replacing AGM battery

peterbelsky · #1 (**permalink**) 10-01-2007

1 of 2 AGM 4d batteries had died on me. They were both new 2.5 years ago. If I replace 1, will it be ok, or is it best to replace these batteries in pairs?

thanks for any insights...

Sasha_V · #2 (**permalink**) 10-01-2007

It depends on whether they are both set up with a cranking cycle or if one is a cranking battery and the other a deep cycle only.

2.5years is very young for an AGM to die. I use AGM's and have had reallly good performance for over 4 years so far...The battery I use to drive our electric trolling motor, which gets hideously abused on a regular basis (fully discharged, occassionally submerged in salt water, thrown around inside a dinghy and the back of a car, etc) is nearing 5 years with no complaints or degredation in performance.

I would get the AGM checked out, and also check the warranty length on it, they may need to give you a freebie. (Ours have a three year warranty).

As a suggestion, you may wish to either check out what killed it in your electrical system (no point sacrificing another AGM) and just fit a cheapy lead acid battery and a meter. See if something is actually going awry in your wiring to cause the premature death.

Sasha

camaraderie · #3 (**permalink**) 10-01-2007

Were they used as part of the same bank or as 2 separate banks?
If they were both used as a single house bank, you are better off replacing both.
I ditto sasha's comments...there is something very wrong with how you are using or charging your agm's if you got a 2.5 year failure unless it was just a defect (but that is unlikely after so much time.).
Questions:
1. Are you a full time cruiser?
2. Are you plugged in at a dock most of the time?
3. What kind of charger do you have?
4. How is your charging system set up?
5. Do you have a readout where you can monitor use of your batteries and charge state?
6. How often are your batteries cycled from half full to full charge?
7. What voltages for bulk/acceptance and float stage have been selected for your charger?
8. Have the same settings been selected for your alternator/regulator?

The more of these you can answer...the more precise our advice can be.

peterbelsky · #4 (**permalink**) 10-01-2007

I am a weekend cruiser using a honda 2000 generator to a flyback 20 3 stage charger. 2 batteries each on its own selector. This is my first season with the boat a catalina 320, and I did as the previous owner instructed. when battery gets down to 50%, run the generator till full. I fear I may have overcharged, thought it never indicated this (the needle never went to overcharged while charging) I would charge every 1 or 2 weeks for 1 to 3 hours, or after 1 or 2 days of usage. When the charger is charging, it does both batteries at the same time.
I do feel that this could be improper charging by me, but can't tell for sure. Out of the blue, one holds a charge, and one does not.
I am confident that the previous owner had correctly paired the charger, batteries, and voltage.

camaraderie · #5 (**permalink**) 10-01-2007

OK...good info. You have 2x 155ah batteries which gives you 155ah available to use before recharging. Your charger puts out 20 amps. This means that once you get down 155ah's you will need to charge for at LEAST 8 hours to get a full charge into your batteries. You have been grossly undercharging your bank if you have indeed been following a 2-3 hour charging cycle when the batts are down to 50%. You need a significantly larger charger to bring your batteries up to speed if you do not have dockside power that you can plug into. I don't know why only one battery went bad but perhaps that answer lies in how they are wired...one battery may be geeting the bulk charge and bleeding off to the other one, leaving the latter chronically depleted and sulfated.
Since you are not full time cruising, I would suggest that you do not need the extra expense of AGM's as they have no benefit beyond being sealed in your situation, and flooded cells are just a bit more tolerant of poor charging regimens and can be equalized to reduce sulfation. AGM's are a wonderful solution for full time cruisers with daily cycling routines and robust charging systems...but are not needed in your situation.

In any event...if you don't have dockside charging available and must rely on your honda you need a charger AT LEAST double the size you have now. It also sounds like you may need a better way to monitor battery use and condition. You might check out the Xantrex Link 10 or 1000.

christyleigh · #6 (**permalink**) 10-01-2007

Quote:

Originally Posted by peterbelsky

I am a weekend cruiser using a honda 2000 generator to a flyback 20 3 stage charger.

Step #1 is to trash the Flyback. On my 99 c320 mine died after 1 year and on many others the Flyback 20 was eating batteries on a regular basis. After posting my woes to the Catalina lists along with many others I eneded up getting a call from Frank Butler - the owner of Catalina - apologizing for the way Flyback was treating the Problem and he sent me a check. Get a Xantrex 20 or 40 to start with to at least take that Flyback piece of crap out of the equation.

peterbelsky · #7 (**permalink**) 10-01-2007

thanks,
I'm not sure I was undercharging, as after each charge, the meter would read 100%. I am going to pull the battery and have it tested. I will also look into testing the integrity of the flyback

jenry · #8 (**permalink**) 10-25-2007

Good idea to get the battery tested first... And whatever you do, don't buy a Xantrex charger. We purchased the Xantrex truecharge 40 amp for our sailboat. After having it for approximately 3 years and using it only a few times, we charged two batteries and the thing burned up. Our 33' sailboat could have easily burned down! We contacted Xantrex and they put us on hold for so long that I hung up and emailed them. It took them about 2 weeks to respond. Basically they said it was out of warranty but they would replace it at a 40% discount. Not good enough. We went to the Annapolis boat show recently and my husband had the battery charger dangling outside of his backpack with "Lemon" written on it, right below the burn markings. Numerous people came up to us and said they had similar experiences. We decided we'd cut our losses ($460.00 new) and even if they GAVE us another one, we wouldn't take it - our boat is worth a lot more than that!

chucklesR · #9 (**permalink**) 10-25-2007

I'm confused as to how it ever showed a full charge, seems to me it could not have, ever.
if you have two batteries set as two banks, each with 155ah, no other supply of power - I'm going to make some assumptions,
a) you charge with the switch set to both
b) you operate on one or the other, not both, for 'safety'
c) when the boat is unattended you leave it in the both position (that would mean 310ah of a bank)
Here's some thot's (you get what you pay for):
If the above is correct 3 hours at full bore on the generator from a 50% level (switch to both, meaning you have 155ah ( half the 310ah ) in the batt's - bulkrate is 60 ah in means the meter should be showing only 69% of charge; and that is ignoring temperature based reductions in charging efficiency.

We can't factor in how much of a charge you are putting on your batteries with the diesel, so we'll assume at some point you are topping off the batteries. I have a wimpy 55ah alternator, I assume yours is about the same size. 55ah does not mean I'm putting in 55ah when the motor's running, it means at best I'm getting 50ish at when running at hull speed level RPM.

if you are leaving the boat with the batteries showing 100% and coming back in 2 weeks to 50%, you have a leak somewhere. AGM's drop less than 2% a month by self discharge and there is no way your boat should be using 75ah or so a day unless you are running a anchor light 24-7.
If you are on a mooring ball and hence the generator/no shore power you need to investigate adding in either solar or wind to DC supply side, the honda is just not keeping up.

In any case, batteries, panels, generators etc cost a chunk I'm sure you would rather use on flatware and linens (beer and rum); before you invest another chunk on some more lead (you monohull owners and your fixation on lead) I'd talk to a local marine electrician about your system. 75 bucks a hour to talk can save a lot of money and frustration down the line.

k1vsk · #10 (**permalink**) 10-25-2007

Xantrex is one of the better quality chargers although it is always possible for problems to occur. Our's has survived for years and works as it was new. Often, the life of any equipment is dependent on how it was used and under what conditions such as improper installation so as to expose it to excessive moisture or excessive heat. Not sure your's was subject to that environment but your example isn't indicative of my experience.

Quote:

Originally Posted by jenry

Good idea to get the battery tested first... And whatever you do, don't buy a Xantrex charger. We purchased the Xantrex truecharge 40 amp for our sailboat. After having it for approximately 3 years and using it only a few times, we charged two batteries and the thing burned up. Our 33' sailboat could have easily burned down! We contacted Xantrex and they put us on hold for so long that I hung up and emailed them. It took them about 2 weeks to respond. Basically they said it was out of warranty but they would replace it at a 40% discount. Not good enough. We went to the Annapolis boat show recently and my husband had the battery charger dangling outside of his backpack with "Lemon" written on it, right below the burn markings. Numerous people came up to us and said they had similar experiences. We decided we'd cut our losses ($460.00 new) and even if they GAVE us another one, we wouldn't take it - our boat is worth a lot more than that!