My Noco Genius 2 has an AGM setting which charges to a slightly higher voltage, than the standard lead acid battery setting.
Battery test results
- Thread starter parshisa
- Start date
My charger has much the same. But I was referring to AGM batteries being charged at a higher amperage, (i.e. "fast charged").
I think that ideal charging amperage would depend on many different things such as which type of AGM (spiral or plate), battery capacity, state of charge, age and health of battery etc. But I'm way out of my zone of knowledge here.. I'm following this thread to learn more.
From a self discharge perspective, colder is better
From an amp hour and CCA perspective, hotter is better.
The electrolyte is a sulfuric acid solution, and the hotter that is, the faster it can chew up the plates.
Only a depleted battery can accept high amperage for any significant period of time.
ALL charging voltage recommendations are assuming the battery is 77 to 80F. Compensating for battery temperature gets more and more important the farther the battery is from this area. Colder temps Ideally require more voltage, hotter temps require lesser voltages. If long term floating the float voltage becomes more and more important, the further from 77f the battery is.
High amperage charging starting with a battery at 90f, can be dangerous, as it will heat up, and once it hits the 1`05f area it really seems to heat up exponentially, and when it reaches 120f all charging should be terminated and battery allowed to cool fully, even if it is still far from being fully charged.
AGMS when well depleted do appreciate the higher amperage recharge. They can get away with slower rate recharging, but not if the deep cycles happen often and back to back. Then the occassional high amp recharge is much appreciated by the AGM.
Most flooded deep cycle batteries say a 10 to 13 % rate of recharge is ideal, for longevity.
Whereas in deep cycle Duty Lifeline/Concorde AGM, says no less than 20%, and Odyssey says 40%.
Ideal and acceptable can be far apart.
Many battery manufacturer recommendations are likely them trying to second guess how their batteries will be used by their owners, and what they will guess what recommendations might give the least warranty returns.
A healthy AGM can indeed achieve fully charge at lower voltages, Deka intimidator agm has a recommended absorption voltage of 14.1 to 14.4.
Lifeline says 14.2 to 14.4
Odyssey says 14.7
Northstar said 14.4 to 14.8v.
The AGM setting on chargers usually holds absorption voltage for longer than for flooded batteries, but they all have their own take on it.
The AGM setting on chargers will also almost always have a higher float voltage setting.
My opinion is the AGM setting would do better on most every battery, flooded or not, expect for long term float, longer than 24 hours or so.
if one believes their AGm to be acting a bit lazy, and they have a higher amperage charging source, then they will have to discharge it a fair amount, like leaving headlights on for 2 to 3 hours, before it can accept the chargers higher amperage for long enough for it to benefit from the higher amperage recharge, but achieving true 100% full is just as important in the quest to return it to it potential remaining maximum performance.
Be wary of high amp recharging at high ambient temps
Do monitor battery case temperatures, not just on top, but the bottoms of the battery, on each of the individual 6 cells.
Ive taken flooded batteries out of service when one cell started heating on the bottom during charging but otherwise was healthy enough to remain in service. I've not noticed this with my AGMS.
AGMS shorter sides, will often bulge outwards, convex, a bit on full charge and can be a bit concave when Not.
Both flooded and AGM can be convex on their shorter sides, when sulfated, or just at end of life from plate corrosion.
Since most chargers revert to float voltage far too early, the higher float voltage on teh AGm setting can allow it to come much closer to a true full charge, in the time the charge is still plugged in, but again too high a float voltage on a flooded battery will cause positive plate corrosion and increase water usage.
From an amp hour and CCA perspective, hotter is better.
The electrolyte is a sulfuric acid solution, and the hotter that is, the faster it can chew up the plates.
Only a depleted battery can accept high amperage for any significant period of time.
ALL charging voltage recommendations are assuming the battery is 77 to 80F. Compensating for battery temperature gets more and more important the farther the battery is from this area. Colder temps Ideally require more voltage, hotter temps require lesser voltages. If long term floating the float voltage becomes more and more important, the further from 77f the battery is.
High amperage charging starting with a battery at 90f, can be dangerous, as it will heat up, and once it hits the 1`05f area it really seems to heat up exponentially, and when it reaches 120f all charging should be terminated and battery allowed to cool fully, even if it is still far from being fully charged.
AGMS when well depleted do appreciate the higher amperage recharge. They can get away with slower rate recharging, but not if the deep cycles happen often and back to back. Then the occassional high amp recharge is much appreciated by the AGM.
Most flooded deep cycle batteries say a 10 to 13 % rate of recharge is ideal, for longevity.
Whereas in deep cycle Duty Lifeline/Concorde AGM, says no less than 20%, and Odyssey says 40%.
Ideal and acceptable can be far apart.
Many battery manufacturer recommendations are likely them trying to second guess how their batteries will be used by their owners, and what they will guess what recommendations might give the least warranty returns.
A healthy AGM can indeed achieve fully charge at lower voltages, Deka intimidator agm has a recommended absorption voltage of 14.1 to 14.4.
Lifeline says 14.2 to 14.4
Odyssey says 14.7
Northstar said 14.4 to 14.8v.
The AGM setting on chargers usually holds absorption voltage for longer than for flooded batteries, but they all have their own take on it.
The AGM setting on chargers will also almost always have a higher float voltage setting.
My opinion is the AGM setting would do better on most every battery, flooded or not, expect for long term float, longer than 24 hours or so.
if one believes their AGm to be acting a bit lazy, and they have a higher amperage charging source, then they will have to discharge it a fair amount, like leaving headlights on for 2 to 3 hours, before it can accept the chargers higher amperage for long enough for it to benefit from the higher amperage recharge, but achieving true 100% full is just as important in the quest to return it to it potential remaining maximum performance.
Be wary of high amp recharging at high ambient temps
Do monitor battery case temperatures, not just on top, but the bottoms of the battery, on each of the individual 6 cells.
Ive taken flooded batteries out of service when one cell started heating on the bottom during charging but otherwise was healthy enough to remain in service. I've not noticed this with my AGMS.
AGMS shorter sides, will often bulge outwards, convex, a bit on full charge and can be a bit concave when Not.
Both flooded and AGM can be convex on their shorter sides, when sulfated, or just at end of life from plate corrosion.
Since most chargers revert to float voltage far too early, the higher float voltage on teh AGm setting can allow it to come much closer to a true full charge, in the time the charge is still plugged in, but again too high a float voltage on a flooded battery will cause positive plate corrosion and increase water usage.
8yr old sulfated 24F pulling a whole 1.0w at 13.56v. how could any alternator handle that?
I bought an inexpensive Konnwei KW208 battery tester and ran a check on my two cars. All testing done at about 40º F after leaving high beams on one minute to remove any surface charge. 2011 Acura TSX with group 24 600CCA East Penn/Walmart Value battery and 2007 Accord V6 with group 35 640 CCA Costco/Interstate. Both batteries were 2 years and 10 months old. The East Penn battery from Walmart tested 100% life at 98% charge. Tested amps were actually 50 amps higher than the battery rating. The Costo/Interstate battery tested 66% life at 95% charge, showing 427amps with a recommendation to replace. The Honda had been starting up with temp in the teens, but noticeably slower cranking than the Acura. My best guess is that the battery could have gone until next winter, but Costco replaced the battery under the three year warranty, no questions asked. The Costco replacement battery was just three weeks old. I charged it, tested it and it measured only 575 amps, so maybe over rated. Interestingly, I checked at the local Walmart and all of their batteries were East Penn, but made in Mexico and more than two months old. I'm in PA and the East Penn/Walmart Value battery I bought three years ago was made in USA and only 11 days old when I bought it. I've read for any given battery size, getting higher current requires using more but thinner plates and sometimes the lower rated batteries will last longer because the plates are less delicate. The factory batteries on both the Honda and Acura lasted the longest and had the lowest CCA ratings. Acura was made in Japan and Honda in USA. Any opinions on this?
a bit of an apples & oranges comparison. the 24 is bigger, it will last longer all other things equal, and likely even if they are not. there's also marketing at play --- the walmart battery is underrated so they can advertise the Maxx as having much higher cca (if the lower tier plus were rated near the Maxx nobody would pay $50 more for the Maxx). further to the point, at least in my local walmart both the 24f value and plus are the exact same battery, but the value is rated 585 and cost $25 less. I measured both on the rack in the store (oh yes I did) and they were both about 710 or so. same case. same apparent weight (judged by lifting). it will be years before it drops below the rated 585.
i think the theory of thinner plates has been debunked for the most part. several dissections online. more or less plates, yes, but not thinner/thicker.
i think the theory of thinner plates has been debunked for the most part. several dissections online. more or less plates, yes, but not thinner/thicker.
Size does matter. The original Honda group 35 battery lasted six years. The first Costco/Interstate replacement also lasted six years. The second Costco/Interstate probably could have gone another year, but I decided to get it replaced just before the 3 year warranty expired based on the test results.
The Acura came with a very small 51R that lasted five years. I replaced it with a Costco/Interstate 51R that died a few months past the 3 year warranty with no real warning. If I tested it before the three year warranty expired, it would have probably failed a load test. I changed the tray and hold down to fit the group 24 that Acura fits to the V6 and bought a Walmart Value battery for just $50. I'm guessing it will last a lot longer.
Back in the late 1970's, I bought a J.C. Penney lifetime battery that I had replaced three times over the 15 years I owned the car. That's the only other time I've used a battery warranty.
The Acura came with a very small 51R that lasted five years. I replaced it with a Costco/Interstate 51R that died a few months past the 3 year warranty with no real warning. If I tested it before the three year warranty expired, it would have probably failed a load test. I changed the tray and hold down to fit the group 24 that Acura fits to the V6 and bought a Walmart Value battery for just $50. I'm guessing it will last a lot longer.
Back in the late 1970's, I bought a J.C. Penney lifetime battery that I had replaced three times over the 15 years I owned the car. That's the only other time I've used a battery warranty.