Dual AGM Battery system

[Doug1]

Look, I’m not saying I’m right. I’m trying to learn how these AGM batteries get fully charged. If AGM batteries require multi stage charging to get to get to 100%, how do you keep them topped off with an old style regulator that has no microchip? Or, are we (cars with old style regulators) running around with batteries at roughly 80% charge that we don’t even notice because they still run the car fine? If we’re running around at 80% then we are shortening the life of an expensive battery. It’s more of a curiosity.

I’m going to contact Odyssey, optima and XS and see if they have anything to add since they are the experts. I’f I get any replies, they will be added to this thread.

[Doug1]

As promised, I am passing on what I learned from the optima tech support person. While we know that not all AGM batteries are alike, some use lithium ion technology, etc, it goes deeper than that. In fact, even using the same storage technology, the best way to charge and maintain them varies. Here are the main takeaways from optima regarding their batteries.

1. If you have an Optima battery, you should have an Optima charger on hand. Just because a charger is designed to charge AGM batteries doesn't mean it charges an Optima battery the best. For Optima they only recommend charging when a battery is 20% discharged which they consider a deep discharge. For keeping the battery topped off they need a constant voltage of between 14.4 volts to 14.8 volts with 14.7 volts being ideal.

2. The battery should never really discharge while in the car if the alternator and regulator are working properly. The alternator should just do a topping off since the power to run the car is from the alternator while it is running. So it is important to start with a battery that has been charged with the proper charger to 100%. An alternator / regulator combination that supplies a constant 14.4-14.8 voltage at the battery is also needed to keep the battery in top condition.

2. The staged charging is more important if the battery is down to 80% or less and then you need to use their specific charger. The tech advised that on other brand of chargers, sometimes the Gel setting or the Flooded setting could be a better solution than the AGM setting! So they don't recommend using any other charger for that reason.

3. If you have two batteries then you should use a device that can make sure the batteries independently get exactly the 14.4 -14.8 volts each that they need. The tech stated she didn't have much expertise in this area but thought a DC-DC charger was a good idea if the alternator could support it.

4. If the car isn't driven regularly, an Optima maintainer should be connected to the car when it is not in use. This will pro-long the life of the battery.

So kudo's to Optima for addressing the question and limiting their answers to what they definitely know. So I need to find someone who is an expert multi-bank charging to address that specific area but the rest of the questions posed were well answered.

[Warthog5]

Everything You talked to them about was with charging the battery via a 110V battery charger.

So an old style alternator can charge an AGM battery but it is not capable of the multi stage charging required to get the AGMs fully charged. An advanced regulator, such as the one on your new cars, can do multi stage charging.

What alt are you running? Be specific.

No a alt. does not multi stage charge. But if the vehicle is run normal it's more of a maintainer.

[Doug1]

Everything You talked to them about was with charging the battery via a 110V battery charger.
What alt are you running? Be specific.
No a alt. does not multi stage charge. But if the vehicle is run normal it's more of a maintainer.

1. I thought it was clear in my posting that optima recommended getting the battery 100% charged using an AC battery charger and then the alternator should keep it topped off after that as long as there was no parasitic loss. But if not, this should do that. If it drops enough from parasitic loss, the AC charger or a maintainer should be used.

2. CD130D upgraded to 200 amps. It's a Tuff Stuff model 8219.

3. It's my understanding that newer regulators can actually do multi stage charging/maintaining but I may be wrong. It would not be the first time. lol

4. The most important thing I have learned in all of this is that you need to get a charger and a maintainer to match your BRAND of battery. Just being AGM aware is still not specific enough because they are all manufactured to different specs. So one brand AGM charger my work poorly on another's AGM battery.

[Doug1]

Odyssey batteries just replied....Good timing!

Basic takeaway, use THEIR charger to get it to 100% and then your alternator needs to keep it there. If it can't, or the car sits for any extended time, use one of THEIR APPROVED chargers or maintainers to keep it topped off.


Thank you for contacting EnerSys/ODYSSEY.

If the battery isn’t getting deeply discharged, then a conventional alternator should be able to maintain the battery. If the battery is discharged due to parasitic loads or auxiliary loads, then external compatible charger or a maintainer to prevent parasitic drain. We have a list of compatible chargers linked on the website Literature page. The following addresses proper maintenance.

ODYSSEY Battery basics. ODYSSEY batteries are an AGM Lead Acid battery however the TPPL (Thin Plate Pure Lead) technology requires that the batteries be charged at a higher amp than most batteries and maintained at a slightly higher voltage than other standard lead acid batteries on the market including some AGMs. They are also truly dual purpose batteries that can be used for both cranking and deep cycling. Due to the technology, proper charge maintenance is critical to maximizing the life and performance of the ODYSSEY battery.



Most conventional batteries are considered fully charged at 12.6-12.7V. The ODYSSEY TPPL AGM battery is not considered fully charged unless it has a resting voltage of at least 12.84V. The usable energy of the ODYSSEY battery is from 11.2V (0% state of charge) OCV to 12.84V OCV (Open Circuit Voltage should be checked 8 - 24 hours post charge with no loads). When the battery goes below 10.0V OCV it is over discharged and is getting into the chemical part of the battery and can cause permanent damage. At less than 10.0V the ODYSSEY limited warranty deems the battery over-discharged due to abuse or neglect (usually unintentional). The ODYSSEY charger/maintainer or any approved maintainer can maintain the ODYSSEY battery indefinitely in or out of the application provided it has enough charging current to counteract the parasitic loads of the application. If the battery becomes over-discharged (below 11.0V OCV) then the sooner the battery can be fully charged the better. If the battery remains connected to the application during storage or extended periods of non-use, to prevent over-discharge and maintain the battery at a full state of charge, an ODYSSEY program approved maintainer would be required and/or disconnecting the battery prevent over discharge. There is a link to a list of ODYSSEY approved 12v chargers located on the ODYSSEY website Literature page for your reference.

The list of approved 12v chargers is provided due to the many chargers that are programmed for the vast majority of batteries on the market that prefer low amp charging and lower float voltages that do not fully charge or maintain the ODYSSEY battery properly. The minimum recommended charging current for an ODYSSEY battery is 40% of the 10 hour amp hour rating of the battery for cyclic or deep discharge applications (for example about 6A for a single 16Ah rated PC680 for example), a constant float voltage of 13.5-13.8V and no constant voltages exceeding 15.0V in any kind of de-sulfation/reconditioning/equalize mode. At greater than 15.0V the battery can overcharge, overheat, and/or go into thermal runaway. Maintaining any ODYSSEY battery at less than 13.5V will bring the battery down and maintain it in an undercharged condition causing sulfation and premature failure. This would not be considered a warrantable manufacturing defect failure.

For seasonal applications (non-daily use applications that set for more than 3 days in a row frequently) regular use of an approved maintainer that meets the charge voltage requirements noted in the previous paragraph is highly recommended during the season and/or a disconnect switch. The preferred storage method is to fully charge the battery before storing and disconnect the battery from the application (shelf storage mode). Stored in or out of the application with no loads, the battery would not require charging for up to 2 years at 77°F or until it reaches 12.0V, whichever comes first before charging is required. The self-discharge rate increases significantly for temperatures above 25°C (77°F) and for every 10°C (18°F) temperature increase the storage time to recharge is decreased by half. Charge maintenance is critical to maximizing the life and performance of the battery. Freezing will not harm the battery and self-discharge rates reduce significantly at colder temperatures.

It is recommended that the ODYSSEY battery be charged if it is less than 12.65V (about 80% state of charge) when put into use as a cranking battery per the ODYSSEY Owner's Manual (link provided on website Literature page for your reference). Most standard alternators are meant to top off a slightly discharged battery and maintain a fully charged battery. Most standard alternators/stators are not meant to be deep discharge recovery chargers and can become damaged if consistently used like one as well as not fully charging the battery with limited use. A battery discharged to below 80% capacity may not reach a full state of charge, regardless of how long you drive the vehicle using a standard alternator. Typical alternators only run at full amp output for a very short period of time before reaching its charging voltage and dropping into a very low amp trickle charge. Luckily enough, ODYSSEY batteries are very efficient at accepting high amp charging for quick charging.

Low amp trickle "charging" a discharged ODYSSEY battery is very inefficient and also causes premature sulfation. With the use of a 6A or higher amp charger that does not exceed 15.0V, the PC680 battery for example, should charge to a high state of charge (at least 85% SOC) then, an approved lower amp trickle maintenance charger should be able to complete charging process without prematurely sulfating the battery. The Cyclic Charge Voltage range printed on the top label of the battery is the recommended voltage at the battery from the applications charging system (alternator or stator). At less than 14.1V the battery may not be getting fully charged for infrequently used applications. You can verify the battery voltage by checking the voltage at the battery at least 8 hours after application use (or off charge) and if the battery voltage is not at least 12.84V then the battery is not considered fully charged. Voltage readings taken right off charge or after use (alternator/stator charging) will be inflated and inaccurate so for a true OCV reading, you should wait at least 8 hours before checking the voltage (OCV) with 24 hours being preferred.

Any lower amp (less the 6A for PC680 for example) charger that floats between 13.5-13.8V at the battery and never exceeds a constant voltage of 15.0V in any kind of automatic reconditioning, equalize, de-sulfation mode can be used as a maintainer only provided the charging current is high enough to counteract the parasitic loads of the application and maintain the acceptable voltage in float mode at the battery. With proper charge maintenance, a comparable Ah rated battery should have a service life of 2-3 times that of the same sized (Ah rated) battery in the same application with the same usage. ODYSSEY batteries have an 8-12 design life and have been known to function successfully well past the design life of 12 years for UPS applications where the battery is maintained at all times. Here is the link to the program approved charger listing from the ODYSSEY website Literature page for your reference. http://www.odysseybattery.com/docume...V_chargers.pdf. Here is the link to the Technical Info page that contains the Procedure to Recover Deeply Discharged ODYSSEY Batteries and ODYSSEY Battery Reconditioning Charge Procedure.
Please contact me if you have any questions or concerns.