Hi Noetimes
It is a known FACT that a standard vehicle alternator cannot fully charge a battery (either a starter or leisure)
For starter batteries its never a problem, a starter battery does 2 things only, one is to start the vehicle (high amperage for very short time) the other is act as a smoothing capacitor for the alternators output.
The starter battery is discharged by a tiny fraction, lets say that the cranking Amps are 300 for 2 seconds, thats a total depletion of .25 Ah, this is soon bought back to original charge (note I do not say fully charged) The rest of the time the alternator supplies the power.
Here is a test I did a few years ago
from fully charged at 12.93v (measured 12 hours after coming off the Sterling charger) connected bulb, it took 6 hours and 17 mins to reach 12.2v (ie flicking over backwards and forwards from 12.3v)
It was then fully recharged on the Sterling, allowed 13 hours to settle the voltage, reading was 12.94v flash 12.93v, the engine on the iveco was started, then I connected the battery using a good solid cable as before and drove this morning for 1 hour 14 mins, as soon as I got back it was connected to the same bulb (55w halogen) connected at 12 : 12 today, it started flashing between 12.3 and 12.2 at 5 : 37 PM today
Same battery, same full charge by Sterling, only difference 1 hour 14 mins of extra "charging" as knocked off 52 mins off usable power !!
Standard batteries vs deep cycle leisure, I tend to agree with you here, most leisure batteries are more hype than content, a proper deep cycle will weigh far more than a standard battery.
Why spend what amounts to a few dollar$ more for a 4 stage deltran?
Charged via alternator the battery gets to 65 % you should not discharge below 50% so out of a 100 Ah battery you got 15 Amps useable (unless you want to fubar the battery in a couple of years max) but consider that 15 amps is 60 Times more than the starter battery ever gets drained when starting the car, thats why the starter lasts it never really gets discharged (unless you leave lights on or have trouble starting)
Anyway back to the deltran (or any 3-4 stage charger) this will charge your battery to 100% so then you have 50 Ah available or 3.33 times more power available.
Hi Bruce
ah I see where you are getting confused now,
If you drive for hours, the voltage when you switch the engine off will stay high for up to 12 hours after you stop, next time you drive back measure the battery the next day there will be a big difference. If 12.8 volts is the fully charged voltage (after 12 hours rest) then after a good run back I will guess that you voltage will be 12.5v ish
Hi Powder
Some of your questions have been answered above.
What a battery will hold is usually written on the side as AH so a starter that says 100 Ah and so called leisure @ 100 Ah hold the same, the leisure should weigh more but rarely does.
Is there a regulator you asked, yes in UK we have Sterling Smart regulator amongst others, this turns an alternator into a 4 stage charger, here is a UK site to the Advanced regulator that I use
http://www.sterling-power.com/htm/ar12vd.htm
Standard alternators are not designed to be good battery chargers; they are designed only to charge an engine start battery sufficiently to start the engine. Because of this inherent design problem associated with the standard regulator, a more advanced regulator is required which in effect converts the alternators from a constant voltage power supply to the latest 4-step constant current battery charger (see battery charger graphs). Because of this improvement in the alternator control system, these regulators dramatically enhance the alternator's charge rates by between 200-2000% depending on how poor the original system is.
The Sterling System is the only real time control system which is in operation 100% of the time. This real time control ensures the high charge cycle is switched off when the batteries are full (regardless of battery bank size or state) and the high charge will automatically reset itself if after the charge has been completed and the output from the batteries exceeds the output from the alternator. Because this is real time-based, this monitoring and control is in operation all the time the engine is running.
The Sterling Regulator is designed to charge batteries as fast as possible and to their maximum capacity without damage to the batteries or alternators. Therefore, we opt for the constant current charging mode and not pulse charging which would double the charge time.
Gotta work now I think I have covered everything
George