AGM charger amps

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Researching AGM battery chargers I found this statement in many places..

“The charging current for an Absorbent Glass Mat (AGM) battery should be between 10 and 25% of the battery's capacity. For example, a 12V 100 Ah AGM battery should be charged with a 12V battery charger with a current between 10A and 25A”

And there’s this chart which is everywhere. The resting voltage is 12.1-12.2 on the digital dash gauge.

IMG_5269.jpg


So what would be the correct amp charger be for my Jeep Cherokee? For example, this is a battery I am thinking about getting.

https://www.batteriesplus.com/produ...cherokee/2019/limited/v6-3.2l-gas/sli94ragmdp
 
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AGMs apparently have a minimum charge rate of C/20 to C/10 for best longevity, but this probably only really matters in applications where the battery gets charged from a deep discharge hundreds of times. A 5-10 A charger should be about right. A 20 A charger may be fine, but you'll pay more for it, it may degrade the battery more, and you probably don't need the convenience of the faster charge rate.

The voltage on your dash isn't the resting voltage, since the ignition would be on and the battery is under some load. 12.2 V with the ignition on is pretty typical with a charged battery.
 
12.2 is under load.. pop the hood and come back in 20min after everything is asleep and check at the battery with a DVM
 
If you look at the specs for the battery, it says the battery's capacity is 81 AmpHours. So, following the C10 to C25 rule of thumb, the charging current can be anywhere between 8.1 to 20.25 amps.
 
Judging from the weight and price of the X2Power battery you linked to, it has TPPL construction (like the Odyssey battery), and is possibly manufactured by Enersys in the USA. It will be happy with a 20A charger.

 
Ok so using a voltmeter resting voltage was 12.4. I have a BatteryMinder 1500 which is not rated for AGM and according to the 10/25 rule not enough power at 1.5 A. Why I’m looking for another charger. The 1510 is a good charger and does a great job for other battery types. My understanding is using non AGM chargers on AGM batteries causes under or overcharging. Because it’s 1.5 A assume that would mean under charging and not hurt the battery. So I decided to find out what it would do. Connected the 1500 overnight in the driveway. Temp was 19F overnight. Was still flashing that it was charging when I checked 5 hours later. In the morning it was completed. This was the voltage it was maintaining at..
IMG_5271.jpeg


I disconnected and waited 1 hour, then 2 hours and tested. Was maintaining a consistent voltage both times.

IMG_5275.jpeg

According to the chart, does this mean this 1510 actually charged the battery to the full capacity?
 
Ok so using a voltmeter resting voltage was 12.4. I have a BatteryMinder 1500 which is not rated for AGM and according to the 10/25 rule not enough power at 1.5 A. Why I’m looking for another charger. The 1510 is a good charger and does a great job for other battery types. My understanding is using non AGM chargers on AGM batteries causes under or overcharging. Because it’s 1.5 A assume that would mean under charging and not hurt the battery. So I decided to find out what it would do. Connected the 1500 overnight in the driveway. Temp was 19F overnight. Was still flashing that it was charging when I checked 5 hours later. In the morning it was completed. This was the voltage it was maintaining at..
View attachment 204269

I disconnected and waited 1 hour, then 2 hours and tested. Was maintaining a consistent voltage both times.

View attachment 204270
According to the chart, does this mean this 1510 actually charged the battery to the full capacity?
your charger is fine for topping off and maintaining AGM batteries but will work very slowly if it gets deeply discharged is all
prolly stop overthinking things lol
 
According to the chart, does this mean this 1510 actually charged the battery to the full capacity?
Yes, there's no reason why a lead-acid charger wouldn't charge an AGM to 100%, or very close to it. AGM batteries can handle up to 14.8 V when charging and 13.8 V float, and most lead-acid chargers will go up to 14.5 V with a 13.2 V float, which is close enough.

You don't really need an AGM-specific charger any more than you need an AGM-specific alternator on your car. They'll both be operating at around 14.0-14.5 V.
 
According to Interstate battery:

This is also why an AGM battery needs special charging. Regular battery charging can break AGM batteries. Regular batteries need 15-17 volts to get the same amps. However, voltage greater than 15 volts can overheat an AGM and generate enough pressure to pop its safety valve. That one-way valve is supposed to relieve excess pressure from the harmless gases that come when a battery’s charging. Too much voltage becomes too much pressure, and pop. Without an airtight seal, an AGM will dry out in hours.

 
Ok so using a voltmeter resting voltage was 12.4. I have a BatteryMinder 1500 which is not rated for AGM and according to the 10/25 rule not enough power at 1.5 A. Why I’m looking for another charger. The 1510 is a good charger and does a great job for other battery types. My understanding is using non AGM chargers on AGM batteries causes under or overcharging. Because it’s 1.5 A assume that would mean under charging and not hurt the battery. So I decided to find out what it would do. Connected the 1500 overnight in the driveway. Temp was 19F overnight. Was still flashing that it was charging when I checked 5 hours later. In the morning it was completed. This was the voltage it was maintaining at..
View attachment 204269

I disconnected and waited 1 hour, then 2 hours and tested. Was maintaining a consistent voltage both times.

View attachment 204270
According to the chart, does this mean this 1510 actually charged the battery to the full capacity?

What brand and type of AGM do you have?
Battery Minder says their standard flooded type chargers like the 1500 are absolutely fine for maintaining an AGM. They only recommend their AGM specific chargers/maintainers (settings) for "Optima, Odyssey, Polaris, Yuasa & Other High Performance Specialty 12 Volt Sealed AGM Lead-Acid Batteries", they claim that regular AGM batteries should use the flooded setting.

Look at the setting options on this Battery Minder....it states "wet/AGM/sealed" for one setting and a separate setting for "Odyssey/PLT"

Also, unless you are running your battery way down, and requires a significant recharge, what you really need is just a battery maintainer, which the Battery Minder 1500 suits that duty absolultely fine.

If your resting voltage is regularly 12.1 to 12.2vt, you need a new battery or you have a constant draw on it.
Call Battery Minder and talk to their techs.
 
Unfortunately Consumer Reports did not test batteries in the Group 94R size. But, they did test the X2 batteries in other sizes and it was a mixed bag. It was number 1 in Group 24F and dead last in Group 65, and they do test several examples purchased from across the USA to ensure reliability in their testing.

For as expensive as they are, and wanting a premium battery, I would avoid. I noticed the Odyssey brand with much more consistent results in CR testing. They did not test them in all sizes, but in the ones they did, they were number 1 twice and number 4 in another. And where it was number 4, they top three were rated 91, and it was rated 90. So not much of a ding against Odyssey, more like number 2 rating.
 
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According to Interstate battery:

This is also why an AGM battery needs special charging. Regular battery charging can break AGM batteries. Regular batteries need 15-17 volts to get the same amps.
I have never seen a smart charger that will charge at 17V during normal charging of "regular" batteries. But some of them can charge well above 15.0V , even in AGM setting, when they are in "recondition" or "repair" mode. In repair mode, current will be limited to avoid battery overheating. The OptiMate chargers can briefly get up to 22V (pulsed) in repair mode.
 
What brand and type of AGM do you have?
Battery Minder says their standard flooded type chargers like the 1500 are absolutely fine for maintaining an AGM. They only recommend their AGM specific chargers/maintainers (settings) for "Optima, Odyssey, Polaris, Yuasa & Other High Performance Specialty 12 Volt Sealed AGM Lead-Acid Batteries", they claim that regular AGM batteries should use the flooded setting.

Look at the setting options on this Battery Minder....it states "wet/AGM/sealed" for one setting and a separate setting for "Odyssey/PLT"

Also, unless you are running your battery way down, and requires a significant recharge, what you really need is just a battery maintainer, which the Battery Minder 1500 suits that duty absolultely fine.

If your resting voltage is regularly 12.1 to 12.2vt, you need a new battery or you have a constant draw on it.
Call Battery Minder and talk to their techs.
It’s the factory Mopar battery. Im not sure who makes that.
 
According to Interstate battery:

This is also why an AGM battery needs special charging. Regular battery charging can break AGM batteries. Regular batteries need 15-17 volts to get the same amps. However, voltage greater than 15 volts can overheat an AGM and generate enough pressure to pop its safety valve. That one-way valve is supposed to relieve excess pressure from the harmless gases that come when a battery’s charging. Too much voltage becomes too much pressure, and pop. Without an airtight seal, an AGM will dry out in hours.


Besides the possibility of venting the battery another concern is what an excessively high voltage might do to the cars electronics. My cars handbook says not to exceed 14.8 volts during charging with the battery still connected to the car. I wouldn't use any of these higher voltage battery repair modes without first disconnecting the battery.
 
I just connected a new “Viking” charger with a digital display. It slowly climbs. Then quickly falls. Does it again. Now it’s just been hanging out at 13.5. Is that what I couldn’t see with my idiot chargers?

IMG_5365.jpeg


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IMG_5361.jpeg
 
Also, it’s not the factory battery. To my surprise looking under the insulating cover it’s a diehard platinum AGM.
 
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