"programmed battery charging"

[G2TDI]

Can someone tell me where to read more about this? I tried to search this site an online but mainly finding info on how to charge (at home) the battery, but I presume this is something that regulates (takes load off) the alternator when not needed.

Found the term here:

VW Passat Goes 2456 Km On One Tank

[Piwoslaw]

"Programmed battery charging" in this case means that the alternator's field is disabled by the car's computer when the battery is charged, reducing engine load. The field is powered up when engine braking, or when the battery's voltage drops.
This is becoming common (Škoda, BMW, and many more), not only in "green" models.

It's pretty much an alternator kill switch, which hypermilers/ecomodders have been using for years, only automated so the driver doesn't worry about it.

[G2TDI]

Originally Posted by Piwoslaw

"Programmed battery charging" in this case means that the alternator's field is disabled by the car's computer when the battery is charged, reducing engine load. The field is powered up when engine braking, or when the battery's voltage drops.
This is becoming common (Škoda, BMW, and many more), not only in "green" models.

It's pretty much an alternator kill switch, which hypermilers/ecomodders have been using for years, only automated so the driver doesn't worry about it.

OK that's what I thought exactly now where/how could I find more info on it? In a DIY fashion? Hey now something hit me, why not have an AC clutch like setup?? That'd be nice thereby not even spinning the alternator when not needed, I presume what you explained happens at the "other end" of the alternator meaning it would still spin just not have any "load" right?

[Piwoslaw]

Correct. If your alt has a field wire then putting it on a relay will allow you to manually (de)activate it. On the other hand, if your alternator's field is self-exciting, then it won't be easy. In that case you can either re-do the internal circuits (AXMonster tried, but didn't get it working, iirc), or you can try A/C clutch pulley, which I don't recall anyone actually doing.

There's quite a bit about alternator killing here, but you can start here and then search for more:
Deceleration Alternator

[G2TDI]

I've got one of these alternator (not my thread or pics) from a Suzuki Samurai:
VWVortex.com - Lightweight Alternator installation on fat Wabbit............

Plan on copying that setup since my TDI block has the same attachments and waterpump

[Piwoslaw]

If you install a lower powered alt then it'll take longer to charge your battery once its voltage drops. The load on the engine will be smaller, but it'll stay on for a longer time. Similarly, installing an underpulley on the alternator to reduce its rpms, and therefore load on the engine, also takes longer to charge the battery. Take that into account if you decide to use a clutch pulley of a different/larger diameter.

What would be ideal is an alternator with a power output close to the max safe level that your battery can be charged, that way you'll get the most out of it when engine braking.

BTW:

Originally Posted by G2TDI

VW Passat Goes 2456 Km On One Tank

Groar isn't much worse - he's done 1900km on a single tank in his '97 Megane

[G2TDI]

Originally Posted by Piwoslaw

If you install a lower powered alt then it'll take longer to charge your battery once its voltage drops. The load on the engine will be smaller, but it'll stay on for a longer time. Similarly, installing an underpulley on the alternator to reduce its rpms, and therefore load on the engine, also takes longer to charge the battery. Take that into account if you decide to use a clutch pulley of a different/larger diameter.

What would be ideal is an alternator with a power output close to the max safe level that your battery can be charged, that way you'll get the most out of it when engine braking.

BTW:

Groar isn't much worse - he's done 1900km on a single tank in his '97 Megane

A smaller pulley would increase RPM (not decrease) the alternator would be spinning at and increase the load just as when you put a smaller pulley on the rear of a bicycle / MC, pretty familiar with all that

As for battery I have this one:
Deka ETX14 Power Sports AGM Battery

I am aware that most AC clutches are larger in diameter but here in Calif there's plenty of junked cars with them so I wouldn't be surprised to find a smaller one.

[G2TDI]

Originally Posted by Piwoslaw

BTW:

Groar isn't much worse - he's done 1900km on a single tank in his '97 Megane

My ultimate goal is to get as close to 3L/100km (80MPG) as possible it's been done with a Mk1 Golf (Rabbit) see my thread here for more info on that http://forums.tdiclub.com/showthread.php?t=305898

Also I've used the 3L VW Lupo as inspiration and a MK5 a university did in Germany.

[Piwoslaw]

Originally Posted by G2TDI

A smaller pulley would increase RPM (not decrease) the alternator would be spinning at and increase the load just as when you put a smaller pulley on the rear of a bicycle / MC, pretty familiar with all that

That depends on where they mounted: whether on the drive or on the recieving end of the accessory belt. Anyway, what I had in mind was such a pulley combo that the alternator spins slower.

BTW: I started reading through your TDI Club thread and you mentioned a 5th gear swap. If you are going all out on this project, then maybe swap for a 6 speed gearbox, as dremd did. He appears to be quite pleased with it.

[G2TDI]

Originally Posted by Piwoslaw

That depends on where they mounted: whether on the drive or on the recieving end of the accessory belt.

Yes naturally but we were only talking about the alternator end here as were you:

Originally Posted by Piwoslaw

Similarly, installing an underpulley on the alternator to reduce its rpms, and therefore load on the engine, also takes longer to charge the battery.