A battery, whether depleted to 50% State of charge, or only to 90% state of charge, will accept 2 to 3 times as much amperage, at 14.7v vs when it is held at only 13.7v. It is 3 times as much when the battery is new and healthy and closer to 2 times when it is midlife or older.
A depleted battery held at 13.7v is infuriating, as it could be recharged to 80% state of charge 3 times faster if the dang voltage regulator would just hold 14.7 vs 13.7v.
The battery itself determines the amperage accepted at the electrical pressure delivered to its terminals. This number is influenced by battery size and health and original resistance as well as temperature and how long its been since its last true full charge, which is closely related to battery health.
These numbers are not made up. I have Ammeters and voltmeters on ALL my multiple adjustable voltage charging sources, and now, because of the Op of this thread, I have dials on my Dashboard controlling my external voltage regulator which controls the alternator, and soon to be plural, alternators.
Back in 2013 or so, I was pestering David Eidell about how to trick the in ECM voltage regulator, as he was the most knowledgeable person on lead acid batteries and alternators I knew of, and still is. We just both had no idea what the voltage regulator inside the engine computer was thinking or expected or required in order to be tricked and not set off the check engine light, and causing some sort of 'limp home' mode. This ultimately was not answered.
On my 1989 B250, tricking the ECM into thinking it is still hooked to the alternator, when it is not, is accomplished with a 10 Ohm 50 watt resistor placed inbetween the two ring terminals which previously were attached to field terminals on the back of the externally regulated alternator. One can then use an external voltage regulator, and the Check engine light will not come on.
I paid way too much for this 'field replacement module' from this outfit:
Kit Gets your Alternator working again, Bypass Alternator Voltage regulator in the computer
alternatorparts.com
in order to figure out it is 10 ohms, and then finding equally spec'd resistors for a fraction of that.
The CEL, will not come on ,Unless the engine computer is expecting to see its own peasly inevitable choice of 13.7v, and the external regulator is holding over 14.7v, for more than 30 seconds.
If it does, then the check engine light comes on and the engine runs a bit crustier as it seems to revert to not reading any of the sensor's inputs. The CElight will go out on the next engine start up, but the crustyness continues until the ECM is reset. It is not an issue in my experience, I just keep it at 14.7v or less and the CEL never comes on.
And while true it is usually less abusive to charge a battery slower, it is not always true.
When the battery is destined to be cycled that night, it is far less abusive to charge it quickly and get it to as high a state of charge as possible, than it is to slow charge it and thus deplete it even further than night and overall allow it to remain at low states of charge and allow the sulfate to harden on the plates, obscuring the surface area for the chemical reaction to occur..
Also, Most AGMS will be ticked to death with light charging currents in deep cycle Duty. COncorde, who make the most respected deep cycle AGM batteries on the market, Lifeline, specifically say the higher charging amperage the better.
scroll to page 20:
There are reports all over the net by Rv-ers, who never bothered to meet Concorde's minimum 20 amps per 100Ah of capacity in deep cycle use that the lifeline tech manual linked clearly specs, who have destroyed the capacity of their expensive battery banks prematurely, by thinking low and slow charging is always best.
I employ Northstar AGM batteries. TPPL AGms, thin plate pure Lead. Very similar to and now the same parent company as Odyssey AGM, a more well known name.
Odyssey AGM says NO LESS than 40 amps per 100Ah of capacity in deep cycle duty.
Page 16
Les$ser AGMS do usually say to limit charging amps to no more than 30 per 100Ah of capacity. I've grossly exceeded this rate on many that say exactly that, without issue , or excessive heating, or gassing.
The whole 'trickle charge it overnight' mentality is the bane of a well discharged long time undercharged battery, and especially AGM batteries.
I wish this old wives tale would not be repeated so mercilessly by those who have zero experience actually testing batteries and observing accurate tools and collecting data in different uses and recharging regimes.
If one had 8+ hours to fully recharge a deeply cycled lead acid battery, then by all means tailor the initial amperage allowed to allow it to reach 100% by the time the battery needs to work again.
But, those AGM batteries that specifically say no less than 20 or 40 amps per 100Ah of capacity, like Lifeline or Odyssey, will have their performance and lifespans kneecapped by the low and slow recharge mentality.
Quality deep cycle flooded/wet/ sloshy batteries like Trojan usually recommend a 10 to 13% rate, but this also assumes one has a significant period of time to recharge the floor scrubber battery or golf cart, before its next use. This recommendation is likely what might yield the least warranty returns if they have guessed exactly how their batteries are going to be treated by a majority of their clients. Their reccommedations are driven as much as by maximum potential profit, as is actually what is best for them and they have adjusted their recommended values more than once in the last 15 years.
in RV usage, deep cycling the battery each night, it is far more important to get the battery to as high a state of charge as possible before the next discharge cycle begins, as partial state of charge cycling is extremely detrimental to the capacity of lead acid batteries.
PSOC cycling means starting the next discharge before a true 100% recharge has occurred, and the lower the % achieved before the next discharge begins, the more detrimental to the battery it becomes. Also when one does indeed have the time and means to then truly fully charge the punch drunk PSOC'd battery, it takes significantly longer to actually attain a 100% true full charge. Not just an hour or two either, think 6 or 8 hours longer being held at 14.4v+ before specific gravity maxes out or stops rising. Allowing only 13.7v on a punch drunk battery, will NEVER truly fully recharge it, no matter how long it is held a 13.7v.
Most smart chargers do a horrible job of topping off a punch drunk battery. One will need to remove the surface charge and restart the charger over and over and over again until they take the charger, swing it by its power cord against the sharpest most immovable object they can find. This of course assumes one is either using a hydrometer on a flooded battery to determine when maximum specific gravity is attained, or on an AGM full charge is determined by the amperage the battery accepts when held at absorption voltages, 14.4+ volts, temperature dependent of course.
And yes Ignorance is bliss, at least until the battery 'no longer holds a charge' at the most inconvenient and expensive possible time to do so.
Also, if one is using a generator to recharge in daily deep cycle duty, it behooves one to achieve 80% state of charge as rapidly as possible. Above ~80% the battery starts limiting what it can accept at any charging voltage so running a generator at higher states of charge, just to achieve the ideal 100%, becomes more and more wasteful of fuel and silence.
I have been successfully tricking the ECM, and running a separate voltage regulator, since January of 2017. I've got several calibrated voltmeters, ammeters, and amp hour counters to keep watch over my deep cycling batteries and can now, finally, achieve excellent lifespans of my lead acid batteries. I can charge them as fast as possible every time my engine is running, and not at 1/3 the possible maximum like when the ECm's voltage regulator decided
13.7 was fine and dandy, which is why this thread was started.
A recharging regimen/ voltage regulation which might be 'just fine' for an engine starting battery, keeping it at relatively high states of charge, and allow it to live 4 years in such a duty, will quickly kill a deeply cycling lead acid battery.
The amount of poor information on the web about the proper care and feeding of lead acid batteries, especially those cycled deeper, intentionally or not, that is spouted by skilled experienced otherwise intelligent mechanics, is rather astounding.
The voltages my ECM would allow, which was 14.9v briefly after start up, then 13.7 90% the rest of the time with occassional spikes to 14.1 or 14.7 had me replacing batteries in less than 2 years and under 250 deep cycles, but arguably would indeed be just fine if the battery were only ever used for stating the engine, which is about 0.25 seconds of a 180 amp load to get it turning, and then about 150 amps until the engine catches. The actual Starter amperage varies with the voltage the battery is able to maintain. But a 1.4KW output starter is going to need very close to a peak of 1800 watts from the battery.
Now knowing just how much time and amperage it takes to keep deeply cycling batteries happy, My last battery lasted ~1200 deep cycles, many of those drawing it well below 50% state of charge, and 6 years. Just before i replaced it, its voltage, when fully charged, was falling to 7.8 during engine cranking.
One other thing I wish would stop being repeated, about lead acid batteries, without qualifying statements, is that short trip driving is alone, a battery killer.
While true that a short trip regimen will never be able to return a well discharged battery to high states of charge, the actual amount used by the starter to start the engine is returned within a minute of starting the modern fuel injected easily starting engine, when the voltage regulator, seeks mid to high 14's after starting the engine, which most do.
Unless short trip driving consists of less than one minute of engine run time,hundreds of time in a row with never a longer drive between, then short trips are not the battery killer they are widely and mercilessly reported as being, over and over, as if sheer repetition makes it so.
Anyway I don't know if a 10 Ohm 50 watt resistor is the magic number for installing between the original wires which attach to field terminals of ALL Dodges with VR's internal to the engine computer, but it is for my '89 B250. In retrospect I would have gotten a resistor capable of dissipating 100 watts of heat, but I used arctic silver thermal epoxy to attach a larger finned heatsink to it. I've added more heatsinking and ventilation to many things.
I've also disconnected my external VR and reattached the wires to the ECM's VR, and it still works like it always did, choosing 14.9v after starting, dropping to 13.7 within 10 minutes and thereafter only briefly spiking to 14.1 or 14.7 or 14.9v.
I never figured out any correlation of when or why the ECM's internal VR decided to revert to 13.7v from 14.9v, as the time after startup in which it did, was always a bit different, and when it spiked to 14.1, 7 or 9v briefly after that, I never noticed any reason as to why. It seemed completely random.
Random and infuriating.
And now, having successfully tricked and bypassed the ECM's VR, can finally treat my hard working deep cycling batteries much closer to ideal.
Actual Ideal, not internet folklore ideal.
I don't use a Mopar voltage regulator, but David walked me through hooking ujp a Transpo 540HD, which is designed for a ford. There are adjustable voltage mopar VR's available now if one prefers.
On the transpo 540 HD there are 4 terminals. The casing of the alternator must be well grounded to battery -.
The terminals are lettered I A S F
I is for idiot light, I ignore this terminal
A is for Always on, Hook to the battery +
S is for switched 12v. I found a quick connector under my dash which becomes live only after engine starting
F is for field. run this wire to either of the two field terminals on the externally regulated alternator. the other terminal must be grounded.
Inside the casing of the transpo 540 there is the blue voltage adjustment potentiometer. with 3 legs. It is potted, but in what appears to be liquid electrical tape. It is a 2K ohm potentiometer. The pot can be lifted and the legs cut with some nice side cut nippers
2 of the legs have continuity and I solder one black 22 awg wire to both of these, and one red 22 awg wire to the other pot leg. These wires goto a Bourns 2k OHM 10 turn potentiometer located on my Dashboard.
Anyway, I absolutely love having this level of voltage control, and so do my batteries. Using AGM's one determines when they have reached full charge by amperage accepted at absorption voltage.
When amperage into my 100 amp hour battery tapers to 0.5 or less, I lower voltage to 13.6, but if cold or at night, with the lights on, 13.6 seems to allow the battery to very slightly and slowly discharge, so I bump it to 13.8v.
If the battery is full and it is midday I will lower voltage to below 13.6v, that way my solar panels, whose voltage regulator( charge controller) set for 13.6v float will take upto 200 watts of load from the alternator to run the engines ignition and fuel pump, which is about 8.2 amps at idle and 12.2 amps at 2K rpm.
If the battery is not full and he sun is out I will set my VR to just under 14.7 so the solar panels contribute all they can, taking upto 200 watts of load off the alternator.
S terminal( which carries very little current from teh switched ignition source, and each time a single alternator cannot meet the amperage demands to achieve or maintain my desired voltage, the other will be turned on.
One is a chrysler 50/120 alternator, one is a 50/120 Nippondenso clone alternator. The chrysler alternator can meets its rating hot, the made in Malaysia Clone alternator, cannot, but will output slightly more than the chrysler from ~ 850 to 1600 rpm or so.
The ND alternator is where my AC compressor used to reside. I've yet to wire it up, but it is nearly perfectly aligned. It might run cooler up here and perform better when hot, since its backside will not be right next to exhaust manifold. The data on its disappointing hot performance, were from when it was located next to manifold.
The space between the dual V belts of the ND alternator, do not match the crank pulley, or the Chrysler alternator or the AC compressor it replaced. I intend to remedy this and run matched belts, if I can acquire them.
But the original alternator was 6mm out of parallel alignment with the crank pulley indicating that V belts are pretty dang tolerant of misalignment, and how many ND alternators out there on similar era dodges are fine with the difference in belt separation?
But ideal means perfect pulley alignment of both matched V belts, so that's where I'll aim.
