Clay -

All AGM batteries are not created equal. In general, they have higher charge acceptance rates as a class compared to SLI flooded cells - but as an example - an Optima doesn't have anywhere near the charge acceptance rate of a Concorde or Lifeline AGM.... and AFAIK, the Concorde/Lifeline AGMs have the highest rate by far of any AGMs.

Optima claims a charge acceptance rate of 2x flooded cell batteries for the marine blue top - that would be roughly 50% of AH capacity and for the Marine starting battery (1000M) would be .5 x 56AH (C/20 rate) = 28.0A max. charge acceptance rate. The blue top deep cycle (D900M) would be .5 x 65AH (C/20 rate) = 32.5A max charge acceptance rate. The yellow tops would appear to be about the same charge acceptance rate as the blue top deep cycle and the red tops appear to be about the same as the lower-rated blue top starting battery rate.

If all of the manufacturer's data and claims are correct, then the Optima batteries accept a charge at 2x the rate of SLI flooded cells, but Concorde/Lifeline batteries accept a charge 8x greater than Optimas and 16x greater than SLI flooded cells. The primary difference is in the amount of lead in the plates. Optimas are spiral wound and only slightly thicker than standard SLIs, while Concorde/Lifeline plates are solid lead. An Optima weighs 38-42 lbs.... my Concorde weighs about 65 lbs. <img src="/forums/images/graemlins/scared.gif" alt="" />

Frank

You won't get higher output unless something is demanding current to satisfy need. IOW, the ABILITY to produce more output doesn't mean that the higher output is produced unless something calls for it..... it could be that the battery has an internal short - get it checked at a reputable shop.

If your voltage regulator allowed the alternator to pump 16v into the battery, there's a chance the battery is damaged.
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The alternator doesn't stop spinning. When the resistance of the battery or curent draw on the system goes low, the regulator pegs the o/p voltage at some determined max level. If that is exceeded, it implies the regulator is not functioning correctly, not that something has called for more power. If there were a significant unexpected current draw, the voltage would in fact drop.

All the quoted o/p numbers (ability) are reman bench tests. I'm assuming they use the same load, rpm etc... so the comparisons are valid.

You point on the battery is correct though. It could be failing under mechnical (vibration) stress that would never be apparent or indicated by simple cold start peformance and a healthy 12.8V on the multimeter. Thats rare in my experience, but then, so is replacing an alternator 4 times..... It could also be low on fluid having been exposed to >16V.

Point is still that a stock Alt rebuild shouldn't be significantly better than stock. If it was designed or rebuilt to do so, OK. It's possible the rebuild company is doing something legit but odd, like building all 90-xxxA mitsu units to meet xxxA spec, but then why did the most recent unit only show 100A?

Paul

Number one might be a regulator failure, brushed, diode meltdown open stator winding.

two and three sure sound like regulator failures to me.

Two thoughts:

1: If the manufacture did perform a perfornace wind and it just happens that a fresh factory unit puts out a bit more than the name plate, odds are the manf is usning low grade aprts on the rebuilds, especially the regulators.

2: If the units are being wound for more output and they are failing what could cause that?

One reason would still be cheap regulators.

Another would be the current draw on the stator (rotating section that generates the demand variable magnetic field was wound to increase its current (or substituted for a another , has a short etc). That increased current causes the regulators oputput transistors to fail.

It never hurts to check the vehicles wiring. A loose connector at the alternators output wire casues whats know as a field dump. The alternator is putting out say 40 amps and it gets momentarily disconnected, with no load the output voltage tries to shoot up. There are / should be Zener diodes in the output circuit to snub the voltage down and prevent the spike from failing the switching diodes, however the Zeners can only handle so much and over time this can fial them.

Once they fail the main diodes would see the full voltage spike and fail as well. So check your fusable link and all battery / alternator connections on the heavy wire from the alternator.


There are two other connections to the alternator:

Connection #2, Sense wire

Make sure the sense wire to the battery is properly connected and not intermitant. Again if the sense wire opens up the regultor thinks the battery is low and tries to put out its maximum output. A bad connection there would cause charging problems.

Third connection:

Also the switched voltage needs to be working properly. There are several diodes in the dash that connect warning lights to the sense wire. The diodes prevnt a back feed of voltage once the vehicle is running. If one was shorted sure what I'm not sure what would happen. The EGR, brake and charge light all tie into the switched voltage.

Those bulbs provide a small ammount of current to get the alternators field so it starts charging when it first starts spinning.

No connection there or low current causes no output till you first rev the engine and get the alternator to self exite.

Make sure the brake bulb and charge bulb is lit when you turn the key to the run position but before the motor is started.

Or it could just be crappy alternators <img src="/forums/images/graemlins/cyclops.gif" alt="" />

Kevin

I checked the connections - no obvious issues either visually or by multimeter.

As far as the dash lights are concerned, they all work as intended, with the exception of the brake light which recently has been staying on after the handbrake is released and until I've travelled 2-3m. I'm chalking that upto a questionable switch. The remaining dash lights are OK and I'd expect them all to glow if the sense wire was an issue. On top of that, the brake warning light needs to operate whether the engine is running or not.

My wiring diagram shows an "alternator relay" in parallel with the sense line, which I think functions to kick start the unit in the manner you describe. I don't think it draws through the bulbs.

BTW, I just located the spec sheet for the 2nd unit. 110A at6k. At least that one lasted nearly 10k...

Paul

If the regulator is functioning properly, but more current is provided by a replacement rotor/stator - which produces more heat - and if the current demand is higher than the OE design - and if the regulator and rectifier are subjected to more heat from the now higher output rotor/stator field, the regulator can fail... and yes you'll get an indication on the voltmeter - but the reason for the failure may well be due to heat. So, yes, the regulator isn't functioning properly - but it may be because it got fried by something calling for more continuous current and the resulting heat production was more than the OE regulator could stand.

With a sudden current draw event, you probably wouldn't see it on our voltmeters since they use a heated coil for pointer movement and it takes some time for changes to appear on the meter. Also, if the current output spike was within the alternator battery lead's ability to transfer - and if the alternator itself was cool, there would be little - if any - voltage drop. What you would soon see if the voltage regulator blew as a result of a sudden current spike... is a permanent change to a higher voltage reading.

Keep a sharp eye on your fuel and temperature gauges. There is a voltage limiter coil that's built into the gauge set and limits gauges to 7v. If alternator/battery voltage gets too high, the gauge unit is toast. When that happened to mine (alternator regulator problem), the fuel gauge stayed too high too long and then dropped fast to "E" and the temperature gauge read a little higher than normal. If that happens you have to replace the gauge set (after you fix the alternator/battery problem).

It sounds like you need to find a good auto electric shop. The gremlins you describe can drive you nuts.

Frank

I used to use an old scholl alternator rebuilder with a shop in the shed in the back yard. He claimed stock Mitsu voltage regulators were marginal, and all the aftermarket he had seen were just time bombs waiting to blow. I don't have his experience, but nothing he ever built for me failed, so I trust his ideas.

Over and above that, this is 'lectron stuff, and I'm still stuck in hole theory...