Re: Voltage stability in old truck

From: James Sweet (jamessweet_at_hotmail.com)
Date: 09/11/04 

Date: Sat, 11 Sep 2004 06:31:39 GMT

"gothika" <Vampyres@nettaxi.com> wrote in message
news:ul05k059fhk74ltns0ehpgb4skirf18hdj@4ax.com...
> On 10 Sep 2004 17:26:40 GMT, Ol' Duffer <DontSend@MeSpam.com> wrote:
>
> >In article <r9f2k0ls3icodo9t6hnulo60g1a7s59vfm@4ax.com>,
> >Vampyres@nettaxi.com says...
> ><snip>
> >> (The main reason the industry switch to 12v systems, 6v batteries just
> >> could not hold up under constant use and the variable charge rates as
> >> well as being limited in the amount of loads from the ever increasing
> >> number of system accessories that were being added to cars.)
> >
> >Actually, the underlying reason is that you need more
> >current to do the same amount of work at low voltage.
> >It was taking like 2 ga. wire for starter motors on
> >some of the larger engines, but at 12V you can do the
> >job with 4 or 6 ga. All the connectors had to be
> >beefier at 6V, corrosion and wire/connector resistance
> >were more problematic.
> >
> >Copper wire being an expensive and [potentially] short
> >supply strategic material, the military bumped most of
> >their systems on up to 24/28 Volts.
> >
> >And we may have not heard the last of it. There has
> >been talk of going to 42 Volts to power the increasing
> >demand of proliferating electronics in automotives.
> >It is unclear how this might be implemented, as this
> >is above what is normally considered "consumer safe"
> >low voltage. Check one of *those* with your tongue!
> >
> >> There was a time when a solid state 6v regulator could be
> >> had, as well as a decent 6v altenator.
> >
> >Check the rebuilders, like Jebco and Triodiode. You can
> >still get 6V regulators, reverse polarity diode packs, etc.
> >
> Yes NOW, but at one time, especially in the late 70's and most of the
> 80's you'd have to go service that specialized in parts restoration
> for antiques. 6v regulators couldn't be had at you're local auto parts
> store.
> and yes you could find a cross at your local farm implement and
> tractor shop, maybe.
> >> BTW if you take a look at the electrical design of virtually any auto
> >> made in the past 30 years you'll see that the function of the
> >> altenator is not to run the entire electrical system of the
> >> engine/car, but to simply charge the battery.
> >
> >Now here you are just dead wrong. Nearly all automotive
> >alternators since the early 70's are equipped with remote
> >sensing so that the alternator will maintain a nearly
> >constant voltage at some point other than the battery.
> >This is done both to reduce the amount of charge/discharge
> >cycling on the battery, thereby improving longevity, and
> >to minimize dimming of lights and similar problems that
> >would be associated with running from a battery in varying
> >states of charge. Turn something on, the alternator picks
> >it up right away. The only times significant current is
> >drawn from the battery is for starting, or at idle if you
> >have so much stuff turned on that the alternator won't
> >carry it all. Watch your ammeter if you don't believe me
> >(if you have one - ammeters are becoming extinct as modern
> >electronically regulated alternators do such a good job
> >you don't have to worry about it). The battery still acts
> >as a huge water dielectric capacitor to smooth alternator
> >ripple, but this is AC which has no net effect on charge
> >and is not hard on the battery.
> Well.. if I'm so wrong try and jump off any auto with a computer/solid
> state ignition and see what happens.
> You HAVE to leave the jumpers on long enough to get a base charge on
> the battery. i.e. you can't just jump it off and disconnect the
> jumpers and have the motor run. The car being jumped IS running off
> the battery of the other car, period.
> In autos going back as late as the 70's the regulator acted as the
> trap isolating the charging circuit from the secondary electrics, in
> later models with computers they took over this function.
> As for load sensing that too is a function of the computer, unless
> you're referring to some of the altenators with internal electronics
> for load balancing and timing. Just talk to any other mechanic about
> these and you'll get the same consensus, total crap.
> I mod alot of electrical systems and when I run across these, mostly
> mitsubishi or nippondenso altenators, I either cross reference them to
> a good marine grade non-electronic alt. with matching solid state
> regulator or modify the exsisting alt. and put in an after market
> brain box to match.
> >
> >There are one-wire alternators made for simpler electrical
> >systems, like tractors, where charging the starting battery
> >is about all it has to do. These are not well-suited for
> >automotive applications, but a lot of backyard mechanics
> >use them in error because they are easy to hook up without
> >having to understand how the electrical system works.
> >Performance varies from fair to poor. Don't even think
> >about using one of these with a high-power sound system,
> >you won't get good results. They are disappearing even
> >from agricultural use as more high-demand electronics
> >make inroads.
> >
> You need to get up to date on your training, virtually all autos now
> run on "isolated charging" electrical systems.
> Don't believe me, rip out the dash board electrics of anything made in
> the past 20-25 years. All low value solid state components that would
> fry in a New York minute if you wired them into the charging circuit.
>
> >> Doubly so with those with computer systems/fuel injection etc....
> >> The regulator and/or the onboard electronics "traps" the charge coming
> >> from the altenator to prevent it use in the system.(this is to prevent
> >> damage to the electronics and engine from using fluctuating voltage.
> >
> >Smoke and mirrors and fuzzy thinking. Nothing in those
> >sentences solid enough even to poke at.
> >
> Nothing fuzzy about it, just standard design in todays auto electrics.
> >> A real no-no when you have an onboard computer, fuel injection and
> >> variable valve controls. They must have smooth, clean constant voltage
> >> to perform properly.)
> >
> >That's a bit misleading. Modern engine systems have
> >built-in filtering and regulation where needed. They
> >are well hardened against anything even a poor charging
> >system is likely to throw at them. They may perform a
> >little *better* with clean power, but it usually takes
> >some kind of major deficiency to bring them down, and
> >most of the time they don't even seem to care.
>
> Dead wrong. I've seen injector manifolds blown clean off when when
> things go horribly wrong.
> You have an computer it runs the injector pump, controls timing and in
> the more sophisticated engine controls valve timing.
> Get any of this out of sync more than a bit and you start blowing
> seals.
> Even more and you'll have alot more flying off.
> I run Bosch Jetronic "J" type on one of my current autos, the standard
> pump pressure is 85psi, however the pump I run can range as high as
> 150psi. You get the valve timing off or have the computer go
> haywire(OR set it up wrong) on this all you'll have left is so much
> scrap metal.
> Seen it happen time after time.
> As for most of the stock oem stuff, you're incorrect they're very
> touchy when it comes to having clean power.
> In fact most of the GM, Ford or Chryslers out today have safety
> interlocks to prevent the engine from running on low batteries.
>
> I Stopped just the other day to help a lady with her 04 model
> Cadillac.
> Her battery went down and someone was trying to help her jump it off.
> Neither new what they were doing.
> I had them leave the jumpers on for about thirty minutes and she
> finally got it to start.(The Caddy wouldn't even start with the jumper
> cables on, the computer locked the system down entirely.)
>

Well this argument is turning into a flame war, however I checked earlier
today on my own car just to make sure I wasn't full of it. The car is
equipped with Bosch LH JetTronic injection which is the only system I'm
fully familiar with. The battery with the car off was sitting at about
12.5v, measured about 12.3v at one of the accessory fuses. Turned the key on
and the voltage sagged slightly to around 11.9 at the fuse. Started up the
car, alternator is an internally regulated Bosch 100A unit, voltage at the
battery jumped up to 13.6v at idle, voltage at the fuse box was just a few
points below that. Rev the engine just slightly and it goes right up to a
rock solid 13.9v, shut off the car and it drops to 12.8v immediately and
then slowly settles a few points lower. The voltage at the fuse box which is
connected directly to the ignition and injection computers, instruments, etc
directly followed the voltage increase with the engine running, it was
higher than the idle voltage of the battery, therefore it's obvious that the
alternator is running things. Yes the battery needs to have a bit of a
charge in order for the engine to start but it's because otherwise the heavy
load of the starter will drop the voltage down too low for the electronics
to function. You can measure this yourself, if you jump a car with a
completely flat battery the voltage will drop down to 6-8v when the starter
cranks, this will cause the computer to not function, something that isn't a
problem on older cars. You've got some valid points but the information
behind them is somewhat lacking and the know it all attitude is far from
helpful.

Come to think of it, I've jumped my other car when the battery was
completely flat by dropping in the good battery from the other car, once
running I was able to disconnect the good battery and put the flat one back
in, engine kept running fine, this is also electronically injected with a
computer. So yes, the alternator will definitly run the car's electrical
system on it's own and it's just basic electrical principal that if
something is drawing power from a battery and something else is pumping
power back into the battery through the very same terminals at the same
time, then the source of energy keeping the battery up is also powering
anything drawing from it.

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