The whole short tripping thing, not leaving the alternator enough time to replace that which the starter used to start the engine, is highly overblown, and seemingly highly misunderstood, especially with modern fuel injected vehicles which start very quickly.
I have actual data on this, with my own vehicle.
An AGM battery can only be determined to be fully charged, when it is held at a voltage in the mid 14's and it can only accept 0.5% of its capacity(20 hour rate) in amperage. So A 100 AH AGM battery which can only accept 0.5 amps at 14.7 volts, can be considered fully charged.
If discharged, to ANY Depth of discharge, when later recharging it, bringing te battery back upto 14.7v holding itthere, and when the amperes required to maintain 14.7v taper to 0.5 amps on a healthy 100 Amp hour AGM it then can be considered fully charged.
SO. I have a 90AH AGM,( group 27 Northstar, 930 CCA, 2.6mOhm). When charging amperage tapers to 0.4amps at 14.7v, it can be considered fully charged.
I have an Accurate shunted digital Ammeter which displays amperge to one decimal. I also have a clampon DC Ammeter and another hall effect sensor ammeter which closely agree with the more reliable shunted Ammeter which uses a 500 amp Deltec 50Mv shunt to measure amperage.
Starting with this chock full battery , held at this fully charged level I crank my 1.4KW rated starter.
1.4KW = 140.00 amps at 10 volts.
1.4KW = 127.27 amps at 11 volts
1400 watts = 116 amps at 12 volts.
When the chrging amperage again tapers back to 0.4 amps at 14.7v, the battery can again be considered fully charged.
So my engine cranks for less than a second before it starts, voltage when I performed this test likely fell to about 11.7 during that 1400KW discharging load. So lets say 120 amps of load.
My Ammeter when cranking the engine as high as I have ever seen it go, was 128 amps.
Ok the engine starts in under a second of the starter cranking, I am watching the ammeter and the voltmeter closely as the alternator starts chargin the battery..
Instantly the voltage rises to 14.7v. Amps start out at about 68 amps, and quickly start tapering while the voltage is held at 14.7v
So How long did it take for amps to taper back to 0.4 amps at 14.7v, indicating the alternator has returned everything that the starte used to start the engine?
45 seconds.
NOw this is a low resistance healthy AGM battery, and I can choose my vehicles voltage, by spinning a dial on my dashboard.
My engine starts very quickly, and being a low resistance battery the voltage does not fall that much duing starting. A flooded battery with mpore resistance would not recharge as quickly, but neither is it going to require much more than 2 minutes to return to the same level as before the starter was engaged.
If voltage fell lower, then higher amperage would be required to feed the 1400 watt starter motor.
If it took longer to start, then not only would voltage fall lower then 11.7v, but it would consume more of the battery capacity to start the engine, and thus take longer for the alternator to return that which the starter used to start the engine.
But to say Short trips never allow the alternator to return that which the starter used to start the engine is largely cattle pellets, not vaild since fuel injection became the norm.
This is proveable time and again, by anyone with an ammeter and a voltmeter.
Once charging amps taper to the same level that the battery( any lead acid battery, flooded, AGm or GEL) was accepting at voltage in the mid 14's volt range before starting the engine, then that which the starter consumed, has been returned.
So will every vehicle choose mid to high 14s after starting? Most will. Lower voltages will increase recharging times as it is lesser pressure, less amps flow. Why not check. How long does your vehicle allow mid 14's after start up?
Regarding too much amperage being damaging to a battery, lets explore the logic of that.
Let's say one has a 130 amp alternator. Lets say it can produce 110 amps at 2K engine rpm
lets say the Lights were left on inadvertently and the otherwise healthy, just discharged 100Ah battery drained to the point it requires a jumpstart. This is likely the 25 to 30% charged range, again, assuming an otherwise healthy battery, and mild ambient temperatures.
the vehicle is sucessfully jumpstarted and the vehicle's alternator is told( by the voltage regulator) to produce as much amperage as required to reach the mid 14 volt level.
using the 100 Ah group 31 battery as an example, depleted to the point it required a jump start, with a voltage regulator fully fielding the alternator in the quest to raise system voltage to the mid to high 14 v range, the healthy flooded grpup 31 starter battery will likely suck up 90 to 100 alternator amps before voltage rises to 14.7v. If too much amperage was going to blow up or fry the battery, then the battery of every jumpstarted vehicle woul likely fail in short order. There would be instructions in the vehicles owner's manual to turn on the headlights and blower motor to high so that the ~35 amp load of those devices would lower the amperage the alternator was feeding the battery.
Does ANY owners manual say to do this after a jumpstart was required?
Now batteries will regularly fail shortly after jumpstarting, but this is NOT from the alternator feeding it too much amperage. It is not as if the voltage regulation will be allowing it to get as high as 16.5 volts with 100+ amps to get there. Batteries fail after jumpstarting because the battery was most likely already heavily compromised/sulfated, and the fact that it takes NO LESS than 3.5 hours to charge a battery from 80% charged to 100% charged, and a lead acid battery always wants to be fully charged. Anything less is detrimental to some degree. Getting the battery to 80% charged however can be done pretty quickly assuming a battery which can still accept high amperage and an alternator capable of proividing it and a voltage regulator commanding the alternator privide enough amperage to get the battery and the wholse system voltage up in the mid 14v range.
That 3.5 hours to get a healthy Lead acid battery from 80% charged to 100% charged, also assumes the voltage is in the mid to high 14 volt range.
Very few vehicles will allow voltages to remain this high for this long, and as a result the battery takes much much longer than 3.5 hours of driving to get from 80% charged to 100%. and a battery drained to the point it required a jumpstart is not happy only getting to 80% charged.
When my battery was newer and healthier it would accept 2/3 more amperage at 14.7 sd it would at 13.7v, now with 5+ years of age, 1000= deep cycles and many thousands of engine starts this is closer to half.
So yes Jump started batteries usually live for a short period thereafter, but not because the alternator was feeding them at an extremely high amperage rate when the battery was well depleted and could accept huge amperages for a long period of time. It fails because it does not get to full charge unless the vehicle owner plugs the battery into a capable charger for long enough to get it as close as the charger is capable of, to 100% state of charge. The fact that most 'smart' chargers rarely hold high enough voltage to get the battery beyond 95% charged is another topic. Smart chargers should really be labelled 'nanny' chargers instead of 'Smart' as they largely prevent overcharging from occuring..
My 120 amp alternator was regularly feeding my group 31 flooded marine battery 80+ amps when I would cycle it to 50% or less overnight powering
some powertools and an office. It lived for 3.5 yers and 600 deep cycles before its perforance reduced to the point I removed it from the vehicle.
My 120 amp alternator has fed as much as 107 amps into my Northstar AGM battery. It turned 5 years old last november and has over 1000 deep cycle on it and thousands of engine starts.
And as far as the alternator overheating when feeding near its rted capacity into depleted batteries, well my current alternator has been in place since June 2015, and about 750 of those 1000+ deep cycles on my Northstar AGM battery. I have data on the temperatures its stator achieves at different outputs and vehicle speeds too, but that also is another topic.
So fear of an alternator not being able to return that which the engine starter used to start the engine is largely baloney, and has not been true since carbuerated vehicles required multiple 10 second starting attempts, and the voltage regulation of those alternators on those vehicles rarely allowed much more than 13.8v into batteries which back in the day pretty much had thicker plates nd higher resistance compared to starting batteries of today.. This is certainly not true of a fuel injected 2004 chevy 4.3 v6 with a 100 amp internally regulated alternator and a thin plate starting battery of this day and age we nthey squeeze as much CCA out of the battery they can for as little lead( PB) weight as possible
If One wants to extend battery life, then they should insure the battery does indeed reach true full chrge, by plugging the battery into a good charger capable of holding mid 14 volts until amperage tapers to 1 to 2% of capacity of flooded batteries, and 0.5% for AGMS and maintenance free starter batteries.
Upgrading the alternator is mostly pointless unless the vehicle is powering 40 amps of stereo or hundred of amps of winches, or otherwise simply cannot maintain 13.5+ volts with all the loads on it when fully fielded.
As much as I ask of my alternator, regularly feeding high quality, low resistance deeply depleted batteries, I would not benefit much at all by a higher rated alternator.
And as one poster said, a higher rated alternator might not be able to produce more amperage than its lower rated counterpart, at low rpms.
Balmar, marine alternators, which are pretty well respected, have amperage vs rpm charts which show several of their higher rated alternators, perform worse at lesser rpms than their lower rated counterparts. This is not universally true of course, but it is a fact that a higher rated alternator is not necessarily going to be able to provide more amperage at engine rpms less than say 2K rpm.
So unless the vehicle in question takes forever to start, and a digital multimeter reveals that voltage never gets up into teh mid 14's after starting, or does not climb up there while underway, then a higher rated alternator is NOT called for.
