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Over the last few days we find our battery bank (totalling 450Ah, sealed regular batteries) reads 10.0v to 10.4v in the morning after a 2-3 hour charging with the engine the evening before. It usually reads about 12.4v to 12.2v. So I suspect at least one of them is no longer retaining a charge.

 

I know extremely little about electrics. I thought it was likely one of the three batteries would be depleted more than the others, and would disconnect it so we could limp along on two batteries until I can replace them all. Taking a voltage reading across each battery post this evening gives me exactly the same reading (10.4v). So it occurs to me that I am actually reading the entire bank. 

 

So, next I'll disconnect them and read each separately. Does this seem like a reasonable course of action? We're cruising for the next month and it would be very much easier to organise the full replacement of the battery bank and delivery to an actual address at the beginning of November. Are we likely to squeeze a month out of two batteries ... or do batteries in a bank tend to deplete at pretty much the same rate over time?

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I don't think your giving your batteries enough charge.

It takes my engine about 4 hours to replace yesterdays use!

Somebody will come along shortly and explain better than i can!

 

Nipper

Edited by nipper
edited because i cant write or spell!
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12 minutes ago, Jim Batty said:

Over the last few days we find our battery bank (totalling 450Ah, sealed regular batteries) reads 10.0v to 10.4v in the morning after a 2-3 hour charging with the engine the evening before. It usually reads about 12.4v to 12.2v. So I suspect at least one of them is no longer retaining a charge.

 

I know extremely little about electrics. I thought it was likely one of the three batteries would be depleted more than the others, and would disconnect it so we could limp along on two batteries until I can replace them all. Taking a voltage reading across each battery post this evening gives me exactly the same reading (10.4v). So it occurs to me that I am actually reading the entire bank. 

 

So, next I'll disconnect them and read each separately. Does this seem like a reasonable course of action? We're cruising for the next month and it would be very much easier to organise the full replacement of the battery bank and delivery to an actual address at the beginning of November. Are we likely to squeeze a month out of two batteries ... or do batteries in a bank tend to deplete at pretty much the same rate over time?

Yes if the batteries are connected together in a bank, pretty much by definition they must have the same terminal voltage. You can only discover their individual characteristics after you disconnect them from each other.

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I would suggest you feel your batteries and see if any are getting hot or look as if they are bulging. If they are going down to 10 volts then you are definitely damaging them. If one cell has gone short in one of the three it will cause this. The best way after the checks above is to charge them and then disconnect them from each other and leave overnight with no load, then measure the voltages, hopefully 2 will be at 12.5 is and only one around 10 volts. But this needs attending to urgently or all 3 will be a write off

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2 hours ago, ditchcrawler said:

I would suggest you feel your batteries and see if any are getting hot or look as if they are bulging. If they are going down to 10 volts then you are definitely damaging them. If one cell has gone short in one of the three it will cause this. The best way after the checks above is to charge them and then disconnect them from each other and leave overnight with no load, then measure the voltages, hopefully 2 will be at 12.5 is and only one around 10 volts. But this needs attending to urgently or all 3 will be a write off

Yes, this is the first thing I did -- none of them are hot ... or seem to bulge. This aberration of 10v in the morning is only in the last couple of days; with readings of 11.9 and 11.7 late last week. I've been shutting off the master 12v switch to the boat when we are away in the day.

 

Will disconnect tomorrow morning (when it's stopped raining and have daylight!) and check. 

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9 hours ago, Jim Batty said:

Yes, this is the first thing I did -- none of them are hot ... or seem to bulge. This aberration of 10v in the morning is only in the last couple of days; with readings of 11.9 and 11.7 late last week. I've been shutting off the master 12v switch to the boat when we are away in the day.

 

Will disconnect tomorrow morning (when it's stopped raining and have daylight!) and check. 

To be sure you will almost certainly need to let them stand for several hours so any faulty battery has a chance to discharge its cell.

 

As Nipper says it sounds as if you have been grossly undercharging them so don't be surprised if the voltage does not drop when disconnected, it may well be that despite no bulges you have allowed/caused them to sulphate so badly they now have only a fraction of their original capacity.

 

11.7 to 11.9 volts is way too deeply discharged for a long life you should be looking at no less than 12.2 volts before recharging ASAP and that will take many hours, four may get you to about 80% charged the rest will take far longer and if you do not fully charge them regularly (say every few days to a week max.) they will be destroyed by sulphation. Voltage is no good for telling you when the batteries are fully charged, you need an accurate ammeter for that.

 

Now you know the folly of sea;led batteries, if you could get at the cells you could test the specific gravity and get a far quicker diagnosis - as long as you had been keeping them topped up which is not a frequent job on modern batteries unless they are faulty of you have over voltage charging..

 

Edited by Tony Brooks
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I agree, the symptoms fit completely with badly sulphated batteries. 

 

This leads me to formulate the MtB Second Universal Law of Boating: 

 

Whatever your LA battery problem, its because you haven't been charging them enough.

 

(The first Universal Law being: The difficulty of any boating manoeuvre is inversely proportional to the number of people watching.)

 

 

  • Greenie 3
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3 minutes ago, Mike the Boilerman said:

I agree, the symptoms fit completely with badly sulphated batteries. 

 

This leads me to formulate the MtB Second Universal Law of Boating: 

 

Whatever your LA battery problem, its because you haven't been charging them enough.

 

(The first Universal Law being: The difficulty of any boating manoeuvre is inversely proportional to the number of people watching.)

 

 

Third law

the amount of problems people have with batteries  is directly related to the number of years the havent lived on a boat

  • Greenie 1
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27 minutes ago, roland elsdon said:

Third law

the amount of problems people have with batteries  is directly related to the number of years the havent lived on a boat

Maybe" inversely related to how many years they have lived on a boat " as more age independent.

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41 minutes ago, Mike the Boilerman said:

(The first Universal Law being: The difficulty of any boating manoeuvre is inversely proportional to the number of people watching.)

directly proportional to the square of the number of onlooers. maybe onlookers.

Edited by system 4-50
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1 hour ago, Mike the Boilerman said:

I agree, the symptoms fit completely with badly sulphated batteries. 

 

This leads me to formulate the MtB Second Universal Law of Boating: 

 

Whatever your LA battery problem, its because you haven't been charging them enough.

 

(The first Universal Law being: The difficulty of any boating manoeuvre is inversely proportional to the number of people watching.)

 

 

When dealing with yet another cleaning of the burner in a heater converted to run on waste oil I formulated snibble's first law of combustion science.

If you burn a lot of shit, you get a lot of burnt shit 

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No not inverse. We started at age 21 with a colecraft with one battery for everything, no solar no for stage charging filament lights no mains. ( and no mooring)

we learned you cant get owt for nowt. ( tilley and oil lamps and gas fridge within 2 months of moving aboard)

so now with 2 batts , solar and led  lights and an  ardvarc we feel electrically sophisticated..

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12 hours ago, Tony Brooks said:

To be sure you will almost certainly need to let them stand for several hours so any faulty battery has a chance to discharge its cell.

 

As Nipper says it sounds as if you have been grossly undercharging them so don't be surprised if the voltage does not drop when disconnected, it may well be that despite no bulges you have allowed/caused them to sulphate so badly they now have only a fraction of their original capacity.

 

11.7 to 11.9 volts is way too deeply discharged for a long life you should be looking at no less than 12.2 volts before recharging ASAP and that will take many hours, four may get you to about 80% charged the rest will take far longer and if you do not fully charge them regularly (say every few days to a week max.) they will be destroyed by sulphation. Voltage is no good for telling you when the batteries are fully charged, you need an accurate ammeter for that.

 

Now you know the folly of sea;led batteries, if you could get at the cells you could test the specific gravity and get a far quicker diagnosis - as long as you had been keeping them topped up which is not a frequent job on modern batteries unless they are faulty of you have over voltage charging..

 

Ouch! 

 

To be fair, the problem I've described has been occurring in the last week. Up until last Friday (for 3 years on this set of batteries) they have never dropped below 12.2v at night, and thanks to the solar panels and all that fine sun this summer they are usually floating at 13.5v during the day. I won't go into their entire history (!), but we essentially 'baby' the batteries. I do admit, though, that running the engine for 4 hours a day to keep them topped up seems a bit excessive for our very basic set-up (12v fridge, LEDs, water pump).

 

Anyway, I tested the three batteries this morning separately and found two of them to be on their way out. So have ordered a new set -- kindly taken delivery of by a local boatyard where we can pick them up and recycle the old ones.

 

Thanks for everyone's help and comments.

 

 

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19 minutes ago, Jim Batty said:

Ouch! 

 

To be fair, the problem I've described has been occurring in the last week. Up until last Friday (for 3 years on this set of batteries) they have never dropped below 12.2v at night, and thanks to the solar panels and all that fine sun this summer they are usually floating at 13.5v during the day. I won't go into their entire history (!), but we essentially 'baby' the batteries. I do admit, though, that running the engine for 4 hours a day to keep them topped up seems a bit excessive for our very basic set-up (12v fridge, LEDs, water pump).

 

Anyway, I tested the three batteries this morning separately and found two of them to be on their way out. So have ordered a new set -- kindly taken delivery of by a local boatyard where we can pick them up and recycle the old ones.

 

Thanks for everyone's help and comments.

 

 

That will be about 60Ah per day then, what about the TV and laptop?

 

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40 minutes ago, Jim Batty said:

I do admit, though, that running the engine for 4 hours a day to keep them topped up seems a bit excessive for our very basic set-up (12v fridge, LEDs, water pump).

 

I have a near identical set-up and need to run my engine for 0 hours per day to keep the batteries 100% charged.

 

Go on, ask me how!

 

(And it isn't by running a suitcase genny four hours a day!)

 

 

 

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1 hour ago, Mike the Boilerman said:

 

I have a near identical set-up and need to run my engine for 0 hours per day to keep the batteries 100% charged.

 

Go on, ask me how!

 

(And it isn't by running a suitcase genny four hours a day!)

 

 

 

Because that is what your smart gauge is telling you???

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3 minutes ago, blackrose said:

I've no need for lithiums or solar panels.. My batteries last 4 days between charges if I need to, staying well above 50%. Mainly due to low power consumption

You are all bleeding Neanderthals.

If you use a load of power, get some Lithiums.

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32 minutes ago, blackrose said:

I've no need for lithiums or solar panels.. My batteries last 4 days between charges if I need to, staying well above 50%. Mainly due to low power consumption

 

My LA batteries last nine months between charges, with solar. And I don't need to worry about low power consumption. 

 

 

 

 

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1 hour ago, Mike the Boilerman said:

 

My LA batteries last nine months between charges, with solar. And I don't need to worry about low power consumption. 

 

 

 

 

 

Nine months between charges? Wow! By the way, ehat do you use the solar panels for if they're not used for charging? Picnic tables perhaps?

 

I don't worry about keeping my power consumption low. I just don't use much power. Once you take the silly 12v fridge out of the equation it's very easy and I don't need to cover my roof with ugly panels or worry about whether the sun is shining.

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