Batteries

[btrayfors]

Originally Posted by The Garbone

Lead acid batteries left on the shelf will discharge roughly 20% per year. Floating is a good idea to keep them charged fully but you need a good charge controller that will not cook the batteries, ideally one that compensates for ambient cell temperature as colder cells hold less than warm cells. I have seen more battery strings go into thermal runaway during a cold snap than during the heat of the summer.

A rule of thumb for lead acid is they are going to need replacement after 5 years, any time after 5 years should be considered a bonus.

"Lead acid battery" is a non-specific term. Flooded batteries, AGM batteries, and gelled batteries are ALL lead-acid batteries.

Flooded LA batteries have a self-discharge rate of 3-20% per month, depending on their age and condition and on ambient temperature. The warmer the temperature, the greater the self-discharge rate.

AGMs and gels have a much lower self-discharge rate.

If you leave a flooded LA battery sitting for a year in warm temperatures, it will be dead and, most likely, you've killed it for good...to the point where recovery is highly unlikely.

Replacement time depends in large part on how willing you are to deal with various degrees of capacity loss. Many users are unaware of the serious degradation of the capacity of their batteries. That's why claims like, "I got 11 years use from my house batteries" mean very little.

Consider the lowly start battery in your vehicle. It begins to lose capacity from the moment it leaves the factory, and it lives in terrible environmental conditions. But, it only takes less than 0.5AH to start your engine....a paltry amount for your 50-100AH car battery.

So....the car starts every time you ask it to. Right up until the morning it doesn't start. The day before your battery was "fine", right? But it may have lost upwards of 80-90% of its capacity, yet had just enough ooomph to start the engine.

Ditto with boats. That's why anecdotal evidence of battery condition and longevity should be viewed as suspect.

Bill

[NewMoon]

Originally Posted by btrayfors

Replacement time depends in large part on how willing you are to deal with various degrees of capacity loss. Many users are unaware of the serious degradation of the capacity of their batteries. That's why claims like, "I got 11 years use from my house batteries" mean very little.
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Ditto with boats. That's why anecdotal evidence of battery condition and longevity should be viewed as suspect.

Bill

Suspect if there's little data the claim is based on, yes.

OTOH, it is only one anecdote, but we pay detailed attention to AH use in our cruising, with a Link 2000 battery monitor. The 12v g31 AGM's I mentioned totaled 210 AH capacity when new. They pumped out 30-70, sometimes 100 AH nightly for 60-100 days almost every summer for 11 years, despite sitting un-exercised most of each year. Only in their last year did I notice they seemed to have an undesirable degree of reduced capacity, so I replaced them with another pair of the same.

[btrayfors]

Originally Posted by NewMoon

Suspect if there's little data the claim is based on, yes.

OTOH, it is only one anecdote, but we pay detailed attention to AH use in our cruising, with a Link 2000 battery monitor. The 12v g31 AGM's I mentioned totaled 210 AH capacity when new. They pumped out 30-70, sometimes 100 AH nightly for 60-100 days almost every summer for 11 years, despite sitting un-exercised most of each year. Only in their last year did I notice they seemed to have an undesirable degree of reduced capacity, so I replaced them with another pair of the same.

Yup! The exception which proves the Rule :-)

For every such story, there are tons which complain about AGMs lasting less than 4-5 years.

Ever notice that the batteries in your computer's UPS seem to last for a shorter time than they used to? UPS units used to use gelled batteries. Some years back, they switched to AGMs, and these seem to have a shorter lifetime than did the gelled batteries.

Richard, it would have been nice to have some objective measurements during those 11 years to see how the original 210AH capacity diminished over time. Unfortunately, this can only be done with rather expensive testers which most boaters don't have OR by a 20-hour load test, which is cumbersome at best.

Bill

[NewMoon]

Originally Posted by btrayfors

Yup! The exception which proves the Rule :-)

For every such story, there are tons which complain about AGMs lasting less than 4-5 years.

Ever notice that the batteries in your computer's UPS seem to last for a shorter time than they used to? UPS units used to use gelled batteries. Some years back, they switched to AGMs, and these seem to have a shorter lifetime than did the gelled batteries.

Richard, it would have been nice to have some objective measurements during those 11 years to see how the original 210AH capacity diminished over time. Unfortunately, this can only be done with rather expensive testers which most boaters don't have OR by a 20-hour load test, which is cumbersome at best.

Bill

Agreed - I don't have detailed measurements like that. And I certainly agree that gel batts make great deep-cycle banks - I've used them too. And 12V flooded, and 6V flooded. For our small power boat with a big diesel, a single batt type - AGM - for both starting and house, makes the most sense.

Most of the stories I've read or heard about AGM's lasting poorly seem to involve AGM's that sit undercharged a lot. They do need to be charged properly, and kept properly charged, as we do with a Balmar alternator and Max Charge regulator, and a Freedom 10 inverter/charger and Link 2000 regulator when plugged in to shore power.

[btrayfors]

Yes, absolutely, AGMs sitting awhile not fully charged will deteriorate quickly.

Also, there seem to be more "catastrophic" failures amongst some AGMs than there should be. One knowledgeable high-end battery manufacturer once told me some of the reasons for this, in his opinion (having to do with interconnecting rods between the plates, sizes & costs, and welding processes).

Bill

[goboatingnow]

Originally Posted by NewMoon

Agreed - I don't have detailed measurements like that. And I certainly agree that gel batts make great deep-cycle banks - I've used them too. And 12V flooded, and 6V flooded. For our small power boat with a big diesel, a single batt type - AGM - for both starting and house, makes the most sense.

Most of the stories I've read or heard about AGM's lasting poorly seem to involve AGM's that sit undercharged a lot. They do need to be charged properly, and kept properly charged, as we do with a Balmar alternator and Max Charge regulator, and a Freedom 10 inverter/charger and Link 2000 regulator when plugged in to shore power.

Gels should never be used on a boat IMHO. They are extremely sensitive to charge parameters and very easily ruined. They are used in ups system because of their extremely low self discharge and ability to mount in any orientation, both features that are useless on boats.

aGMs and Gels have characteristics that are designed for other uses, neither have any benefits , on a boat, over good quality flooded accessible wet cells.

Don't waste money on AGMs or Gels, buy a tubular traction battery instead or at least a semi traction one , make sure the cells are accessible

Dave

[Maine Sail]

Originally Posted by goboatingnow

Gels should never be used on a boat IMHO. They are extremely sensitive to charge parameters and very easily ruined. They are used in ups system because of their extremely low self discharge and ability to mount in any orientation, both features that are useless on boats.

aGMs and Gels have characteristics that are designed for other uses, neither have any benefits , on a boat, over good quality flooded accessible wet cells.

Don't waste money on AGMs or Gels, buy a tubular traction battery instead or at least a semi traction one , make sure the cells are accessible

Dave

Yet I have many customers well past 10 years on GEL's. They are easily one of the longest lasting batteries I have ever seen in the marine environment.

I have one customer with a 1998 Tartan 4100 who's GEL batteries were installed by the dealer in 1998. They still test at above 90% using both Midtronics and Argus analyzers. They are not difficult to charge but you need to do it correctly and have the proper charge settings. All his charge equipment has been set to 14.1V for the last 15 years. Granted this boat was lightly cycled for the first 8 years but still 15 years is pretty impressive and to date is the longest lasting bank I have worked on..

I am one of the biggest fans of deep cycle flooded batts on a $$ to Ah to cycle life calculation, but GEL's can be a great battery for boats..

[btrayfors]

Originally Posted by goboatingnow

Gels should never be used on a boat IMHO. They are extremely sensitive to charge parameters and very easily ruined. They are used in ups system because of their extremely low self discharge and ability to mount in any orientation, both features that are useless on boats.

aGMs and Gels have characteristics that are designed for other uses, neither have any benefits , on a boat, over good quality flooded accessible wet cells.

Don't waste money on AGMs or Gels, buy a tubular traction battery instead or at least a semi traction one , make sure the cells are accessible

Dave

Dave,

Sorry, I can't agree with you re: gels on boats. In my experience and testing, gels are a great choice for SOME boats. I have two gelled golf carts in my basement right now which spent their first 10 years on a sailboat, and have spent the last four years in my shop, two years of that in detailed, extensive testing. They STILL test very good.

You're right about charging parameters, though. If you're going to use gels, you have to be careful about charging voltages. AGMs are more forgiving and have charging profiles very similar to those of flooded LA batteries.

I certainly agree with the notion that for many boats flooded LA batteries are the way to go, preferably the 6V or 2V variety due to their having thicker plates and able to withstand many more cycles and more punishment than either AGMs or gels.

Bill

[Maine Sail]

Originally Posted by NewMoon

Suspect if there's little data the claim is based on, yes.

OTOH, it is only one anecdote, but we pay detailed attention to AH use in our cruising, with a Link 2000 battery monitor. The 12v g31 AGM's I mentioned totaled 210 AH capacity when new. They pumped out 30-70, sometimes 100 AH nightly for 60-100 days almost every summer for 11 years, despite sitting un-exercised most of each year. Only in their last year did I notice they seemed to have an undesirable degree of reduced capacity, so I replaced them with another pair of the same.

You've well exceeded even Deka's own "white coat/white glove" lab testing. Deka rates their AGM's at 500 cycles at 50% DOD.... They rate their GEL batteries at double that or 1000 cycles at 50% DOD.....

Even on the low end of your estimates it seems you've pulled about 660 cycles, and on the high end about 1100 cycles.. I'd say you got your money's worth..

[sailorboy1]

I wonder just how long this break period takes. My Deka 6V house bank is almost 2 years old and still doesn't seem to have the capacity they are labeled (they do act the same now as when new).

Just what is a "cycle" far as this break in to get to capacity?

[Kettlewell]

I have to add one more favorable report on gel batteries. Back in the early '90s I bought some Sonnenschein gel batteries for the catamaran I had at the time. The only charging sources I had were some solar panels, a small Rutland wind generator, and an outboard that put out 10 amps max. None of the sources had any sort of regulation whatsoever other than me keeping an eye on an analog volt meter. I would disconnect various panels or the wind generator to control charging. Almost never plugged into a dock, and if I did I used a cheap automotive battery charger. Those batteries were totally abused--deep cycled thousands of times as we lived aboard for 12 years at that time. Finally, after 10 years I retired the batteries not because they were dead, but because I was afraid they would die on me.

[btrayfors]

THE SLOW BUT DRAMATIC DEATH OF A FLOODED GOLF-CART BATTERY

My house batteries consist of six Trojan T-105 golf-cart (flooded) batteries in two banks....two under the nav seat to starboard and four under the aft cabin berth to port. They are always connected together and are treated as one large bank.

I have tested these batteries periodically for several years, using a sophisticated industry-standard inductance tester (the Midtronics MDX-650).

These batteries have been on charge 24/7 most of their lives, being maintained by a Victron Multi-Plus 12/2500/120. This inverter/charger has been programmed for relatively high absorption, float, and repeat absorption voltages for the past couple of years. They have only been equalized infrequently in their lives (less than five times) and I have recorded the benefits of that treatment.

After removing the charger a couple of days ago, letting the house batteries sit with very little current drain, today I tested and recorded their capacity readings (MCA). As has been the case since I went to the elevated voltages regime, all the batteries tested very, very good....as good or better than new. Except one....house battery #B3. This one of the six batteries in the house bank experienced a very dramatic drop in capacity from its level just five months ago.

For 6.5 years this battery was in service and tested very good or better. Then, suddenly and for no known reason, it lost some 50% of its capacity while the other five batteries in the house bank still test like new.

There was no water loss, no overheating, no contamination, no high-resistance terminal loss, nor anything else external that I can think of which could have precipitated this sudden loss of capacity.

It's interesting that the Midtronics tester repeatedly reported errors like "unstable battery", "temperature anomaly", etc. before I was able to get two reliable readings.

Note also that this battery had been testing somewhat lower than the others for the past 18 months (red/yellow/green) before the sudden drop recorded today (blue).

Here's the comparison in tested capacity among the six batteries over the past 18 months.



I disconnected this battery and its mate (which still tests like new) from the house bank and will probably do something not generally advised, i.e., find a used T-105 and stick in into the house bank to replace the bad one, then see how long the whole shebang remains serviceable. I probably wouldn't do this except for the fact that these batteries have got to be nearing the end of their useful life due to their age, and I want to experiment a bit and see how much longer they'll maintain a high capacity.

Bill

[CarlF]

I've gone back to gels after a disappointing time with AGM's (the AGM's had a sudden death after just 3 years. The previous gels were just showing a little weakness at 8 years when I replaced them with AGM's).

I'd also found the AGM's far more trouble than the Gels. With the Gel's you set absorption to 14.1V, float at 13.7v and make sure the charger temp sensor is working. Then forget about them for eight years.

With the AGM's, you have to worry about getting them to 100% charge - no easy thing in some cruising situations. And with Lifelines, you need to equalize. (I still don't understand why Lifelines are equalized and other AGM's don't - the chemistry is about the same, right? )

Carl