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I have 3 x110 ah open cell lead acid leisure batteries, kept charged by 70 amp Alternator, 100 Watt solar, and shoreline Nocco Genius 7.2 amp smart charger.

Also 110 ah starter battery linked by a new split charge relay.

All batteries were replaced a couple of months ago, but have given problems ever since.

As a leisure boater, the alternator charging is used for about a weeks cruising each month. The rest of the time they are left permanently on solar and the smart charger.

 

When out cruising, the engine warning light and buzzer occasionally come on for a few minutes at a time after about an hours cruising.

After just one day's cruising, the fridge fails to start without running the engine, and overnight the Tracer MPPT shows a red low battery warning light.

The hydrometer readings are showing all cells as between 10.9 and 11.1 volts, and one battery dry, with the other two OK level of acid.

The mechanic replaced the dry leisure battery about 6 weeks ago, but it is dry again now, and now tells me he found them all dangerously hot, almost boiling.

The starter battery has remained fully charged and in good condition throughout with no problems at all.

The initial voltage from the alternator is showing 14.36 v both sides of the split charge relay.

 

In summary, the new leisure batteries are well and truly knackered, the fridge can't run overnight when cruising, the solar display shows red after first day's cruising when engine is off, and the Isuzu control panel buzzes at random after about an hour's cruising.

 

The mechanic says he thinks the Nocco charger is causing the batteries to overheat when on extended shoreline power, but can provide no evidence to support this.

I am not sure that would account for all the symptoms either.  I'm also not convinced a 7.2 amp trickle charger would deliver enough oomph to boil 3 x 110 ah batteries.

 

Can any of our electrical gurus suggest a plausible scenario that would account for this range of symptoms?

Any help/suggestions would be mightily appreciated.

Thanks.

 

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Do you have a pic or a diagram of your wiring schematic? It could be that the faulty leisure battery is the "first in line" with +ve and -ve terminals from the charger(s) connected directly to it, then the other batteries, split charge relay and start battery are further downstream. Thus, a 14.36V reading on the 'alternator' isn't really from the alternator, but say the last battery in line; and the first is getting an overvoltage - say from a loose connection and a 1V or thereabouts voltage drop.

 

Its overvoltage that causes electrolyte to be lost, not amount of current. Normally the battery would be able to moderate it to an acceptable level though.

Edited by Paul C
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You need to find out what voltage the battery charger gets up to because at 7.2 Amp charger on 330Ah is definitely enough to boil them left on permanently if it does not have voltage regulation or the regulator has failed. To get to fully charged you need perhaps only 1 Amp or less. My 690Ah bank if left charging at 14.4 volts will get down to just belowth 2 Amp. 7.2 Amp is not a trickle charger. If I continued to force 7.2 Amp through mine the voltage would rise and boil them. Check the charger as it may well have failed to work properly.

Edited by PeterF
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Questions:

What is your power usage when out cruising and the engine is off?  Fridge, telly, hi-fi, screens, device charging etc?  How many watts or amps for each, and how long.  A mini power audit ideally.

 

What are the voltage settings for the solar controller?

 

What are the voltage outputs from the charger?

What are voltages at the alternator, the  starter battery and the domestic battery when the buzzer sounds.

 

What is the domestic battery voltage just before you start up of a morning, and immediately after starting?

 

Do you have a reasonably accurate ammeter? One with a shunt or Hall effect sensor?  If so what is the current when first starting the engine in the morning while cruising, and just before you shut down at the end of the cruising day?

 

 

N

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Thank you gents.  That is some enlightening info.

I do not have all the info requested, and the boat is 60 miles away.

However I can say we use very little electricity.  No gadgets, gizmos etc.  Just a small 12v fridge, led lights and water pump.

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Another thing on the battery charger, it should be the type that goes to float at a lower voltage when left long term, 13.8V or lower. My Victron inverter/charger goes down to 13.2V for long term. 14.4V absorption for 4 hours, then 13.7V float for 24hrs, then 13.2V storage if no further use after the 24 hour float period.

Edited by PeterF
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Can I point out that a hydrometer does not read voltages, it reads numbers that relate to the specific gravity (relative density) of water and if the figures the OP gives are taken as 1.09 and 1.11 then they are very well discharged. Note: Most hydrometers omit the decimal point because it is assumed the user knows where it goes into the number.

 

It is usually held that a cell difference of more than 0.03 or 0.025 from Lucas between any two cells indicates the battery is faulty. Yours have a difference of 0.02 so not yet in the faulty stage but getting there.

 

The dry battery indicates excess gassing so in the absence of the voltage readings others have requested I would begin to suspect cells shorting in that battery. Get it charging on the alternator at (say) 1200 rpm and after half an hour or so feel the battery tops. If the dry one is hotter than the rest then it is almost certain faulty with cell shorts. Ditto if individual cells are gassing more than the rest.

 

 

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I like the throway line "just a small 12v fridge"...

Any fridge  can consume a lot of power whether they'r compressor or absorbption type. 

The difficulty is measureing how many amp-hours yours consumes and then deciding hor to reduce it.

 

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5 minutes ago, OldGoat said:

I like the throway line "just a small 12v fridge"...

Any fridge  can consume a lot of power whether they'r compressor or absorbption type. 

The difficulty is measureing how many amp-hours yours consumes and then deciding hor to reduce it.

 

 

True, I did not notice that. If it's a 3 way running on 12V then we may well be talking about 200 Ah a day minus what the charging puts in. In fact that 7.5 amp charger can't cover it by about 0.5 amps.

 

OP - more info needed about the fridge, make, model or photo, and how you use it so we can rule this out.

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3 minutes ago, Tony Brooks said:

 

True, I did not notice that. If it's a 3 way running on 12V then we may well be talking about 200 Ah a day minus what the charging puts in. In fact that 7.5 amp charger can't cover it by about 0.5 amps.

 

OP - more info needed about the fridge, make, model or photo, and how you use it so we can rule this out.

Indeed. My old Electrolux 122 now over 30 years old uses about 7 amps continuous, my  12 amp charger only just coped with it last week whilst I serviced the gas side of it, cleaning burner, jet and sweeping the flue, now back on song again.

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8 minutes ago, bizzard said:

Indeed. My old Electrolux 122 now over 30 years old uses about 7 amps continuous, my  12 amp charger only just coped with it last week whilst I serviced the gas side of it, cleaning burner, jet and sweeping the flue, now back on song again.

If you believe the Thetford blurb then our 3 year old 3 way absorption fridge pulls a continuous 20 amps when it is on 12v :blink:

 

Thankfully it will only run on 12v when the engine is running otherwise it could very quickly flatten the domestic battery!!

 

Sat in traffic the voltage at the battery steadily drops as the alternator struggles to cope with the fridge and the engine demands on the alternator.

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38 minutes ago, Tony Brooks said:

Can I point out that a hydrometer does not read voltages, it reads numbers that relate to the specific gravity (relative density) of water and if the figures the OP gives are taken as 1.09 and 1.11 then they are very well discharged. Note: Most hydrometers omit the decimal point because it is assumed the user knows where it goes into the number.

 

It is usually held that a cell difference of more than 0.03 or 0.025 from Lucas between any two cells indicates the battery is faulty. Yours have a difference of 0.02 so not yet in the faulty stage but getting there.

 

The dry battery indicates excess gassing so in the absence of the voltage readings others have requested I would begin to suspect cells shorting in that battery. Get it charging on the alternator at (say) 1200 rpm and after half an hour or so feel the battery tops. If the dry one is hotter than the rest then it is almost certain faulty with cell shorts. Ditto if individual cells are gassing more than the rest.

 

 

You are quite right of course. The figures are SG 1.09 to 1.10.

The fridge is a standard 12v Lec type, and is only switched on when cruising.

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1 minute ago, Rebotco said:

You are quite right of course. The figures are SG 1.09 to 1.10.

The fridge is a standard 12v Lec type, and is only switched on when cruising.

 

Thanks, so as long as it has sufficient gas charge and the thermostat is working we can assume between 40 and 50Ah per day, minus whatever the charging is supplying. I think that makes shorting cells more likely.

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7 minutes ago, Naughty Cal said:

If you believe the Thetford blurb then our 3 year old 3 way absorption fridge pulls a continuous 20 amps when it is on 12v :blink:

 

Thankfully it will only run on 12v when the engine is running otherwise it could very quickly flatten the domestic battery!!

 

Sat in traffic the voltage at the battery steadily drops as the alternator struggles to cope with the fridge and the engine demands on the alternator.

Mine is quite a small fridge absorbtion too. On mine and probably on yours too the 12v heating element, like that in an ironing iron is just a flexible unit strapped to the exchanger with a metal band.

 

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1 hour ago, PeterF said:

You need to find out what voltage the battery charger gets up to because at 7.2 Amp charger on 330Ah is definitely enough to boil them left on permanently if it does not have voltage regulation or the regulator has failed. To get to fully charged you need perhaps only 1 Amp or less. My 690Ah bank if left charging at 14.4 volts will get down to just belowth 2 Amp. 7.2 Amp is not a trickle charger. If I continued to force 7.2 Amp through mine the voltage would rise and boil them. Check the charger as it may well have failed to work properly.

 

Yes, what does that 7.2 amps reduce over time? I think the OP said it was a smart charger but what is the float voltage and amps?

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2 minutes ago, Col_T said:

Would a shorting cell give rise to the reported

?

 

No, but it would give rise to the apparent flat batteries in the morning. I suspect there is a charging fault but until we get the voltage and current readings I am loth to comment on that. One thing for sure is that a single battery in a bank should not be dry.

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7.2 Amps @14.4 Volts is 104 Watts, plenty enough to boil 3 110Ah batteries to destruction over time. Does the current not fall as the batteries charge? It should if the battery charger is suitable for continuous connection.

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1 minute ago, Tracy D'arth said:

7.2 Amps @14.4 Volts is 104 Watts, plenty enough to boil 3 110Ah batteries to destruction over time. Does the current not fall as the batteries charge? It should if the battery charger is suitable for continuous connection.

Thanks all.  Here's a link to the charger's specifications  HERE

Sorry I can't get to the boat for other info requested for a couple of weeks.

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5 minutes ago, Rebotco said:

Thanks all.  Here's a link to the charger's specifications  HERE

Sorry I can't get to the boat for other info requested for a couple of weeks.

Are you sure it is working in the correct mode? I did not see in the spec that it was suitable to be left connected and working indefinitely, rather that it was just for charging batteries then being disconnected but I did speed read it so I may have missed it.

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16 minutes ago, Tracy D'arth said:

7.2 Amps @14.4 Volts is 104 Watts, plenty enough to boil 3 110Ah batteries to destruction over time. Does the current not fall as the batteries charge? It should if the battery charger is suitable for continuous connection.

 

 

I have a Halfords 12v battery charger which I use for equalisation charges.

It is only 4 amps but whilst the current appears to be 'fixed' I have yet to find the upper limit to the voltage.

 

I actually left it on for a few hours (it normally only gets an hour or so and gets to around 15v) with an 'old' battery. On approaching the battery it sounded like a volcano about to erupt and the voltmeter showed over 16.5 volts I turned it off.

 

A 'smart' charge it is not.

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22 minutes ago, Rebotco said:

Thanks all.  Here's a link to the charger's specifications  HERE

Sorry I can't get to the boat for other info requested for a couple of weeks.

 

Apart from the words "smart charger" in the description I can't see anything in the specs to indicate that this is in fact what most of us would understand as a smart (3 stage) charger which can be left switched on indefinitely charging the batteries. Also the % readout at the top of the picture might actually indicate the opposite! 

 

If nothing else appears to be at fault I would get yourself a proper smart charger and a new set of batteries. 

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2 hours ago, blackrose said:

 

7.2 amps being the maximum output?

I have a 5amp Cetek smart charger from auto days, it can bring all my six agms up to 13.something if left on 24 hours. 

Not ideal, but it's all I've got!

I don't like leaving anything switch on when I leave the boat.

It looks as though you may have killed your batteries, hope not.

Edited by LadyG
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