I care for My AGMs with some of the best charging and monitoring devises available & agree with your post.
http://www.bestconverter.com/Boondocker-...ml#.Wu0kH9PwbFw
http://www.bestconverter.com/Trimetric-2030RV-Battery-System-Monitor_p_557.html#.Wu0kONPwbFw
Originally Posted By: wrcsixeight
Say one has a charger that is capable of 50 amps.
If the charger's maximum voltage setpoint is 14.0 volts, when hooked to a depleted battery, it will pump 50 amps into the battery until the voltage that the charger sees at its output terminals, reaches 14.0 volts. In order to not Exceed 14.0 volts the amperage tapers, and wil keep tapering as the battery fills as less and less amperage is required to maintain that 14.0 volts
Obviously a 50 amp charger can get the battery to 14.0v faster than a 10 amp charger, but ultimately it is the battery itself, which dictates how much amperage it can or Will accept, at a certain electrical pressure( voltage)
One can have the worlds best AGM battery, and the worlds best 300 amp charger/ alternator, but if the battery only needs 0.6 amps to be held at 14.7 volts, that is all it will accept.
The higher the electrical pressure, the more amperage can flow int the battery, upto a point.
voltages over 14.8v at 77F are fondling the extremes, but a charger seeking 14.8v will recharge a battery much faster than a same amperage charger only seeking 14.4v.
Last night I set my power supply to 13.6. the battery was 87% charged according to my amp hour counter. 12 hours later the battery was still not fully charged. My solar took it upto 14.7v, once the sun was high enough, and 2.5 hours later, after being held at 14.7v, the amperage required to maintain the battery at 14.7v tapered to 0.4, at which point my solar controller is programmed to go back to float voltage, of 13.6v.
There is lots of misunderstandig of volts and amps and battery charging. II know it was a mystery to me before I had a voltmeter and ammeter, and I made many wrong assumptions, but but but.
The battery dictates how many amps it will accept at the voltage it receives, and the more discharged the battery the more amps it will accept.
A sulfated battrey will require few amps to be brought upto absorption voltages( 14.4v+) and this sulfated battery will show a healthy rested voltage, but a small load will knock down that resting voltage to the low 12s or into the 11's, where a healthy battery will hold 12.6v+.
Beware of your charging source's green light. It does NOT mean the battery is fully charged, nor that it is still healthy.
And also remember it is the alternators voltage regulator, which controls how many amps flow, as it is trottling the alternator in order t oseek a certani electrical pressure, and this pressure is not intended to quickly recharge a deeply discharged battery, back to full.
And also, those who check their system voltage and see 14+ volts shortly after engine starting, should not assume thag is the voltage always allowed. it is likely it drops to the mid 13's in short oder, and My battery in my system, time and again,wil accept 2/3 more amperage at 14.7 compared to 13.6v.
I can change my system voltage at the twist of a dial on my dashboard and see battery terminal voltage, and how many amps are required to maintain that voltage. I can do the same with my plug in charging source, although that is limited to 40 amps, where as y alternator has 112 amps to work with, at high rpm and only when still cool. it is rated for 120 amps but at 2K rpm my engine requires 12.2 amps to power the fuel pump and ignition, and the field current dictated by the voltage regulator in order to attain the voltage I have chosen.
AGMs like higher charging rates, but their charge voltages are similar to flooded. I often shoose the AGm setting on my shumacher smart charger, when charging a flooded as number 1, it will keep the voltage, usually from exceeding 14.8v, and since it is basicaly guaranteed to bot hold the battery at 14.8v long enough, when it does drop to float voltage, much more chargnig happens at the AGNm float voltage of 13.6v compred to the flooded setting of 13.2v.
If one really wants to extract maximum batery life and performance from their lead acid battery, they need to insure that the batter yis getting fully charged, and no, your whizz bang smart fellate you afterwards alpha and omega smart charger, are not doing what you think they are, as they can't as every battery's requirements to reach full chrge, changes as the battery ages, and how it ages is dependent on how it is recharged.
Whether any of this is important to a thin plate cheapo starting battery is of course debatable, but those who do cycle their batteries deeper, more regularly, and want or expect their high $$ agm to endure, need to know what the battery requires, and generally what it reqires is more. More time held at 14.4 to 14.7v, and a higher amp charging source to get it there faster and more importantly hold it there until the battery is indeed full, not drop to 13.6v float voltage prematurely, as most every charger will do.
Premature efloatulation kills batteries, but especially AGM's.
The lesser $$ Agms recommend rates of no more than 30 amps per 100AH of capacity, but unless the battery is 95F plus when depleted and 30+ amps were initiated, I would not stress the higher than recommended rate.
The 'trickle charge is always best' mentality is only true on a still healthy battery, and only when there is no time limit on the charging of the depleted battery to actually get it full. And it is argueable that a battery drained to 10% state of charge should spend as little time as possible that low, and that a higher amp charging source should be employed even if one has all the time in the world to recharge it to 100% at a slower amperage rate.
Given that there are very few chargers out there capable of 25+ amps, and that many larger AGMS would do much much better with 40+ amps available initially to get them to 14.4v+, all the regularly marketed garage chargers are kind of a joke, and a fisting of the consumer's rectum.
Absorption voltage, is basically the maximum voltage the battery can and should be brought upto.
Absorption voltages on Gel bateries might be as low as 14.1 volts
Absorption voltage as recommended by AGM battery manufactures range from 14.2 to 14.9v
Absorption voltages as recommended bt battery manufacturers of flooded battery is range from 14.2 to 14.82 volts.
A flooded battery can be 'equalized' this is an intentional overcharge and voltage can be brought as high as 16.2v, but this should only be held auntil the specifi gravity stops rising or the amperage required to maintain 16.2 v starts increasing.
Only Lifeline, or Sunextender AGM batteries, made by COncorde, csay they can be 'conditioned' in an attempt to restore capacity caused by chronic undercharging, or recharging at too low an amperage rate when deplted regularly to the 50% range, or less. Their recommended max voltage is 15.5v, but only to be allowed after a normal full recharge at 14.4v, holding the battery there until amps taper to 0.5% of capacity.
All voltages assume a battery temperature of 77F. Colder requires higher voltages, hotter requires lesser voltages.
Chronically undercharging Lead acid batteries leads to their premature demise.
Fully contemptuous of the available smart chargers and their algorithms, i use an Adjustable voltage power supply, capable of 40 amps, and an Ammeter is used to decide how long to hold the absorption voltage I have set.
The time the battery requries it be held at absorption varies on battery temperature, the depth of the cycle, how many cycles have accumulated since its last full recharge, and the amperage rate initially applied when the battery first started getting charged. No timer based absorption stage would get it right, except under very specific circumstances, yet most every smart charger uses a timer based absorption charge duration, and most every one will fall well short of a full chrge, and that reaching that true full charge is very important with AGM batteries, especially those whose manufacturers do not condont eh c'conditioning' voltages when capacity has obviously decreased.
As far as Northstar and Odyssey, well Odyssey's capacity recovering procedure is to drain the battery to 10V under a relatively high amperage load, and then recharge at a 40% rate, 40 amps for a 100Ah battery, until 15v is reached, and then held until amps taper to near Zero, then repeat.
I have not gone anywhere near this far, but when my NorthStar AGM starts underperforming, based on voltage held under load for a certain amount of capacity removed, the high amp recharge from a well depleted state returns performance. It is a 90 AH battery, I can lug in 2 charging sources for 65 amps of charge rate. It will accept 65 amps for 22 minutes from 30% state of charge before voltage at battery terminals rises to 14.7v, and then it requires 5.5 more hours held at 14.7v before amps taper to 0.45 or less, and the next discharge cycle the voltages it holds are significntly higher than before the high amp reharge, and it is not just because the battery is still warm from the high amp recharging as the next nights discharge and the next dozen the voltage held for AH removed are still superior to before the high ampo recharge.
Beware of the 'trickle charge' mentality, but especially so on Lead acid batteries that actually work for a living.
