dshepp806

NO SIR,...I've a 911, 3.2 liter from April, 1989. Silver Anniversary Edition (noted in the sig, I hope)

dshepp806

Thanks for the reply, Loren. Back to "marriage requirements",....what relevant battery specs are relative to the 90 amp alt?

Good footnote on revs when driving her after an extended rest period (in my case: ONLY 3 days MAX,....once in a while, she may sit for 4-5 days (weather dependent, sometimes)....

Thanks for your comments.

Doyle

Lorenfb

"what relevant battery specs are relative to the 90 amp alt?"

No 'monster' batteries. Most all standard size batteries are O.K.
More CCAs result in more required (demanded) charging amps,
i.e. the larger batteries have a lower internal series resistance
(impedance).

If the engine hasn't run for a while (week or more) and the battery may
be low, just let the engine idle for a few minutes so the alt won't be
over stressed charging a low battery. This should be the case for all
vehicles.

The images show a 911 3.2 @ 90 amps (left '84-'89), the 2nd shows a 964/993 ('89-'98)
@ 115 amps (right). Left is a Valeo (Paris-Rhone) and the other is a Bosch.
Valeo is a distributor for Paris-Rhone. The Bosch 115 amp has a little fan
on the rear in addition the standard front fan which turns at a different
RPM than the alt shaft. The Bosch alt shaft has a spline slot versus a hex slot
in the Paris-Rhone.

rusnak

Interesting. There was quite a bit of discussion many years ago about how Carrera 3.2s eat alternators. Since I have a need for stereo cables and a large batt clamp, I've been running a smaller battery, but still one with around 1,000 cca. I don't recall the running amps. But I do put the battery on a float charger probably once a month, to avoid stressing the alternator. My last alternator lasted over 100,000 miles. I've not experienced any alternator problems whatsoever in over 190,000 miles of 3.2 911 driving almost every day.

dshepp806

Help me with the relevant (battery) specs as to "monster" batteries...

Or,...your DieHards (specifically, the one used in the 911) carries what specs for CCA's, CA's and charge current (worst condition).

Thanks,

Doyle

dshepp806

Rusnak, I think all this info is good (especially as related to "eating alts"). Looks like we may have the reason why such a destructive appetite.

Without question, I plan to see just what this 911's alternator is outputting under a full load WITH a fully charged battery..can't help myself (now).

As to open circuit voltage/battery charge, would one just use the Bentley table on 270-5, as follows:

Open-circuit voltage State of charge

12.6 volts or more Fully charged
12.4 volts 75% charged
12.2 volts 50% charged
12.0 volts 25% charged
11.7 volts Fully discharged

This is the table I used to watch my old battery over time. Do you guys consider this table adequate/accurate?

Thanks,

Doyle

rusnak

I think it's a good idea to maintain a full charge on the battery that you have now. It's good for both the battery and the alternator. As a rule, I don't let the alternator charge a weak battery, which is why I throw the float charger on there so often. The AC or heater blower, radio, window defrost, etc definitely put enough load already. And I always have the engine blower on, so there is not any room to charge a weak battery, as Loren noted.

dshepp806

Loren,..have you any observations on (added) over-voltage protection for the DME? If one is needed at all........maybe I should say "wanted", instead of "needed".....just very curious on this specific area. Since you work on 'em, I think you may have a take or two on this.

Doyle

dshepp806

I think I may go ahead and invest in a trickle charger, taking the attentive approach that you mentioned Rusnak. Will have to research the archives on the products available.

This "charge requirement" seems to be the dividing line as to alt health,..and, as both you and Loren mention, this can vary (drastically) based upon use, etc.
Trickle makes perfect sense....IF it's an extended time period. It seems like one would have to do lots of investigative work with various charge states and quantifying the charge current demand relative to charge state. I would sometimes see my old battery at 12.2 volts after 3 days of sitting,..of course she would crank fine,..but there was a time when she "held" the charge much longer, and at a higher state of charge.

Doyle

Lorenfb

"have you any observations on (added) over-voltage protection for the DME?"

There's a very simple protection circuit (resistor/zener 27 volts), but this has no effect
as an over-charging alt has damaged many DMEs, i.e. exceeded 27 volts. An OEM
alt regulator (Paris-Rhone) should always be used. I've seen rebuilt Bosch alts using
the same regulator with new brushes (may be good when tested but over-voltage when
hot in the engine) or a cheap junk regulator. An over-voltage protection needs to be within
the DME relay.

Note: A fully charged battery should not demand of the alt more than 5-10 amps
after the engine has run for while. Some 'monster' batteries demand 20-30 amps
continuously from the Paris-Rhone alt charging at 14.7 volts.

dshepp806

Thanks, Loren.

Sounds like the "protection circuit's success" is certainly voltage dependent. Guess it would take a somewhat large zener.....Have you observations on the Valeo reg?

Your comments on the charge current demands are striking! What a HUGE difference in demand!. Surely, this WILL be measurable once I dig into this current demand quantification. I had no idea it would be large of a differential, and should be easily measured.....holy cow: 20-30 amps at fully charged? WTF?

Thanks for the info!

Best!

Doyle

Ed Hughes

Could Porsche have started sliding 964 alts into the last of the '89 3.2's? I'm not sure if they'd even be compatible with the 3.2 fan/shroud, so I'm just asking...

Lorenfb

"Could Porsche have started sliding 964 alts into the last of the '89 3.2's?"

No they didn't. The 964/993 with the updated climate control system,
ABS, air bag, etc., needed the 115 amp alt & not the 911 3.2. The
confusion arises because both the 3.2 and 964 were both produced
in 1989. So some alt listings may only show the later alt thinking that
both engines used it.

whalebird

Good discusion guys. I have wondered if the overvolt protection relay from a Benz could be integrated into a DME relay position. Right off, the OVP relay has round pins, not the spade type. OK, one could fasion an "adapter" if all outputs are compatible. Loren, you have a Benz overvolt relay lying around?
there are red top ones, black top ones, and maybe green. They were superscesions of each other IIRC and compatible with back dating within the benz products. The latest version (red top IIRC) is the latest. For "Benz", I mean all 201, 202, 107, 124, 126, 129, and others share the same part.
The OVP relay is the one with a fuse on top under a clear flip top cover. Some may have actually had 2 fuses.

rusnak

I see a potential upgrade for the markeplace. Hey, I wonder if Pelican Parts would agree to carry it? I'll bet most of the base parts could be purchased at Radio Shack, except for the relay of course.