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Old 12-10-2012, 01:36 AM   #1
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Equalizing AGM batteries?

Hi all. There is a lot here about equalizing batteries but not much about AGM batteries. I have just taken my 1999 Mirada to an RV specialist (that I sort of trust) and he has said that because my five 100 AH AGM batteries were purchased over about a year, that they will never work well in unison as a bank.
Can I equalize them in some way? Or do I have to start again with five brand new batteries purchased at the same time?
At over $600 a battery here in New Zealand I am loathe to throw away $3000 of batteries unless I have to! I think there is also a lead acid battery at the front of the coach that is part of the house battery bank, does that make a difference?
The RV guy is putting a new roof on at present and increasing the size of the cabling running from the panels to the controller and then the batteries. The firm do bus conversions for a living and so his knowledge of power systems is pretty sound.
Any info about getting the AGM batteries to work together would be appreciated.
Cheers (and an early Merry Xmas to you all)

Graham Gracie in a 1999 Mirada, V10 Petrol. New Zealand, Suzuki Escudo 2001 2.5L V6. Mini poodle, Pierre and mini schnauzer, Maddie.
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Old 12-10-2012, 02:03 AM   #2
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I'm curious what problems are you seeing?

Why do you think they aren't working right?

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Old 12-10-2012, 02:15 AM   #3
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I am having difficulty knowing what charge is left and what current is being used at any one time. I have a 3000 watt inverter to run most plugs and a 600 W inverter to run a 32" LCD TV. After a couple of hours at night watching tele, the red flashing lights come on on my solar controllers suggesting that I am running low on battery power. This happens at 12.6 V. I have heard that you don't want to let the batteries get much below 75% or you can damage them.
My problem is I don't what voltage is represented by 75%, so I am being safe rather than sorry. The folk who installed my solar panels have not done a lot of motor home work and so I am a little worried I am paying for them to learn what they doing, hence the independent check.
My question really is "do you have to buy all of your AGM batteries at the same time for them to work properly, or is there some way you can get them to talk to each nicely and not have one older battery pull the others in the bank down?" That is what I understand "equalizing" to do. Do AGM batteries need this process like lead acid?
Graham Gracie in a 1999 Mirada, V10 Petrol. New Zealand, Suzuki Escudo 2001 2.5L V6. Mini poodle, Pierre and mini schnauzer, Maddie.
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Old 12-10-2012, 02:55 AM   #4
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Equalizing lead acid batteries is a process designed to de-sulphate the battery plates by carrying out a controlled overcharge. Battery plates tend to acquire a sulphate coating over time which then hinders the chemical action between the electrolyte and the plate. It's common practice for wet cell batteries. For AGM batteries it varies by battery manufacturer. I would suggest to research or contact the specific battery manufacturer for thier recommendations.
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Old 12-10-2012, 03:02 AM   #5
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Read the first paragraph of this link.
Curious why you need two inverters off your batteries when the LCD could also work off the larger 3000 watt inverter.
Some more info on AGM's. Read the full thread, info on Solar.
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Old 12-10-2012, 03:16 AM   #6
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Here are some good links to help you understand when and how to equalize your battery bank. Good luck and keep us posted.
All about battery equalization

Lifeline AGM Batteries Charging Procedure
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Old 12-10-2012, 07:30 AM   #7
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Most AGM battery manufacturers do NOT recommend equalizing an AGM battery. Trojan, for example, specifically states that their AGMs should never be equalized. Lifeline (Concorde Battery) is the only brand I know of that specifically approves of equalizing their AGMs.

As for buying your batteries all at the same time, that is indeed the preferred practice. However, I seriously doubt if buying them all within one year is going to cause you a problem unless something happened in that year to damage one or more of the batteries. I think your specialist is being ultra-conservative in this case.

Nor would I be concerned that the battery voltage goes below 12.6v. That is the nominal voltage at 100% charge, so of course the voltage will soon drop below that when under load. It is widely accepted in the battery industry that you can discharge to 50% without any long term effect. That's about 12.0v with no load or somewhere in the 11.6-11.9 range if their is a modest load on the batteries.
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Old 12-10-2012, 08:01 AM   #8
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Got the 600 watt inverter first, just didn't remove it when I got the larger one. The ambient current drain on the larger inverter just to run the tv is much higher - this gives me a lower current draw choice.

Thanks for all the information and links. As usual it brings up more questions, but it is really good to tap into the experience and knowledge here.
One last question - what about the mix of five AGM's with the one lead acid?
Graham Gracie in a 1999 Mirada, V10 Petrol. New Zealand, Suzuki Escudo 2001 2.5L V6. Mini poodle, Pierre and mini schnauzer, Maddie.
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Old 12-10-2012, 08:13 AM   #9
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When you put multiple batteries in the same bank, you definitley want them of the same size, type and brand. In other words, identical. It is also recommended they be of the same age. This mostly guarentees they will be more identical. If one is weaker it can drag the others down to it's level. So there was some truth to what you were told. I suspect with AGMs you may still be fine. You can always have them load tested to see how close they are.

As you've already heard, equalizing may not be recommend with your AGMs, depending on brand. Of course the equalizing they are talking is 15-16 volts 1 or 2 times a year.

To equalizie is merely boiling the batteries to mixup the electrolite to rid them of stratifcation. When you drive a coach, the batteries are subected to 14.3 - 14.5v, more than enough to boil them. My Progresive Dymamics PD9200 converter/charger (3 stage) also has an automatic equalization mode which subjects the batteries to 14.4v for 30 mins every 24 hrs. This keeps them in tip top shape without doing any special equalizing.

Regarding that wet cell battery, I highly doubt that is part of the bank. Most likely the chassis/starting battery. If it is part of the bank, you want to get rid of it.

Regarding battery voltage. When a battery bank is at 12.7v, without any drain and off a charger for an hour, it is fully charged. Under the same conditions if it's at 12.0v, it is 50% discharged. This is the point you want to begin charging with a deep cycle wet cell battery for longest life, not sure with AGMs but easily found out.

Nothing against AGMs except they are expensive and not necessary unless used in living space IMHO.

You can get four 6v deep cycle GC batteries here in the US for $400 and give you 480 AH. For $600 you can have 720 AH. Much better than 500 AH for $3000. Surely there are plenty of golf carts in NZ and those batteries have to be much cheaper than AGMs as they are here. Just an option if some day your AGMs don't work for you.
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Old 12-10-2012, 08:30 AM   #10
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Keeping batteries happy and long lived is a balancing act. The key is knowledge and the place to start is Deep Cycle Battery FAQ and Car and Deep Cycle Battery FAQ, Battery Manufacturers and Brand Names List, and
Part of this balancing act is knowing the ‘state of charge’/’depth of discharge’ and the only way you can do that accurately is to monitor what goes in and what comes out.
The only certain way to know batteries are full is by using a battery monitor I have a Vectron Battery monitors - Victron Energy which are the simplest to wire and use and the 602S will monitor both the starter battery and house battery. The alternative is the Trimetric TriMetric Battery System | Bogart Engineering
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Old 12-11-2012, 09:28 AM   #11
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on my coach the heart freedom manual describes function of charging very very good here is the link and just page down to charging http://www.xantrex.com/documents/Dis...ner_manual.pdf and three stage charging is the only real way to get it done proper in my opinion as described in the manual...
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Old 12-11-2012, 05:44 PM   #12
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Check this link. Lots of great info on RV electrical systems and AGM batteries.

Craig and Joan
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Old 03-22-2013, 02:51 PM   #13
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I have a question Can I instal 4 AGM battery, and 2 acid Battery for engine Cranking
on Beaver 2005 Patriot Thunder Cat C13 Gigifern Tank.
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Old 03-22-2013, 03:37 PM   #14
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HI gigifern,
If the 4 AGM batteries are for the house part of the coach and the other two batteries are for the automotive part of the coach, the answer is yes. That setup will work fine.

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