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  1. #1
    Join Date
    Apr 2007
    Posts
    102

    Default 12 volt Electrical Battery Problems. Where is all the power going?

    My service battery bank consists of two 110 Ah lead acid batteries. They are a little over three years old. They are charged from an old LEAB smart-charger in port and two 100 watt solar panels. We also have a suitcase generator if we need a top up. We never use the engine to merely charge the batteries unless we are motoring out of port.

    We run two fridges together they take 8 amps approximately. At the moment we are in Ancona Marina hence the need for lots of cool drinks. In the last couple of weeks we've just been motoring out into the bay to swim and SUP. The batteries are 100% full when we leave and we motor out so no loss of power during the journey (you'd think).The fly in the ointment is that the battery bank will not run the two fridges. We are out for six hours even running the full six hours that's 48 amps, one quarter of the battery capacity and four amps in from the solar panels minimum.

    I have a NASA battery monitor and within an hour the batteries have fallen off a cliff from 100% to 60% in an hour ( I understand the limitations of this instrument but broadly speaking we can say there is a BIG power drop). I immediately condemned the batteries and removed them with intention of buying new today. However, I had a single 110 AH battery which I wired in as a temporary measure overnight. I also let the free standing fridge run on the "old" batteries and they have produced the required amperage so far.

    As a test, I switched off the mains battery charger. Damn me the new battery dropped like a stone just like the old batteries.

    Where are all those amps going?
    "To know that we know what we know, and to know that we do not know what we do not know, that is true knowledge".
    Nicolaus Copernicus

  2. #2
    Join Date
    Apr 2002
    Location
    Cornwall
    Posts
    8,906

    Default Re: 12 volt Electrical Battery Problems. Where is all the power going?

    What charge does the monitor show going into the batteries from the mains charger ?

    Brian
    Kddpowercentre VASR charge

  3. #3
    Join Date
    Apr 2007
    Posts
    102

    Default Re: 12 volt Electrical Battery Problems. Where is all the power going?

    Quote Originally Posted by halcyon View Post
    What charge does the monitor show going into the batteries from the mains charger ?

    Brian
    Good morning Brian,

    Thanks for your reply.

    The reading varies of course as the batteries charge. I am running both fridges at the moment off the single 110 Ah battery. Because the NASA meter has been set for the 2 X 110 Ah then I assume that there will be a false %age reading. At the moment it shows 8.3 amps. But something I have always found strange is that the LEAB mains chargers shows 22 amps. There has always been an inconsistency.

    I ran the freestanding fridge (takes 3 to 4 amps) from 1800 last night on one of the 110 Ah batteries and there was not enough to power it by 0300. It was fully charged at 1800 showing 13.0 volts and even at one point whilst disconnected showing over 15 volts! Does this indicate a problem? Never heard of this high reading before.
    "To know that we know what we know, and to know that we do not know what we do not know, that is true knowledge".
    Nicolaus Copernicus

  4. #4
    Join Date
    Apr 2005
    Location
    Exmouth, Devon
    Posts
    738

    Default Re: 12 volt Electrical Battery Problems. Where is all the power going?

    My guess is something wrong with solar setup. Look at the volts/amps display with sun out and fridge running. If it doesn't look right, isolate or switch off everything except panel input and see what the BM1 shows as power going in.

    If you're getting nothing, solar charge is probably not connected through BM shunt. If it's showing less than expected, check the solar kit.
    allGadgets Marine
    www.allgadgets.co.uk

  5. #5
    Join Date
    Apr 2005
    Location
    Exmouth, Devon
    Posts
    738

    Default Re: 12 volt Electrical Battery Problems. Where is all the power going?

    Don't forget the amps reading on BM is a NET figure of input and output.
    allGadgets Marine
    www.allgadgets.co.uk

  6. #6
    Join Date
    Apr 2002
    Location
    Cornwall
    Posts
    8,906

    Default Re: 12 volt Electrical Battery Problems. Where is all the power going?

    Quote Originally Posted by tgpt21 View Post
    Good morning Brian,

    Thanks for your reply.

    The reading varies of course as the batteries charge. I am running both fridges at the moment off the single 110 Ah battery. Because the NASA meter has been set for the 2 X 110 Ah then I assume that there will be a false %age reading. At the moment it shows 8.3 amps. But something I have always found strange is that the LEAB mains chargers shows 22 amps. There has always been an inconsistency.

    I ran the freestanding fridge (takes 3 to 4 amps) from 1800 last night on one of the 110 Ah batteries and there was not enough to power it by 0300. It was fully charged at 1800 showing 13.0 volts and even at one point whilst disconnected showing over 15 volts! Does this indicate a problem? Never heard of this high reading before.
    Sounds like surface charge problems.

    What you need to do is find out some facts, what is engine charge and voltages, what is mains charge and voltages, what is solar panel and voltages, that is with fridges off. This will give you what is happening on charge, with no charge, check your power loading, that is each fridge, radio, lights. Now make a note of what is switched on, fridges etc, and check your charge levels and voltages again.

    It may be that you are getting to low a charge voltage, thus a low capacity, then when charging you get a surface charge that gives you the look of a charged battery.

    Do not try and assume, get facts.

    Brian
    Kddpowercentre VASR charge

  7. #7
    Join Date
    Jul 2006
    Location
    Emsworth Hants
    Posts
    12,524

    Default Re: 12 volt Electrical Battery Problems. Where is all the power going?

    >The reading varies of course as the batteries charge. I am running both fridges at the moment off the single 110 Ah battery.

    That could be the problem I've never seen a boat with two fridges, long distance sailing you go on a great many.

  8. #8
    Join Date
    Aug 2011
    Location
    On the Celtic Fringe
    Posts
    14,259

    Default Re: 12 volt Electrical Battery Problems. Where is all the power going?

    I just ignore the percentage power available on the NASA instrument, voltage and amps are the two figures that I am interested in.
    Cynical Scottish almost retired engineer who sails a Gib'Sea 96.

  9. #9
    Join Date
    Jul 2005
    Posts
    3,315

    Default Re: 12 volt Electrical Battery Problems. Where is all the power going?

    The NASA battery monitor is in essence an Amp hour counting battery monitor ( it has some slightly smarter technology but this plays little roll in the display). Therefore if you have programmed in a battery size of 220 Ahr and the display has dropped from 100% to 60% SOC in one hour the meter has measured an average current draw of around 0.4x220= 88A (this is ignoring Peukert equation).

    So the display should be showing a current draw of this order of magnitude.

    If it does not. The most likely explanation is the programmed battery capacity is incorrect.

    Is the programmed battery capacity incorrectly set to 22Ahrs rather than 220Ahrs?

  10. #10
    Join Date
    Apr 2007
    Posts
    102

    Default Re: 12 volt Electrical Battery Problems. Where is all the power going?

    Hi Mike,
    Thank you for your reply.

    I understand the net input/output idea. The solar panels are connected to the battery meter. Although I do plan to dive in and redo all the connections.

    The second fridge is a Mobicool box type thing which is very good. It is connected to a 12 volt cigar lighter connection when we are at sea. I've just this moment noticed it is when the voltage reaches 12.6 that it cannot be driven off this connection. Yet I have connected it directly to the "old" recently removed and suspect 110 Ah battery it is working OK despite there only being 12.5 across the terminals connected.
    "To know that we know what we know, and to know that we do not know what we do not know, that is true knowledge".
    Nicolaus Copernicus

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