Anyone know how a regulator works?
should it put out a fixed regulated supply to the battery , or is the regulated supply voltage variable, depending on load?.
If i disconnect the output wire on mine it shows approx 30v, if i then plug it back into the charging circuit it gives 18v.

TIA
confused from Leeds

I'd ask on the Yahoo BEC site - though you may not get a reply till Monday am as they are mostly on at work.

think ive read that its fairly constant at any speed, around 14V. just a guess.

someone said the battery is really 13.6 volts, not 12.

dunno about yours though!!!

in your battery you have 6 cells, each gives a supply voltage of aproximately 2.2v, so simple maths tels us that: 6 times 2.2 is: 13.2v

to charge the battery you need slightly over 13.2v, usually from 13.8-14.4v. Remember when driving, your car uses the alternator for electrical power, not the battery (the battery is only supposed to be there to start the engine).

now your alternator spins at a variable speed in proportion to your engine speed, using a principle of electrickery called self inductance the alternator generates a voltage (its the one you may remember many years ago from school physics 'the old pass a wire through a magnetic feild, and create electricity from thin air trick' ). So as your alternator spins faster the output voltage will increase (typicly any where from 10-30v)

so we need some device to 'regulate' the voltage from the alternator to the afore mentioned 13.8-14.4v, so we use a regulator (how they come up with these names is beyond me)

now we know that all the electrical parts on your vehicle are 12v items, but the loads are variable (eg your headlamps use (x) amps, your horn uses (y) amps and your heater will use (z) amps, but you will not necesarrily want all 3 items on at once, ie the more you switch on the greater the load), so the load imposed on the alternator will be typicly varying throughout a journey

because the regulator output voltage is fixed, the current will vary with loads placed upon it ( a good practical demonstration is: go out at night and start your car, then turn on your main beams and heater, you will notice that at tickover the revs drop momentarily, this is the extra cuttent being drawn from your alternator)

this drop in revs shows us a couple of things: 1, a good working system will adapt to varying electrical loads 2, switching on things will draw power from your engine, and consequently you will use more fuel

so to answer you Q's

the voltage should be fixed

yes if you remove your regulator, you will get 30v, but 18v sounds a little high, i'd considder maybe replacing it or at least finding a known good one and plugging it in your system to see the differance

hope this is of some use to you, and not too long

here endeth the lesson

if i'm talking through my hole, please feel free to correct me / ridicule / point / laugh etc etc etc