AGM Batteries. seem to be dying.

Stu Jackson · May 4, 2009

AGMs

It sounds to me like there's there's a small possiblity that something may be left on when you leave even though you turn your main DC switch off. In order to do any investigation, you need to determine what the battery voltages are when you leave and when you return. Do you have a battery monitor? Is there a drain between when you leave and when you return? The TrueCharge 40 is a good unit, and by not keeping you boat plugged in all the time, you are doing the right thing.

"Is this ok to charge like this?" The wost things for batteries is undercharging and overcharging.

The real question is, without a battery monitor, how do you know after all these years that you have actually fully recharged the batteries?

Until I installed our Link 2000 I didn't know that I was leaving my house bank not fully charged. Leaving batteries undercharged will shorten their lives dramatically.

For a discussion about Battery Charging Techniques, see: http://c34.org/bbs/index.php/topic,4338.0.html

Ross · May 4, 2009

Re: AGMs

I use AGM batteries on my boat and they hold a charge from December to April without losing more than a quarter volt. I turn of everything when I leave the boat. As Stu advised put a volt meter on the batteries and monitor it. 3-4 years is not old for a battery but from your discription of use I think that you are taking out more than you are putting in.

tsmwebb · May 4, 2009

Stu Jackson said:
...
The real question is, without a battery monitor, how do you know after all these years that you have actually fully recharged the batteries?...

When the acceptance rate approaches zero amps the battery is as charged as it will every be.

For the OP, if you are discharging your bank to the point where nominal 12 volt stuff will no longer run then you will need tens of hours on a large capacity charger to fully recharge them. Also, you are killing your batteries by drawing them down so far. Generally AGMs have a low self discharge rate so it is very likely that you have a load on despite having your main switch off. It doesn't take too many cycles to zero to kill even an expensive lead acid battery like yours. They may already be dead. Sorry.

I know this has been discussed before, but monitoring batteries is a mix of art and science. AFIK, all monitors will accumulate errors and will need to be reset. Too, as the battery ages you will need to adjust the size of the bank and the "efficiency" both of which change over time and both of which are hard to measure. If you have a good quality multi-stage charger and you let it run for a few days it will charge your battery to its full available capacity. You don't need a monitor for that.

--Tom.

Stu Jackson · May 4, 2009

tsmwebb said:
If you have a good quality multi-stage charger and you let it run for a few days it will charge your battery to its full available capacity. You don't need a monitor for that.

I agree with Tom about that. But it's the other side of the coin here: if you charge for a few days you are SURE to fill your house bank. But you said you don't leave the boat plugged in, so the monitor would help to let you know what you are doing in terms of getting that full charge. You could leave it plugged in for a week to assure that full charge. The point of the link I provided was pretty much that concept.

If you leave your boat plugged in (meaning shorepower charger is ON) all week, you'll always start with a full bank. It's when you come back to your slip after a sail and don't want to leave the boat plugged in that you NEED to know what's happening. After over 25 years of sailing and working on boat electrical systems for the past 11 years, I am convinced that a battery monitor, at least for the house bank, is one of the best investments you can make.

tsmwebb · May 4, 2009

Stu Jackson said:
...I am convinced that a battery monitor, at least for the house bank, is one of the best investments you can make.

Maybe. I have one and I think it is worthwhile for me. We are long term cruisers and run about 90% plus on solar with weekly or so top offs. We do not stay continuously plugged in at the dock -- even with a galvanic isolator I worry about stray current and fire). The monitor does provide a feel for how full the battery is. But, if you don't know the ins and outs of battery monitoring you can be seriously mislead by your monitor. Tracking battery usage is no simple thing.

The link you gave is interesting. For the OP the idea of using a cheap timer to shut his charger off after a day is, IMO, very attractive. But, I wonder how much a monitor would help him. He knows he's running his battery flat and he knows (or should now know) that he isn't fully charging it in a few hours. Even if the monitor is perfectly correct it is just going to report bad news all the time. I think he needs to: 1) remove the load 2) fully charge his battery and probably 3) run an equalization charge. Then he can move onto details like monitoring.

--Tom.

Ross · May 4, 2009

Brobins75 , You don't have enough battery power to start your engine. I think it is time for an energy audit and budget. If you are plugged into the power grid use 115 volt lighting and power for work and entertainment. Let your batteries charge and shut off all of the posible battery loads.

sailingdog · May 4, 2009

As previously stated, you probably have two different problems here, both of which need to be addressed.

First, you probably have some parasitic loads on the batteries, which are drawing them down constantly. Finding the loads and correcting them is a priority. It could be as simple as the memory function on a stereo or a bilge pump that is cycling.

Second, you need to fully charge the batteries on a regular basis. By only leaving the charger on for 3-4 hours at a time, it is very unlikely that you're fully charging the batteries, ever. You don't say how big your battery bank is, but only the very smallest of battery banks would get anything like a full charge in 3-4 hours.

Another issue, that hasn't been mentioned thus far, is that you state your batteries are 3 and 4 years old. Mixing batteries of different ages and origins can cause problems, especially if the batteries weren't properly charged and maintained. It could also be that there is a weak battery that is drawing the others down...

More information about what size and type of batteries you have and how they are connected together would be useful. I would agree that getting and installing a good battery monitor will make a huge difference. Knowing what the batteries are going through will help you keep them in good condition and help extend their lifespan.

Another possible solution would be to get a small solar panel and use it for maintenance charging the batteries. I added a 25 watt panel to my boat for winter storage for just that purpose. By doing so, I avoided having to have the boat plugged in during the winter. If you're interested in solar power on boats, I'd recommend you read the primer on it I wrote on my blog.

tsmwebb · May 4, 2009

sailingdog said:
...
First, you probably have some parasitic loads on the batteries, which are drawing them down constantly. Finding the loads and correcting them is a priority. It could be as simple as the memory function on a stereo ...

Good point. Stereos may be wired directly to the battery so that their memory isn't cleared when you power down. That wouldn't be too bad if they only maintained their memories but some keep themselves warmed up and that takes noticeable amperage. My Clarion M5475 draws over 2 amps when "off". YMMV, but well worth checking on.

--Tom.

sailingdog · May 4, 2009

I did a write up a while back for checking for parasitic loads and ground leaks, which is relatively simple to do... This is from a post I wrote a year ago:

If you want to test to see if you have a DC-based ground leak, the test for that is rather simple. The steps for seeing if you have a DC-ground leak are as follows:

First—the preliminary diagnosis test:

1) Turn off all equipment and disconnect any solar panels
2) Disconnect the positive side of the battery banks.
3) Leave the main battery isolation switch turned on for the bank in question
4) Set the meter to VDC mode, range appropriate for your battery bank
5) Connect the meter between the positive terminal and the disconnected cable

The meter should give no reading. If it reads XX volts for your XX VDC system, one of two things is happening.

1) You've left some equipment connected and turned on. This could be a bilge pump, a power feed to a stereo for the radio's memory and clock functions, or a hard-wired fume detector.

2) If you've disconnected all the "hard-wired" equipment and still get a reading, then you've most likely got a ground leak in your boat's DC system.

The Ground Leak Check:

1) Set the meter in Ohm mode and set it to the lowest range (x1).
2) Connect the leads of the Ohm-meter (or multimeter in Ohm mode) to the disconnected positive lead and the negative terminal of the battery.

The meter is now reading the resistance of any circuit to ground that exists in the boat's wiring. The reading on the Ohm meter display can help you identify the cause of the leak.

0-10 Ohms means it is most likely a piece of equipment left on
10-1k Ohms is a low-drain piece of equipment left on, or a serious ground leak
1k-10k Ohms is a minor leak
10k+ Ohms is an insignificant leak

How Big is The Leak?

The ammeter function of the multi-meter can tell you what the current leakage is. If your meter can read up to 10 Amps DC, then you can use it to measure amperage for leaks down to about 1.3 Ohms resistance on a 12 VDC system, or 2.6 Ohms for a 24 VDC system.

To see how big the leak is, put the probes on the positive battery post and the disconnected cable. The meter readings can be interpreted as shown:

<1mA — insignificant leakage
1–10mA — minor leakage
10mA–1A — major leak or some equipment left on
>1A — Usually some equipment left on.

Chuckbear · May 4, 2009

One thing sellers of AGM batteries fail to tell the buyer is that if the battery is not charged to 100% after each discharge you shorten the life of the battery. You really need to get the batteries up to a full charge and at this point they will probably need a good equalization. The question will be, do you have the equipment to equalize them. Chuck

Chuckbear · May 4, 2009

Here is some advise I received a while back from what I consider an expert on AGM batteries.

From: John Bierrie
Subject: lv-ab: AGM batteries, used to be (advice on batteries?)
I was not all that impressed with the article you mention [Sail Magazine, February 1999. ed.], even though I have been a proponent for AGM batteries for awhile now. Some things were glossed over, others missed entirely. Of course, under the circumstances, it was expected... The author works for West Marine, West Marine sells them and have not been selling as many as they want to.
The yard I work for has been using AGM's almost exclusively for the last four to five years. In that time we have returned 1 battery that we know of out of over 100 installed. We are not a "self service" yard, so all the work done on the boats is done by us and recorded, tracked, etc.
In general, AGM's, are, in my limited opinion, terrific batteries. They can be mounted in any position, almost any location and will take all the neglect you want to throw at them, as long as they are kept within the extremes. They will not tollerate over charging. If you exceed 16V for any length of time, you will kill them very quickly. If you run them dead, you are in for some work to get them back to life. Alternator sizing is very important.

Over-charging.

If you want to replace your batteries next week, charge them at 16V for a few hours and you will be pulling them. Exceeding even 15.5V for much more time will do the same. I.E., don't use an automotive type charger. The setup you mention should work, fine.

Going Dead.

They may not go dead very easily, but if they do, you have to have the capability of "equalizing" them to get them back. When AGM's go dead, they will charge back up under normal charge parameters just like they normally do, slightly faster maybe, but they will not hold that charge. I.E., their true capacity will be greatly diminished. If you find that the batteries reach 13.1 volts and yet as soon as a load is put on them they start dropping down much faster than normal you need equalization. Oh, yes, equalizing a sealed battery is not a good thing to do, but Lifeline will heartily recommend it as soon as they hear what you have to say the problem is.
15.5V for 3 hours is an AGM's equalization parameter. If you have a newer Link 2000 with an AGM battery selection (#3), then it "may" have this parameter in it. Some do, some don't. If not, set it for Lead Acid (#1) and raise the ambient temp to max... 120? and let it run for 3 hours. That will do 15.75V which is ok. This is of course, AFTER you have charged them normally and they "show" full charge.
Now, with the Link 2000 and Heart Inverter/Charger, and access to shore power, this is easy. Since cruisers "often" run batteries dead, accidentally of course, and do not always have access to shore power, you should consider having the capability of putting out that 15.5V off your alternator so you could accomplish this if you needed to away from the dock.

Alternator sizing and life expectancy.

A MAJOR issue with AGM batteries. AGM batteries will accept, in real life, a charge rate of 75% or more of their AH capacities. This means, a 200 AHr AGM battery can be charged at 150 Amps with no problem. The average cruiser will have 400 - 600 AH capacities, but I know of few, if any, alternators capable of putting out 300+ Amps. Another good point about the AGM's is that they will be quite happy with a charger that does not meet this parameter, they will just charge slower, unlike Lead Acid batteries which will loose capacity if charged at a lower than proper rate. BUT, AGM's will suck in everything they can get ahold of!
A "high output" alternator can mean different things to different people and something entirely different to a set of AGM's. If you have a couple of 8D AGM's, they will provide something in excess of 400 AH. They will, during the Bulk Charging Phase be able to draw around 300 Amps. Since you don't have an alternator of that size, they will pull EVERYTHING the alternator can give it. If your alternator is not capable of putting out Max charge current for any length of time, you will watch it burn up.
Balmar alternators (very good) are conservatively rated. A 100 Amp alternator will, generally, put out 125 amps when pressed. They are also capable of temps which exceed 280 deg. F., though the company does not like you reaching that range. We have watched this very alternator put out 132 Amps for over 45 minutes trying to charge three 8D's. The temp of the alternator, with a cooling fan blowing right on it, exceeded 300 deg. F. before the Bulk Charging Phase was done and things calmed down. We added a second Balmar in this installation.
I.E., most alternators are rated at an amount the manufacturer does not "expect" you to operate at for any length of time. The AGM will test that capacity and then some. Make sure your choice of alternator can truly handle what you are asking it to do or you will be replacing it.
Again, AGM's are, to me, terrific batteries, but there are certain things which need to be taken into account when you switch to them. The above are just three of the more important points to consider, the last, being something rarely mentioned in any store, as the cost of a new alternator can often put people off.
Date: Thu, 18 Feb 1999 02:38:09 -0500
From: John Bierrie
Just to add a bit to this discussion. I spent quite a bit of time on the phone with a tech at Balmar yesterday. He confirmed (based upon his own testing) virtually everything in the referenced post. The bit of information I want to add is that Balmar makes a smart regulator that senses alternator temp. and reduces current output when the temp. gets to a certain point (220 degrees sticks in my mind, but might be the wrong number). They designed this regulator specifically to deal with the AGM battery "problem".
Jeff,
This is a very good point to remember and goes one more step towards understanding that AGM batteries (as great as they may be) are not simple "plug and play" replacements for lead acid or gel cels. Like many other things, one should look at this from a "systems" approach and select equipment appropriately.

tsmwebb · May 6, 2009

brobins75 said:
my truecharge 40 has a setting for "equalize". it looks like you gotta stick a pin in the hole to get it to equalize?

Yes, they generally try to make you think about equalizing. You could fry lots of expensive electronics if you forgot to disconnect them.

For the rest: http://www.lifelinebatteries.com/manual.pdf might prove informative. There is a fair bit of "advertising" in it but once you get past that many of your questions will be answered. The good stuff (and it is very good) is chapter 5, appendix B and appendix C. Even, if you don't have Lifeline (tm) batteries the charing regiment should be similar. But, if you are using some other brand you probably ought to get their manual.

20 years is a very, very big ask for a lead acid battery. The number of years you get depends greatly on how you use them. Very much ball park and off the top of my head: if you get 10 years you're doing remarkably well, 7 is good, 5 is ok...

--Tom.

Stu Jackson · May 6, 2009

brobins75 said:
what does equalizing involve? Also, I am nervous about leaving the boat plugged in and the charger running. Ive never noticed a problem, but the moment i do leave it on, i will have one.

Download and read the Ample Power Primer, Technical Documents, here: http://www.amplepower.com/technical_documents/index.html

tsmwebb · May 6, 2009

brobins75 said:
great, the truecharge 40 manual says "..equalizes only flooded lead-acid batteries. it does not equalize sealed lead-acid batteries since they can be damaged by this process. If the battery type selector is set for gel or agm, and you try to equalize them, the indicator lights ......but will not enter equalization mode."

Please read chpt 5.5 of the manual I linked. It covers this in complete detail. If you decide to condition your battery you can tell the charger that it is a flooded battery.

--Tom.

Ron20324 · May 6, 2009

Brobins, I have the TRCG 40 also. If you have equipment on your boat you really should believe what the owners manual tells you for the proper treatment /use of your charger. It will tell you important stuff like: "If possible, disconnect all loads from the battery.The charger detects a battery is fully charged when its charging current drops below a preset limit. (It will never drop if you have a load, drawing amps.) The presence of electrical loads on the battery may interfere with this detection (to see if battery is fully charged) method".... Also the part that says it "equalizes only flooded lead-acid betteries. If the battery selector is set for Gel or AGM... the TRCH does not enter equalization mode". UPDATE: way back in the TRCH owners manual it finally adds that you may equalize, but only if the battery manufacturer promotes that function.

On your schematic I'm not sure why you have a red line from the TRCH to the fuse panel since you have a switch for that- unless you are trying to drive your equipment straight from the TRCH? I'm not sure that's the best idea unless you've operated the units mode switch to the 13.5 volt setting. And yes, you should charge for a full day at least.

Good point, T.S.: Note that if you go to the T.S.'s link to the 5.5, that the battery you have may not allow for the same proceedures as in the 5.5 information. Check your battery's capability!

sailingdog · May 7, 2009

Your wiring diagram has me asking a few questions. Like why you have the TC40 two outputs hooked up through the battery switch, and why one of them goes to the main DC panel of the boat?

In general, I usually see most AC chargers connected to the batteries directly or to the power post of the batteries directly.... If yours are wired on the wrong side of the switch, even when the AC shorepower and the charger's AC circuit breaker are on, you may not be charging the batteries, unless both the battery switch and the circuit breakers are on as well.

I would highly recommend connecting one set of the TC40's to the positive battery post on the battery switch on the battery side of the switch... This means that you can leave the entire DC system shut down and still use the TC40 to charge the batteries. Put the fuse for overload protection in the line, using something like a MaxiFuse block.

brobins75 said:
here is a quick sketch of how i wired things.

AGM Batteries. seem to be dying.

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