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Old 07-07-2009, 20:57   #1
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AGM Battery / Charging Issues

I have just had a problem where 2 Concorde lifeline 27T marine starting batteries have failed in two weeks. These are port and starboard engine starting batteries in my catamaran. Both batteries show 12.7 volts (full charge), but when the starter engages the voltage drops to near zero. This is the behavior I would expect if there was a high resistance internal break in the battery. It is my understanding that AGMs and in particular Concorde lifelines are very resistant to such problems, which is usually caused by vibration, shock, or high temperatures. I am concerned that I may have an issue in my charging system that may have damaged the batteries. If so I would like to fix it before installing new batteries.

The electrical system consists of two Group 27 AGM starting batteries. Two 4D AGM house batteries, 2 55amp alternators, 4 75 watt solar panels, a 40 amp xantrex battery charger with a temperature sensor, Trace C35 Solar Controller set up for 3 stage AGM charging. Float Voltage is set for 13.1 volts on the solar. The charger is currently floating slightly below 13.1 volts due to summer temperatures. The batteries are connected together through a Xantrex Pathmaker with disconnect set at 13.1 volts. There are manual battery switches in the system but they are left in the on position. When the engines are running I see 14.1 volts on my batteries. I checked all battery terminal and system wiring for broken/loose or corroded connections on all switches and the starters. Everything was clean and tight.

I have the start batteries out of the boat and plan to take them to the local dealer for testing tomorrow. The batteries are both 7 years old and it may be that one has had the problem for some time and the other has been carrying the load. Two weekends ago the port engine cranked very slowly and I started it by combining it with the house bank. The starboard engine started with no problems. I de-combined the batteries and attempted to start each engine. The voltage on the boat engine dropped to zero and the engine failed to crank. The starboard engine voltage dropped to about 10.5 and it cranked and started normally. I did not have time to remove the faulty battery so I planned to do it this past weekend. This weekend the starboard engine also failed to crank and running the same test resulted in zero volts on both batteries while attempting to crank. Both engines started immediately when I switched on the battery combiner and tied in the housebank.

So for the opinions I seek.
  • Is it just to be expected that old batteries treated in basically the same way will fail in the same manner within a very short time of each other?
  • Is there something in my system that has gone bad and is killing my batteries?
  • What should I test before installing replacement batteries?
  • Could I be having problems with my starters?
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Old 07-07-2009, 23:16   #2
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Not knowing your batteries specs your system sounds about right, though I wonder why you need two starter batteries if they are just wired up in parallel.
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Old 08-07-2009, 05:43   #3
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I'd say they died of old age. My Lifeline Group 27 start battery lasted six and a half years before it croaked.
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Old 08-07-2009, 08:18   #4
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Seven years is a decent lifespan. Even AGM's die from old age.
It sounds like your batteries died from the buildup of hard sulphate which would be normal in your situation.

The main causes of dead batteries are;
A. Catastrophic Failure
1. Poor Construction, Faulty welding of the components, contamination of the electrolyte, the quality of the lead
2. Overcharging, overcharging which causes thermal runaway. Basically your battery overheats from oxygen recombining with the negative plate, etc. Causes all kinds of internal damage. AGM are the most prone to this, Gells are more resistant, flooded batteries are the most resistant

B. Progressive
1. Hard sulphate, battery shows a fully charged voltage but under a load dies, caused by low charging rates at full charge over extended periods of time. Batteries intended for backups for power failures (phone systems) are designed to resist this.
2. Dendrites, standing for long periods of time partially discharged with or without a very low charge rate promotes the growth of lead structures between the plates (occurs both in AGM`s and flooded cells but not likely in Gell`s) shorting out the battery resulting in dead cells
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Old 08-07-2009, 08:42   #5
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Hud, you are probably correct, but since they went bad so close together I was just looking for ideas on anything that might have precipitated it. Even old people don't always die of natural causes.

Theonecalledtom, they are wired in parallel only when the combiner is enabled. My usual practice is to start the engines while still connected to dock power and let the engines warm up. As the charger is still turned on, the combiner (left on Auto) is enabled. The water temperature just got warm enough a few weeks ago so that the float voltage is less than the disconnect voltage of the combiner. Now that the combiner is disengaged, at least when the solar panels are not putting out power, the problem has shown up. The other issue is that my engines pretty much start on the first turn, so even if the capacity was low, if the battery had enough juice to turn it over once I wouldn't know I had a problem. I was anchored out in late May however and had no trouble starting either engine, though Admittedly I started them in mid-morning on a sunny day so the combiner may have been enabled by the solar output.

Thanks Mesquaukeem, hard sulphate does sound like the failure mode I'm seeing. Does equalization prevent or reverse this? I've recently read that lifelines can be equalized though this is not recommended for AGMs in general. My starter batteries do indeed get used very little and sit at float voltage for long periods of time. Should I make equalization part of my normal maintenance routine a couple of times a year?
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Old 08-07-2009, 10:08   #6
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There is a lot of controversy concerning equalizing AGM. Some say never. Some say 2-4 times a year at 15.5 volts for 2-4 hours. It would be an idea to contact the manufacturer.
These types of batteries are sealed. The idea is to recombine the hydrogen and oxygen.

Flooded batteries should be equalized every 10-40 days at 15.75 volts for 2-12 hours depending on who you want to believe.
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Old 08-07-2009, 12:23   #7
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A couple of things I would check/try before replacing the start batteries.
1. Check ground connections from the engines/starters back to the batteries.
2. Try a house battery to start the engines. If it works - try one last time with a start battery.

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Old 08-07-2009, 15:27   #8
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They are pretty small batteries , take them in for a load test. 7 years is about the max life I would suspect....
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Old 26-09-2010, 04:01   #9
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How to determine the right float voltage

In my 42 feet Noordkaper (steel, self built), I decided to use the best(?) electricity system available. So I installed 4 Northstar AGM's, resulting in 290 Ah (24V). A second altenator (Mastervolt) on the main engine, via an Alpha-pro regulator, and a Victron 24V-70A multiplus are used for loading. So far so good.
Based on Northstar information I set the values for bulk and absorption quite high - 29.5V; I cannot change the float voltage however, but agreed to go back to the Victron shop and let them change the value.
Now the problem. Both Victron and Northstar give me different information on the float voltage. Victron has the voltage on 26.5V - quite low.
Northstar wants me to set it to 28.8V or even 29.5V, to get the best results.
I have no capacity problem, but want to go for best lifetime of the batteries.
What to do?

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Old 26-09-2010, 06:55   #10
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Quote:
Originally Posted by mesquaukee View Post
1. Hard sulphate, battery shows a fully charged voltage but under a load dies, caused by low charging rates at full charge over extended periods of time.
I have never heard of a low charge rate on a fully charged battery being the cause of sulfation. Sulfation occurs when a battery is left in a discharged state and begins when the specific gravity goes below 1.225 or the static voltage goes below around 12.4v. Maintaining a float charge on a battery not in use prevents sulfation. Perhaps continuously re-charging a discharged battery with a very low charge rate could allow sulfation during the repeated long charge periods.

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Old 26-09-2010, 07:51   #11
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29.5 volts is what I have been told is a proper voltage to use for EQUALIZATION. EQUALIZATION is done once or twice a year to mix things up in the battery to undo effects of sulfation. The process must be very closely monitored, the caps need to be loosened because the battery will be gassing, and boiling, care must be taken to ventilate, and the battery temperature and electrolyte levels must be monitored closely, and the process stopped when too hot or electrolyte too low.

28.8 is the voltage level that my batteries are to be BULK charged. The bulk charge time is set to get near full charge.

28.8 is also the voltage for ADSORPTION charge. In this mode the battery is brought to full charge. The rate of charge is reduced to a very low level to avoid gassing and over heating.

26.5 volts is the the proper FLOAT value for my battery. This is the constant volt level that is held while the boat is in storage. It is the highest level that can be applied with no gassing.

Two things should be controlling:
1. Your battery manufacturer recommendations.
2. You must have charging equipment capable of managing these charge modes properly.

My system is a 1400 Ah, 24 volt, Rolls battery comprised of 12 2 volt cells.

My previous equipment was comprised of similar Varta 2 volt cells, and they were still functioning with slightly diminished capacity after 13 years.
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Old 27-09-2010, 00:42   #12
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AGM different?

13 Years seem like an excellent lifetime, that's for sure. However AGM batteries require a higher bulk/absorption voltaged when charged, and Northstar claims that their batteries require even higher values, therefore the 29.5V. Also the normal of 20% of the Ah capacity as a max for the charge current does not apply to Northstar batteries (no limit is the claim, but I use 80A, which is approx 25%).
I've checked the batteries when bulk charging, and find no noticeable heating.
I feel I should follow the battery manufactorer's recommendation, but hesitate because Victron also seems very knowledgeable about the fundamentals.

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Old 05-10-2010, 16:03   #13
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Quote:
Maintaining a float charge on a battery not in use prevents sulfation.
Not technically correct. Floating any lead acid battery for an extended length of time without periodically subjecting the batteries to > than float voltage will cause sulfation.

With AGM thin plate pure lead (TPPL) batteries, like Northstar, an extended float with no usage or conditioning at a higher voltage will cause sulfation and electrolyte stratification.

Regarding using the information from the charger manufacturer or the battery manufacturer; Victron understands their equipment, Northstar understands their batteries. Use the appropriate advice for the corresponding equipment.

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Old 05-10-2010, 16:53   #14
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Quote:
Originally Posted by Jaap View Post
13 Years seem like an excellent lifetime, that's for sure. However AGM batteries require a higher bulk/absorption voltaged when charged, and Northstar claims that their batteries require even higher values, therefore the 29.5V. Also the normal of 20% of the Ah capacity as a max for the charge current does not apply to Northstar batteries (no limit is the claim, but I use 80A, which is approx 25%).
I've checked the batteries when bulk charging, and find no noticeable heating.
I feel I should follow the battery manufactorer's recommendation, but hesitate because Victron also seems very knowledgeable about the fundamentals.

Jaap
Maximum acceptance rate to charge an AGM is 100% of the rated amp hours. A 20% acceptance rate is for wet cells. The little secret the battery manufacturers of the AGM don't always tell you is that every time you charge the battery and don't recharge to 100%, you shorten the life of the battery. Chuck
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