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  1. #1
    Join Date
    Feb 2017
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    Türkiye
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    1,705

    Default Battery charger - how much shore power to keep charged

    For those of you who don't know already I'm not very tech savvy so apologies in advance. I've volunteered to keep an eye on a boat in the marina here for another Paddy who won't be back again until the spring. My duties are simple enough to run the engines every few weeks and top up the shore power credit if needed. The shore power is connected 24/7 to keep the batteries charged but everything else is switched off at the breakers. Checking the shore power meter it appears to be using 1.5Kw per day. Is that excessive just for battery charging with no draw on the batteries?

  2. #2
    Join Date
    Mar 2002
    Location
    Greenwich
    Posts
    7,746

    Default Re: Battery charger - how much shore power to keep charged

    That is huge - over 110 Amp hours.

    I can put in a maximum of about 12 amp hours a day via a small solar panel and it’s much more than adequate and has the battery charged by mid morning.

    Something is seriously awry - either there is a huge load using power on the boat, the meter is very wrong or you are reading the meter wrongly.

  3. #3
    Join Date
    Aug 2011
    Location
    On the Celtic Fringe
    Posts
    14,517

    Default Re: Battery charger - how much shore power to keep charged

    Is somebody using your electric point for free?
    Cynical Scottish very nearly retired engineer who sails a Gib'Sea 96.

  4. #4
    Join Date
    Sep 2017
    Posts
    2,022

    Default Re: Battery charger - how much shore power to keep charged

    Quote Originally Posted by Irish Rover View Post
    For those of you who don't know already I'm not very tech savvy so apologies in advance. I've volunteered to keep an eye on a boat in the marina here for another Paddy who won't be back again until the spring. My duties are simple enough to run the engines every few weeks and top up the shore power credit if needed. The shore power is connected 24/7 to keep the batteries charged but everything else is switched off at the breakers. Checking the shore power meter it appears to be using 1.5Kw per day. Is that excessive just for battery charging with no draw on the batteries?
    I never leave a charger on when away from the boat, if its switched off if cant go duff & boil the batteries or kill its self

  5. #5
    Join Date
    Jan 2004
    Location
    Bricks & mortar: Italy. Boat: Aegean
    Posts
    10,515

    Default Re: Battery charger - how much shore power to keep charged

    Quote Originally Posted by Irish Rover View Post
    Checking the shore power meter it appears to be using 1.5Kw per day. Is that excessive just for battery charging with no draw on the batteries?
    I'm assuming you mean 1.5kW-hour, which is what utility meters usually tell you. Sure it's not 0.15kWh? 1.5kWh is high for simply maintaining float charge. It implies a constant 5A at 12V (which would be somewhat less at the batteries because of inefficiencies). I'd expect less for a healthy, fully charged battery bank of typical size. How big is the battery bank? If there are there any battery instruments it would be useful to know the amps actually being delivered. And how long had the batteries been on charge when you got the 1.5kWh figure? If the batteries were still being brought up to full charge, it wouldn't be so surprising.
    Last edited by macd; 13-11-19 at 09:25.
    All epigrams are false

  6. #6
    Join Date
    Feb 2017
    Location
    Türkiye
    Posts
    1,705

    Default Re: Battery charger - how much shore power to keep charged

    Quote Originally Posted by macd View Post
    I'm assuming you mean 1.5kW-hour, which is what utility meters usually tell you. Sure it's not 0.15kWh? 1.5kWh is high for simply maintaining float charge. It implies a constant 5A at 12V (which would be somewhat less at the batteries because of inefficiencies). I'd expect less for a healthy, fully charged battery bank of typical size. How big is the battery bank? If there are there any battery instruments it would be useful to know the amps actually being delivered. And how long had the batteries been on charge when you got the 1.5kWh figure? If the batteries were still being brought up to full charge, it wouldn't be so surprising.
    The batteries should have been fully charged when I started measuring. The owner was here for 2 weeks getting work done on the boat. He had it out for a couple of runs and the shore power was connected all the time he was here. I took a reading the morning after he left and again each of the two following mornings. It had used 15 of the meter units each day and I asked the Marina Office this morning what the units represented. They told me divide by 10 for Kw. I don't know the battery details but I'll try to have a look when I'm back in the marina. I'm not really familiar with the layout of the boat which is an old 1972 Grand Banks Classic with wooden hull.

  7. #7
    Join Date
    Dec 2003
    Posts
    5,685

    Default Re: Battery charger - how much shore power to keep charged

    Quote Originally Posted by Irish Rover View Post
    For those of you who don't know already I'm not very tech savvy so apologies in advance. I've volunteered to keep an eye on a boat in the marina here for another Paddy who won't be back again until the spring. My duties are simple enough to run the engines every few weeks and top up the shore power credit if needed. The shore power is connected 24/7 to keep the batteries charged but everything else is switched off at the breakers. Checking the shore power meter it appears to be using 1.5Kw per day. Is that excessive just for battery charging with no draw on the batteries?
    Seems very high. How big is the battery bank?

    If there's no typo/data-misreading here, and if this isn't a huge battery bank, then there may be a problem; potentially a serious one, or perhaps something has been inadvertently left switched on, perhaps directly connected to the batts?

  8. #8
    Join Date
    Sep 2017
    Posts
    2,022

    Default Re: Battery charger - how much shore power to keep charged

    ask the marina to add another meter inline to monitor the original

  9. #9
    Join Date
    Jun 2017
    Posts
    809

    Default Re: Battery charger - how much shore power to keep charged

    Quote Originally Posted by dom View Post
    Seems very high. How big is the battery bank?

    If there's no typo/data-misreading here, and if this isn't a huge battery bank, then there may be a problem; potentially a serious one, or perhaps something has been inadvertently left switched on, perhaps directly connected to the batts?
    Yes, not impossible to have a 60W continuous load somewhere.

  10. #10
    Join Date
    Jan 2004
    Location
    Bricks & mortar: Italy. Boat: Aegean
    Posts
    10,515

    Default Re: Battery charger - how much shore power to keep charged

    Quote Originally Posted by dom View Post
    If there's no typo/data-misreading here, and if this isn't a huge battery bank, then there may be a problem; potentially a serious one, or perhaps something has been inadvertently left switched on, perhaps directly connected to the batts?
    What he said, Rover.
    I'm also still a little suspicious about the meter readings. There surely must be some units marked on the meter. Could you take a photo for us?
    All epigrams are false

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