Re: [Amel Yacht Owners] AGM battery equalisation

ngtnewington Newington


On my last boat I got nearly 10 years from my battery bank AGM’s and it was only because I left a lamp on and forgot to turn off the power when I left the boat for two weeks that they died. The lamp was not LED and there was no wind….…but I was not cruising full time. When not on the boat it was generally hauled out and the wind generator kept the bank at 100% for months at a time. On average I spent 4 months of the year aboard, rarely in marinas. The trick is to never discharge the bank below 60% but more importantly to bring it to 100% every week. This not easily done unless connected to shore power which is why solar and/or wind is so important. It really is as simple as that….the new generation of AGM’s (Firefly carbon foam) are supposed to tolerate the normal cruising lifestyle better and can be discharged lower, accept charge faster and do not suffer as badly. Reports are good but they are not readily available….it seams to me that changing 12 batteries every three years is crazy and expensive and  not very eco….to be avoided. Really the answer is to get the bank up to 100% every day or two and have enough solar or whatever to break-even on a day to day basis. My philosophy is to have a smaller bank of 8 batteries but to have enough solar and wind power so that the bank would only discharge at night and be topped off every day or so. Occasionally if cloudy and calm then some generating would have to be done…. or move anchorage and motor!! I also am careful to turn off inverters when not in use and come from the old school so am a bit of an AMP watcher. I guess it is interesting to see where the amps go. On the 54 I turn off the SSB breaker that powers the 24v:12v converters and also turn off most instruments when not actually being used. I have converted all the lamps to LED and in general turn stuff off.


Amelia (Aml 54 019)

On 10 Feb 2019, at 17:38, Bill Rouse brouse@... [amelyachtowners] <amelyachtowners@...> wrote:


I believe that the 12.3 battery has failed. The 12.5 batteries are nearing the same point, with probably less than 1 year. 

I would disconnect the pair that has the 12.3 and move things so that one of the 12.5 batteries is also disconnected. In other words, 1 pair of the worst batteries are disconnected from the bank. Then I would start looking for the best place to buy and replace all of the batteries. I am going to guess that you should do this within about 6-8 months.

I am sure that you will find some owner that gets longer than 4 years life, but I will assure you he is not discharging his batteries at anchor as you are. I met a guy in Turkey who according to him got 12 years life from his batteries. Within 5 minutes of leaving the marina, they failed.😀


Bill Rouse
Amel School  
720 Winnie St
Galveston Island, TX 77550
+1(832) 380-4970

On Sun, Feb 10, 2019 at 10:32 AM sharongbrown@...[amelyachtowners] <amelyachtowners@...> wrote:

First, many thanks for all your advice, it is much appreciated. I have 6 pairs for my 24v system. The pairs and voltages, after being fully charged (i.e. drawing 1A) and left disconnected for 12 hours, are as follows:

12.7 12.6 12.5 12.5 12.6 12.6 12.5 12.6 12.5 12.6 12.7 12.3

(I did that in two separate lots of 6 each so as to maintain power to the boat)

I'm afraid I don't quite understand what you mean balancing out the voltages. What do you think I should do with the one at 12.3v? Get rid of it, or pair it up with something else? 

Understood about 3-4 year expected life although I was hoping it may be a bit longer!


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