulbs, and even more by turning off the dipped beams while the main beams are lit, and that should extend my night-time driving range by about 20%.

I'm so glad I did all that current measurement though as I can now improve fuel efficiency by about 3mpg simply by not using the blower. I was in the habit of using it on speed 2 all the time, which I realise now was using a massive 6.8A. There'll be times I have to use it of course but I've been experimenting with not using it and so far it's been fine almost all the time.